Quadplexer and quadplexer component The present invention refers to quadplexers, in particular to quadplexer topologies, and to electrical components providing quadplexer functionality.

Quadplexers are electrical circuits that can combine and/or separate for different RF signals, each signal having its own center frequency. To that end, a quadplexer has a common port and one input port or one output port for each individual signal. Typically, a quadplexer has a common port, two input ports and two output ports. Via in input port an input sig- nal, e.g. a transmit signal, can be received from an external circuit environment and can be led to the common port. Via an output port, e.g. a receive port, an output signal can be led from the common port to the corresponding output port and provided to an external circuit environment.

The quality of a quadplexer depends on the separation levels, i.e. the separation between different paths in the

quadplexer, and to the insertion loss of the respective sig ^¬ nal paths .

Known quadplexers utilize a shunt coil electrically connected between the common port and ground to decouple the

quadplexer' s RF filter elements. However, known quadplexers show non-optimal behaviour with respect to separation levels and insertion loss. In particu ^¬ lar, quadplexers for carrier aggregation (CA) working with frequency bands with at least one narrow gap between fre ^¬ quency bands have a deteriorated right skirt steepness and an unwanted high insertion loss. Thus, a quadplexer that is compatible with carrier aggrega ^¬ tion, has an improved right skirt steepness and a reduced in ^¬ sertion loss is desired.

Further, the trend towards miniaturization demands components with good electrical properties and small spatial dimensions.

Accordingly, further desired is a quadplexer component that fulfils these requirements. To that end, a quadplexer and a quadplexer component accord ^¬ ing to the claims are provided. Dependent claims provide pre ^¬ ferred embodiments.

The quadplexer or the quadplexer topology comprises a common port, a first filter structure and a second filter structure. The first filter structure has an input port, an output port, a common port and a first filter element with an input port. The second filter structure has an input port, an output port, a common port, and a first filter element with an input port. The common port of the quadplexer is coupled to the common port of the first filter structure and to the common port of the second filter structure. The input port of the first filter element of the first filter structure is coupled to the input port of the first filter element of the second filter structure. Further, the quadplexer comprises an induc ^¬ tive element. The input port of the first filter element of the first filter structure and the input port of the first filter element of the second filter structure are coupled to the common port of the quadplexer via the inductive element.

Such a topology utilizes an inductive element in a new fash- ion that surprisingly improves insertion loss and filter steepness, especially for carrier aggregation compatible quadplexers with a narrow band gap between adjacent frequency bands. If the quadplexer comprises one filter element as a transmit filter, then in particular the roll-off of the transmission filter is improved.

It is possible that the common port of the quadplexer is di ^¬ rectly connected to the common port of the first filter structure and to the common port of the second filter struc- ture . Further, it is possible that the input port of the first filter element of the first filter structure is di ^¬ rectly connected to the input port of the first filter ele ^¬ ment of the second filter structure. A direct connection between ports can be established by elec ^¬ trically connecting the ports via a conductive path, e.g. a signal conductor consisting of a conductive material such as a metal or an alloy. It is possible that the input port of the first filter ele ^¬ ment of the first filter structure and the input port of the second filter element of the second filter structure are electrically connected to the common port of the quadplexer via the inductive element.

It is possible that the quadplexer further comprises a second filter element in the first filter structure and a second filter element in the second filter structure. It is further possible that the first filter element of the first filter structure and the first filter element of the second filter structure are bandpass filters. If the first filter structure and/or the second filter structure comprises a second filter element, then the respective second filter element can also be a bandpass filter.

Each of the first filter element of the first filter struc- ture, the second filter element of the first filter struc ^¬ ture, the first filter element of the second filter structure and the second filter element of the second filter structure can be a transmit filter or a receive filter. However, it is preferred that the first filter element of the first filter structure is a receive filter and that the first filter element of the second filter structure is a receive filter, the second filter element of the first filter struc ^¬ ture and the second filter element of the second filter structure can be transmit filters.

Correspondingly, the first filter structure can establish a filter functionality similar to that of a duplexer. Also, the second filter structure can establish a filter functionality comparable to that of a second duplexer.

The input port of the first filter structure can be a signal port for transmit signals that can be obtained from an exter ^¬ nal circuit environment. The output port of the first filter structure can be a receive port provided to receive reception signals to an external circuit environment. Correspondingly, the input port of the second filter structure can be a trans ^¬ mit port provided for obtaining RF signals of an external circuit environment and the output port of the second filter structure can be a receive port via which reception signals can be provided to an external circuit environment . External circuit environments can be amplifiers, such as low noise amplifiers for reception signals and power amplifiers for transmit signals.

Correspondingly, the quadplexer can provide two different re- ception signals and receive two different transmit signals. Transmit signals are combined at the common port of the quadplexer. Reception signals that are both received via the common port are distributed to the respective reception ports .

Especially when the quadplexer is suited for a carrier aggre ^¬ gation mode, then three or more signals selected from recep ^¬ tion signals and receive signals can propagate simultaneously in the quadplexer while high separation levels and low inser- tion losses are provided.

It is possible that the quadplexer further comprises an im ^¬ pedance matching circuit between the first filter element of the first filter structure and the second filter element of the first filter structure. Further, it is possible that the quadplexer comprises an impedance matching circuit between the first filter element of the second filter structure and the second filter element of the second filter structure. The impedance matching circuits within the corresponding filter structures establish impedance transformation in order to decouple the respective first and second filter elements of the corresponding filter structure for transmit and receive signals .

The impedance matching circuits can comprise impedance ele- ments such as capacitive elements, inductive elements, net ^¬ works consisting of capacitive elements and inductive ele ^¬ ments and similar circuit elements such as strip lines.

It is possible that the second filter element of the first filter structure is coupled or directly connected to the com ^¬ mon port of the first filter structure. Further, it is possi ^¬ ble that the second filter element of the second filter structure is coupled or directly connected to the common port of the second filter structure.

Thus, it is possible that the impedance element electrically couples the first filter element of the first filter struc ^¬ ture to the second filter element of the first filter struc ^¬ ture and the first filter element of the second filter struc ^¬ ture to the second filter element of the second filter struc ^¬ ture .

It is possible that the first filter structure is a first du- plexer and the second filter structure is a second duplexer.

It is possible that the quadplexer' s filter elements are electro-acoustically active filter elements.

Electro-acoustically active filter elements can establish bandpass filters or band rejection filters with a low inser ^¬ tion loss in the pass band and a high separation level. Fur ^¬ ther, such filters can provide duplexers and quadplexers with high isolation levels. Electro-acoustically active filter elements comprise electro- acoustic resonators that utilize the piezoelectric effect to convert between RF signals and acoustic waves. To that end, electrode structures and a piezoelectric material are com ^¬ bined in an electro-acoustic resonator and two or more elec ^¬ tro-acoustic resonators are combined to establish an electro- acoustically active RF filter. Resonators can be SAW resonators (SAW = surface acoustic wave) , BAW resonators (BAW = bulk acoustic wave) or GBAW res ^¬ onators (GBAW = guided bulk acoustic wave) . In SAW resonators and in GBAW resonators interdigitated electrode fingers are arranged on a piezoelectric material, e.g. lithium tantalate or lithium niobate. In BAW resonators a piezoelectric layer is sandwiched between a bottom electrode and a bottom elec ^¬ trode layer and a top electrode in a top electrode layer. A BAW resonator can be an FBAR resonator (FBAR = film acoustic bulk resonator) or a SMR-type resonator. An FBAR resonator has the sandwich structure arranged above a cavity to acous ^¬ tically decouple the sandwich structure from its environment. A resonator of the SMR-type has the sandwich structure ar ^¬ ranged on an acoustic mirror comprising layers of different acoustic impedance.

It is possible that the quadplexer' s filter elements comprise a ladder-type like topology. In a ladder-type topology series resonators are electrically connected in series in a signal path. Shunt resonators arranged in shunt paths electrically connect the signal path to ground.

However, DMS-filters or similar SAW topologies are also pos ^¬ sible (DMS = double mode SAW) . It is possible that the first filter element of the first filter structure is coupled to the output port of the first filter structure and the first filter element of the second filter structure is coupled to the output port of the second filter structure.

Thus, the first filter elements are receive filters and the output ports of the corresponding filter structures are the reception ports.

It is possible that the quadplexer comprises further imped ^¬ ance elements. In each filter structure an impedance element can be coupled to the input port and an impedance element can be coupled to the output port

Thus, it is possible that one impedance element electrically connects the output port to the first filter element and a second impedance element connects the input port to the sec- ond filter element of one or of both filter structures.

These two additional impedance elements per filter structure can provide impedance matching to provide a defined imped ^¬ ance, e.g. 50 ohm, at the respective port.

The above-described quadplexer topology can be realized in a quadplexer component. Correspondingly, a quadplexer component comprises a quadplexer as described above. All circuit con ^¬ stituents of the quadplexer are monolithically integrated in a multilayer component.

The circuit constituents are the circuit elements needed to establish the quadplexer functionality of the quadplexer. A monolithical integration provides a component with small spa ^¬ tial dimensions and the topology as described above allows good electrically properties despite the narrow distances be ^¬ tween the circuit components. Thus, although circuit compo- nents and signal lines are arranged in a closed configura ^¬ tion, a high isolation level can be provided.

It is possible that the inductive elements are established as structured metallizations and metallization layers between dielectric layers.

It is possible that the quadplexer and the corresponding quadplexer component can be used with Band 12 and Band 26 signals. Transmission signals of Band 12 and transmission signals of Band 26 have frequency components of frequency bands that are close together. When the quadplexer should be used in a carrier aggregation mode then good electrical prop ^¬ erties are provided despite the close proximity of the two transmission bands.

The quadplexer component can consist of a laminate module having only six laminate layers.

It is possible to combine other bands together. The

transmission and/or reception frequencies, channel spacings and band gaps will largely depends on the overall

specification of the design requirement.

The mentioned bands refer to the generally known standard valid at the filing date of the present application.

Central aspects of the quadplexer and details of preferred embodiments are shown in the accompanying schematic figures: Fig. 1 shows circuit elements of an equivalent circuit dia ^¬ gram of the quadplexer. Fig. 2 shows an equivalent circuit diagram of a quadplexer comprising four filter elements.

Fig. 3 shows circuit elements of an equivalent circuit dia ^¬ gram comprising impedance matching circuits.

Fig. 4 shows circuit elements of an equivalent circuit dia ^¬ gram of a quadplexer comprising bandpass filters.

Fig. 5 shows circuit elements of an equivalent circuit dia- gram of a quadplexer where the common ports of the filter structures are connected to the impedance matching circuits.

Fig. 6 shows the possibility of electrically connecting the common port of the quadplexer to an antenna.

Fig. 7 shows additional possible circuit elements.

Fig. 8 shows a perspective view on circuit constituents ar- ranged in a quadplexer component having small spa ^¬ tial dimensions.

Fig. 9 and 10 show different details of metallization layers of a quadplexer component in a horizontal plane. Fig. 11 shows a comparison between insertion losses of a conventional quadplexer and of the quadplexer ac ^¬ cording to the above-described embodiments for Band 12 transmissions.

Fig. 12 shows corresponding insertion losses for Band 26.

Fig. 13 shows a comparison of isolation levels for Band 12. Fig. 14 shows isolation levels for a Band 26.

Fig. 15 shows isolation levels for the transmission signals of band 12 and reception signals of band 26. Fig. 16 shows isolation levels for band 26 transmission signals and band 26 reception signals.

Fig. 17 shows voltage standing wave ratio values at the an ^¬ tenna port for conventional quadplexers and for the present quadplexer.

Fig. 18 to 21 show frequency-dependent impedance-matching values . Fig. 22 to 25 show frequency-dependent impedance values at the input and output ports of the quadplexer.

Fig. 1 shows an equivalent circuit diagram with circuit ele ^¬ ments of the quadplexer QPX. The quadplexer QPX has a first filter structure FS1 and a second filter structure FS2. The first filter structure FS1 has an input port TX1, an output port RX1 and a common port CP1. The second filter structure FS2 has an input port TX2, an output port RX2 and a common port CP2. The common port of the first filter structure FS1 and the common port of the second filter structure FS2 are coupled or connected to the common port CP of the quadplexer QPX.

Further, the first filter structure FS1 has a first filter element FE1. The second filter structure FS2 has a first fil ^¬ ter element FE1. Both filter elements FE1 have an input port IP1. The input port IP1 of the first filter element FE1 of the first filter structure FS1 and the input port IP1 of the first filter element FE1 of the second filter structure FS2 are electrically coupled or connected. An inductive element IE electrically couples the input ports IP1 of the first fil ^¬ ter elements FE1 to the common port CP of the quadplexer QPX.

This topology provides good electrical properties in particu ^¬ lar when the quadplexer works in a carrier aggregation mode utilizing frequency bands having at least two pass bands with a close pass band distance.

Figure 2 shows the possibility of having a second filter ele ^¬ ment FE2 in the first filter structure FS1 and a second fil ^¬ ter element FE2 in the second filter structure FS2. The first filter elements FE1 in the two filter structures can be reception filters. The two second filter elements FE2 in the two filter structures can be transmit filters.

Fig. 3 shows the possibility of providing impedance matching circuits IMC between the first filter element FE1 and the second filter element FE2 of the corresponding filter structures . Figure 4 shows the possibility of utilizing band pass filters as first FE1 and second FE2 filter elements in the filter structures . Fig. 5 shows the possibility of directly connecting the com ^¬ mon ports CP1, CP2 to the corresponding impedance matching circuits IMC of the filter structures.

Fig. 6 shows the common port CP being connected to an RF an- tenna ANT, transmit signals can be emitted and reception sig ^¬ nals can be received via the antenna ANT.

Fig. 7 shows the possibility of arranging matching elements ME in the impedance matching circuits IMC. The matching ele- ments ME can be arranged between the input ports of the first filter elements FE1 and the common ports CP1, CP2 of the fil ^¬ ter structures. The ports of the second filter elements FE2 of the filter structures which are output ports if the second filter elements are transmit filters, can be directly con- nected to the common ports of the filter structures and to the common port of the quadplexer QPX.

Further, between an input port and an output port of the fil ^¬ ter structures and the corresponding transmit or receive fil- ter of the filter structures, one additional inductive ele ^¬ ment IE can be provided to establish a defined port imped ^¬ ance, e.g. 50 ohm.

Fig. 8 illustrates a perspective view onto a plurality of circuit constituents packed close together to provide small spatial dimensions while maintaining good electrical proper ^¬ ties, in particular a high isolation level. Fig. 9 shows details of a metallization layer in which signal conductors are structured to electrically connect different ports of the quadplexer. Fig. 10 illustrates the possibility of creating inductive el ^¬ ements in a spiral coil manner created by correspondingly shaped signal conductors in a metallization layer.

Fig. 11 shows simulated insertion losses for transmission signals (lower frequencies) and reception signals (higher frequencies) for Band 12 for conventional quadplexers utiliz ^¬ ing a shunt coil SH and for a quadplexer as described above utilizing a series coil SE . For the above-described

quadplexer topology insertions losses are reduced as is clearly recognizable in curves SE (transmission signals) and SE' (reception signals) . Further, the pass band steepness at the right flank for transmission signals (curve SE) is improved . Fig. 12 shows corresponding curves for Band 26 transmission and reception signals: curve SH denotes transmission signals of a conventional duplexer utilizing a shunt coil approach. Curve SE denotes the insertion loss for the improved

quadplexer. Curves SH' and SE' show insertion losses for the corresponding reception frequencies.

In Fig. 13 the isolation levels for conventional duplexer to ^¬ pology (curve SH) and for the improved quadplexer top (curve SE) are shown for the frequency ranges around the transmis- sion and reception frequency of Band 12. The isolation levels are improved for the improved topology. . Fig. 14 shows the corresponding curves for the isolation in the frequency range of Band 26 transmission signals and Band 12 reception signals. Also, as can be seen in Figure 15, the isolation in the fre ^¬ quency range around Band 12 transmission signals and recep ^¬ tion signals of Band 26 are strongly improved for the repre ^¬ sented quadplexer. As Figure 16 shows, the topology as described above clearly fulfills the isolation requirements for the Band 26 transmis ^¬ sion frequencies and Band 26 reception frequencies.

As Fig. 17 shows, voltage standing wave ratios (VSWR) at the common port of the presented quadplexer configuration also fulfill the necessary requirements.

From Figs. 18 to 21 it can be clearly seen that the described topology provides good impedance matching at the antenna port (curves SE) for the Band 12 transmission frequencies, the

Band 12 reception frequencies, the Band 26 transmission fre ^¬ quencies and the Band 26 reception frequencies.

Fig. 22 to 25 show the frequency-dependent impedances at the corresponding input or output port for conventional topology (curve SH) and the present topology (curve SE) . The presented topology allows for good impedance matching at each of the four ports. The presented quadplexer and the present quadplexer component are not limited to the features described above or shown in the figures. Quadplexers can comprise further circuit compo ^¬ nents and quadplexer components can comprise further metalli ^¬ zation layers or dielectric layers.

List of Reference Signs

RF antenna

common port of the quadplexer

common port of the first filter structure common port of the second filter structure first filter element

second filter element of a filter structure first filter structure

second filter structure

inductive element

impedance matching circuit

input port of the first filter element

matching elements

quadplexer

quadplexer component

reception ports

frequency-dependent parameter of the presented quadplexer design

frequency-dependent parameter of a conventional quadplexer design

transmission ports