WO2012011310A1 - Demultiplexer - Google Patents

Abstract

The disclosed demultiplexer is provided with a first and a second demultiplexing circuit. The first demultiplexing circuit includes a first filter having a first pass band and a second filter having a second pass band; the second demultiplexing circuit includes a third filter having a third pass band, to the outside of the of the frequency band which includes the first and second pass bands. The input impedance of the first demultiplexing circuit has first reactance components which are inductive or capacitive in the first pass band, and has second reactance components, which are of the opposite polarity to the first reactance components, in the second pass band; if the first reactance components are inductive, the input impedance of the second demultiplexing circuit is capacitive in the first pass band and inductive in the second pass band, and if the first reactance components are capacitive, the input impedance is inductive in the first pass band and capacitive in the second pass band.

Description

Duplexer

The present invention relates to a duplexer.

Multiband-compatible mobile phones capable of making calls and transmitting / receiving data using a plurality of communication methods have become widespread. A multi-band mobile phone includes a duplexer that separates a multi-band signal on which signals of a plurality of frequency bands are superimposed for each frequency band. In the field of mobile communication, a small-sized and low-loss duplexer that can separate more frequencies is desired.

A demultiplexer (multiplexer) that demultiplexes signals of three or more frequency bands has a more complicated circuit configuration than a diplexer. As the number of frequencies to be separated increases, it becomes difficult to design a circuit with low loss in all passbands and high attenuation in all stopbands.

There is a disclosure example of a duplexer that separates a multiband signal into three or more frequency bands (Patent Document 1). In this disclosed example, received signals are separated into three or more frequency bands using distributed constant lines arranged in multiple stages.

JP 2007-266897 A

Various embodiments of the present invention provide a duplexer capable of separating a multiband signal into three or more frequency bands while keeping insertion loss low. Other problems will be understood from the following detailed description and the accompanying drawings.

A duplexer according to an embodiment of the present invention includes an input terminal for inputting a reception signal from an antenna, and a first branch circuit disposed between the input terminal and the first and second output terminals. When,
A second branching circuit disposed between the input terminal and the third output terminal, wherein the first branching circuit is between the input terminal and the first output terminal. A first filter disposed and having a first passband; and a second filter disposed between the input terminal and the second output terminal and having a second passband, The second branching circuit is disposed between the input terminal and the third output terminal, and has a third passband outside a frequency band including the first and second passbands. The input impedance of the first branching circuit has an inductive or capacitive first reactance component in the first passband and the first reactance component in the second passband The second reactance component of the opposite polarity The input impedance of the second branching circuit is capacitive in the first passband and inductive in the second passband when the first reactance component is inductive, When the first reactance component is capacitive, it is inductive in the first passband and capacitive in the second passband.

Various embodiments of the present invention provide a duplexer capable of separating a multiband signal into three or more frequency bands while keeping insertion loss low.

1 is a circuit diagram showing a duplexer according to an embodiment of the present invention. Smith chart showing input impedance of low frequency side branching circuit according to one embodiment of the present invention The Smith chart which shows the input impedance of the high frequency side branching circuit concerning one Embodiment of this invention 1 is a circuit diagram showing a duplexer according to an embodiment of the present invention. 1 is a circuit diagram showing a duplexer according to an embodiment of the present invention. 1 is an equivalent circuit diagram of a duplexer according to an embodiment of the present invention. Smith chart showing input impedance of duplexer according to one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention The graph showing the attenuation characteristic of the duplexer concerning one embodiment of the present invention

Various embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing a duplexer 100 according to an embodiment of the present invention. The duplexer 100 is mounted on a mobile phone, for example, and separates a multiband signal input from an antenna (not shown) via an input terminal 102 into signals of individual frequency bands, and the separated signals are output to the output terminals 116, Output from 118 and 120 to a receiver (not shown). The transmission lines or circuits connected to the input terminal 102 and the output terminals 116, 118, 120 are each matched to a characteristic impedance of 50Ω.

Between the input terminal 102 and the output terminal 116 and the output terminal 118, a low frequency side branching circuit 140 for transmitting a low frequency side signal among the input signals is provided, and between the input terminal 102 and the output terminal 120 is provided. Is provided with a high frequency side branching circuit 160 for transmitting a high frequency side signal among the input signals. The low frequency side branching circuit 140 includes, for example, a distributed constant line 104, a matching circuit 108, and surface acoustic wave (SAW) filters 110 and 112. The high frequency side branching circuit 160 includes, for example, the distributed constant line 106 and the SAW filter 114.

The SAW filters 110, 112, and 114 have pass bands in different frequency bands, and output the passed signals to the corresponding output terminals 116, 118, and 120, respectively. For example, the pass band of SAW filter 110 is 869-894 MHz allocated for reception of band V of UMTS (Universal Mobile Telecommunications System), and the pass band of SAW filter 112 is in the L1 band of GPS (Global Positioning System). It is assigned 1574 to 1576 MHz. The pass band of the SAW filter 114 is, for example, 2110-2170 MHz allocated for reception of band I of UTMS. In the present specification, the pass bands of the SAW filters 110, 112, and 114 may be referred to as “first pass band”, “second pass band”, and “third pass band”, respectively. A signal in a frequency band corresponding to the first to third passbands is superimposed on the multiband signal received from the antenna.

The SAW filter 114 is designed to have a pass band outside the frequency band including the first and second pass bands. In other words, the pass band of the SAW filter 114 exists outside the frequency band from 869 MHz to 1576 MHz, with the lower limit of 869 MHz being the lower limit of the first pass band and the high frequency end being 1576 MHz being the upper limit of the second pass band. To do. The band I of UTMS shown as an example of the pass band of the SAW filter 114 has a pass band from 2110 to 2170 MHz, and this pass band is located on the high frequency side outside 869 MHz to 1576 MHz.

As another embodiment of the present invention, instead of the high frequency side branching circuit 160 or in addition to the high frequency side branching circuit 160, a signal on the lower frequency side than the pass band of the low frequency side branching circuit 140 is used. A demultiplexing circuit for transmission can be provided. Such a branching circuit includes one or more filters having a pass band on the low frequency side of the frequency band including the first and second pass bands.

In the low frequency side branching circuit 140, a matching circuit 108 composed of one or a plurality of lumped constant type reactance elements is disposed in front of the SAW filters 110 and 112, and between the matching circuit 108 and the input terminal 102. The distributed constant line 104 is arranged. The distributed constant line 104 has a line length L1. The distributed constant line 104 delays the phase of the passing signal by the amount of phase shift corresponding to the line length L1. The line length L1 of the distributed constant line 104 is determined so that the input impedance of the low frequency side branching circuit 140 viewed from the input terminal 102 side is sufficiently high in the third passband. As long as the signal in the third passband does not leak to the low frequency side branching circuit 140, the distributed constant line 104 can be omitted.

The matching circuit 108 includes a capacitor, an inductor, or a combination thereof, which is a lumped element type reactance element. It is assumed that the arrangement and element values of the reactance elements constituting the matching circuit 108 are not affected by the high frequency side branch circuit 160 (that is, the low frequency side branch circuit 140 is electrically connected to the high frequency side branch circuit 160). It is determined that the reactance components of the input impedance of the low frequency side branching circuit 140 viewed from the input terminal 102 side have opposite polarities in the first passband and the second passband, assuming that they are separated. It is done. As will be described below, the input impedance of the low frequency side branching circuit 140 changes under the influence of the reactance element included in the high frequency side branching circuit 160 in a state where the input impedance is connected to the high frequency side branching circuit 160. However, the matching circuit 108 is designed by excluding the influence of the high frequency side branching circuit 160 from the calculation of the impedance. In this way, the input impedance of the low-frequency side branching circuit 140 is the reactance component in the first passband and the reactance component in the second passband when the low-frequency side branching circuit 140 is evaluated as a single unit. Are adjusted to have opposite polarities. When the low frequency side demultiplexing circuit 140 includes the distributed constant line 104, the reactance component in the first pass band and the reactance component in the second pass band in a state in which the phase shift rotation by the distributed constant line 104 is added. Designed to have opposite polarities.

By designing the matching circuit 108 in this way, the input impedance of the low-frequency side branching circuit 140 is 50Ω in the first passband whose resistance component (real part) is substantially the same as the characteristic impedance of the transmission line. In addition, while the reactance component (imaginary part) is inductive or capacitive, the resistance component is approximately 50Ω in the second passband and the reactance component has a polarity opposite to that of the reactance component in the first passband. Adjusted. For example, if the reactance component in the first passband of the input impedance of the low-frequency side branching circuit 140 (hereinafter sometimes referred to as “first reactance component” in this specification) is capacitive, the second The reactance component in the pass band (hereinafter, sometimes referred to as “second reactance component” in this specification) becomes inductive. On the other hand, if the first reactance component is inductive, the second reactance component is capacitive. The input impedance of the low frequency side branching circuit 140 in the first passband and the second passband may be in a complex conjugate relationship.

In the high frequency side branching circuit 160, the distributed constant line 106 is disposed between the input terminal 102 and the SAW filter 114. The phase rotation in the distributed constant line 106 adjusts the input impedance of the high frequency side branching circuit 160 so that the high frequency side branching circuit 160 functions as an inductor or a capacitor for the signals in the first and second passbands. The Whether the high frequency side branching circuit 160 functions as an inductor or a capacitor is determined according to the polarities of the first and second reactance components. For example, when the low frequency side branching circuit 140 is designed so that the first reactance component is capacitive and the second reactance component is inductive, the high frequency side branching circuit 160 serves as an inductor in the first passband. The phase of the input signal is rotated by the distributed constant line 106 so that it functions and functions as a capacitor in the second passband. On the other hand, when the low frequency side demultiplexing circuit 140 is designed so that the first reactance component is inductive and the second reactance component is capacitive, the high frequency side demultiplexing circuit 160 is in the first passband. The input impedance of the high frequency side branching circuit 160 is adjusted so as to function as a capacitor and as an inductor in the second passband.

By connecting the high frequency side branch circuit 160 configured in this way to the low frequency side branch circuit 140, the input impedance in the first pass band of the low frequency side branch circuit 140 is capacitive when not connected. The input impedance in the second pass band is rotated from the inductive region when not connected to the capacitive region. As a result, the first and second reactance components each approach “0”, and impedance matching of the low frequency side branching circuit 140 is realized with high accuracy.

The above-described duplexer 100 according to an embodiment of the present invention can be used when demultiplexing signals in a plurality of frequency bands distributed over a wide band, or when each signal is in a wide band. Since it is difficult to completely open the input impedance of the high-frequency side branch circuit 160 in each of the pass signals of the frequency-side branch circuit 140 (signals in the first and second pass bands) distributed in a wide band, the first The signals in the first and second passbands leak to the high frequency side branch circuit 160. Therefore, in one embodiment of the present invention, the impedance of the single low frequency side branch circuit 140 is adjusted so as to cancel the influence of the high frequency side branch circuit 160 on the matching state of the low frequency side branch circuit 140. The As a result, even when the pass band extends over a wide band, the pass signal can be transmitted while maintaining the matching state.

Further, the duplexer 100 according to the embodiment of the present invention described above can reduce the amount of phase shift of the input signal as compared with the duplexer described in Patent Document 1 in which distributed constant lines are provided in multiple stages. As a result, the insertion loss of the passing signal can be kept low. Moreover, the line length of the distributed constant lines 104 and 106 can be shortened, and the duplexer 100 can be miniaturized. As described above, the duplexer 100 according to the embodiment of the present invention can separate a multiband signal into three frequency bands while keeping the insertion loss low.

Next, a duplexer according to another embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing a duplexer 400 according to another embodiment of the present invention. 1 that are substantially the same as the components of the duplexer 100 in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted as appropriate. In the duplexer 400, the SAW filter 114 and the SAW filter 404 are connected in parallel at the subsequent stage of the distributed constant line 106. Between the SAW filter 404 and the SAW filter 114 and the distributed constant line 106, a matching circuit 402 including a lumped constant reactance element such as a capacitor or an inductor is disposed. The signal that has passed through the SAW filter 404 is output from the output terminal 406 to a receiver at the subsequent stage.

The SAW filter 404 has a pass band on the same side as the third pass band outside the frequency band including the first and second pass bands. The pass band of the SAW filter 404 is, for example, 2400-2480 MHz. 2400-2480 MHz is a frequency band assigned to Bluetooth (“Bluetooth” is a registered trademark of Bluetooth SIG, INC.) (Hereinafter, the pass band of the SAW filter 404 is referred to as “fourth pass band”). Sometimes called). The fourth pass band is on the high frequency side outside the frequency band including the first pass band 869-894 MHz and the second pass band 1574-1576 MHz (that is, the lower limit of the first pass band). The SAW filter 404 is also located on the high frequency side of the 869 MHz to 1576 MHz frequency band having the lower frequency end of 869 MHz and the upper limit of the second pass band of 1576 MHz. Are connected in parallel with a SAW filter 114 having

The matching circuit 402 includes a capacitor, an inductor, or a combination thereof, which is a lumped element type reactance element. The arrangement and element values of the reactance elements constituting the matching circuit 402 are determined based on the same policy as that of the matching circuit 108, for example. That is, the matching circuit 402 assumes that there is no influence by the reactance element included in the low-frequency side branching circuit 140, and the reactance component of the input impedance of the high-frequency side branching circuit 460 is equal to the third passband and the fourth passband. Designed to have opposite polarities in the passband. Due to the function of the matching circuit 402, the input impedance of the high frequency side branching circuit 460 is 50Ω in the third passband, and the resistance component is almost the same as the characteristic impedance of the transmission line, and the reactance component is inductive or capacitive. Yes, the resistance component of the fourth pass band is approximately 50Ω, and the reactance component has the opposite polarity to the reactance component in the third pass band. That is, if the reactance component (third reactance component) of the impedance of the high frequency side branching circuit 460 in the third pass band is capacitive, the reactance component (fourth reactance component) in the fourth pass band becomes inductive. Become. On the other hand, if the third reactance component is inductive, the fourth reactance component is capacitive. Thus, the impedance of the high-frequency side branching circuit 460 alone in the third and fourth passbands is at a position rotated from the matching state to the capacitive region or the inductive region substantially along the isoconductance circle.

Similarly to the distributed constant line 106, the distributed constant line 104 has the low frequency side branch circuit 140 replaced with the high frequency side branch circuit 460 in the third and fourth passbands according to the polarities of the third and fourth reactance components. The phase of the input signal from the input terminal 102 is rotated so as to function as an inductor or a capacitor. For example, when the low frequency side branch circuit 140 is designed so that the third reactance component is capacitive and the fourth reactance component is inductive, the low frequency side branch circuit 140 is an inductor in the third passband. And the input signal is phase rotated so that it functions as a capacitor in the fourth passband. By combining the low-frequency side branch circuit 140 configured in this way with the high-frequency side branch circuit 460, both the third and fourth reactance components approach “0”. In this manner, the duplexer 400 according to the embodiment of the present invention can perform impedance matching with higher accuracy than the case of the high frequency side demultiplexing circuit 460 alone.

As the SAW filter 404, a SAW filter whose pass band is a band other than the above-mentioned 2400-2480 MHz can be used. For example, a filter whose pass band is a frequency band close to the third pass band corresponding to band I can be used. In this case, the matching circuit 402 is configured such that the reactance component of the input impedance of the high frequency side branching circuit 460 has the same polarity in the third passband and the fourth passband. As a result, the input impedance of the high-frequency side branching circuit 460 is 50Ω in the third and fourth passbands, the resistance component of which is almost the same as the characteristic impedance of the transmission line, and the reactance component is inductive or capacitive. Become. The distributed constant line 104 rotates the phase of the input signal from the input terminal 102 so that the low-frequency side branching circuit 140 functions as an inductor or a capacitor with respect to the signals in the third and fourth passbands. . Whether to function as an inductor or a capacitor is determined according to the polarities of the third and fourth reactance components. For example, when the third and fourth reactance components are capacitive, the phase of the input signal is rotated so that the low frequency side branching circuit 140 functions as an inductor in the third and fourth passbands. Conversely, when the third and fourth reactance components are inductive, the phase of the input signal is rotated so that the low frequency side branching circuit 140 functions as a capacitor in the third and fourth passbands. By combining the low-frequency side branch circuit 140 configured in this way with the high-frequency side branch circuit 460, both the third and fourth reactance components approach “0”. In this manner, the duplexer 400 according to the embodiment of the present invention can perform impedance matching with higher accuracy than the case of the high frequency side demultiplexing circuit 460 alone.

The input impedance in the fourth pass band of the high frequency side branching circuit 460 may be adjusted so that the resistance component is approximately 50Ω and the reactance component is approximately “0”. In this case, in order to prevent the signal in the fourth pass band from leaking to the low frequency side branch circuit 140, the impedance in the fourth pass band of the low frequency side branch circuit 140 is completely opened by the distributed constant line 106. Adjusted to In another embodiment, the input impedance in the third pass band of the high frequency side branching circuit 460 is adjusted so that the resistance component is approximately 50Ω and the reactance component is substantially “0”. The impedance in the third pass band may be adjusted to be completely open by the distributed constant line 106.

As described above, the duplexer 400 according to the embodiment of the present invention can separate a multiband signal into four frequency bands while keeping insertion loss low.

Next, a duplexer according to another embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a duplexer 500 in another embodiment of the invention. Among the components of the duplexer 500, those substantially the same as the components of FIG. 1 or FIG. 4 are denoted by the same reference numerals as the corresponding components of FIG. 1 or FIG. Omitted. In the duplexer 500, SAW filters 114, 204, and 504 are arranged in parallel in the high frequency side branch circuit 560. The SAW filter 504 has a pass band, for example, 1930-1990. 1930-1990 MHz is a frequency band allocated for reception of UMTS band II (hereinafter, may be referred to as “fifth pass band”). The signal that has passed through the SAW filter 504 is output from the output terminal 506 to a subsequent receiver or the like. The SAW filter 504 has a pass band on the high frequency side outside the frequency band including the first pass band 869 to 894 MHz and the second pass band 1574 to 1576 MHz.

Between the SAW filters 114, 204, and 504 and the distributed constant line 106, a matching circuit 502 including a lumped constant type reactance element is disposed. The arrangement and element values of the reactance elements constituting the matching circuit 502 are determined based on the same policy as in the matching circuit 402. In one embodiment of the present invention, the fifth pass band corresponding to UMTS band II is close to the third pass band corresponding to band I. In this case, with respect to the input impedance of the high frequency side branching circuit 560, the reactance component has the same polarity in the third passband and the fifth passband, and in the third passband and the fourth passband. They are adjusted to have opposite polarities. Due to the function of the matching circuit 502, the input impedance of the high-frequency side branching circuit 560 is 50Ω in the third and fifth passbands, the resistance component of which is almost the same as the characteristic impedance of the transmission line, and both reactance components are induced. The resistance component of the fourth passband is approximately 50Ω, and the reactance component has a polarity opposite to that of the reactance component in the third and fifth passbands. In the present specification, the reactance component of the input impedance in the fifth pass band of the high frequency side branching circuit 560 may be referred to as a fifth reactance component.

The distributed constant line 104 adjusts the phase of the input signal from the input terminal 102 so that the low-frequency side branching circuit 140 functions as an inductor or a capacitor with respect to the signals in the third, fourth, and fifth passbands. Rotate. Whether to function as an inductor or a capacitor is determined according to the polarities of the third, fourth, and fifth reactance components. For example, when the high frequency side branch circuit 560 is designed such that the third and fifth reactance components are capacitive and the fourth reactance component is inductive, the low frequency side branch circuit 140 is the third and fifth The phase of the input signal is rotated so that it functions as an inductor in the fourth passband and as a capacitor in the fourth passband. By combining the low-frequency side branch circuit 140 configured in this way with the high-frequency side branch circuit 560, impedance matching can be performed with higher accuracy than in the case of the high-frequency side branch circuit 560 alone.

The frequency characteristic of the input impedance of the low frequency side branching circuit 140 in the duplexer 500 designed in this way is illustrated in the Smith chart of FIG. FIG. 2 shows the input impedance of the low frequency side branching circuit 140 alone. In the figure, markers M1 and M2 represent the center frequencies of the first and second passbands, respectively. As shown in the figure, the input impedance of the low frequency side branching circuit 140 is approximately 50Ω at the center frequency (M1) of the first passband and capacitive by the distributed constant line 104 and the matching circuit 108. And has a resistance component of approximately 50Ω and an inductive reactance component at the center frequency (M2) of the second passband. In this way, the impedance of the low frequency side branching circuit 140 alone in the first and second passbands rotates from the matching state (the center of the Smith chart) to the capacitive region or the inductive region substantially along the equal resistance circle. It is plotted at the position.

FIG. 3 illustrates frequency characteristics of the input impedance of the high frequency side branch circuit 560 in the duplexer 500. FIG. 3 shows an example of the input impedance of the high frequency side branch circuit 560 when the input impedance of the low frequency side branch circuit 140 is capacitive in the first passband as shown in FIG. In the figure, markers M1 and M2 represent the center frequencies of the first and second passbands, respectively. The high frequency side branching circuit 560 functions as an inductor with respect to a signal in a frequency band included in the inductance condition region 302 in FIG. The inductance condition region 302 is located on the relatively high impedance side of the inductive region of FIG. In the example shown in FIG. 3, since the frequency band corresponding to the first pass band is included in the inductance condition region 302, the first pass band signal transmitted through the low frequency side branching circuit 140 is Thus, the high frequency side branching circuit 560 functions as an inductor. On the other hand, the high frequency side branching circuit 560 functions as a capacitor for a signal in a frequency band included in the capacitance condition region 304 in FIG. The capacitance condition region 304 is located on the relatively high impedance side of the capacitive region of FIG. In the example shown in FIG. 3, since the frequency band corresponding to the second pass band is included in the capacitance condition region 304, the signal in the second pass band transmitted through the low frequency side branching circuit 140 is used. Thus, the high frequency side branching circuit 560 functions as a capacitor.

By combining the high-frequency side branching circuit 560 configured in this way with the low-frequency side branching circuit 140, the high-frequency side branching circuit 560 functions as an inductor for the signal in the first passband. Due to the function of the inductor, the impedance of the first passband indicated by M1 in FIG. 2 moves to the vicinity of the center of the Smith chart in the inductive region direction along the equal conductance circle. Further, since the high frequency side branching circuit 560 functions as a capacitor for the signal in the second pass band, the impedance of the second pass band indicated by M2 in FIG. 2 is in the direction of the capacitance region along the isoconductance circle. Move to near the center of the Smith chart. In this way, by combining the high frequency side branch circuit 560 with the low frequency side branch circuit 140, matching can be performed with higher accuracy than in the case of the low frequency side branch circuit 140 alone. With respect to the duplexers 100 and 400, matching can be performed with high accuracy by combining the low frequency side branch circuit and the high frequency side branch circuit according to the same principle.

Next, another example of impedance adjustment in the fifth passband of the high frequency side branching circuit 560 will be described. The input impedance in the fifth passband of the high frequency side branching circuit 560 may be adjusted so that the resistance component is approximately 50Ω and the reactance component is approximately “0”. In this case, in order to prevent the signal in the fifth pass band from leaking to the low frequency side branch circuit 140, the impedance in the fifth pass band of the low frequency side branch circuit 140 is completely opened by the distributed constant line 106. Adjusted to Since the fifth pass band is located between the third pass band and the fourth pass band, the input impedance of the low frequency side branching circuit 140 is adjusted to be inductive in the third pass band, and the fourth pass It is possible to adjust to a high impedance (fully open) close to infinity in the fifth pass band, while adjusting to the capacitive in the band. By connecting the low-frequency side branching circuit 140 configured in this way to the high-frequency side branching circuit 560, the third and fourth reactance components are respectively “0” without degrading the matching state in the fifth passband. The high-frequency side branching circuit 560 can be accurately matched in each of the third, fourth, and fifth passbands.

FIG. 6 is an equivalent circuit diagram of the duplexer 500. As shown in the figure, the matching circuit 108 includes a capacitor 604 disposed between the connection point P1 between the SAW filter 110 and the SAW filter 112 and the SAW filter 110, and a connection point between the connection point P1 and the capacitor 604. And an inductor 602 disposed between the ground and the ground. The element values of these capacitors and inductors are determined so that the reactance component of the input impedance of the low frequency side branching circuit 140 has opposite polarities in the first passband and the second passband. For example, the inductance value of the inductor 602 is 3 nH, and the capacitance of the capacitor 604 is 4 pF. The line length of the distributed constant line 106 is, for example, 16.25 mm.

The matching circuit 502 is connected to a capacitor 606 disposed between the connection point P2 of the SAW filters 114, 204, and 504 and the SAW filter 114, and a capacitor 612 disposed between the connection point P2 and the SAW filter 204. A capacitor 618 disposed between the point P2 and the SAW filter 504, an inductor 608 disposed between a connection point between the capacitor 606 and the SAW filter 114 and the ground, and terminals on both sides of the capacitor 612 and the ground Inductors 610 and 614 respectively disposed between them, and inductors 616 and 620 respectively disposed between terminals on both sides of the capacitor 618 and the ground. The element values of these capacitors and inductors are such that the reactance components of the input impedance of the high frequency side branching circuit 560 have opposite polarities in the third passband and the fourth passband, and the third passband and the fifth passband Are set to have the same polarity in each pass band. For example, the capacitors 606, 612, and 618 have capacitances of 3pF, 4pF, and 3pF, respectively, and the inductors 608, 610, 614, 616, and 620 have inductance values of 3nH, 6.5nH, 15nH, 2nH, and 8nH, respectively. The line length of the distributed constant line 104 is 15.25 mm.

The SAW filters 110, 114, and 504 are configured to convert an input unbalanced signal into a balanced signal and output the balanced signal. For example, the SAW filter 114 includes a pair of balanced output terminals 634 and 636, and an inductor 622 for matching impedances when the balanced output terminals 634 and 636 are viewed from the SAW filter 114 side is disposed between these terminals. Similarly, the SAW filter 504 includes a pair of balanced output terminals 640 and 642, and an impedance matching inductor 626 is disposed between these terminals. The inductance values of the inductors 622 and 626 are, for example, 8 nH and 10 nH, respectively. As is clear from the comparison between FIGS. 5 and 6, the output terminal 120 includes balanced output terminals 634 and 636, and the output terminal 506 includes balanced output terminals 640 and 642. It is not always necessary to provide an inductor between the balanced output terminals. For example, the SAW filter 110 includes a pair of balanced output terminals 628 and 630, but no inductor is disposed between these terminals.

An inductor 624 is disposed between a connection point between the SAW filter 204 and the output terminal 638 and the ground. The inductor 624 matches the impedance of the SAW filter 204 viewed from the output terminal 638. The inductance value of the inductor 624 is, for example, 10 nH.

FIG. 7 is a Smith chart showing the impedance viewed from the input terminal 102 of the duplexer 300 according to the embodiment of the present invention. The impedance shown in FIG. 7 was measured by sweeping the frequency from 500 MHz to 3 GHz. As is clear from FIG. 7, the markers M1-M5 corresponding to the first to fifth pass bands are all distributed in the vicinity of 50Ω, and the impedances are matched in each of the first to fifth pass bands. It was confirmed that

8 to 12 are graphs showing simulation results of attenuation characteristics of the duplexer 500 represented by the equivalent circuit diagram of FIG. FIG. 13 is an enlarged graph showing a part of the simulation results shown in FIGS. These attenuation characteristics are obtained from Agilent Technologies, Inc., headquartered in California, USA. This is simulated using the circuit simulator ADS. 8 to 13, the horizontal axis represents the frequency in GHz, and the vertical axis represents the magnitude of the S parameter (S21) indicating the attenuation characteristic in dB. 8, the curve 801 represents the attenuation characteristic between the input terminal 102 and the output terminal 116, the curve 901 in FIG. 9 represents the attenuation characteristic between the input terminal 102 and the output terminal 118, and the curve 1001 in FIG. In FIG. 11, the curve 1101 represents the attenuation characteristic between the input terminal 102 and the output terminal 406, and in FIG. 12, the curve 1201 represents the attenuation characteristic between the input terminal 102 and the output terminal 506. .

As is clear from FIGS. 8 and 13, the attenuation between the input terminal 102 and the output terminal 116 is sufficiently small at about 2.8 dB at 869 to 894 MHz allocated to the band V of UMTS, and the other bands Big enough. As is clear from FIGS. 9 and 13, the attenuation between the input terminal 102 and the output terminal 118 is sufficiently small at about 1.6 dB in 1574 to 1576 MHz assigned to the GPS L1 band. Large enough in the bandwidth. As is clear from FIGS. 10 and 13, the attenuation between the input terminal 102 and the output terminal 120 is sufficiently small at about 3.2 dB at 2110-2170 MHz allocated to the band I of UMTS. Big enough. As is apparent from FIGS. 11 and 13, the attenuation between the input terminal 102 and the output terminal 206 is sufficiently small at about 3.8 dB at 2400-2480 MHz allocated to Bluetooth, and is sufficiently large in other bands. large. Finally, as is apparent from FIGS. 12 and 13, the attenuation between the input terminal 102 and the output terminal 506 is sufficiently small at about 3.2 dB in 1930-1990 MHz allocated to the band II of UMTS. Large enough in other bands. Thus, the insertion loss when the multiband signal on which the UMTS band I, band II, band V, GPS, and Bluetooth signals are superimposed using the duplexer 500 is demultiplexed by 5 is Small enough as a vessel.

The circuit configuration of the duplexer shown in FIG. 1, FIG. 4, or FIG. 5 can be changed as appropriate. For example, one or more SAW filters can be added as appropriate in addition to the SAW filters explicitly shown in each figure. For example, in the low frequency side demultiplexing circuit 140 of the demultiplexer 500, by arranging another SAW filter in parallel with the SAW filters 110 and 112, the received signal can be demultiplexed into six frequency bands. For example, a SAW filter having a pass band (hereinafter also referred to as “sixth pass band”) at 925 to 960 MHz can be arranged in parallel with the SAW filters 110 and 112. 925 to 960 MHz corresponds to a frequency band allocated for reception of UMTS band VIII. Since the first passband and the sixth passband are relatively close to each other, the impedance in the sixth passband of the low frequency side branching circuit 140 seems to have the same polarity as the impedance of the first passband. Can be adjusted. In this case, the input impedance of the low frequency side branching circuit 140 is 50Ω in which the resistance component is substantially the same as the characteristic impedance of the transmission line in the first and sixth pass bands, and the reactance component is inductive or capacitive. The resistance component in the second passband is approximately 50Ω, and the reactance component has the opposite polarity to the reactance component in the first and sixth passbands.

In another example of impedance adjustment of the sixth pass band, the input impedance of the low frequency side branching circuit 140 in the sixth pass band is such that the resistance component is approximately 50Ω and the reactance component is substantially “0”. You may adjust. In this case, the impedance in the sixth pass band of the high frequency side branching circuit 560 is adjusted to be completely open by the distributed constant line 106. Thus, since the sixth passband is located between the first passband and the second passband, the first passband is adjusted to be inductive and the second passband is adjusted to be capacitive. In this case, it is possible to adjust to the full opening located between them. *

The embodiments of the present invention are not limited to the modes explicitly described above, and various changes can be made. For example, in addition to those explicitly pointed out in this specification, a SAW filter can be added as appropriate. As an example, a SAW filter having a pass band of UMTS band III can be added to the high frequency side branch circuits 160, 460, 560, and a SAW filter having a pass band of UMTS band XI is used as the low frequency side branch circuit. 140 can be added. In this way, the received signal can be separated into 7 or 8 different frequency bands. The pass band of the SAW filter is not limited to that specified in the present specification, and a filter having a pass band corresponding to the frequency band of the signal to be demultiplexed is used as appropriate.

The structure of each duplexer demonstrated in this specification is an illustration, The circuit structure can be changed suitably. For example, instead of the distributed constant lines 104 and 106, a matching circuit composed of distributed constant elements is provided, the phase of the input signal is adjusted by this matching circuit, and the high frequency side branch circuit 160 is connected to the low frequency side branch circuit 140. May function as an inductor or a capacitor. The distributed constant lines 104 and 106 may be omitted, and the matching circuits 108, 402, and 502 may be directly connected to the input terminals.

The SAW filters 110, 112, 114, 404, and 504 may be dielectric filters. The duplexer according to the present invention can be mounted on various wireless communication devices other than the mobile phone. The duplexer according to the present invention can be miniaturized by being built in an LTCC (low temperature co-fired ceramics) multilayer circuit board.

In addition, various modifications can be made to the above-described embodiment without departing from the spirit of the present invention.

100, 400, 500 splitter 140 Low frequency side branch circuit 160, 460, 560 High frequency side branch circuit 104, 106 Distributed constant line 108, 402, 502 Matching circuit 110, 112, 114, 404, 504 SAW filter 604 , 606, 612, 618 Capacitors 602, 608, 610, 614, 616, 620, 622, 624, 626 Inductors

Claims (15)

An input terminal for inputting a received signal from the antenna;
A first branching circuit disposed between the input terminal and the first and second output terminals;
A second branching circuit disposed between the input terminal and a third output terminal;
With
The first branching circuit includes:
A first filter disposed between the input terminal and the first output terminal and having a first passband;
A second filter disposed between the input terminal and the second output terminal and having a second passband;
Including
The second branching circuit is disposed between the input terminal and the third output terminal, and has a third passband outside a frequency band including the first and second passbands. Including three filters,
The input impedance of the first branching circuit has an inductive or capacitive first reactance component in the first passband and has a polarity opposite to that of the first reactance component in the second passband. Has two reactance components,
The input impedance of the second branching circuit is capacitive in the first passband and inductive in the second passband when the first reactance component is inductive, and the first Inductive in the first passband and capacitive in the second passband when the reactance component is capacitive;
Duplexer. The second demultiplexing circuit comprises:
A fourth passband disposed between the input terminal and the fourth output terminal and having a fourth passband on the same side as the third passband outside the frequency band including the first and second passbands; Further comprising four filters,
The input impedance of the second branching circuit has an inductive or capacitive third reactance component in the third passband and has a polarity opposite to that of the third reactance component in the fourth passband. Has 4 reactance components,
The input impedance of the first branching circuit is capacitive in the third passband and inductive in the fourth passband when the third reactance component is inductive, and the third Inductive in the third passband and capacitive in the fourth passband when the reactance component is capacitive;
The duplexer according to claim 1. The second demultiplexing circuit comprises:
A fourth passband disposed between the input terminal and the fourth output terminal and having a fourth passband on the same side as the third passband outside the frequency band including the first and second passbands; Further comprising four filters,
The input impedance of the second branching circuit has a fourth reactance component having an inductive or capacitive third reactance component in the third passband and having the same polarity as the third reactance component in the fourth passband. Having a reactance component;
The input impedance of the first branching circuit is capacitive in the third and fourth passbands when the third and fourth reactance components are inductive, and the third and fourth reactance components Is inductive in the third and fourth passbands when is capacitive,
The duplexer according to claim 1. The second branching circuit is disposed between the input terminal and the fourth output terminal, and is on the same side as the third pass band outside the frequency band including the first and second pass bands. Further includes a fourth filter having a fourth passband,
The input impedance of the second branching circuit has an inductive or capacitive third reactance component in the third passband, and the input terminal and the fourth output terminal in the fourth passband To match the characteristic impedance of
When the input impedance of the first branching circuit is a high impedance that is close to infinity in the fourth passband, and the third reactance component is inductive, a capacitance is provided in the third passband. And inductive in the third when the third reactance component is capacitive,
The duplexer according to claim 1. The second demultiplexing circuit is disposed between the input terminal and the fifth output terminal, and further includes a fifth filter having a fifth passband between the third and fourth passbands. Prepared,
An input impedance of the second branching circuit matches a characteristic impedance of the input terminal and the fifth output terminal in the fifth passband;
The input impedance of the first branching circuit is a high impedance close to infinity in the fifth passband,
The duplexer according to any one of claims 2 to 4. The third and fourth passbands outside the frequency band including the first and second passbands, wherein the second branching circuit is disposed between the input terminal and the fifth output terminal. And a fifth filter having a fifth passband on the same side as
An input impedance of the second branching circuit has a fifth reactance component having the same polarity as the third reactance component in the fifth passband;
The input impedance of the first branching circuit is capacitive in the fifth passband when the fifth reactance component is inductive and the input impedance of the first branch circuit is capacitive when the fifth reactance component is capacitive. Inductive in the fifth passband,
The duplexer according to any one of claims 2 to 4. The first filter is disposed between the input terminal and the sixth output terminal, and further includes a sixth filter having a sixth passband between the first and second passbands. Prepared,
An input impedance of the first branching circuit matches a characteristic impedance of the input terminal and the sixth output terminal in the sixth passband;
The input impedance of the second branching circuit is a high impedance close to infinity in the sixth passband;
The duplexer according to any one of claims 1 to 6. The first and second passbands are disposed between the input terminal and the sixth output terminal, and the first and second passbands are outside a frequency band including the third and fourth passbands. And a sixth filter having a sixth passband on the same side as
The input impedance of the first branching circuit has a sixth reactance component having the same polarity as the first reactance component in the sixth passband;
The input impedance of the second branching circuit is capacitive in the sixth passband when the sixth reactance component is inductive, and the input impedance of the second branch circuit is capacitive when the sixth reactance component is capacitive. Inductive in the sixth passband,
The duplexer according to any one of claims 1 to 6. The duplexer according to any one of claims 1 to 8, wherein the first demultiplexing circuit includes a first distributed constant line connected to the input terminal. The duplexer according to any one of claims 1 to 9, wherein the second demultiplexing circuit includes a second distributed constant line connected to the input terminal. A first capacitor disposed between a connection point of the first and second filters and the first filter;
A first inductor disposed between a terminal on the input terminal side of the first capacitor and ground;
The duplexer according to claim 1, comprising: A second capacitor disposed between a connection point of the third, fourth, and fifth filters and the third filter;
A third capacitor disposed between a connection point of the third, fourth, and fifth filters and the fourth filter;
A fourth capacitor disposed between a connection point of the third, fourth and fifth filters and the fifth filter;
A second inductor disposed between a connection point between the second capacitor and the third filter and ground;
Third and fourth inductors respectively disposed between terminals on both sides of the fourth capacitor and ground;
Fifth and sixth inductors respectively disposed between terminals on both sides of the fifth capacitor and ground;
The duplexer according to claim 5, further comprising: The duplexer according to any one of claims 7 to 12, wherein at least one of the first to sixth filters is a surface acoustic wave filter. The duplexer according to any one of claims 7 to 12, wherein at least one of the first to sixth filters is a dielectric filter. A wireless communication device comprising the duplexer according to any one of claims 1 to 14.

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