JP2015023557A - Electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic circuit capable of obtaining an excellent frequency characteristic.SOLUTION: An electronic circuit 100 of the invention comprises: a switch 12 that comprises ports A-D, and selects a port to be connected with an antenna 10 from the ports A-D; a duplexer 22 connected between the port B among the ports A-D and terminals Tx22 and Rx22; a duplexer 24 connected between the port C among the ports A-D and terminals Tx24 and Rx24, and having a passband different from a first filter; and an inductor L1 one end of which is connected with the port D among the ports A-D and the other end is grounded. The switch 12 selects the ports B, C, and D among the ports A-D if at least one of transmission and reception of a signal included in a communication band of the duplexer 22, and at least one of transmission and reception of a signal included in the passband of the duplexer 24 are performed at the same time.

Description

  The present invention relates to electronic circuits.

  The functions of communication devices such as mobile phones are expanding to the Internet. In order to cope with an increase in communication data, technologies such as LTE (Long Term Evolution) -Advanced are being developed. In LTE-Advanced, CA (Carrier Aggregation) is used for high throughput. In CA, a plurality of frequency bands are used simultaneously. For example, in inter-band CA, a plurality of frequency bands are received and a plurality of frequency bands are transmitted at the same time to increase the bandwidth, increase the speed, and expand the data amount. In a CA-compatible module, a plurality of filters or duplexers are used to share a plurality of frequency bands. Since the impedance of one duplexer becomes high in the passband of the other duplexer, signal loss is suppressed and good frequency characteristics are obtained. Patent Documents 1 and 2 describe a technique for realizing high impedance between a plurality of duplexers. A module corresponding to three or more frequency bands includes a switch and a plurality of duplexers or filters. The switch selects from three or more duplexers or filters according to the frequency band and connects to the antenna.

Japanese Patent Laid-Open No. 10-247801 JP 2012-28895 A

  However, it has been difficult to make one duplexer or filter high impedance in two frequency bands. As a result, the frequency characteristic is deteriorated. In view of the above problems, an object of the present invention is to provide an electronic circuit capable of obtaining good frequency characteristics.

  The present invention includes a switch that includes a plurality of ports, and that selects a port connected to an antenna from the plurality of ports, and a first filter connected between a first port and a first terminal among the plurality of ports. And a second filter connected between a second port and a second terminal of the plurality of ports and having a pass band different from that of the first filter, and one end serving as a third port of the plurality of ports. A first matching circuit that is connected and grounded at the other end, and includes at least one of transmission and reception of a signal included in the communication band of the first filter and a signal included in the pass band of the second filter When at least one of transmission and reception is performed simultaneously, the switch is an electronic circuit that selects the first port, the second port, and the third port among the plurality of ports .

  In the above configuration, when the switch selects the first port, the second port, and the third port, the second filter is opened when viewed from the switch at a frequency included in the pass band of the first filter. The first filter can be opened when viewed from the switch at a frequency included in the pass band of the second filter.

  In the above configuration, when the switch selects the first port and the second port and does not select the third port, the second filter viewed from the switch at a frequency included in the pass band of the first filter. The reactance component may be equal to the reactance component of the first filter viewed from the switch at a frequency included in the pass band of the second filter.

  In the above configuration, the first duplexer includes the first filter, the second duplexer includes the second filter, at least one of transmission and reception of a signal included in the communication band of the first duplexer, and the second duplexer. The switch selects the first port, the second port, and the third port from among the plurality of ports when at least one of transmission and reception of a signal included in the passband is simultaneously performed. Can do.

  In the above configuration, a third filter connected between a fourth port and a third terminal of the plurality of ports and having a pass band different from the first filter and the second filter is provided. When at least one of transmission and reception of a signal included in the communication band of the filter and at least one of transmission and reception of a signal included in the pass band of the third filter are performed simultaneously, the switch includes the first port and the The fourth port may be selected and the second port and the third port may not be selected.

  In the above-described configuration, when the switch selects the first port and the fourth port and does not select the second port and the third port, the frequency is included in the passband of the first filter from the switch. The third filter can be opened when viewed, and the first filter can be opened when viewed from the switch at a frequency included in the pass band of the third filter.

  In the above configuration, the first duplexer includes the first filter, the third duplexer includes the third filter, at least one of transmission and reception of a signal included in the communication band of the first duplexer, and the third duplexer. The switch selects the first port and the fourth port and does not select the second port and the third port when at least one of transmission and reception of signals included in the passband is simultaneously performed. can do.

  In the above configuration, the first matching circuit may include at least one of an inductor and a capacitor.

  The above configuration includes a second matching circuit connected between the first port and the first filter, and a third matching circuit connected between the second port and the second filter. It can be configured.

  ADVANTAGE OF THE INVENTION According to this invention, the electronic circuit which can acquire a favorable frequency characteristic can be provided.

FIG. 1 is a block diagram illustrating an electronic circuit according to the first embodiment. FIG. It is a block diagram which shows the example of 1. FIG. FIG. It is a block diagram which shows the example of 4. FIG. 3B and FIG. 3C are Smith charts illustrating the impedance of the duplexer. FIG. FIG. 6 is a block diagram showing an example of 5. FIG. 4B and FIG. 4C are Smith charts illustrating the impedance of the duplexer. FIG. 5A is a block diagram illustrating an electronic circuit according to a comparative example. FIG. 5B and FIG. 5C are Smith charts illustrating the impedance of the duplexer. FIG. 6 is a block diagram illustrating an electronic circuit according to a modification. FIG. 7 is a circuit diagram showing an example of a matching circuit. FIG. 8 is a block diagram illustrating an electronic circuit according to the second embodiment.

  Embodiments will be described with reference to the drawings.

  The first embodiment is an example in which the impedance is optimized using the inductor L1. FIG. 1 is a block diagram illustrating an electronic circuit 100 according to the first embodiment. As shown in FIG. 1, the electronic circuit 100 includes a switch 12, matching circuits 14, 16 and 18, duplexers 20, 22 and 24, and an integrated circuit (IC) 26. The IC 26 includes a power amplifier (PA) 26a and a low noise amplifier (LNA) 26b. The IC 26 performs signal processing such as up-conversion and down-conversion. The PA 26a amplifies the transmission signal. The LNA 26b amplifies the received signal. The electronic circuit 100 is used for a module for communication equipment, for example.

  The duplexer 20 (third duplexer) includes a transmission filter 20a and a reception filter 20b. The duplexer 22 (first duplexer) includes a transmission filter 22a and a reception filter 22b. The duplexer 24 (second duplexer) includes a transmission filter 24a and a reception filter 24b. Each filter is a band-pass filter such as a surface acoustic wave (SAW) filter.

  The switch 12 is a semiconductor switch having four ports A to D. One end of the matching circuit 14 is connected to the port A (fourth port), and the other end is connected to one end of the transmission filter 20a and the reception filter 20b. The other end of the transmission filter 20a is connected to the PA 26a via a transmission terminal Tx20 (third terminal). The other end of the reception filter 20b is connected to the LNA 26b via a reception terminal Rx20 (third terminal). Similarly to the connection of the ports A to IC 26, the port B (first port), the matching circuit 16, the duplexer 22, the transmission terminal Tx22 and the reception terminal Rx22 (both are the first terminals), the PA 26a, and the LNA 26b are connected. Similarly to the connection of ports A to IC 26, port C (second port), matching circuit 18, duplexer 24, transmission terminal Tx24 and reception terminal Rx24 (both are second terminals), PA 26a and LNA 26b are connected. Matching circuits 14, 16 and 18 match the impedance between the duplexers and the impedance between the antenna 10 and each duplexer. One end of the inductor L1 (first matching circuit) is connected to the port D (third port), and the other end is grounded.

  Duplexers correspond to different frequency bands. The duplexer 20 corresponds to, for example, W-CDMA (Wideband Code Division Multiple Access) Band3. The duplexer 22 corresponds to, for example, W-CDMA Band7. The duplexer 24 corresponds to, for example, W-CDMA Band1. Hereinafter, W-CDMA may be omitted and only Band may be described.

Ｎｏ．１〜３の例では１つの周波数帯域の信号の送受信を行う。Ｎｏ．４および５の例はＣＡの例であり、２つの周波数帯域の信号を同時に送受信する。 Signal transmission and reception (transmission / reception) will be described. The switch 12 selects a port from ports A to D according to the frequency band to be used, and connects to the antenna 10. Table 1 is a table showing the relationship between frequency bands and ports.

No. In the examples 1 to 3, transmission / reception of signals in one frequency band is performed. No. Examples 4 and 5 are examples of CA, which simultaneously transmit and receive signals in two frequency bands.

  An example using one frequency band will be described. No. in Table 1 As shown in FIGS. 1 to 3, when one frequency band is used, the switch 12 turns on one port and turns off the other ports.

  FIG. 1 is a block diagram illustrating an example of 1 (transmission and reception of a Band3 signal). IC26 is omitted. As shown in FIG. 2 and Table 1, the switch 12 turns on the port A and turns off the other ports. The transmission signal is input from the transmission terminal Tx20 to the transmission filter 20a. The transmission signal is filtered by the transmission filter 20 a and transmitted from the antenna 10 via the switch 12. The reception signal is received by the antenna 10 and input to the reception filter 20b via the switch 12. The reception signal filtered by the reception filter 20b is output from the reception terminal Rx20. Since the ports B and C are OFF, the transmission signal and the reception signal are not input to the duplexers 22 and 24. No. in Table 1 In the examples of 2 and 3, no. Signals are transmitted and received in the same manner as in the first example.

  Next, an example of CA that uses two frequency bands simultaneously will be described. In CA, no. Two frequency bands are used as shown in 4 and 5. No. 4 (Band3 signal and Band7 signal are simultaneously transmitted and received) will be described. FIG. It is a block diagram which shows the example of 4. As shown in FIG. 3A and Table 1, the switch 12 turns on the ports A and B and turns off the ports C and D.

  FIG. 3B is a Smith chart illustrating the impedance of the duplexer 20. The dashed ellipse in FIG. 3B indicates the impedance Z7 in the Band7 frequency band (transmission band and reception band). FIG. 3C is a Smith chart illustrating the impedance of the duplexer 22. The dashed ellipse in FIG. 3C indicates the impedance Z3 in the Band3 frequency band. The impedance means the impedance viewed from the switch 12. As shown in FIG. 3B, the impedance Z7 is located near the right end of the Smith chart. That is, the impedance Z7 increases to infinity or near infinity. As shown in FIG. 3C, the impedance Z3 is located at the right end of the Smith chart. That is, when viewed from the switch 12, the duplexers 20 and 22 are opened in the frequency band of the other party. For this reason, the Band 3 signal is less likely to flow to the duplexer 22 and is likely to flow to the duplexer 20. The Band 7 signal hardly flows to the duplexer 20 and easily flows to the duplexer 22. Transmission and reception of the Band3 signal and the Band7 signal can be performed simultaneously.

  However, as will be described later in the comparative example, it is difficult to open the duplexer 22 opened to the Band 3 to the Band 1 as well. In the first embodiment, the duplexer is optimized for two bands by the inductor L1.

  No. in Table 1 5 (Band 7 signal and Band 1 signal are simultaneously transmitted and received) will be described. FIG. FIG. 6 is a block diagram showing an example of 5. As shown in FIG. 4A and Table 1, the switch 12 turns on the ports B, C, and D, and turns off the port A.

  FIG. 4B is a Smith chart illustrating the impedance of the duplexer 24. The dashed ellipse in FIG. 4B shows the impedance Z7 in the Band7 frequency band. FIG. 4C is a Smith chart illustrating the impedance of the duplexer 22. The dashed ellipse in FIG. 4C indicates the impedance Z1 in the Band1 frequency band. As shown in FIG. 4B, the impedance Z7 is located at the right end of the Smith chart. As shown in FIG. 4C, the impedance Z1 is located at the right end. Thus, according to the first embodiment, by connecting the inductor L1, the duplexers 22 and 24 as viewed from the switch 12 are opened in the frequency band of the other party. For this reason, the Band 7 signal hardly flows to the duplexer 24 and easily flows to the duplexer 22. The Band 1 signal hardly flows to the duplexer 22 and easily flows to the duplexer 24. Since signal leakage is suppressed, good frequency characteristics with little signal loss can be obtained. It becomes possible to simultaneously transmit and receive signals in two frequency bands (Band 1 and Band 7).

表２に示すように、１つの周波数帯域の信号を送受信する場合（Ｎｏ．６〜８）は実施例１と同様、スイッチ１２は１つのポートをＯＮにし、他の２つのポートはＯＦＦにする。ＣＡを行う場合（Ｎｏ．９および１０）、スイッチ１２は２つのポートをＯＮにし、他の１つのポートはＯＦＦにする。比較例においても図３（ｂ）および図３（ｃ）に示したように、デュプレクサ２０および２２は互いに相手方の通過帯域において開放する。 A comparative example will be described. FIG. 5A is a block diagram illustrating an electronic circuit 100R according to a comparative example. As shown in FIG. 5A, the inductor L1 is not provided. The IC 26 is omitted. Table 2 shows the relationship between frequency bands and ports.

As shown in Table 2, when transmitting and receiving a signal in one frequency band (Nos. 6 to 8), the switch 12 turns on one port and the other two ports turn off as in the first embodiment. . When performing CA (Nos. 9 and 10), the switch 12 turns on two ports and turns off the other one port. Also in the comparative example, as shown in FIGS. 3B and 3C, the duplexers 20 and 22 are opened in the other party's passband.

  No. An example of 10 (transmission and reception of a Band7 signal and a Band1 signal) will be described. As shown in FIG. 5A and Table 2, the switch 12 turns on the ports B and C and turns off the port A. FIG. 5B is a Smith chart illustrating the impedance of the duplexer 24. FIG. 5C is a Smith chart illustrating the impedance of the duplexer 22. Since the matching circuit 18 is optimized with respect to Band 3, as shown in FIG. 5B, the impedance Z7 is located below the right end of the Smith chart. As shown in FIG. 5C, the impedance Z1 is located below the right end. Thus, in the comparative example, the duplexers 22 and 24 are not opened in the other's passband. Accordingly, the Band 7 signal leaks to the duplexer 24, and the Band 1 signal leaks to the duplexer 22. As described above, it is difficult to optimize the duplexer 22 for both Band3 and Band1.

  The reactance component of the duplexer 22 in the Band1 frequency band and the reactance component of the duplexer 24 in the Band7 frequency band are substantially equal. That is, the shift amount ΔZ7 from the right end of the Smith chart of the impedance Z7 shown in FIG. 5B is substantially equal to the shift amount ΔZ1 from the right end of the impedance Z1 shown in FIG. Therefore, if the impedances of the duplexers 22 and 24 are rotated to the upper side of the Smith chart by the same amount, the impedance can be made close to infinity. According to the first embodiment, as shown in FIG. 4A, the inductor L1 is commonly connected to the duplexers 22 and 24. Therefore, the impedances of the duplexers 22 and 24 change by the same amount. As a result, the impedance in the other party's frequency band can be made infinite. The impedance is preferably infinite and in the vicinity of infinite, but it should be high enough to cause no practical problem. For example, a high impedance such that a signal in the frequency band of the other party hardly flows is preferable.

  The modification of the first embodiment is an example using the capacitor C1. FIG. 6 is a block diagram illustrating an electronic circuit 110 according to a modification. As shown in FIG. 6, one end of the capacitor C1 is connected to the port D, and the other end is grounded. When the impedance is shifted to the upper side from the right end of the Smith chart, the impedance can be made close to infinity by rotating the impedance downward by the capacitor C1. By connecting an inductor or a capacitor to the switch 12 as shown in FIG. 3A and FIG. 6, the duplexer can be opened. Since the configuration is simple, the cost and size of the electronic circuit can be reduced.

  Examples of the matching circuits 14, 16 and 18 will be described. FIG. 7 is a circuit diagram showing an example of a matching circuit. As shown in FIG. 7, the capacitor C <b> 2 is connected in series between the terminal 30 and the terminal 32. One end of the inductor L2 is connected between the terminal 30 and the capacitor C2, and one end of the inductor L3 is connected between the capacitor C2 and the terminal 32. The other ends of the inductors L2 and L3 are grounded. A matching circuit may be used instead of the inductor L1 in FIG. That is, a circuit including at least one of an inductor and a capacitor may be connected to the port D of the switch 12.

  The second embodiment is an example in which a filter is provided in place of the duplexer. FIG. 8 is a block diagram illustrating an electronic circuit 200 according to the second embodiment. As shown in FIG. 8, a reception filter 20b is connected to port A, a reception filter 22b is connected to port B, and a reception filter 24b is connected to port C. The switch 12 selects ports A to D as shown in Table 1. Similarly to the example shown in FIG. 3B, the reception filter 20b is opened in the band 7 pass band, and the reception filter 22b is opened in the band 3 pass band as in the example shown in FIG. By connecting the inductor L1, the reception filter 24b is opened in the band 7 passband as in the example shown in FIG. 4B, and reception is performed in the band 1 pass band as in the example shown in FIG. 4C. The filter 22b is opened. According to the second embodiment, as in the first embodiment, signals in two frequency bands can be received and good frequency characteristics can be obtained.

  Only the reception filter or only the transmission filter may be provided. You may provide both a duplexer and a filter. For example, the reception filter 20 b is connected to port A, the reception filter 24 b is connected to port C, and the duplexer 22 is connected to port B. No. in Table 1 In the example of 4, the reception of the Band3 and Band7 signals and the transmission of the Band7 signal are possible at the same time. No. in Table 1 In the example of 5, the reception of the Band1 and Band7 signals and the transmission of the Band7 signal are possible at the same time.

  The filter may be an elastic wave filter such as a filter using a boundary acoustic wave filter and an elastic thin film resonator (FBAR), or may be a filter other than the elastic wave filter. The switch 12 may have two ports or four or more ports. The number of filters and duplexers connected to the switch 12 may be two, or four or more.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

10 antenna 12 switch 14, 16, 18 matching circuit 20, 22, 24 duplexer 20a, 22a, 24a transmission filter 20b, 22b, 24b reception filter 100, 110, 200 electronic circuit A to D port L1, L2, L3 inductor C1, C2 capacitor Tx20, Tx22, Tx24 Transmission terminal Rx20, Rx22, Rx24 Reception terminal

Claims (9)

A switch comprising a plurality of ports and selecting a port connected to an antenna from the plurality of ports;
A first filter connected between a first port and a first terminal of the plurality of ports;
A second filter connected between a second port and a second terminal of the plurality of ports and having a passband different from the first filter;
A first matching circuit having one end connected to a third port of the plurality of ports and the other end grounded,
When at least one of transmission and reception of a signal included in the communication band of the first filter and at least one of transmission and reception of a signal included in the passband of the second filter are performed simultaneously, the switch An electronic circuit, wherein the first port, the second port, and the third port are selected from among the ports. When the switch selects the first port, the second port, and the third port;
At a frequency included in the passband of the first filter, the second filter is opened when viewed from the switch,
2. The electronic circuit according to claim 1, wherein the first filter is opened when viewed from the switch at a frequency included in a pass band of the second filter. When the switch selects the first port and the second port and does not select the third port;
The reactance component of the second filter viewed from the switch at a frequency included in the passband of the first filter is the reactance component of the first filter viewed from the switch at a frequency included in the passband of the second filter. The electronic circuit according to claim 1, wherein the electronic circuit is equal to: A first duplexer including the first filter; a second duplexer including the second filter;
When at least one of transmission and reception of a signal included in the communication band of the first duplexer and at least one of transmission and reception of a signal included in the passband of the second duplexer are performed simultaneously, the switch 4. The electronic circuit according to claim 1, wherein the first port, the second port, and the third port are selected from among the ports. 5. A third filter connected between a fourth port and a third terminal of the plurality of ports and having a passband different from the first filter and the second filter;
When at least one of transmission and reception of a signal included in the communication band of the first filter and at least one of transmission and reception of a signal included in the pass band of the third filter are performed simultaneously, the switch 5. The electronic circuit according to claim 1, wherein a port and the fourth port are selected, and the second port and the third port are not selected. 6. When the switch selects the first port and the fourth port and does not select the second port and the third port;
At a frequency included in the passband of the first filter, the third filter is opened as viewed from the switch,
6. The electronic circuit according to claim 5, wherein the first filter is opened when viewed from the switch at a frequency included in a pass band of the third filter. A first duplexer including the first filter; a third duplexer including the third filter;
When at least one of transmission and reception of a signal included in the communication band of the first duplexer and at least one of transmission and reception of a signal included in the pass band of the third duplexer are performed simultaneously, the switch 7. The electronic circuit according to claim 5, wherein a port and the fourth port are selected, and the second port and the third port are not selected.   The electronic circuit according to claim 1, wherein the first matching circuit includes at least one of an inductor and a capacitor. A second matching circuit connected between the first port and the first filter;
The electronic circuit according to claim 1, further comprising a third matching circuit connected between the second port and the second filter.

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