JP2006157174A - Antenna branching filter and surface acoustic wave filter for antenna branching filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna branching filter that eliminates the need for a phase shifter for ensuring the attenuation at a low frequency pass band while realizing a low insertion loss. <P>SOLUTION: In the antenna branching filter configured with a low pass SAW filter 20 and a high pass SAW filter 30, the high pass SAW filter 30 is configured with: a SAW tank circuit 50 adopting a configuration comprising a SAW resonator 51 and a coil 52 connected in parallel with the resonator 51, providing a high impedance at a pass band frequency of the low pass SAW filter and providing a low impedance at a pass band frequency of the high pass SAW filter; one IDT; and a longitudinal coupling resonator type filter 60 comprising a pair of IDTs located at both sides of the IDT and whose output terminals are connected in common, and a reflector, providing a large attenuation at the pass band frequency of the low pass SAW filter and applying filter processing to the pass band frequency of the high pass SAW filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna duplexer that demultiplexes a transmission frequency and a reception frequency with a surface acoustic wave (SAW) filter in order to transmit and receive using a common antenna, and a SAW filter for the antenna duplexer.

  In a wireless communication system in which a device having a bidirectional wireless communication function such as a portable telephone and this type of device is used as a communication terminal, transmission and reception using a single antenna of the communication terminal are possible. The transmission / reception processing is performed by separating the transmission signal and the reception signal by the antenna duplexer using the frequency difference.

  A small SAW device suitable for signal processing in the VHF / UHF frequency band is frequently used as the antenna duplexer. The SAW device uses a wave transmitted to the surface of an elastic body. As shown in FIG. 15, the SAW device has a comb-shaped electrode (IDT: interdigital transducer) 101 arranged on a piezoelectric substrate, and an electric signal and an elastic surface. Electro-mechanical mutual conversion between waves is performed to give a frequency selection (band filter) characteristic, and a reflector (reflector) 102 is attached to give a high Q resonance characteristic.

  A configuration example of a conventional antenna duplexer using such a SAW device is shown in FIG. In this example, a low frequency side SAW that filters (frequency selection) received radio waves (for example, center frequency 826.5 MHz) to one antenna 10 and outputs it to a reception processing unit (not shown) in the apparatus. The filter 20 and a high-frequency SAW filter 30 that applies a filtering process (frequency selection) to a transmission signal (for example, a center frequency of 877.5 MHz) from a transmission processing unit (not shown) in the apparatus and applies them to the antenna 10 are integrated. The SAW duplexer configuration provided in FIG. The low-frequency side SAW filter 20 and the high-frequency side SAW filter 30 are designed to obtain a desired filter characteristic by ladder-connecting a plurality of SAW resonators.

  Furthermore, a phase shifter 40 is provided between the high frequency side SAW filter 30 and the antenna 10. This phase shifter 40 increases the impedance in the pass frequency band of the low-frequency side SAW filter 20 by phase-shifting the transmission frequency signal appearing on the antenna 10, and the transmission current is shunted to the low-frequency side SAW filter 20 side. Reduce insertion loss. Conversely, the phase shifter 40 shifts the received radio wave from the antenna 10 to increase the impedance in the pass frequency band of the high frequency side SAW filter 30, and the received radio wave is shunted to the high frequency side SAW filter 30 side. To reduce losses.

  Note that the frequencies of the transmission radio wave and the reception radio wave may be opposite to the above case in a wireless communication system in which the low band side SAW filter 20 is the transmission side and the high band side SAW filter 30 is the reception side.

  Various antenna duplexers using SAW devices have been proposed in addition to the configuration of FIG. 16 (see, for example, Patent Document 1). In this document, for example, a longitudinally coupled resonator type SAW filter is employed in order to prevent spurious when a plurality of SAW filters are packaged into one from affecting the filter characteristics of the low-frequency side SAW filter.

JP 2003-289234 A

  Conventionally, in a SAW duplexer configuration in which a pair of SAW filters in which SAW resonators are connected in a ladder shape are connected in parallel to a single antenna, as shown in FIG. While realizing the insertion loss, it is difficult to secure the attenuation amount in the low pass band at the same time.

  As means for solving this problem, in the conventional configuration shown in FIG. 16, in addition to the SAW resonator, a phase shifter 40 is provided immediately below the antenna port. This phase shifter 40 uses a λ / 4 microstrip line, a lumped constant circuit component, etc., but in order to realize this circuit, an external circuit is additionally required in addition to the SAW chip. There were problems of increased area and volume and increased costs.

  In addition, although there is no description of the phase shifter in the said patent document 1, in order to ensure attenuation | damping amount in a low passband simultaneously, implement | achieving low insertion loss, it is equivalent to the phase shifter 40 of FIG. It is necessary to improve the performance as a duplexer by providing the same, and in this case, there is a similar problem.

  Further, in response to the recent demand for a SAW duplexer having a balanced output, there is a problem that a balanced output cannot be obtained in the filter in the case of the conventional ladder type configuration.

  An object of the present invention has been made under such a background, and an antenna duplexer capable of ensuring attenuation in a low pass band while realizing low insertion loss without using a phase shifter and An object of the present invention is to provide a SAW filter for an antenna duplexer.

The antenna duplexer of the present invention connects a pair of surface acoustic wave filters, each composed of a high-frequency side surface acoustic wave filter and a low-frequency side surface acoustic wave filter, to a common antenna, and transmits a transmission signal from a transmission processing unit. An antenna duplexer that filters one of the pair of surface acoustic wave filters and applies it to the antenna, and filters the received radio wave from the antenna with the other of the pair of surface acoustic wave filters and outputs it to the reception processing unit In
The high-frequency surface acoustic wave filter is
Provided on the antenna side, configured by connecting a surface acoustic wave resonator and a coil in parallel, exhibiting a high impedance with respect to a passband frequency of the low frequency surface acoustic wave filter, and the high frequency A surface acoustic wave tank circuit having a pass characteristic and a reflection characteristic exhibiting a low impedance with respect to the passband frequency of the side surface acoustic wave filter,
The surface acoustic wave tank circuit is provided in series on the opposite side of the antenna, and includes at least one IDT and at least a pair of IDTs whose output ends are commonly connected on both sides of the IDT. A longitudinally coupled resonator type filter for attenuating the signal of the passband frequency of the low-frequency surface acoustic wave filter and filtering the signal of the passband frequency of the high-frequency surface acoustic wave filter;
It is provided with.

  The longitudinally coupled resonator type filter is attenuated with respect to the signal of the passband frequency of the low-frequency surface acoustic wave filter, for example, when the attenuation is about 25 dB. Specific embodiments of the present invention include, for example, a configuration in which a series circuit of a surface acoustic wave resonator and a coil is connected in parallel between the surface acoustic wave tank circuit and the longitudinally coupled resonator type filter, the antenna and the surface A configuration in which surface acoustic wave resonators are connected in series with an acoustic wave tank circuit, or the longitudinally coupled resonator type filter has a plurality of longitudinally coupled resonator type filters whose output ports have substantially the same phase in parallel. For example, a configuration in which the filter processing current is branched to each longitudinally coupled resonator type filter may be used.

  Further, the longitudinally coupled resonator type filter is configured by connecting a pair of longitudinally coupled resonator type filters connected to IDT electrodes in parallel so that the phases of the signals on the input side can be taken out in opposite phases, and the pair of longitudinally coupled resonators. A configuration may be adopted in which a balanced output is obtained at the output port of the filter. Note that the phase of the signal on the input side can be extracted in the opposite phase to each other. For example, the phase of the signal on the input side is shifted by 0 ° and 180 °, respectively (if the phase is shifted by 0 °, the phase remains unchanged). It means that it is taken out.

Furthermore, the present invention can also be used as a high-frequency surface acoustic wave filter in the antenna duplexer of the present invention. That is, another invention is a surface acoustic wave filter for an antenna duplexer that is connected in parallel to a low-frequency surface acoustic wave filter to constitute a pair of surface acoustic wave filters, and is connected to a common antenna.
Provided on the antenna side, configured by connecting a surface acoustic wave resonator and a coil in parallel, exhibiting a high impedance with respect to a passband frequency of the low frequency surface acoustic wave filter, and the high frequency A surface acoustic wave tank circuit having a pass characteristic and a reflection characteristic exhibiting a low impedance with respect to the passband frequency of the side surface acoustic wave filter,
The surface acoustic wave tank circuit is provided in series on the opposite side of the antenna, and includes at least one IDT and at least a pair of IDTs whose output ends are commonly connected on both sides of the IDT. A longitudinally coupled resonator type filter that attenuates the passband frequency of the low-frequency surface acoustic wave filter and filters the passband frequency of the high-frequency surface acoustic wave filter;
The transmission signal from the transmission processing unit is filtered and applied to the antenna, or the received radio wave from the antenna is filtered and output to the reception processing unit.

  According to the present invention, in an antenna duplexer having a SAW duplexer configuration with a low-frequency side SAW filter and a high-frequency side SAW filter, a SAW resonator and a coil in parallel with the SAW resonator are arranged on the side close to the antenna of the high-frequency side SAW filter. By providing the connected SAW tank circuit, the impedance of the low-frequency surface acoustic wave filter with respect to the passband frequency is set to a high impedance. By providing a longitudinally coupled resonator type filter in series with the SAW tank circuit, the signal level in the frequency region lower than the passband frequency of the low-frequency surface acoustic wave filter is attenuated, and the low-frequency surface acoustic wave filter The signal level of the passband frequency is greatly attenuated. Further, coupled with the SAW tank circuit, the signal level of the passband frequency of the low-frequency surface acoustic wave filter is greatly attenuated. Focusing on the SAW tank circuit, this improves the attenuation of the passband frequency of the low-frequency surface acoustic wave filter at the same time as rotating the phase counterclockwise to make the reflection impedance high impedance (closer to open). There is an effect.

  Accordingly, there is no need to provide a phase shifter with external connection as in the prior art, and there are advantages that the device size can be reduced and costs can be reduced. In addition, the combination of the SAW tank circuit and the longitudinally coupled resonator type filter reduces the attenuation amount of the high frequency side SAW filter in the low frequency range compared to the conventional SAW duplexer configuration using a ladder type filter for the high frequency side SAW filter. Can improve. Furthermore, a balanced output type duplexer configuration can be easily realized by connecting two longitudinally coupled resonator type filters in parallel with each other at the portion closest to the high frequency side filter port.

  In general, an antenna duplexer having a SAW duplexer configuration requires three antenna ports 11, a high-frequency side port 12, and a low-frequency side port 13 as electrical ports, as shown in FIG. 1 and the like. As the SAW duplexer configuration, one low frequency side SAW filter 20 and one high frequency side SAW filter 30 are mounted, and they are connected at an “A” point directly below the antenna port 11.

  Assuming that the frequency in the passband of the low-frequency side SAW filter 20 is f-LOW and the frequency in the passband of the high-frequency side SAW filter 30 is f-Hi, as viewed from point A, the frequency in the f-LOW is high. The side SAW filter 30 needs to be designed to have a high reflection impedance, and the f-Hi frequency needs to be designed so that the low band side SAW filter 20 has a high reflection impedance. Without these characteristics, the insertion loss of the filter is deteriorated.

  In the first embodiment of the present invention, as shown in FIG. 1 as a basic configuration, a SAW resonator 51 and a SAW tank circuit 50 in which a coil 52 is connected in parallel to the SAW resonator 51 are connected to the antenna side ( A longitudinally coupled resonator type filter 60 using a SAW element is connected in series to the high frequency side filter port 12 side of the SAW tank circuit 50 provided on the antenna port 11 side).

In FIG. 1, the configuration of the low-pass SAW filter 20 is shown as a T-type ladder type using five SAW resonators 21 including examples to be described later. Good. Further, the piezoelectric substrate forming the respective SAW _{elements, L i TaO 3, L i} NbO 3, including quartz, may be a wafer for SAW devices with piezoelectric effect.

  A specific configuration and operation of the SAW tank circuit 50 and the longitudinally coupled resonator filter 60 in the antenna duplexer having the above configuration will be described.

  As shown in FIG. 2, the SAW tank circuit 50 has a SAW resonator 51 provided with reflectors 54 on both sides of one IDT 53, and a coil 52 connected in parallel to the SAW resonator 51. It is supposed to be configured. With this configuration, the SAW tank circuit 50 has a transmission characteristic (gain characteristic) in which the horizontal axis is frequency and the vertical axis is attenuation in FIG. 3A, and the reflection characteristic (reflection coefficient and impedance) according to Smith chart in FIG. Characteristic), the passband frequency f-LOW of the low-frequency side SAW filter 20 exhibits a phase characteristic (high impedance) close to OPEN and prevents its passage, thereby reducing the loss of the frequency f-LOW. In addition, a low impedance is exhibited with respect to the passband frequency f-Hi of the high frequency side SAW filter 30 to reduce the attenuation.

  In other words, the SAW tank circuit 50 rotates the phase counterclockwise with respect to the passband frequency f-LOW of the low-frequency side SAW filter to simultaneously bring the reflection impedance close to OPEN (high impedance), and f -It has the effect of improving the attenuation in LOW. In an actual design, the resonance frequency, electrode shape, electrode pitch, electrode film thickness, electrode finger crossing width, electrode index width, number of electrode fingers, excitation weight, electrode finger reflection amount, and coil 52 constant of the SAW resonator 51 are set. By selecting, such characteristics can be obtained. Specifically, for example, a coil of 0.1 nH to 200 nH can be used.

  In addition, a single electrode is normally used for the IDT 52 constituting the SAW resonator 51 of the SAW tank circuit 50, but only the IDT may be a double electrode or a mixture of a single electrode and a double electrode. Further, the coil 52 of the SAW tank circuit 50 has a structure such as a discrete part (externally attached individual part), a printed board wiring, a bonding wire, a strip line, a microstrip line, etc. I do n’t mind anything.

  Next, the longitudinally coupled resonator type filter 60 filters the passband frequency of the high frequency side SAW filter 30, and its configuration example is as shown in FIG. One IDT 61 to which the signal f-Hi is applied and a pair of IDTs 62 and 62 are provided on both sides, and the output terminals of the pair of IDTs 62 and 62 are connected in common to obtain a filter output of three IDTs. Furthermore, it is set as the structure which provided the pair of reflectors 63 and 63 for obtaining high Q value at the both ends of the sequence direction of a pair of IDT61 and 62. As shown in FIG.

  The longitudinally coupled resonator type filter 60 having this configuration includes f-LOW so that the pass characteristic (gain characteristic) is shown in FIG. 5A and the reflection characteristic (phase characteristic) is shown in FIG. 5B. It also serves to lower the signal level in the low frequency region, and the attenuation at f-LOW is as good as 25 dB. Here, the characteristics of the longitudinally coupled resonator type filter 60 alone are that the reflection phase at the f-LOW is not high impedance, and is not suitable for the SAW duplexer configuration, and the phase is rotated by some method in the f-LOW. It is necessary to increase the impedance.

  Therefore, in the present embodiment, a high-frequency SAW filter configuration in which the SAW tank circuit 50 is added in series with the longitudinally coupled resonator type filter 60 is adopted. The frequency characteristics in this case are shown in FIG. As shown in the figure, the SAW tank circuit 50 further improves the amount of attenuation in addition to achieving a good amount of attenuation with respect to the signal level at f-LOW by the longitudinally coupled resonator type filter 60. Therefore, an attenuation amount of 45 dB is obtained comprehensively. Further, as can be seen from the reflection characteristic of FIG. 6B, the impedance at the f-LOW also approaches OPEN due to the phase rotation action of the SAW tank circuit 50, and the filter characteristic of the duplexer configuration is good.

  FIG. 7 shows the pass characteristics of the high frequency side SAW filter 30 to which the present embodiment is applied. In the low frequency range, a good attenuation is obtained compared to the conventional characteristics shown in FIG. I understand.

  FIG. 8 shows frequency characteristics when a general ladder filter is connected as the low-pass SAW filter 20 to the high-pass SAW filter 30 in FIG. As is clear from the figure, the attenuation amount in f-LOW is 50 dB or more, and the insertion loss of the low-frequency SAW filter is hardly deteriorated.

  As described above, according to the above-described embodiment, it is possible to obtain good characteristics as an antenna duplexer without providing a phase shifter by external connection, and to reduce the device size and reduce the cost. It can be suitably used for a mobile phone or the like.

(Other embodiments)
FIG. 9 shows the connection point between the SAW tank circuit 50 and the longitudinally coupled resonator type filter 60 and the reference potential (in this example, the ground potential) in order to bring the reflection phase of the high frequency side SAW filter closer to OPEN. A series circuit 70 in which a SAW resonator 71 and a coil 72 are connected in series is provided between them. That is, the series circuit 70 corresponds to a parallel SAW resonator 70 connected in parallel between the SAW tank circuit 50 and the longitudinally coupled resonator filter 60.

  FIG. 10 shows that a series SAW resonator 80 having a SAW resonator configuration is interposed between the antenna port 11 and the SAW tank circuit 50 in order to bring the reflection phase of the high frequency side SAW filter 30 closer to OPEN. The configuration is as follows. In the configuration of FIG. 10, the parallel SAW resonator 70 shown in FIG. 9 may be used in combination.

  FIG. 11 shows that in the configuration of FIG. 9, two longitudinally coupled resonator filters 60P and 60N are connected in parallel as the longitudinally coupled resonator type filter 60, and the phases of these two output ports are 180 ° different from each other. The IDTs 61, 62 and 62 are configured to realize a balanced output type antenna duplexer. FIG. 12 shows an example of the configuration of this longitudinally coupled resonator type filter 60. With respect to one longitudinally coupled resonator type filter 60P, an output signal can be obtained with the same phase as the input of the unbalanced signal. In addition, with respect to the other longitudinally coupled resonator type filter 60N, the IDTs 61, 62, 62 are configured so that an output signal whose phase is inverted with respect to the input of the unbalanced signal is obtained. More specifically, the IDTs 62 and 62 on both sides in both filters 60P and 60N have the same configuration, and the arrangement of the electrode fingers of each IDT 61 in the center is changed, so that the signal applied to the IDTs 62 and 62 is the same in one filter 60P. A signal is extracted from the IDT 61 in phase, and the signal is extracted from the IDT 61 in the opposite phase to the signals applied to the IDTs 62 and 62 in the other filter 60N. In FIG. 11, the parallel SAW resonator 70 may be omitted, or the serial SAW resonator 80 of FIG. 10 may be provided. Further, when the high frequency side SAW filter 30 is used as the reception side, it can function as a balanced input port.

  FIG. 13 improves the power handling capability of the filter 60 by reducing the filter processing current flowing into one SAW element of the longitudinally coupled resonator type filter 60. In the figure, a pair of longitudinally coupled resonator filters 60 and 60 whose output ports have substantially the same phase are connected in parallel, and the current is divided into two to improve the power durability. In this example, there are two branches, but if a plurality of longitudinally coupled resonator filters are connected in parallel, the power durability can be further improved. 12, the parallel SAW resonator 70 may be omitted, or a serial SAW resonator 80 may be provided as shown in FIG.

  FIG. 14 shows a case where the high-frequency SAW filter and the low-frequency SAW filter are not formed as an integral structure, but are configured on an independent piezoelectric substrate and packaged to form a SAW duplexer. In the figure, the high-frequency side SAW filter 30 and the low-frequency side SAW filter 20 are separated from each other, and two antenna ports 10A and 10B are provided for each of the filters 20 and 30 in order to operate as a duplexer. Connects the two antenna ports 10A and 10B. In this case, the connection can be made by an external circuit of the device (for example, on the printed board or inside the antenna switch IC).

  The present invention is realized as an antenna duplexer combining the high-frequency surface acoustic wave filter 30 and the low-frequency surface acoustic wave filter 20 as described above, but the high-frequency side configured as shown in FIG. The SAW filter for an antenna duplexer including the surface acoustic wave filter 30 is also established, and the above-described effects can be obtained by using the high-frequency surface acoustic wave filter 30.

  In the above-described embodiments, the longitudinally coupled resonator type filters 60, 60P, 60N are not limited to the three-electrode structure, and can be applied to longitudinally coupled resonator type filters having at least two IDTs. For example, the filter characteristics can be further enhanced as a longitudinally coupled resonator type filter having a five-electrode structure.

1 is a basic configuration diagram of the present invention. The figure which shows the structural example of a SAW tank circuit (embodiment). SAW tank circuit pass and reflection characteristics. The figure which shows the structural example of a longitudinally coupled resonator type filter (embodiment). Transmission and reflection characteristics of a longitudinally coupled resonator filter. Transmission characteristics and reflection characteristics when a longitudinally coupled resonator type filter and a SAW tank circuit are connected. Frequency characteristics of the high frequency side SAW filter. Frequency characteristics of SAW filter for antenna duplexer. The block diagram of other embodiment (the 1). The block diagram of the other embodiment (the 2). The block diagram of the other embodiment (the 3). The block diagram of other embodiment (the 4). The block diagram of other embodiment (the 5). The block diagram which shows the structural example of a longitudinally coupled resonator type filter. A configuration example of a SAW device. The structural example of the conventional antenna duplexer. Frequency characteristics of a conventional antenna duplexer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Antenna 20 Low band side SAW filter 30 High band side SAW filter 40 Phase shifter 50 SAW tank circuit 51 SAW resonator 52 Coil 60, 60P, 60N Vertical coupling resonator type filter 70 Parallel SAW resonator 71 SAW resonator 72 Coil 80 Series SAW resonator

Claims (10)

A pair of surface acoustic wave filters composed of a high-frequency side surface acoustic wave filter and a low-frequency side surface acoustic wave filter are connected to a common antenna, and a transmission signal from a transmission processing unit is transmitted to one of the pair of surface acoustic wave filters. In the antenna duplexer that applies the filter processing to the antenna, filters the received radio wave from the antenna with the other of the pair of surface acoustic wave filters, and outputs the filtered signal to the reception processing unit.
The high-frequency surface acoustic wave filter is
Provided on the antenna side, configured by connecting a surface acoustic wave resonator and a coil in parallel, exhibiting a high impedance with respect to a passband frequency of the low frequency surface acoustic wave filter, and the high frequency A surface acoustic wave tank circuit having a pass characteristic and a reflection characteristic exhibiting a low impedance with respect to the passband frequency of the side surface acoustic wave filter,
The surface acoustic wave tank circuit is provided in series on the opposite side of the antenna, and includes at least one IDT and at least a pair of IDTs whose output ends are commonly connected on both sides of the IDT. A longitudinally coupled resonator type filter for attenuating the signal of the passband frequency of the low-frequency surface acoustic wave filter and filtering the signal of the passband frequency of the high-frequency surface acoustic wave filter;
An antenna duplexer characterized by comprising:   The antenna duplexer according to claim 1, wherein a series circuit of a surface acoustic wave resonator and a coil is connected in parallel between the surface acoustic wave tank circuit and the longitudinally coupled resonator type filter.   3. The antenna duplexer according to claim 1, wherein a surface acoustic wave resonator is connected in series between the antenna and the surface acoustic wave tank circuit.   The longitudinally coupled resonator type filter is configured by connecting a pair of longitudinally coupled resonator type filters connected to IDT electrodes in parallel so that the phases of the signals on the input side can be extracted in opposite phases, and the pair of longitudinally coupled resonators. 4. The antenna duplexer according to claim 1, wherein a balanced output is obtained at an output port of the type filter.   The longitudinally coupled resonator type filter has a configuration in which a plurality of longitudinally coupled resonator type filters whose output ports have substantially the same phase are connected in parallel, and the filter processing current is branched to each longitudinally coupled resonator type filter. The antenna duplexer according to claim 1, wherein: In a surface acoustic wave filter for an antenna duplexer configured to form a pair of surface acoustic wave filters together with a low-frequency side surface acoustic wave filter,
Provided on the antenna side, configured by connecting a surface acoustic wave resonator and a coil in parallel, exhibiting a high impedance with respect to a passband frequency of the low frequency surface acoustic wave filter, and the high frequency A surface acoustic wave tank circuit having a pass characteristic and a reflection characteristic exhibiting a low impedance with respect to the passband frequency of the side surface acoustic wave filter,
The surface acoustic wave tank circuit is provided in series on the opposite side of the antenna, and includes at least one IDT and at least a pair of IDTs whose output ends are commonly connected on both sides of the IDT. A longitudinally coupled resonator type filter that attenuates the passband frequency of the low-frequency surface acoustic wave filter and filters the passband frequency of the high-frequency surface acoustic wave filter;
A surface elasticity for an antenna duplexer, characterized in that a transmission signal from a transmission processing unit is filtered and applied to the antenna, or a received radio wave from the antenna is filtered and output to a reception processing unit. Wave filter.   7. A surface for an antenna duplexer according to claim 6, wherein a series circuit of a surface acoustic wave resonator and a coil is connected in parallel between the surface acoustic wave tank circuit and the longitudinally coupled resonator type filter. Elastic wave filter.   8. The surface acoustic wave filter for an antenna duplexer according to claim 6, wherein a surface acoustic wave resonator is connected in series between the antenna and the surface acoustic wave tank circuit.   The longitudinally coupled resonator type filter is configured by connecting a pair of longitudinally coupled resonator type filters connected to IDT electrodes in parallel so that the phases of the signals on the input side can be extracted in opposite phases, and the pair of longitudinally coupled resonators. 9. The surface acoustic wave filter for an antenna duplexer according to claim 6, wherein a balanced output is obtained at an output port of the type filter. The longitudinally coupled resonator type filter has a configuration in which a plurality of longitudinally coupled resonator type filters whose output ports have substantially the same phase are connected in parallel, and the filter processing current is branched to each longitudinally coupled resonator type filter. The surface acoustic wave filter for an antenna duplexer according to any one of claims 6 to 9.

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