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Title:
EXTRACTOR FILTER ELEMENT, FILTER UNIT AND ARRANGEMENT THEREWITH
Document Type and Number:
WIPO Patent Application WO/2019/161984
Kind Code:
A1
Abstract:
A filter element (FEl) comprising a first port (PI) connectable to an antenna, a second port (P2) and a third port (P3) is specified, wherein • a band pass filter (BP) is arranged between the first port and the second port, the band pass filter being configured to transmit frequencies in a first frequency range (FR1), • a notch filter (NF) is arranged between the first port and the third port, the notch filter being configured to block transmission of at least a part of frequencies in the first frequency range, and • the notch filter comprises at least one parallel LC resonator connected to the first port and at least one shunt series LC resonator in a basic unit (BU). The notch filter and the band pass filter form an extractor. Furthermore, a filter unit (FU) comprising the filter element and a further filter element (FE) and a filter arrangement (FA) comprising the filter unit and a multiplexer (MU) are specified to allow for separation of multiple bands.

Inventors:
MARKOV KOSTYANTYN (DE)
SEVSKIY GEORGIY (DE)
Application Number:
PCT/EP2019/050427
Publication Date:
August 29, 2019
Filing Date:
January 09, 2019
Export Citation:
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Assignee:
RF360 EUROPE GMBH (DE)
International Classes:
H03H7/46; H03H7/01; H04B1/00
Domestic Patent References:
WO2014024761A12014-02-13
Foreign References:
JP2009159328A2009-07-16
US20160126922A12016-05-05
US20140197902A12014-07-17
US20170294896A12017-10-12
US20070191055A12007-08-16
DE102016112993A12018-01-18
Other References:
METHOT F: "CONSTANT IMPEDANCE BANDPASS AND DIPLEXER FILTERS", RF DESIGN, PRIMEDIA BUSINESS MAGAZINES & MEDIA, OVERLAND PARK, KS, US, vol. 9, no. 11, November 1986 (1986-11-01), XP001086415
Attorney, Agent or Firm:
EPPING HERMANN FISCHER PATENTANWALTSGESELLSCHAFT MBH (DE)
Download PDF:
Claims:
Claims

1. Filter element (FE1) comprising a first port (PI)

connectable to an antenna, a second port (P2) and a third port (P3) ,

wherein

- a band pass filter (BP) is arranged between the first port and the second port, the band pass filter being configured to transmit frequencies in a first frequency range (FR1),

- a notch filter (NF) is arranged between the first port and the third port, the notch filter being configured to block transmission of at least a part of frequencies in the first frequency range, and

- the notch filter comprises at least one parallel LC

resonator (PLC) connected to the first port and at least one shunt series LC resonator (SLC) .

2. The filter element according to claim 1,

wherein the first frequency range includes frequencies between 3.3 GHz and 3.8 GHz .

3. The filter element according to claim 1 or 2,

wherein the filter element is formed as a POG component.

4. The filter element according to any of the preceding claims ,

wherein a first tuning element (TE1) is arranged between the at least one parallel LC resonator and the at least one series LC resonator.

5. The filter element according to any of the preceding claims ,

wherein a second tuning element (TE2) is arranged between a side of the parallel LC resonator facing away from the first port and ground.

6. The filter element according to any of the preceding claims ,

wherein the at least one parallel LC resonator and the at least one series LC resonator form a basic unit setup (BU) which is repeated one or more times within the notch filter.

7. The filter element according to any of the preceding claims ,

wherein the band pass filter has at least a first and a second series shunt resonator with at least one parallel resonator arranged between the first and the second series shunt resonator.

8. A filter unit (FU) comprising at least one filter element according to one of the preceding claims.

9. The filter unit according to claim 8,

wherein the filter unit includes a further filter element ( FE2 ) .

10. The filter unit according to claim 9,

wherein the further filter element includes at least one electroacoustic resonator (EAR) .

11. The filter unit according to claim 9 or 10,

wherein the filter element and the further filter element are arranged on a common substrate.

12. The filter unit according to any of claims 9 to 11, wherein the further filter element is configured to extract WLAN and/or geopositioning frequencies.

13. A filter arrangement (FA) comprising a filter unit according to any of claims 9 to 12,

wherein the filter arrangement comprises a multiplexer (MU) .

14. The filter arrangement according to claim 13,

wherein the further filter element is arranged between the filter element and the multiplexer.

Description:
EXTRACTOR FILTER ELEMENT, FILTER UNIT AND

ARRANGEMENT THEREWITH

The present application refers to a filter element, a filter unit, and a filter arrangement.

Wireless communication devices such as mobile phones use signals in different frequency ranges. In particular the signals may come from a common antenna and thus need to be separated, filtered and forwarded to the corresponding transmitter. For instance, future devices will need to support the 5G standard which uses higher frequencies than the 3G or 4G standard.

It is an object of the present application to provide a filter element that is capable of extracting frequencies in a high frequency band such as the 5G low band from other frequency bands to be used for mobile communication.

These and other objects are inter alia met by a filter element according to claim 1. Furthermore a filter unit and a filter arrangement are specified. Dependent claims provide further embodiments.

A filter element comprising at least three ports is

specified. For instance the filter element comprises exactly three externally connectable ports. For instance a first port is connectable to an antenna.

In the following, the signal path is described for

frequencies to be received by the antenna unless otherwise specified. However, the signal path may also be inverted, i.e. the antenna may also be used to transmit radiation. In particular, the antenna may be configured both for receiving and transmitting radiation in at least one frequency range.

According to at least one embodiment of the filter element, the filter element comprises a bandpass filter. The bandpass filter is in particular arranged between the first port and a second port. Thus an electrical signal passing from the first port to the second port and vice versa needs to pass the bandpass filter.

The term "arranged between" used in connection with elements or ports of the filter element or other electronic components refers to the signal path between those elements or ports rather than to the actual spatial relationship unless

otherwise specified.

For instance the bandpass filter is configured to transmit frequencies in a first frequency range. In particular the first frequency range includes frequencies above 3 GHz.

According to at least one embodiment of the filter element the filter element comprises a notch filter. For instance the notch filter is arranged between the first port and a third port. In particular the notch filter is configured to block transmission of at least a part of or all of the frequencies in the first frequency range. In other words, the notch filter acts as a band reject filter for frequencies in the first frequency range. For example the notch filter is configured to reflect at least a part of or all of the frequencies in the first frequency range. For instance, at least 10 % or at least 50 % of the overall signal strength of frequencies in the first frequency range is reflected at the notch filter.

The notch filter and the bandpass filter may be coordinated with one another such that the notch filter reflects

frequencies that are to be transmitted through the bandpass filter. Accordingly, the bandpass filter may be configured to reflect frequencies which are to be transmitted through the notch filter.

According to at least one embodiment of the filter element, the notch filter comprises at least one parallel LC

resonator. In other words, the notch filter comprises at least one inductive element and at least one capacitive element electrically connected to one another in parallel. In particular the parallel LC resonator is contacted to the first port.

The term "connected to" refers both to a direct electrical connection without any intervening element and a connection via another electronic component.

The inductive element may be implemented via metallization structures and a layer stack of dielectric layers on a substrate such as a glass substrate. The capacitive element may have a metal insulator metal (MIM) structure.

For instance, the parallel LC resonator is that resonator of the notch filter which is closest to the first port. In other words there is no resonator in the signal path between the first port and the parallel LC resonator of the notch filter. At that position the parallel LC resonator may result in a high reflectance for frequencies to be blocked by the notch filter .

According to at least one embodiment of the filter element the notch filter comprises at least one shunt series LC resonator. In particular the shunt series LC resonator is connected to a distal end of the parallel LC resonator when seen from the first port. A resonance frequency of the parallel LC resonator and a resonance frequency of the series LC resonator may be the same or at least essentially the same. Alternatively, the parallel LC resonator and the series LC resonator may have detuned resonance frequencies, for instance by at most 0.8 GHz or by at most 0.5 GHz.

In at least one embodiment of the filter element, the filter element comprises a first port connectable to an antenna, a second port and a third part wherein a bandpass filter is arranged between the first port and the second port, the bandpass filter being configured to transmit frequencies in a first frequency range. A notch filter is arranged between the first port and the third port, the notch filter being

configured to block transmission of at least a part of frequencies in the first frequency range. The notch filter comprises a parallel LC resonator connected to the first port and at least one shunt series LC resonator.

It has been found that resonators using inductive and

capacitive elements are better suited for notch filters which are supposed to block transmission of frequencies having frequencies above 3 GHz. At the same time, insertion losses for frequencies outside the first frequency range can be kept very low. In particular the entire notch filter, and/or the entire bandpass filter and/or the entire filter element may be completely free of electroacoustic resonators. It has been found that the standard designs of filters using

electroacoustic resonators are not suited for this frequency range right away.

When seen from the first port, the parallel LC resonator causes the filter element to behave as an open circuit for frequencies in the first frequency range so that these frequencies are reflected and may be transmitted through the bandpass filter. The shunt series LC resonator alone, in contrast, would behave as a short circuit for frequencies in the first frequency range so that these frequencies would get lost at the notch filter.

According to at least one embodiment of the filter element, the first frequency range includes frequencies between 3.3 GHz and 3.8 GHz. Thus the bandpass filter is capable of extracting frequencies in the 5G low band.

According to one embodiment of the filter element, the filter element is formed as a POG (passives-on-glass ) component.

Thus the filter element may be formed by dielectric and electrically conductive layers on a glass substrate. A comparably expensive substrate such as a piezoelectric substrate required for electroacoustic resonators may be dispensed with.

According to at least one embodiment of the filter element the filter element comprises a first tuning element. The first tuning element may be arranged between the at least one parallel LC resonator and the at least one series LC resonator. For instance the first tuning element is an inductive element. The inductive element may be implemented via metallization structures and a layer stack of dielectric layers on the glass substrate, for instance.

According to at least one embodiment of the filter element, the filter element comprises a second tuning element. For instance the second tuning element is arranged between a side of the parallel LC resonator facing away from the first port and ground. The first tuning element may be a capacitive element. For instance the capacitive element may have a metal insulator metal (MIM) structure.

The term "second tuning element" does not necessarily require the presence of a first tuning element. Rather, the numbering is simply used in order to distinguish the tuning elements from one another. This also applies to other elements and the ports .

The first tuning element and/or the second tuning element may be configured to provide a phase tuning and/or matching.

According to at least one embodiment of the filter element, the at least one parallel LC resonator and the at least one series LC resonator form a basic unit setup which is repeated one or more times within the notch filter. In particular the basic units may be connected in series. The values for the individual elements, i.e. the resonators and the tuning elements, if applicable, may vary among the units. Using more than one basic unit setup, the skirts of the frequency bands to be transmitted or blocked can be formed steeper, for instance . According to at least one embodiment of the filter element, the bandpass filter has at least a first and a second series shunt resonator with at least one parallel resonator arranged between the first and the second series shunt resonator.

In particular the filter element may be configured as an extractor that extracts frequencies in the first frequency range, for instance frequencies of the 5G low band, at the second port and provides the further frequencies to be used for wireless communication at the second port. In particular, the further frequencies include both frequencies above and below the first frequency range.

Furthermore, a filter unit comprising at least one filter element is specified. The filter element may include one or more features of the filter element described above. For instance, the filter element may be configured as an

extractor .

According to at least one embodiment of the filter unit, the filter unit includes a further filter element. For example the further filter element is connected to the filter

element, for instance to its third port. The further filter element may provide frequencies of a further frequency band at a fourth port. The filter element may be arranged between the first port and the further filter element. In other words, the further filter element may be arranged downstream of the filter element when seen from the first port.

According to at least one embodiment of the filter unit, the further filter element includes at least one electroacoustic resonator. In particular, the further filter element may include at least one of: a surface acoustic wave (SAW) resonator, a bulk acoustic wave (BAW) resonator, a GBAW

(guided bulk acoustic wave) , a TFSAW (thin film SAW)

resonator .

Electroacoustic resonators employ the piezoelectric effect to convert between RF signals and acoustic waves. In SAW

resonators comb-shaped electrode structures with

interdigitating electrode fingers are arranged on a

piezoelectric material. Excited acoustic waves propagate at a surface of the piezoelectric material. In BAW resonators a piezoelectric material is sandwiched between a bottom

electrode and a top electrode. This sandwich construction can be arranged on a cavity or on an acoustic mirror.

The further filter element may comprise a piezoelectric substrate or at least a piezoelectric layer. For instance, the further filter element may comprise LiTaCg (lithium tantalate) or LiNbCg (lithium niobate) as piezoelectric material .

According to at least one embodiment of the filter unit, the filter element and the further filter element are arranged on a common supporting carrier. The common supporting carrier may be electrically connected to the filter element and to the further filter element. For instance, the common

supporting carrier may be a laminate substrate on which both the filter element and the further filter element are

arranged, for instance laterally side-by-side. In other words, the common supporting carrier may mechanically support a filter element using LC resonators only and a further filter element including at least one electroacoustic

resonator . According to at least one embodiment of the filter unit, the further filter element is configured to extract WLAN and/or geopositioning frequencies such as GNSS or GPS. In other words the further filter element may act as an extractor for one or more frequency bands whereas the further frequencies are provided at a sixth port. In addition, the filter unit may act as extractor for the first frequency range as

described in connection with the filter element.

Furthermore, a filter arrangement is specified. The filter arrangement may comprise a filter element or a filter unit wherein the filter element or the filter unit may have one or more features of the filter element or the filter unit described above.

According to at least one embodiment of the filter

arrangement, the filter arrangement comprises a multiplexer. The term "multiplexer" includes a diplexer as well as higher order multiplexers. For instance, a port of the diplexer is connected to the antenna and the signal received from the antenna is split into a high frequency fraction and a low frequency fraction. For instance the high frequency fraction includes 5G high band frequencies and the low frequency fraction includes 2G, 3G, 4G low-, mid-, and high-bands.

According to at least one embodiment of the filter

arrangement the further element is arranged between the filter element and the multiplexer. In particular the

multiplexer may be arranged downstream of the filter element and the further filter element when seen from the antenna. As the frequencies of the 5G low-band have already been

extracted at the filter element, the frequency distance between the frequency bands to be separated at the diplexer is comparably large. Consequently a comparably simple setup for the diplexer is sufficient for an efficient signal separation .

Further configurations and conveniences are described in the following in more detail in combination with the figures. The figures and the size ratios of the elements illustrated in the figures relative to one another are not to be regarded as being to scale. Rather, individual elements may be

illustrated on an exaggeratedly large scale for greater ease of depiction and/or better comprehension.

Identical, similar or identically acting elements are

provided with the same reference signs in the figures.

In the Figures:

Figures 1A, IB and 1C show an exemplary embodiment of a filter element wherein Figure IB illustrates the filter characteristics of the bandpass filter and Figure 1C

illustrates the filter characteristics of the notch filter;

Figures 2A and 2B show an exemplary embodiment of a notch filter wherein Figure 2B shows the resulting Smith chart;

Figures 3A and 3B show an exemplary embodiment of a notch filter wherein Figure 3B shows the resulting Smith chart;

Figure 4 an exemplary embodiment of a notch filter;

Figure 5 an exemplary embodiment of a bandpass filter with the resulting frequency characteristics; Figure 6 frequency characteristics of a filter element according to an exemplary embodiment;

Figure 7A a schematic representation of a filter arrangement according to an exemplary embodiment;

Figure 7B a schematic representation of a filter unit in side view according to an exemplary embodiment, and

Figure 7C a three-dimensional representation of a filter unit according to an exemplary embodiment.

The filter element FE1 according to Figure 1A includes a first port PI to be connected to an antenna, a second port P2 and a third port P3. A bandpass filter BP is arranged in a signal path between first port PI and second port P2. A notch filter NF is arranged in a signal path between first port PI and third port P3.

The bandpass filter BP is configured to transmit frequencies in a first frequency range FR1 which is between 3.3 and 3.8 GHz as shown in Figure IB. Of course, however, the filter element FE1 may be configured to extract frequencies in another frequency range, in particular for frequencies above 3 GHz.

As shown in Figure IB, low insertion losses may be obtained within the first frequency range FR1 whereas frequencies smaller than the first frequency range FR1 or larger than the first frequency range FR1 are blocked by the bandpass filter BP. Those frequencies may pass the notch filter NF as shown in Figure 1C. For frequencies in the first frequency range FR1, in contrast, the notch filter NF blocks, in particular reflects, the signal so that this signal may be extracted at the second port P2.

As shown in Figure 2A, the notch filter NF may comprise a parallel LC resonator PLC and a shunt series LC resonator SLC. When seen from first port PI the shunt series LC

resonator SLC would alone, i.e. in absence of the parallel LC resonator PLC, behave as a short-circuit for the frequencies to be blocked by the notch filter as the associated Smith chart shows. The Smith charts in Figures 2A and 2B illustrate the dependency of the impedance as a function of the

frequency between 0.5 GHz and 8 GHz.

Parallel LC resonator PLC, however, results in a phase shift of 180° so that the notch filter reflects the frequencies to be blocked by the notch filter as shown in the associated Smith chart. The Smith chart for the notch filter including the shunt series LC resonator and the parallel LC resonator is shown in Figure 2B, indicating that frequencies between 3.3 and 3.8 GHz are reflected efficiently whereas the notch filter is impedance-matched for the remaining frequencies.

As shown in Figure 3A, the notch filter acts as a low pass for a second frequency range FR2 with frequencies smaller than frequencies of the first frequency range FR1. The corresponding equivalent circuit EC1 is illustrated as well. In a third frequency range FR3 with frequencies larger than frequencies of the first frequency range FR1, the circuit behaves as a high pass. Equivalent circuit EC2 for this frequency range is shown as well. For instance, the second frequency range FR2 includes frequencies between 0.5 GHz and 2.8 GHz. The third frequency range may include frequencies between 4.7 and 8 GHz . Curve 300 shows the insertion loss. Frequencies within the frequency range FR1 are efficiently blocked by the notch filter NF. Frequencies within the frequency ranges FR2 and FR3, in contrast, are transmitted with very low losses. The blocked frequencies in the frequency range FR1 are

efficiently reflected as curve 301 illustrating the

reflectance indicates.

Figure 3A further illustrates the impact of the shunt series LC resonator SLC and the parallel LC resonator PLC on the frequency behaviour of the notch filter NF. The resonance frequencies of the parallel LC resonator PLC and the series LC resonator SLC may be slightly detuned with respect to one another in order to obtain a more pronounced broadband blocking band.

For phase tuning and/or matching purposes the filter element may include a first tuning element TE1 and/or a second tuning element TE2. In the exemplary embodiment shown, the first tuning element TE1 is as an inductive element arranged between the parallel LC resonator PLC and the series LC resonator SLC. The second tuning element TE2 is embodied as a capacitive element which connects the distal end of parallel LC resonator PLC when seen from the first port PI to ground. However, other tuning elements may be used as well.

Figure 3B shows the associated Smith chart which clearly indicates that the frequencies to be blocked, namely the frequencies in the first frequency range FR1, are efficiently reflected whereas the notch filter is impedance-matched both for lower frequencies in the second frequency range FR2 and for higher frequencies in the third frequency range FR3. The simulations demonstrate that even a comparably simple setup using just one parallel LC resonator PLC and just one shunt series LC resonator SLC, for instance in combination with two tuning elements TE1, TE2, may result in a notch filter NF which is highly reflective in the first frequency range FR1 and impedance matched in broad frequency ranges below and above the first frequency range. However, the notch filter NF may include further elements such as resonators.

As shown in Figure 4 the parallel LC resonator PLC and the series LC resonator SLC may form a basic unit BU which is repeated one or more times. In the embodiment shown, the notch filter NF includes three basic units BU electrically connected in series. The values for the individual passive elements of the basic units BU may vary from basic unit to basic unit.

An exemplary embodiment of a bandpass filter BP is shown in Figure 5, together with the resulting frequency behaviour.

The bandpass filter includes at least one parallel LC resonator PR arranged between a first shunt series resonator SSR1 and a second series shunt resonator SSR2. In the embodiment shown the bandpass filter includes two parallel resonators PR and two series shunt resonators SSR1, SSR2 arranged alternately in the signal path.

Curve 501 shows the resulting insertion loss whereas curve 500 shows the reflectance. Consequently the bandpass filter efficiently transmits frequencies in the first frequency range FR1 and reflects frequencies larger and smaller than frequencies of the first frequency range FR1. The overall performance of the filter element FE1 is shown in Figure 6 wherein curve 601 shows the reflectance when seen from the first port PI, curve 602 shows the insertion loss between the first port PI and the second port P2 and curve 603 shows the insertion loss between the first port PI and the third port P3. Thus the filter element FE1 acts as an extractor for frequencies in the frequency range between 3.3 GHz and 3.8 GHz. At the same time frequencies lower than and frequencies larger than the first frequency range can pass through the notch filter with low losses. Consequently, the filter element FE1 including the band pass BP and the notch filter NF are perfectly matched to each other to provide a very broad-band operation.

The frequencies provided at the third port P3 with low losses in particular include WLAN frequencies, geopositioning frequencies, 5G high band frequencies as well as cellular 2G, 3G, 4G low-, mid- and high-band frequencies.

A filter arrangement FA is schematically shown in Figure 7A. The filter arrangement FA comprises a further filter element FE2. The further filter element FE2 is arranged downstream of the filter element FE1 when seen from the first port PI. For instance the further filter element FE2 is embodied as a double extractor which extracts, for instance, WLAN

frequencies at a forth port P4 and geopositioning frequencies such as GPS or GNSS frequencies at a fifth port P5. Of course, the filter filter element FE2 may also be configured to extract only one frequency band or more than two frequency bands instead, if appropriate.

The remaining frequencies are provided at a port P6 which is fed to a multiplexer MU, for instance a diplexer. The diplexer may separate frequencies of the 5G high band located in the frequency range between 4.4 and 5 GHz from cellular 2G, 3G, 4G low-mid-and high-band frequencies.

In the configuration shown in Figure 7A the filter element FE1, which is configured to extract the 5G low band

frequencies, is arranged closest to the antenna so that the losses for this frequency band are as low as possible.

Afterwards the further filter element F2 extracts the

geopositioning frequencies which typically have a comparably small signal strength.

The filter element FE1 and the further filter element FE2 form a filter unit FU.

The frequency distance between the remaining frequencies to be used, for instance the 5G high band on the one hand and cellular 2G, 3G, 4G low-, mid-, and high-band frequencies on the other hand is comparably large, so that a comparably easy setup for the multiplexer MU is sufficient for efficient separation. For instance, the 5G high band frequencies are provided at seventh port P7 and cellular 2G, 3G, 4G low-, mid-, and high-band frequencies are provided at eighth port P8.

Therefore, the described order of the filter element FE1, the further filter element FE2 and the mulitplexer MU is

particularly suitable for efficient signal extraction.

However, in principle it is also possible to change the order of the filter element FE1, the further filter element FE2 and the multiplexer MU, if appropriate. An embodiment of a filter unit FU is shown in Figure 7B in a side view. The filter element FE1 and the further filter element FE2 are arranged on a common supporting carrier CSC, for instance a laminate substrate.

The further filter FE2 as shown in Figure 7C includes a plurality of electroacoustic resonators EAR, for instance SAW resonators. However, other electroacoustic resonators, in particular those mentioned in the general part of the

description may be used.

The further filter element FE2 may include at least a

piezoelectric layer or a piezoelectric substrate. Filter element FE1, in contrast, may be formed as a POG component.

The filter element FE1 and the further filter element FE2 are electrically connected to the common supporting carrier CSC. In particular, all pads for external electrical connection of the filter unit FU may be provided at a side of the common supporting substrate which faces away from the filter element FE1.

Using the filter arrangement described, a common antenna may be used for receiving and/or transmitting radiation in all frequency bands to be used in electronic devices such as mobile phones, in particular including the 5G low-band and high-band frequencies.

The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of

characteristics, which particularly includes every combination of any features which are stated in the claims, even if this feature or this combination of features is not explicitly stated in the claims or in the examples.

List of Reference Signs

BP bandpass

BU basic unit setup

CSC common supporting carrier

EAR electroacoustic resonator

EC1 equivalent circuit

EC2 equivalent circuit

FA filter arrangement

FU filter unit

FE1 filter element

FE2 further filter element

MU multiplexer

NF notch filter

P1,P2, P8 port

PLC parallel LC resonator

PR parallel resonator

SLC series LC resonator

SSR1 first series shunt resistor

SSR2 second series shunt resistor

TE1 first tuning element

TE2 second tuning element

300 curve

301 curve

500 curve

501 curve

601 curve

602 curve

603 curve