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Title:
METHOD FOR AUTOMATIC ADJUSTMENT OF TUNABLE PASSIVE ANTENNAS, AND RADIO TRANSCEIVER USING THIS METHOD
Document Type and Number:
WIPO Patent Application WO/2019/197930
Kind Code:
A1
Abstract:
A radio transceiver of the invention comprises: 4 tunable passive antennas (11) (12) (13) (14) which form a multiport antenna array (1); 4 sensing units (31) (32) (33) (34); 4 feeders (21) (22) (23) (24); a radio unit (8); and a control unit (6). An antenna system comprising the 4tunable passive antennas and the 4 feeders has 4 user ports. The radio unit receives, from a wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols. The radio unit applies 4 excitations to the user ports.The radio unit delivers antenna adjustment instructions. The control unit delivers one or more antenna control signals to the tunable passive antennas.

Inventors:
BROYDE, Frederic (12 chemin des Hauts de Clairefontaine, Maule, 78580, FR)
CLAVELIER, Evelyne (12 chemin des Hauts de Clairefontaine, Maule, 78580, FR)
Application Number:
IB2019/052454
Publication Date:
October 17, 2019
Filing Date:
March 26, 2019
Export Citation:
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Assignee:
TEKCEM (12 chemin des Hauts de Clairefontaine, Maule, 78580, FR)
International Classes:
H04B7/0413; H01Q5/50; H03H7/38; H03H7/40; H04B1/04; H04B1/18
Domestic Patent References:
WO2017103687A12017-06-22
Foreign References:
US20170179601A12017-06-22
US20020053953A12002-05-09
FR1870443A2018-04-12
US8063839B22011-11-22
US8325097B22012-12-04
US9077317B22015-07-07
US20160051400W2016-09-12
US9698484B12017-07-04
Other References:
A. PETOSA, IEEE ANTENNAS AND PROPAGATION MAGAZINE, vol. 54, no. 5, October 2012 (2012-10-01)
Download PDF:
Claims:
CLAIMS

1. A method for automatically adjusting N tunable passive antennas (11) (12) (13) (14) of an antenna system, where N is an integer greater than or equal to 2, each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an influence on said one or more characteristics, said at least one parameter being adjustable by electrical means, said at least one parameter being mainly determined by at least one antenna control signal, the antenna system having m user ports, where in is an integer greater than or equal to 2, the antenna system being a part of a radio transceiver for communicating in a wireless network, the radio transceiver allowing, at a given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas, the method comprising the steps of:

receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols (801), each of said data symbols being referred to as“authorized data symbol”;

applying m excitations to the m user ports, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols;

sensing one or more electrical variables at each of the user ports, to obtain“sensing unit output signals”, each of the sensing unit output signals being mainly determined by at least one of the electrical variables sensed at one of the user ports;

estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals; and

utilizing said q real quantities depending on an impedance matrix presented by the user ports, to obtain the one or more antenna control signals.

2. The method of claim 1, wherein the radio transceiver requests, from the wireless network, a permission to use, for excitations intended for an adjustment, one or more data symbols.

3. The method of claim 2, wherein the radio transceiver specifies the one or more data symbols to which said authorization applies.

4. The method of claim 1 , wherein the wireless network specifies the one or more data symbols to which said authorization applies.

5. The method of any one of the previous claims, wherein each of the excitations has a complex envelope, the complex envelopes of the m excitations being linearly independent in the set of complex functions of one real variable, regarded as a vector space over the field of complex numbers.

6. A radio transceiver for communicating in a wireless network, the radio transceiver comprising:

an antenna system comprising N tunable passive antennas (11) (12) (13) (14), where N is an integer greater than or equal to 2, each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an influence on said one or more characteristics, said at least one parameter being adjustable by electrical means, the antenna system having m user ports, where m is an integer greater than or equal to 2, the radio transceiver allowing, at a given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas;

m sensing units (31) (32) (33) (34), each of the sensing units delivering one or more “sensing unit output signals”, each of the sensing unit output signals being mainly determined by one or more electrical variables sensed at one of the user ports;

a radio unit (8), the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols (801), each of said data symbols being referred to as“authorized data symbol”, the radio unit being utilized to apply m excitations to the m user ports, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports; and

a control unit (6), the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals.

7. The radio transceiver of claim 6, wherein the sensing unit output signals delivered by each of the sensing units comprise: a first sensing unit output signal proportional to a first electrical variable, the first electrical variable being a voltage across one of the user ports; and a second sensing unit output signal proportional to a second electrical variable, the second electrical variable being a current flowing in said one of the user ports.

8. The radio transceiver of claim 6, wherein the sensing unit output signals delivered by each of the sensing units comprise: a first sensing unit output signal proportional to a first electrical variable, the first electrical variable being an incident voltage at one of the user ports; and a second sensing unit output signal proportional to a second electrical variable, the second electrical variable being a reflected voltage at said one of the user ports.

9. The radio transceiver of any one of the claims 6 to 8, wherein the radio transceiver requests, from the wireless network, a permission to use, for excitations intended for an adjustment, one or more data symbols.

10. The radio transceiver of claim 9, wherein the radio transceiver specifies the one or more data symbols to which said authorization applies.

11. The radio transceiver of any one of the claims 6 to 8, wherein the wireless network specifies the one or more data symbols to which said authorization applies.

12. The radio transceiver of any one of the claims 6 to 11, wherein each of the excitations has a complex envelope, the complex envelopes of the m excitations being linearly independent in the set of complex functions of one real variable, regarded as a vector space over the field of complex numbers.

Description:
Method for automatic adjustment of tunable passive antennas,

and radio transceiver using this method

FIELD OF THE INVENTION

The invention relates to a method for automatically adjusting a plurality of tunable passive antennas of a radio transceiver which communicates in a wireless network by utilizing these tunable passive antennas, the wireless network being possibly a cellular wireless network. The invention also relates to a radio transceiver using this method.

The French patent application No. FR1870443 of 12 April 2018, entitled“Precede pour reglage automatique d’antennes passives accordables et emetteur-recepteur radio utilisant ce precede” is incorporated by reference.

PRIOR ART

A tunable passive antenna comprises at least one antenna control device having at least one parameter having an effect on one or more characteristics of said tunable passive antenna, said at least one parameter being adjustable, for instance by electrical means. Adjusting a tunable passive antenna means adjusting at least one said at least one parameter. Each of said one or more characteristics may for instance be an electrical characteristic such as an impedance at a specified frequency, or an electromagnetic characteristic such as a directivity pattern at a specified frequency. A tunable passive antenna may also be referred to as“reconfigurable antenna”. Some authors consider three classes of tunable passive antennas: polarization-agile antennas, pattem-reconfigurable antennas and frequency-agile antennas. The state of the art regarding frequency-agile antennas is for instance described in the article of A. Petosa entitled “An Overview of Tuning Techniques for Frequency- Agile Antennas”, published in IEEE Antennas and Propagation Magazine, vol. 54, No. 5, in October 2012. As explained in this article, many different types of antenna control device may be used to control one or more characteristics of a tunable passive antenna. An antenna control device may for instance be:

- an electrically controlled switch or change-over switch, in which case a parameter of the antenna control device having an effect on one or more characteristics of the tunable passive antenna may be the state of the switch or change-over switch;

- an adjustable impedance device, in which case a parameter of the antenna control device having an effect on one or more characteristics of the tunable passive antenna may be the reactance or the impedance of the adjustable impedance device at a specified frequency; or

- an actuator arranged to produce a mechanical deformation of the tunable passive antenna, in which case a parameter of the antenna control device having an effect on one or more characteristics of the tunable passive antenna may be a length of the deformation. If an antenna control device is an electrically controlled switch or change-over switch, it may for instance be an electro-mechanical relay, or a microelectromechanical switch (MEMS switch), or a circuit using one or more PIN diodes or one or more insulated-gate field-effect transistors (MOSFETs) as switching devices.

An adjustable impedance device is a component comprising two terminals which substantially behave as the terminals of a passive linear two-terminal circuit element, and which are consequently fully characterized by an impedance which may depend on frequency, this impedance being adjustable.

An adjustable impedance device having a reactance which is adjustable by electrical means may be such that it only provides, at a given frequency, a finite set of reactance values, this characteristic being for instance obtained if the adjustable impedance device is:

- a network comprising a plurality of capacitors or open-circuited stubs and one or more electrically controlled switches or change-over switches, such as electro-mechanical relays, or microelectromechanical switches, or PIN diodes or insulated-gate field-effect transistors, used to cause different capacitors or open-circuited stubs of the network to contribute to the reactance; or

- a network comprising a plurality of coils or short-circuited stubs and one or more electrically controlled switches or change-over switches used to cause different coils or short-circuited stubs of the network to contribute to the reactance.

An adjustable impedance device having a reactance which is adjustable by electrical means may be such that it provides, at a given frequency, a continuous set of reactance values, this characteristic being for instance obtained if the adjustable impedance device is based on the use of a variable capacitance diode; or a MOS varactor; or a microelectromechanical varactor (MEMS varactor); or a ferroelectric varactor.

Many methods exist for automatically adjusting a single tunable passive antenna, for instance the methods disclosed in the patent of the United States of America No. 8,063,839 entitled“Tunable antenna system”, and in the patent of the United States of America No. 8,325,097 entitled“Adaptively tunable antennas and method of operation therefore”. Such methods cannot be used for automatically adjusting a plurality of tunable passive antennas, when the interactions between the tunable passive antennas are not negligible.

A first method for automatically adjusting a plurality of tunable passive antennas may be derived from the approach employed in the patent of the United States of America No. 9,077,317, entitled“Method and apparatus for automatically tuning an impedance matrix, and radio transmitter using this apparatus”, which discloses a method for automatically adjusting a multiple-input-port and multiple-output-port tuning unit, using different excitations applied successively to m user ports, where m is an integer greater than or equal to 2. This first method is applicable to a radio transmitter using a plurality of antennas simultaneously. This first method may be used when the interactions between the tunable passive antennas are not negligible. To automatically adjust m tunable passive antennas, this first method uses m or more different excitations applied successively to the m user ports. Unfortunately, this method is usually not compatible with the specifications of a radio transmitter used for MIMO wireless communication, because the generation of a sequence of m or more different excitations applied successively entails a prolonged emission of electromagnetic waves, which is usually not compatible with the requirements of all MIMO emission modes of applicable standards, for instance the LTE-Advanced standards.

This problem is solved in a second method for automatically adjusting a plurality of tunable passive antennas, disclosed in the international application PCT/IB2016/051400 of 11 March 2016 (WO 2017/103687) and in the patent of the United States of AmericaNo. 9,698,484, both entitled“Method for automatically adjusting tunable passive antennas, and automatically tunable antenna array using this method”, in which the excitations need not be applied successively.

A block diagram of an automatic antenna system implementing the first method for automatically adjusting a plurality of tunable passive antennas, or the second method for automatically adjusting a plurality of tunable passive antennas, is shown in Figure 1. The automatic antenna system shown in Fig. 1 has m = 4 user ports (311) (321) (331) (341), the m user ports presenting, at a given frequency, an impedance matrix referred to as“the impedance matrix presented by the user ports”, the automatic antenna system comprising:

m = 4 tunable passive antennas (11) (12) (13) (14), the m tunable passive antennas operating simultaneously in a given frequency band, the m tunable passive antennas forming a multiport antenna array (1), each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled by utilizing said at least one antenna control device, said at least one antenna control device having at least one parameter having an effect on said one or more characteristics, said at least one parameter being adjustable by electrical means;

m sensing units (31) (32) (33) (34), each of the sensing units delivering two“sensing unit output signals”, each of the sensing unit output signals being determined by one electrical variable sensed (or measured) at one of the user ports;

m feeders (21) (22) (23) (24), each of the feeders having a first end coupled to a signal port of one and only one of the tunable passive antennas, each of the feeders having a second end coupled to one and only one of the user ports, through one and only one of the sensing units;

a signal processing unit (5), the signal processing unit estimating q real quantities depending on the impedance matrix presented by the user ports, where q is an integer greater than or equal to m, using the sensing unit output signals caused by m excitations applied to the user ports, the signal processing unit delivering an“adjustment instruction” as a function of said q real quantities depending on the impedance matrix presented by the user ports; and a control unit (6), the control unit receiving the adjustment instruction from the signal processing unit (5), the control unit delivering“control signals”, the control signals being determined as a function of the adjustment instruction, each of said parameters being mainly determined by one or more of the control signals.

The first method for automatically adjusting a plurality of tunable passive antennas, or the second method for automatically adjusting a plurality of tunable passive antennas are based on closed-loop control, and they do not include the description of a fast control technique, so that a full automatic adjustment of the plurality of tunable passive antennas requires several iterations, each iteration comprising the following steps: applying m excitations to the m user ports; estimating q real quantities depending on the impedance matrix presented by the user ports; delivering an adjustment instruction; and delivering control signals. In order to be compatible with the requirements of the standards typically applicable to MIMO wireless networks, each iteration must typically use, for the excitations, one or more data symbols (for instance OFDMA or SC-FDMA data symbols) comprising resource elements allocated to reference signals (also referred to as“pilots”) for MIMO channel estimation. This has two undesirable consequences: first, the reference signals of a data symbol used for the excitations of an iteration give an incorrect estimate of the MIMO channel, since the channel is modified at the end of the iteration; and second, said full automatic adjustment is very slow, because the reference signals are not very frequent.

Thus, the prior art does not teach a method for automatically adjusting a plurality of tunable passive antennas, which is sufficiently fast, which is compatible with the requirements of the standards typically applicable to MIMO wireless networks, and which does not entail an incorrect estimate of the MIMO channel.

SUMMARY OF THE INVENTION

The purpose of the invention is a method for automatically adjusting a plurality of tunable passive antennas, without the above-mentioned limitations of known techniques, and also a radio transceiver using this method.

In what follows, X and Y being different quantities or variables, performing an action as a function of X does not preclude the possibility of performing this action as a function of Y. In what follows,“having an influence” and“having an effect” have the same meaning. In what follows,“coupled”, when applied to two ports (in the meaning of circuit theory), may indicate that the ports are directly coupled, in which case each terminal of one of the ports is connected to (or, equivalently, in electrical contact with) one and only one of the terminals of the other port, and/or that the ports are indirectly coupled, in which case an electrical interaction different from direct coupling exists between the ports, for instance through one or more components. The method of the invention is a method for automatically adjusting N tunable passive antennas of an antenna system, where N is an integer greater than or equal to 2, each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an influence on said one or more characteristics, said at least one parameter being adjustable by electrical means, said at least one parameter being mainly determined by at least one antenna control signal, the antenna system having m user ports, where in is an integer greater than or equal to 2, the antenna system being a part of a radio transceiver for communicating in a wireless network, the radio transceiver allowing, at a given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas, the method comprising the steps of:

receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”;

applying m excitations to the m user ports, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols;

sensing one or more electrical variables at each of the user ports, to obtain“sensing unit output signals”, each of the sensing unit output signals being mainly determined by at least one of the electrical variables sensed at one of the user ports;

estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals; and

utilizing said q real quantities depending on an impedance matrix presented by the user ports, to obtain the one or more antenna control signals.

The method of the invention may for instance be such that the radio transceiver requests, from the wireless network, a permission to use, for excitations intended for an adjustment, one or more data symbols; and that, afterwards, the radio transceiver receives said radio signal providing an authorization. In this case, the method of the invention may for instance be such that the radio transceiver specifies the one or more data symbols to which said authorization applies.

The method of the invention may for instance be such that the wireless network specifies the one or more data symbols to which said authorization applies.

The method of the invention may for instance be such that the excitations exist only inside one or more resource elements of the one or more authorized data symbols.

The given frequency may for instance be a frequency greater than or equal to 150 MHz. The specialist understands that an impedance matrix presented by the user ports is a complex matrix of size m by m. We will use Z,· to denote the impedance matrix presented by the user ports. Z,· depends on the frequency. Z, · also depends on the one or more antenna control signals, so that the method of the invention uses closed-loop control.

Each of the N tunable passive antennas has a port, referred to as the“signal port” of the antenna, which can be used to receive and/or to emit electromagnetic waves. Each of the tunable passive antennas comprises at least one antenna control device, which may comprise one or more terminals used for other electrical connections. It is assumed that each of the tunable passive antennas behaves, at the given frequency, with respect to the signal port of the antenna, substantially as a passive antenna, that is to say as an antenna which is linear and does not use an amplifier for amplifying signals received by the antenna or signals emitted by the antenna. As a consequence of linearity, it is possible to define an impedance matrix presented by the tunable passive antennas, the definition of which only considers, for each of the tunable passive antennas, the signal port of the antenna. This matrix is consequently of size N x N. Because of the interactions between the tunable passive antennas, this matrix need not be diagonal. In particular, the invention may for instance be such that this matrix is not a diagonal matrix.

As said above in the prior art section, each of said one or more characteristics may for instance be an electrical characteristic such as an impedance at a specified frequency, or an electromagnetic characteristic such as a directivity pattern at a specified frequency.

It is said above that the radio transceiver allows, at the given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas. In other words, the radio transceiver is such that, if a power is received by the m user ports at the given frequency, a part of said power received by the m user ports is transferred to an electromagnetic field radiated by the tunable passive antennas at the given frequency, so that a power of the electromagnetic field radiated by the tunable passive antennas at the given frequency is equal to said part of said power received by the m user ports. For instance, the specialist knows that a power of the electromagnetic field radiated by the tunable passive antennas (average radiated power) can be computed as the flux of the real part of a complex Poynting vector of the electromagnetic field radiated by the tunable passive antennas, through a closed surface containing the tunable passive antennas.

To obtain that the radio transceiver allows, at the given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas, each of the tunable passive antennas may, if m = N, for instance be coupled, directly or indirectly, to one and only one of the user ports, as shown below in the presentation of the first embodiment. More precisely, if m = N, for each of the tunable passive antennas, the signal port of the antenna may for instance be coupled, directly or indirectly, to one and only one of the user ports. For instance, an indirect coupling may be a coupling through a feeder and/or through a sensing unit. For suitable values of the antenna control signals, said transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas may for instance be a transfer of power with small or negligible or zero losses, this characteristic being preferred. An apparatus implementing the method of the invention is a radio transceiver for communicating in a wireless network, the radio transceiver comprising:

an antenna system comprising N tunable passive antennas, where N is an integer greater than or equal to 2, each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an influence on said one or more characteristics, said at least one parameter being adjustable by electrical means, the antenna system having m user ports, where in is an integer greater than or equal to 2, the radio transceiver allowing, at a given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas;

m sensing units, each of the sensing units delivering one or more“sensing unit output signals”, each of the sensing unit output signals being mainly determined by one or more electrical variables sensed at one of the user ports;

a radio unit, the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”, the radio unit being utilized to apply m excitations to the m user ports, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports; and

a control unit, the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals.

For instance, each of said electrical variables may be a voltage, or an incident voltage, or a reflected voltage, or a current, or an incident current, or a reflected current. For instance, each of said electrical variables may be sensed (or measured) at one of said user ports.

As explained above, if m = N, it is for instance possible that each of the tunable passive antennas is coupled, directly or indirectly, to one and only one of the user ports. As explained above, if m = N, it is for instance possible that, for each of the tunable passive antennas, the signal port of the antenna is coupled, directly or indirectly, to one and only one of the user ports.

It is for instance possible that each of the m user ports is coupled, directly or indirectly, to a port of the radio unit, said port of the radio unit delivering one and only one of the excitations.

The specialist understands that the radio transceiver of the invention is adaptive in the sense that said parameters are varied with time as a function of the sensing unit output signals, which are each mainly determined by one or more electrical variables.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics will appear more clearly from the following description of particular embodiments of the invention, given by way of non-limiting examples, with reference to the accompanying drawings in which:

Figure 1 shows a block diagram of an automatic antenna system, and has already been discussed in the section dedicated to the presentation of the prior art;

Figure 2 shows a block diagram of a radio transceiver of the invention (first embodiment);

Figure 3 shows a resource grid of a wireless network;

Figure 4 shows a block diagram of a radio transceiver of the invention (fourth embodiment);

Figure 5 shows a block diagram of a radio transceiver of the invention (fifth embodiment);

Figure 6 shows a block diagram of a radio transceiver of the invention (sixth embodiment).

DETAILED DESCRIPTION OF SOME EMBODIMENTS First embodiment.

As a first embodiment of a device of the invention, given by way of non-limiting example, we have represented in Figure 2 the block diagram of a radio transceiver for communicating in a wireless network, the radio transceiver comprising:

N= 4 tunable passive antennas (11) (12) (13) (14), the tunable passive antennas operating simultaneously in a given frequency band, the tunable passive antennas forming a multiport antenna array (1), each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an effect on said one or more characteristics, said at least one parameter being adjustable by electrical means; N feeders (21) (22) (23) (24), each of the feeders having a first end which is directly coupled to a signal port of one and only one of the tunable passive antennas, an antenna system comprising the N tunable passive antennas and the N feeders, the antenna system having m = N user ports, each of the feeders having a second end which is one of the user ports;

m sensing units (31) (32) (33) (34), each of the sensing units delivering two“sensing unit output signals”, each of the sensing unit output signals being determined by an electrical variable sensed (or measured) at one of the user ports;

a radio unit (8), the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”, the radio unit applying m excitations to the m user ports through the sensing units, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports; and

a control unit (6), the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals.

Each of the tunable passive antennas is coupled to one and only one of the user ports. More precisely, for each of the tunable passive antennas, the signal port of the antenna is indirectly coupled to one and only one of the user ports, through one and only one of the feeders. Moreover, each of the user ports is coupled to one and only one of the tunable passive antennas. More precisely, each of the user ports is indirectly coupled to the signal port of one and only one of the tunable passive antennas, through one and only one of the feeders. The given frequency band only contains frequencies greater than or equal to 300 MHz.

Each of the sensing units (31) (32) (33) (34) may for instance be such that the two sensing unit output signals delivered by said each of the sensing units comprise: a first sensing unit output signal proportional to a first electrical variable, the first electrical variable being a voltage across one of the user ports; and a second sensing unit output signal proportional to a second electrical variable, the second electrical variable being a current flowing in said one of the user ports. Said voltage across one of the user ports may be a complex voltage and said current flowing in said one of the user ports may be a complex current. Alternatively, each of the sensing units (31) (32) (33) (34) may for instance be such that the two sensing unit output signals delivered by said each of the sensing units comprise: a first sensing unit output signal proportional to a first electrical variable, the first electrical variable being an incident voltage (which may also be referred to as“forward voltage”) at one of the user ports; and a second sensing unit output signal proportional to a second electrical variable, the second electrical variable being a reflected voltage at said one of the user ports. Said incident voltage at one of the user ports may be a complex incident voltage and said reflected voltage at said one of the user ports may be a complex reflected voltage.

Each of the m user ports is indirectly coupled to a port of the radio unit (8), through one and only one of the sensing units, said port of the radio unit delivering one and only one of the excitations. Each of the one or more antenna adjustment instructions may be of any type of digital message. The one or more antenna adjustment instructions are delivered during one or more adjustment sequences. The duration of an adjustment sequence is less than 100 microseconds. The specialist understands that the radio transceiver uses closed-loop control to automatically adjust the tunable passive antennas.

The specialist sees that the radio transceiver allows, at a given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas. In other words, the radio transceiver is such that, if a power is received by the m user ports at the given frequency, a part of said power received by the m user ports is transferred to an electromagnetic field radiated by the tunable passive antennas at the given frequency, so that a power of the electromagnetic field radiated by the tunable passive antennas at the given frequency is equal to said part of said power received by the m user ports. The radio transceiver also allows, at said given frequency, a transfer of power from an electromagnetic field incident on the tunable passive antennas to the m user ports. Additionally, the tunable passive antennas (11) (12) (13) (14) are such that, at said given frequency, for suitable values of the one or more antenna control signals, a low-loss transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas can be obtained (for radio emission), and a low- loss transfer of power from an electromagnetic field incident on the tunable passive antennas to the m user ports can be obtained (for radio reception). Thus, it is possible to say that the radio transceiver allows, at said given frequency, for suitable values of the one or more antenna control signals, a low-loss transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas, and a low-loss transfer of power from an electromagnetic field incident on the tunable passive antennas to the m user ports.

The suitable values of the one or more antenna control signals are provided automatically.

The radio transceiver is a portable radio transceiver, so that the radio unit (8) also performs functions which have not been mentioned above, and which are well known to specialists. For instance, the wireless network may be a wireless communication network based on an LTE- Advanced architecture, or a wireless communication network based on a 5G New Radio architecture.

Figure 3 shows a possible resource grid (800) of the uplink of the wireless communication network. Here, the uplink of the wireless communication network uses single carrier frequency division multiple access (SC-FDMA) so that a data symbol (801) of the resource grid is an SC- FDMA symbol, corresponding to a known duration. Usually, SC-FDMA is regarded as orthogonal frequency division multiple access (OFDMA) with a DFT-based precoder. This is what is done in Fig. 3, where a subcarrier (802) of the resource grid corresponds to a known frequency interval, and where a resource element (803) corresponds to a data symbol (801) and a subcarrier (802). Thus, the data symbol (801) is also an OFDMA symbol.

The specialist understands that Z u depends on the frequency and on the electromagnetic characteristics of the volume surrounding the tunable passive antennas. In particular, the body of the user has an effect on Z u , and Z u depends on the position of the body of the user. This is referred to as“user interaction”, or“hand effect” or“finger effect”. The specialist understands that the radio transceiver may automatically compensate a variation in Z u caused by a variation in a frequency of operation, and/or automatically compensate the user interaction.

In order to respond to variations in the electromagnetic characteristics of the volume surrounding the tunable passive antennas and/or in the frequency of operation, a new adjustment sequence starts shortly after each change of the frequency of operation, and no later than 10 milliseconds after the beginning of the previous adjustment sequence.

In this first embodiment, N= m = 4. Thus, it is possible that N is greater than or equal to 3, it is possible that N is greater than or equal to 4, it is possible that m is greater than or equal to 3, and it is possible that m is greater than or equal to 4.

Second embodiment.

The second embodiment of a device of the invention, given by way of non- limiting example, also corresponds to the radio transceiver shown in Figure 2, and all explanations provided for the first embodiment are applicable to this second embodiment.

In this second embodiment, the radio transceiver uses the tunable passive antennas simultaneously for MIMO radio communication.

Additionally, in this second embodiment, the radio transceiver requests, from the wireless network, a permission to use, for excitations intended for an internal adjustment of the radio transceiver, one or more data symbols, and the radio transceiver specifies the one or more data symbols to which said authorization applies. More precisely,

the radio transceiver sends, to the wireless network, a radio signal requesting a permission to use one or more data symbols to send, inside one or more resource elements of said one or more data symbols, radio signals caused by excitations intended for an internal adjustment of the radio transceiver; the radio transceiver specifies the one or more data symbols to which said permission will apply;

the wireless network sends a radio signal granting an authorization to use said one or more data symbols, each of said one or more data symbols being referred to as“authorized data symbol”; and

the radio transceiver is authorized to send, inside one or more resource elements of the one or more authorized data symbols, and only inside one or more resource elements of the one or more authorized data symbols, radio signals caused by excitations intended for an internal adjustment of the radio transceiver, said radio signals being not meant to be used by the wireless network to obtain information on the MIMO channel.

A full automatic adjustment of the tunable passive antennas requires several iterations, each iteration comprising the following steps: applying said m excitations to the m user ports; estimating said q real quantities depending on an impedance matrix presented by the user ports; delivering one of said antenna adjustment instructions; and delivering said one or more antenna control signals. Each of the excitations having a complex envelope, the complex envelopes of the m excitations are linearly independent in the set of complex functions of one real variable, regarded as a vector space over the field of complex numbers. Each iteration uses, for the excitations, only one authorized data symbol, and only m resource elements in this authorized data symbol, by utilizing the signal processing technique disclosed in the first embodiment of said patent of the United States of America No. 9,698,484, and in the first embodiment of the international application number PCT/IB2016/051400, filed on 11 March 2016 (WO 2017/103687), entitled“Method for automatically adjusting tunable passive antennas, and automatically tunable antenna array using this method”.

Since said radio signals are not meant to be used by the wireless network to obtain information on the MIMO channel, each iteration does not use, for the excitations, one or more data symbols comprising resource elements allocated to reference signals for MIMO channel estimation. Thus, an iteration does not entail an incorrect estimate of the MIMO channel. Moreover, the authorized data symbols form a group that spans over a short period of time, so that a full automatic adjustment of the tunable passive antennas is sufficiently fast. Thus, we see that the invention overcomes the limitations of prior art.

Third embodiment.

The third embodiment of a device of the invention, given by way of non-limiting example, also corresponds to the radio transceiver shown in Figure 2, and all explanations provided for the first embodiment are applicable to this third embodiment.

In this third embodiment, the wireless network specifies the one or more data symbols to which said authorization applies, that is to say, the authorized data symbols. More precisely, the wireless network sends a radio signal granting an authorization to use one or more data symbols, each of said one or more data symbols being referred to as“authorized data symbol”; and

the radio transceiver is authorized to send, inside one or more resource elements of the one or more authorized data symbols, and only inside one or more resource elements of the one or more authorized data symbols, radio signals caused by excitations intended for an internal adjustment of the radio transceiver, said radio signals being not meant to convey meaningful data, and said radio signals being not meant to be used by the wireless network to obtain information on the MIMO channel.

A full automatic adjustment of the tunable passive antennas requires several iterations, each iteration comprising the following steps: applying said m excitations to the m user ports; estimating said q real quantities depending on an impedance matrix presented by the user ports; delivering one of said antenna adjustment instructions; and delivering said one or more antenna control signals. Each of the excitations has a complex envelope, the complex envelopes of the m excitations being linearly independent in the set of complex functions of one real variable, regarded as a vector space over the field of complex numbers. Each iteration uses, for the excitations, only one authorized data symbol, and only m resource elements in this authorized data symbol, by utilizing the signal processing technique disclosed in the third embodiment of said patent of the United States of America No. 9,698,484, and in the first embodiment of said international application number PCT/IB2016/051400.

Since said radio signals are not meant to be used by the wireless network to obtain information on the MIMO channel, each iteration does not use, for the excitations, one or more data symbols comprising resource elements allocated to reference signals for MIMO channel estimation. Thus, an iteration does not entail an incorrect estimate of the MIMO channel. Moreover, the authorized data symbols form a group that spans over a short period of time, so that a full automatic adjustment of the tunable passive antennas is sufficiently fast. Thus, we see that the invention overcomes the limitations of prior art.

Fourth embodiment.

As a fourth embodiment of a device of the invention, given by way of non-limiting example, we have represented in Figure 4 the block diagram of a radio transceiver for communicating in a wireless network, the radio transceiver comprising:

N= 4 tunable passive antennas (11) (12) (13) (14), the tunable passive antennas operating simultaneously in a given frequency band, each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an effect on said one or more characteristics, said at least one parameter being adjustable by electrical means; N feeders (21) (22) (23) (24), each of the feeders having a first end which is directly coupled to a signal port of one and only one of the tunable passive antennas, each of the feeders having a second end;

a multiple-input-port and multiple-output-port network (7) having m = 4 input ports and N output ports, each of the output ports being coupled to the second end of one and only one of the feeders, an antenna system comprising the N tunable passive antennas, the N feeders and the multiple-input-port and multiple-output-port network, the antenna system having m user ports, each of the input ports being one of the user ports; m sensing units (31) (32) (33) (34), each of the sensing units delivering one or more “sensing unit output signals”, each of the sensing unit output signals being mainly determined by one or more electrical variables sensed at one of the user ports;

a radio unit (8), the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”, the radio unit applying m excitations to the m user ports through the sensing units, one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports; and

a control unit (6), the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals.

The multiple-input-port and multiple-output-port network is such that the radio transceiver allows, at any frequency in the given frequency band, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas.

Fifth embodiment.

As a fifth embodiment of a device of the invention, given by way of non-limiting example, we have represented in Figure 5 the block diagram of a radio transceiver for communicating in a wireless network, the radio transceiver comprising: N = 4 tunable passive antennas (11) (12) (13) (14), each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an effect on said one or more characteristics, said at least one parameter being adjustable by electrical means;

N feeders (21) (22) (23) (24), each of the feeders having a first end which is directly coupled to a signal port of one and only one of the tunable passive antennas, each of the feeders having a second end;

a multiple-input-port and multiple-output-port tuning unit (4) having m = 4 input ports and n = N output ports, the multiple-input-port and multiple-output-port tuning unit comprising p adjustable impedance devices, where p is an integer greater than or equal to 2m = 8, the p adjustable impedance devices being referred to as the“adjustable impedance devices of the tuning unit” and being such that, at a given frequency greater than or equal to 300 MHz, each of the adjustable impedance devices of the tuning unit has a reactance, the reactance of any one of the adjustable impedance devices of the tuning unit being adjustable by electrical means, each of the output ports being coupled to the second end of one and only one of the feeders, an antenna system comprising the N tunable passive antennas, the N feeders and the multiple-input-port and multiple-output-port tuning unit, the antenna system having m user ports, each of the input ports being one of the user ports;

m sensing units (31) (32) (33) (34), each of the sensing units delivering one or more “sensing unit output signals”, each of the sensing unit output signals being mainly determined by one or more electrical variables sensed at one of the user ports;

a radio unit (8), the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”, the radio unit being used to apply m excitations to the m user ports (through the sensing units), one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports, the radio unit delivering one or more“tuning unit adjustment instructions”; and a control unit (6), the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being mainly determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals, the control unit delivering one or more “tuning control signals” to the multiple-input-port and multiple-output-port tuning unit, each of the one or more tuning control signals being determined as a function of at least one of the one or more tuning unit adjustment instructions, the reactance of each of the adjustable impedance devices of the tuning unit being mainly determined by at least one of the one or more tuning control signals.

The multiple-input-port and multiple-output-port tuning unit is such that the radio transceiver allows, at the given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas.

Sixth embodiment.

As a sixth embodiment of a device of the invention, given by way of non-limiting example, we have represented in Figure 6 the block diagram of a radio transceiver for communicating in a wireless network, the radio transceiver comprising:

N = 4 tunable passive antennas (11) (12) (13) (14), each of the tunable passive antennas comprising at least one antenna control device, one or more characteristics of said each of the tunable passive antennas being controlled using said at least one antenna control device, said at least one antenna control device having at least one parameter having an effect on said one or more characteristics, said at least one parameter being adjustable by electrical means;

a switching unit (9), the switching unit comprising N antenna ports each coupled to one and only one of the tunable passive antennas through a feeder (21) (22) (23) (24), the switching unit comprising n = 2 antenna array ports, the switching unit operating in an active configuration determined by one or more“configuration instructions”, the active configuration being one of a plurality of allowed configurations, the switching unit providing, in any one of the allowed configurations, for signals in a given frequency band and for any one of the antenna array ports, a bidirectional path between said any one of the antenna array ports and one and only one of the antenna ports;

a multiple-input-port and multiple-output-port tuning unit (4) having m = 2 input ports and n output ports, the multiple-input-port and multiple-output-port tuning unit comprising p adjustable impedance devices, where p is an integer greater than or equal to 2m = 8, the p adjustable impedance devices being referred to as the“adjustable impedance devices of the tuning unit” and being such that, at a given frequency, each of the adjustable impedance devices of the tuning unit has a reactance, the reactance of any one of the adjustable impedance devices of the tuning unit being adjustable by electrical means, each of the output ports being coupled to one and only one of the the antenna array ports, an antenna system comprising the N tunable passive antennas, the N feeders, the switching unit and the multiple-input-port and multiple-output-port tuning unit, the antenna system having m user ports, each of the input ports being one of the user ports;

m sensing units (31) (32), each of the sensing units delivering one or more“sensing unit output signals”, each of the sensing unit output signals being mainly determined by one or more electrical variables sensed at one of the user ports;

a radio unit (8), the radio unit delivering the one or more configuration instructions, the radio unit receiving, from the wireless network, a radio signal providing an authorization to use, for excitations intended for an adjustment, one or more data symbols, each of said data symbols being referred to as“authorized data symbol”, the radio unit being used to apply m excitations to the m user ports (through the sensing units), one and only one of the excitations being applied to each of the user ports, the excitations existing inside one or more of the one or more authorized data symbols, the radio unit estimating q real quantities depending on an impedance matrix presented by the user ports, where q is an integer greater than or equal to m, by utilizing the sensing unit output signals, the radio unit delivering one or more“antenna adjustment instructions”, at least one of the one or more antenna adjustment instructions being determined as a function of the q real quantities depending on an impedance matrix presented by the user ports, the radio unit delivering one or more“tuning unit adjustment instructions”; and

a control unit (6), the control unit delivering one or more“antenna control signals” to the tunable passive antennas, each of the one or more antenna control signals being mainly determined as a function of at least one of the one or more antenna adjustment instructions, each said at least one parameter of each said at least one antenna control device of each of the tunable passive antennas being mainly determined by at least one of the one or more antenna control signals, the control unit delivering one or more “tuning control signals” to the multiple-input-port and multiple-output-port tuning unit, each of the one or more tuning control signals being determined as a function of at least one of the one or more tuning unit adjustment instructions, the reactance of each of the adjustable impedance devices of the tuning unit being determined by at least one of the one or more tuning control signals.

The switching unit and the multiple-input-port and multiple-output-port tuning unit are such that the radio transceiver allows, at the given frequency, a transfer of power from the m user ports to an electromagnetic field radiated by the tunable passive antennas. For instance, each of the one or more configuration instructions may be determined as a function of:

one or more localization variables, each of the one or more localization variables depending on a distance between a part of a human body and a zone of the apparatus for radio communication;

a frequency used for radio communication with the tunable passive antennas;

one or more additional variables, each of the additional variables lying in a set of additional variables, the elements of the set of additional variables comprising: communication type variables which indicate whether a radio communication session is a voice communication session, a data communication session or another type of communication session; a speakerphone mode activation indicator; a speaker activation indicator; variables obtained using one or more accelerometers; user identity variables which depend on the identity of the current user; reception quality variables; and emission quality variables.

The elements of said set of additional variables may further comprise one or more variables which are different from the localization variables and which characterize the grip with which a user is holding the apparatus for radio communication.

Each of the one or more configuration instructions may for instance be determined using a lookup table.

Each of the one or more configuration instructions, each of the one or more antenna adjustment instructions and each of the tuning unit adjustment instructions may be of any type of digital message. The one or more configuration instructions, the one or more antenna adjustment instructions and the tuning unit adjustment instructions are delivered during several adjustment sequences.

INDICATIONS ON INDUSTRIAL APPLICATIONS

The method of the invention is a fast and accurate method for automatically adjusting a plurality of tunable passive antennas. The radio transceiver of the invention can quickly, accurately and automatically adjust its tunable passive antennas.

The method and the radio transceiver of the invention provide the best possible characteristics using very close tunable passive antennas, hence presenting a strong interaction between them. The invention is therefore particularly suitable for mobile radio transmitters and transceivers, for instance those used in portable radiotelephones or portable computers.