JP2007019696A - High-frequency switching circuit, radio equipment, and signal path switching unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency switching circuit, whose frequency band is made wide and which has small passage loss and leakage, radio equipment, and a signal path switching unit. <P>SOLUTION: One of a plurality of input/output terminals 100, 200, ..., N00 is selectively connected to another terminal 1000, and transmission lines 101, 201, ..., N01 are connected between the plurality of input/output terminals and the terminal 1000; and series resonance circuit networks 102, 202, ..., N02, each having a varactor for switching and inductive reactance resonating with the varactor in series at a necessary frequency previously specified when the varactor is off and parallel resonance circuit networks 103, 203, ..., N03, each having capacitive reactance resonating with the inductive reactance in parallel at the necessary frequency are connected respectively between the plurality of input/output terminals and the ground. The capacity value of the capacitive reactance set equal to the capacity value at the varactor being off. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-frequency switch circuit, a wireless device, and a signal path switch, and more particularly, a high-frequency switch circuit in a frequency band from a microwave band to a millimeter wave band, and the high-frequency switch for switching between an antenna and a signal transmission / reception circuit. The present invention relates to a radio device equipped with a circuit, and a signal path switch equipped with the high-frequency switch circuit for switching a signal path.

  In a wireless communication system, an RF switch (high frequency switch) is used for switching transmission / reception and switching signal paths when sharing an antenna and plays an important role. In particular, since the switch for transmission / reception switching is located between the transmission amplifier or the low noise amplifier and the antenna, the insertion loss, isolation, frequency characteristics, distortion characteristics, etc. of the switch greatly affect the performance of the system. . The influence of the switch insertion loss directly causes deterioration of transmission power and reception NF (Noise Figure: Noise figure), and the influence of low isolation causes wraparound of the signal and occurrence of spurious.

  Therefore, the RF switch is an important device that affects the overall performance of the apparatus. In particular, in the quasi-millimeter wave band and higher, other RF circuits have no performance margin, so the importance of the RF switch is further increased, and low loss, high isolation, and high breakdown voltage are required. Currently, most switch elements of the quasi-millimeter wave band or more used at a practical level are mounted with PIN (p-intrinsic-n) diode parts that can obtain low loss characteristics.

  However, as the frequency increases, performance degradation due to chip-to-chip connection becomes significant, and high-speed switching of switches is required as communication speed increases, and there is a demand for miniaturization and portability to reduce power consumption. Expectations for MMIC (Monolithic Microwave IC) switches using FET (Field Effect Transistor) elements from the standpoints of becoming stronger and requiring lower product costs Is growing.

  For example, as shown in FIG. 12, a SPDT (Single Pole Double Throw) switch has been developed as an MMIC switch using an FET element, as shown in FIG. . That is, as an SPDT switch using an FET, a type of series / parallel FET as shown in FIG. 12A, or a combination of a transmission line and a parallel FET as shown in FIG. There is something.

12A and 12B, 1 is an antenna connection terminal connected to the antenna, 2 is a transmission circuit connection terminal connected to the transmission circuit, 3 is a reception circuit connection terminal connected to the reception circuit, Reference numerals 4, 5, 6, and 7 denote switch switching control terminals.

  Reference numerals 21 and 26, 31 and 36 are FETs serving as switching elements on the transmission side and the reception side, respectively, and 25 and 27, 35 and 37 are high resistances for cutting off high-frequency signals on the transmission side and reception side, respectively. Numerals 22 and 32 are quarter wavelength transmission lines using distributed constant lines such as microstrip lines. The quarter-wave transmission lines 22 and 32 function as impedance converters that invert the impedance state.

  In these types shown in FIGS. 12A and 12B, the gate voltages of the FETs 21, 26, 31, and 36 are controlled by control signals from the switch switching control terminals 4, 6, 5, and 7, respectively. Switch between drain and source to low impedance or high impedance, connect antenna connection terminal 1 to either input / output terminal of transmission circuit connection terminal 2 or reception circuit connection terminal 3 with low loss, and conversely The input / output terminal is set to an isolation state.

However, the impedance when the FETs 21, 26, 31, and 36 are OFF decreases by 1 / jωC _off with respect to the frequency due to the influence of the drain-source capacitance C _off . Therefore, at frequencies above the quasi-millimeter wave band, there is a problem that the impedance when the FET is OFF cannot be increased and isolation cannot be sufficiently achieved.

As a method for solving this problem, as described in Japanese Patent Laid-Open No. 8-213802 “High Frequency Switch Circuit” shown in Patent Document 1, an inductor is inserted in series with the FET, and the capacitance C _off when the FET is OFF There is a method of obtaining a high impedance when the FET is OFF by making the inductor and the series resonance.

FIG. 13 shows a circuit configuration of a conventional SPDT switch using resonance. In FIG. 13, the same parts as those in FIG. Reference numerals 29 and 39 denote inductors or inductive reactances connected in series with the FETs 21 and 31, respectively. 22B and 32B are transmission lines using distributed constant lines such as microstrip lines, but unlike FIG. 12B, the line length is a value larger than ¼ wavelength (the line impedance Z is the characteristic impedance Z _0. In this case, the transmission circuit connection terminal 2 and the reception circuit connection terminal 3 are connected via capacitive reactances 28 and 38, respectively, and the antenna connection terminal 1 is connected to the capacitive reactance 11. Connected through. The connection point with the antenna connection terminal 1 is connected to the ground via a resistor 12 having a large resistance value.

The inductive reactances 29 and 39 connected in series with the switching elements FETs 21 and 31 respectively have inductance values that are in series resonance with the drain-source capacitance C _off of the FETs 21 and 31 when the FETs 21 and 31 are OFF at a predetermined frequency. Has been adjusted. In the SPDT switch of FIG. 13, the FET 21 on the transmission side is turned off to cut off the connection between the antenna connection terminal 1 and the transmission circuit connection terminal 2, and the FET 31 on the reception side is turned on to turn on the antenna connection terminal 1 and the reception circuit connection terminal 3. FIG. 14 shows a configuration of a simple equivalent circuit when the two are connected with low loss.

In this example, at the frequency where ω = 1 / (L · C _off ) ^1/2 , the impedance of the series resonance portion of L of the inductive reactance 29 and the capacitive reactance C _off when the FET 21 is OFF is 0, From the antenna connection terminal 1, the transmission circuit connection terminal 2 side appears to be shorted to ground. For this reason, when the transmission-side FET 21 is turned off and the reception-side FET 31 is turned on at the above-described use frequency ω, it can be regarded as a more simplified equivalent circuit as shown in FIG. By optimizing the circuit network shown in FIG. 15 as a bandpass filter for a required frequency, it is possible to minimize the passage loss from the antenna connection terminal 1 to the reception circuit connection terminal 3 on the ON side.
JP-A-8-213802

  However, in the conventional high-frequency switch circuit shown in FIG. 13, in order to optimize the band-pass filter, the two transmission lines 22B and 32B used have high impedance, and the line length is ¼ wavelength or more. (Electric length is 90 degrees or more). Since such a transmission line has a narrow line width and a long length, the power loss of the signal by the line becomes large. In addition, when the filter characteristics are optimized, it is difficult to achieve impedance matching over a wide band.

FIG. 16 shows the equivalent of the conventional SPDT switch circuit of FIG. 13, that is, the equivalent circuit of the conventional high frequency switch circuit shown in FIG. 14, when 25 GHz is used as the required frequency, the ON side pass loss is minimized and the OFF side pass loss is maximized. As shown, the ON-side and OFF-side pass characteristics when each parameter is optimized are shown. According to the calculation results in which each parameter is optimized, the impedance of the transmission lines 22B and 32B is 84Ω, and the line length, that is, the electrical length is 118 degrees. The capacitance value C _off of the capacitive reactance when the FETs 21 and 31 are OFF is 0.086 pF, and the inductance value L of the inductive reactances 29 and 39 for series resonance at 25 GHz is 0.464 nH. . The capacity value _{C 1} of the capacitive reactance 28, 38 inserted respectively in the transmitting side and the receiving side 0.1 pF, the capacitance value _{C 2} of the capacitive reactance 11 connected to the antenna connection terminal 1 is a 3.0pF .

  As is apparent from FIG. 16, the frequency that can be passed with low loss when ON and the frequency that can be cut off when OFF are both in a narrow band, and furthermore, impedance matching is not well achieved. Also, the passage loss is as large as 0.1 dB or more. In addition, this calculation result does not take into account the loss of the transmission lines 22B and 32B at all, and therefore, actually, the passage loss is even larger.

  As described above, the conventional resonance type high frequency switch circuit has a problem that the frequency is in a narrow band and the passage loss is increased.

  The present invention has been made in view of such problems, and an object thereof is to provide a high-frequency switch circuit, a wireless device, and a signal switching device that widen the frequency band and that has low passage loss and leakage.

  The present invention comprises the following technical means in order to solve the above-mentioned problems.

  In the high-frequency switch circuit that selectively connects one of the plurality of input / output terminals to another terminal, the first technical means includes a transmission line between each of the plurality of input / output terminals and the other terminal. In addition, a variable capacitance element for switching between each of the plurality of input / output terminals and the ground, and series resonance with the variable capacitance element at a predetermined frequency specified when the variable capacitance element is switched off A series resonant network having an inductive reactance and a capacitive network having a capacitive reactance that resonates in parallel with the inductive reactance at the required frequency, respectively, and the capacitance value and switch of the capacitive reactance It is characterized in that the capacitance values of the variable capacitance elements when turned off can be the same value.

  In a high-frequency switch circuit that selectively connects one of a plurality of input / output terminals to another terminal, a second technical means includes a transmission line between each of the plurality of input / output terminals and the other terminal. In addition, a variable capacitance element for switching between each of the plurality of input / output terminals and the ground, and series resonance with the variable capacitance element at a predetermined frequency specified when the variable capacitance element is switched off Each having a series resonant network having an inductive reactance and a capacitive network having a capacitive reactance resonating in parallel with the inductive reactance at the required frequency. Having a capacitor, the capacitance value of the capacitive reactance is larger than the capacitance value of the capacitor, and the transmission line has a line length of Characterized in that less than a quarter wavelength at the main frequency.

  The third technical means uses a transistor, a diode, or a combination of a transistor and a diode as the variable capacitance element for switching in the high-frequency switch circuit described in the first or second technical means. It is characterized by.

  According to a fourth technical means, in the high-frequency switch circuit according to the third technical means, a transistor used as the variable capacitance element, a transistor having the same gate width as the diode, or a diode is used as the capacitive reactance. And

  According to a fifth technical means, in a wireless device that transmits and receives signals by switching between an antenna, a transmission circuit, and a reception circuit by a high-frequency switch circuit, the first to fourth technical means are used as the high-frequency switch circuit. Any one of the high-frequency switch circuits described above is used.

  According to a sixth technical means, in the signal path switcher for selectively switching a plurality of signal paths, the high-frequency switch circuit according to any one of the first to fourth technical means as a signal path selective switching means. It is characterized by using.

  According to the high-frequency switch circuit, the radio device, and the signal path switching device of the present invention, the inductive reactance is connected in series to the variable capacitance element serving as the switching element, and the high-frequency switch using LC series resonance at a predetermined frequency specified in advance. Since the circuit employs a configuration in which a capacitive reactance that resonates in parallel with the inductive reactance at the required frequency is employed, the following effects can be achieved.

  When a signal path is selectively switched from one input / output terminal to another input / output terminal, the input / output terminal set on the input side is set to the output side. Further, it is possible to reduce the signal passing loss to the input / output terminals, and to reduce the leakage of signals to the remaining input / output terminals that are not selected on either the input side or the output side.

  In addition, by matching the impedances of the ON side circuit and the OFF side circuit of the switching element, it is possible to achieve a wide band of pass characteristics.

  Furthermore, by adding a shunt capacitor to the high frequency switch circuit, it is possible to further reduce the size and loss of the high frequency switch circuit.

  Therefore, by installing such a high-frequency switch circuit in a wireless device or a signal path switching device, the insertion loss of the switch circuit can be reduced in a communication system having a wide frequency band from the microwave band to the millimeter wave band. It is possible to reduce signal leakage.

  Hereinafter, an example of the best embodiments of the high-frequency switch circuit, the wireless device, and the signal switching device according to the present invention will be described in detail with reference to the drawings regarding the high-frequency switch circuit.

  One embodiment of the circuit configuration of the high-frequency switch circuit of the present invention is shown in FIG. As shown in FIG. 1, a high-frequency switch circuit for selectively connecting any one of the plurality of input / output terminals 100, 200,..., N00, for example, the input / output terminal 100 to another terminal 1000. .., N01 are connected between another terminal 1000 and a plurality of input / output terminals 100, 200,..., N00 by distributed constant lines such as microstrip lines, respectively. .

  Further, between the plurality of input / output terminals 100, 200,..., N00 and the ground, a series having a variable capacitance element serving as a switching element and an inductive reactance that resonates in series with the OFF capacitance value of the variable capacitance element. Resonant networks 102, 202,..., N02 are connected to capacitive networks 103, 203,..., N03 having a capacitive reactance that resonates in parallel with the inductive reactance. Here, the capacitance values of the variable capacitance elements of the series resonant networks 102, 202,..., N02 when switched off and the capacitance values of the capacitive reactances of the capacitive networks 103, 203,. adjust. That is, the capacitive networks 103, 203,..., N03 constitute a parallel resonant network that resonates in parallel with the inductive reactances of the series resonant networks 102, 202,.

  In order to explain the operating principle of the high-frequency switch circuit of the present invention shown in FIG. 1, as an example of a plurality of input / output terminals, an SPDT switch having two input / output terminals that can be selectively connected to another terminal Will be described. FIG. 4 shows a circuit configuration example of the SPDT switch of this embodiment. In FIG. 4, the same parts as those of the conventional high-frequency switch circuit of FIG. 12B are denoted by the same reference numerals, detailed description thereof is omitted, and newly added parts will be described below. . Reference numerals 23 and 33 denote inductors or inductive reactances connected in series with the FETs 21 and 31, respectively. Reference numerals 24 and 34 denote conductances or capacitive reactances connected in parallel to the FETs 21 and 31 and the inductive reactances 23 and 33, respectively.

The correspondence between FIG. 4 and FIG. 1 is as follows. The antenna connection terminal 1 in FIG. 4 corresponds to the input / output terminal 1000 in FIG. 1, and the transmission circuit connection terminal 2 and the reception circuit terminal 3 correspond to, for example, the input / output terminals 100 and 200 in FIG. Further, the FET 21, the inductive reactance 23, the FET 31, and the inductive reactance 33 correspond to, for example, the series resonant networks 102 and 202 in FIG. 1, respectively, and the switching elements FET 21 and 31 that are variable capacitance elements are capacitive when OFF. The inductance values of the inductive reactances 23 and 33 are adjusted so as to form a series resonance circuit at a required frequency specified in advance by the reactance C _off and the inductive reactances 23 and 33.

On the other hand, the capacitive reactances 24 and 34 correspond to the capacitive networks 103 and 203 in FIG. 1, respectively, and the capacitive reactances so as to form a parallel resonant circuit at the required frequency with the inductive reactances 23 and 33. The capacitance values 24 and 34 are adjusted. Reference numerals 22 and 32 denote transmission lines using distributed constant lines such as microstrip lines, and as in FIG. 12B, the line length is ¼ wavelength (electrical length 90 degrees), and the line impedance Z is the characteristic impedance Z. The case of ₀ is shown.

In the SPDT switch circuit of FIG. 4, the transmission-side FET 21 is turned off to cut off the connection between the antenna connection terminal 1 and the transmission circuit connection terminal 2, and the reception-side FET 31 is turned on to connect the antenna connection terminal 1 to the reception circuit connection terminal. FIG. 5 shows a configuration of a simple equivalent circuit in the case where 3 is connected with low loss. As shown in FIG. 5, the inductive reactance 23 on the transmission side is connected to the ground via the capacitive reactance C _off when the switching element FET 21 is OFF, but the inductive reactance 33 on the receiving side is connected to the switching element FET 31. Since the drain and source of the semiconductor device are in a conductive state, when used in a high frequency region, the state is the same as when directly connected to the ground.

In this example, the inductance L of the inductive reactance 23 and the capacitance when the FET 21 is OFF are set on the transmission side where the switching element FET 21 is set to the OFF side at a frequency where ω = 1 / (L · C _off ) ^1/2. The impedance of the series resonance portion with the reactive reactance C _off becomes 0, and the transmission circuit connection terminal 2 appears to be shorted to the ground. Therefore, when the transmission line 22 having the impedance inverting function has a frequency of ω = 1 / (L · C _off ) ^1/2 and a length of ¼ wavelength, the antenna connection terminal 1 The impedance on the transmission side appears to be almost infinite, and is in an open state, that is, an isolated state.

On the other hand, on the receiving side where the switching element FET 31 is set to the ON side, the drain and source of the switching element FET 31 are in a conductive state, and in the high frequency region, the inductance L of the inductive reactance 33 is equal to the state connected to the ground. Become. Therefore, the antenna connection terminal 1 is connected to the reception circuit connection terminal 3 via the characteristic impedance Z ₀ of the transmission line 32. By matching with the impedance of the reception circuit, the reception circuit has a low loss. Can receive signals.

Further, when attention is paid to the capacitive reactances 24 and 34 connected in parallel with the inductive reactances 23 and 33 forming the series resonant network, at a frequency where ω = 1 / (L · C ₁ ) ^1/2. , the impedance of the parallel resonance part of the capacitance value _{C 1} of the inductance L and the capacitive reactance 24, 34 of the inductive reactance 23, 33 becomes infinite.

Therefore, at a frequency where ω = 1 / (L · C _off ) ^1/2 = 1 / (L · C ₁ ) ^1/2 , the equivalent circuit of FIG. From the terminal 1, the transmission circuit connection terminal 2 side in which the switching element FET21 is set to OFF is brought into a substantially completely isolated state, while the reception circuit connection terminal 3 side in which the switching element FET31 is set to ON is shown in FIG. Unlike the prior art shown in ( ₁₎ , only the line of impedance Z0 of the transmission line 32 is used, and further loss reduction is possible.

Therefore, when the impedance Z ₀ of the transmission lines 22 and 32 is set to the same value as the input / output impedances of the transmission circuit on the transmission circuit connection terminal 2 side and the reception circuit on the reception circuit connection terminal 3 side, the switching elements FET 21 and 31 It is possible to minimize the signal passing loss when the signal is ON.

Note that the equivalent circuit of FIG. 6 is established at a certain frequency of ω = 1 / (L · C _off ) ^1/2 = 1 / (L · C ₁ ) ^1/2 as described above. Therefore, when the SPDT switch circuit in this embodiment is used at a required frequency of 25 GHz, 20 GHz when each parameter is optimized to minimize the ON side passage loss and maximize the OFF side passage loss. FIG. 7 shows the ON-side and OFF-side pass characteristics in the frequency band of ˜30 GHz. According to the calculation result of optimization of each parameter, the impedance of the transmission lines 22 and 32 is 50Ω, the line length, that is, the electrical length is 90 degrees, and the capacitance value C _off of the capacitive reactance when the FETs 21 and 31 are OFF is 0. In the case of .33 pF, the capacitance value C ₁ of the capacitive reactances 24 and 34 connected in parallel is also 0.33 pF, and the inductance value L of the inductive reactances 29 and 39 for series resonance and parallel resonance at 25 GHz is 0.12 nH.

  The pass characteristic of the present embodiment shown in FIG. 7 is such that the pass loss on the ON side is smaller and the bandwidth is wider than the pass characteristic of the conventional SPDT switch shown in FIG. The reason for this is that in the SPDT switch of this embodiment in which capacitive reactances 24 and 34 that resonate in parallel with the inductive reactances 23 and 33 are arranged as shown in the characteristic graphs of the Smith charts of FIGS. Compared to the conventional SPDT switch, impedance matching between the ON side circuit portion and the OFF side circuit portion can be easily achieved in a relatively wide frequency band centering on the required frequency of 25 GHz.

FIG. 8 shows a calculation result of the impedance (Z1) of the OFF-side circuit portion on the transmission side and the impedance (Z2) of the ON-side circuit on the reception side for the conventional SPDT switch shown in FIG. In FIG. 8, 10 is an antenna-side load R _A , 20 is a transmission circuit load R _S , and 30 is a reception circuit load R _R. In FIG. 8, matching can be achieved when Z1 = Z2 ^* (conjugate complex number), but as shown in the Smith chart of FIG. 8, the ON side circuit portion and the OFF side circuit portion have a wide frequency band centered on 25 GHz. It can be seen that it is difficult to achieve matching.

On the other hand, FIG. 9 shows the calculation of the impedance (Z1) of the OFF-side circuit portion on the transmission side and the impedance (Z2) of the ON-side circuit portion on the receiving side for the SPDT switch according to one embodiment of the present invention shown in FIG. An example of the result is shown. In FIG. 9, 10 is the antenna side load R _A , 20 is the transmission circuit load R _S , and 30 is the reception circuit load R _R. As shown in the Smith chart of FIG. 9, in this example, Z1 = Z2 = 50Ω at the specified required frequency of 25 GHz, indicating a state where matching is achieved. It can also be seen that characteristics close to the matching condition Z1 = Z2 ^* (conjugate complex number) are easily obtained at frequencies of several GHz around the center of 25 GHz. As a result, the SPDT switch shown in the present embodiment has the characteristics that the ON-side pass loss is small, the broadband and the in-band inclination are small, as compared with the conventional SPDT switch.

  Further, in the high-frequency switch circuit of this embodiment, the transmission lines 22 and 32 having a frequency of 25 GHz, an impedance of 50Ω, and a line length of ¼ wavelength (electrical length of 90 degrees) are used. Compared with a conventional SPDT switch using transmission lines 22B and 32B having a length longer than ¼ wavelength, loss due to transmission lines 22 and 32 can be reduced.

  Next, as a different embodiment of the circuit configuration of the high-frequency switch circuit of the present invention, a more specific circuit configuration of FIG. 1 will be described with reference to FIG. 2, as the series resonant networks 102, 202,..., N02 in the high-frequency switch circuit of the present invention shown in FIG. 1, as shown in FIG. 4, the variable capacitance elements 102a, 202a,. , N02a and inductive reactances 102b, 202b,..., N02b are respectively connected in series, while the capacitive networks 103, 203,..., N03 shown in FIG. .., N03a using the variable capacitance elements 103a, 203a,..., N03a serving as switching elements, and a case where the inductive reactances 102b, 202b,.

  Here, the variable capacitance elements 102a, 202a,..., N02a and the variable capacitance elements 103a, 203a,..., N03a may be configured by transistors, diodes, or a combination thereof represented by FETs.

Further, as described above, in the high-frequency switch circuit of the present invention, the capacitance values C _off when the variable capacitance elements 102a, 202a,..., N02a that are in series resonance with the inductive reactances 102b, 202b,. .., N02b and the variable capacitance elements 103a, 203a,..., N03a that resonate in parallel with each other ideally have the same capacitance value when OFF.

  On the other hand, in general, when a capacitor is realized using the monolithic microwave integrated circuit MMIC, the minimum size is determined due to process limitations, so that it is very difficult to obtain a capacitance value of 0.1 pF or less. . For this reason, there is a method in which capacitors having a value larger than 0.1 pF are connected in parallel. However, if the capacitors are connected in many stages, the physical length of the capacitor becomes a problem or the area becomes large. There is also.

  In order to obtain the same capacitance value in both cases including such a case, it is effective to use a transistor or a diode having the same gate width as that of the switching element as a capacitive reactance for parallel resonance.

  Next, still another embodiment of the high-frequency switch circuit of the present invention will be described with reference to FIG. 3, except for the transmission lines 101a, 201a,..., N01a and the shunt capacitor 1001, it is the same as the high frequency switch circuit shown in FIG. The transmission lines 101a, 201a,..., N01a are transmission lines whose lengths are shortened to less than ¼ wavelength (electrical length is less than 90 degrees) at the required frequency, unlike the case of FIG. Thus, when shortening to a transmission line shorter than a quarter-wave transmission line, it is necessary to additionally insert a shunt capacitor as described in Japanese Patent No. 2666966 “Impedance Conversion Circuit”. In the embodiment, for example, transmission line 101a, 201a,..., N01a of transmission line 101a, 201a,. A method of adding a shunt capacitor 1001 to the input / output terminal 1000 side is shown in FIG.

  If this method of adding the shunt capacitor 1001 is used, it is possible to use a shorter line as the length of the transmission lines 101a, 201a,..., N01a, and the SPDT switch can be further reduced in size and loss. .

  FIG. 10 shows an SPDT switch circuit configuration example in which the SPDT switch shown in FIG. 4 is further added with a shunt capacitor 1001 (shown as capacitive reactance 13 in FIG. 10) on the antenna connection terminal 1 side. As an equivalent circuit in this case, similarly to the equivalent circuit shown in FIG. 5, the FET 21 on the transmission side is turned off to cut off the connection between the antenna connection terminal 1 and the transmission circuit connection terminal 2, and the FET 31 on the reception side is turned on to connect the antenna. A simple equivalent circuit configuration when the terminal 1 and the receiving circuit connection terminal 3 are connected with low loss is shown.

3, the capacitive reactance 13 (capacitance value C ₃ ) in FIG. 10 is the inductive reactance of the series resonant networks 102, 202,..., N02 shown in FIG. A role of performing parallel resonance with the inductive reactances 23 and 33 (inductance value L), and a role of shortening the transmission line lengths of the transmission lines 101A, 201a,..., N01a shown in FIG. It plays a smaller set the capacitance value _{C 3} than the capacitance value _{C 1} of the capacitive reactance 24 and 34.

When the SPDT switch circuit in this embodiment is used at a required frequency of 25 GHz, the frequency band of 20 GHz to 30 GHz when each parameter is optimized so as to minimize the ON side passage loss and maximize the OFF side passage loss. FIG. 11 shows the ON-side and OFF-side pass characteristics in FIG. According to the calculation results obtained by optimizing the parameters, the impedance of the transmission lines 22A and 32A is 81Ω, the line length, that is, the electrical length is 36 degrees, and the capacitance value C _off of the capacitive reactance when the FETs 21 and 31 are OFF is 0. In the case of .33 pF, the capacitance value C ₁ of the capacitive reactances 24 and 34 connected in parallel to the FETs 21 and 31 is 0.43 pF, and the capacitance value C ₃ of the newly added shunt capacitor is connected in parallel to the FETs 21 and 31, respectively. The inductance value L of the inductive reactances 29 and 39 for series resonance and parallel resonance at 25 GHz is 0.12 nH, which is 0.19 pF smaller than the capacitance value C ₁ of the capacitive reactances 24 and 34.

  The pass characteristic of the present embodiment shown in FIG. 11 is such that the ON side pass loss is smaller and the bandwidth is wider than the pass characteristic of the conventional SPDT switch shown in FIG.

  As described above, the high-frequency switch circuit of the present invention can broaden the frequency of a high-frequency signal and can reduce passage loss and leakage, and can be applied to various devices that handle high-frequency signals. can do. For example, by applying the high-frequency switch circuit of the present invention as a high-frequency switch circuit in a wireless device that transmits and receives signals by switching between an antenna, a transmission circuit, and a reception circuit, it is possible to reduce the bandwidth of signals, pass loss, and leakage. A high-performance wireless device that can be reduced can be configured. Alternatively, by using the high-frequency switch circuit of the present invention for a signal path switching unit that selectively switches a plurality of signal paths, a signal path switching unit capable of widening a signal, reducing passage loss and leakage is configured. Is also possible.

It is a block diagram which shows one Embodiment of the circuit structure of the high frequency switch circuit of this invention. It is a block diagram which shows embodiment from which the circuit structure of the high frequency switch circuit of this invention differs. It is a block diagram which shows further different embodiment of the circuit structure of the high frequency switch circuit of this invention. It is a block diagram which shows the structural example of the SPDT switch which is one Example of the high frequency switch circuit of this invention. FIG. 5 is an equivalent circuit diagram showing a configuration in which the SPDT switch of FIG. 4 is replaced with an equivalent circuit. FIG. 6 is an equivalent circuit diagram obtained by simplifying the equivalent circuit of FIG. 5. In the SPDT switch equivalent circuit of FIG. 5, at 25 GHz, ON side and OFF side 20 GHz to 30 GHz are optimized when each parameter is optimized so that the ON side passing loss is minimized and the OFF side passing loss is maximized. It is a characteristic view which shows the passage characteristic in a frequency band. It is a characteristic graph which shows the calculation result of the impedance (Z1) of the OFF side circuit part of a transmission side, and the impedance (Z2) of a ON side circuit of a receiving side about the conventional SPDT switch of FIG. 6 is a characteristic graph showing an example of calculation results of impedance (Z1) of an OFF-side circuit portion on the transmission side and impedance (Z2) of an ON-side circuit portion on the reception side for the SPDT switch that is an example of the present invention of FIG. FIG. 6 is an equivalent circuit diagram showing a configuration example further different from FIG. The SPDT switch equivalent circuit of FIG. 10 has an ON side and an OFF side of 20 GHz to 30 GHz when the parameters are optimized so that the ON side passage loss is minimized and the OFF side passage loss is maximized at 25 GHz. It is a characteristic view which shows the passage characteristic in a frequency band. It is a block diagram which shows the circuit structure of the SPDT switch using the conventional FET. It is a block diagram which shows the circuit structure of the SPDT switch using the conventional resonance. FIG. 14 is an equivalent circuit diagram showing a configuration in which the SPDT switch of FIG. 13 is replaced with an equivalent circuit. FIG. 15 is an equivalent circuit diagram in which the equivalent circuit of FIG. 14 is further simplified. The equivalent circuit of the conventional high-frequency switch circuit shown in FIG. 14 has an ON side and an OFF side when the parameters are optimized so that the ON side passage loss is minimized and the OFF side passage loss is maximized at 25 GHz. It is a characteristic view which shows a passage characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna connection terminal, 2 ... Transmission circuit connection terminal, 3 ... Reception circuit connection terminal, 4, 5, 6, 7 ... Switch switching control terminal, 10 ... Antenna side load, 11 ... Capacitive reactance, 12 ... Register, 13 ... capacitive reactance (shunt capacitor), 20 ... transmission circuit load, 21, 26 ... FET, 21a ... capacitive reactance when FET21 is OFF, 22 ... 1/4 wavelength transmission line, 22A ... transmission line with less than 1/4 wavelength 22B ... transmission line larger than ¼ wavelength, 23 ... inductive reactance, 24 ... capacitive reactance, 25,27 ... high resistance, 28 ... capacitive reactance, 29 ... inductive reactance, 30 ... receiver circuit load, 31, 36... FET, 32... 1/4 wavelength transmission line, 32A... Transmission line less than 1/4 wavelength, 32B... Transmission greater than 1/4 wavelength 33, inductive reactance, 34 ... capacitive reactance, 35, 37 ... high resistance, 38 ... capacitive reactance, 39 ... inductive reactance, 100, 200, ..., N00, 1000 ... input / output terminals, 101, 201 , ..., N01 ... transmission line, 101a, 201a, ..., N01a ... transmission line (less than ¼ wavelength), 102, 202, ..., N02 ... series resonant network, 102a, 202a, ..., N02a ... variable capacitance element 102b, 202b, ..., N02b ... inductive reactance, 103, 203, ..., N03 ... capacitive network, 103a, 203a, ..., N03a ... variable capacitance element, 1001 ... shunt capacitor.

Claims (6)

  In the high-frequency switch circuit that selectively connects one of the plurality of input / output terminals to another terminal, each of the plurality of input / output terminals has a transmission line between each of the plurality of input / output terminals, and the plurality of the plurality of input / output terminals. Between the input / output terminals and the ground, there is a variable capacitance element for switching and an inductive reactance that resonates in series with the variable capacitance element at a predetermined frequency when the variable capacitance element is switched off. A series resonant circuit, and a capacitive network having a capacitive reactance that resonates in parallel with the inductive reactance at the required frequency, respectively, and the capacitance value of the capacitive reactance and the variable capacitive element when switched off A high frequency switch circuit characterized by having the same capacitance value.   In the high-frequency switch circuit that selectively connects one of the plurality of input / output terminals to another terminal, each of the plurality of input / output terminals has a transmission line between each of the plurality of input / output terminals, and the plurality of the plurality of input / output terminals. Between the input / output terminals and the ground, there is a variable capacitance element for switching and an inductive reactance that resonates in series with the variable capacitance element at a predetermined frequency when the variable capacitance element is switched off. A series resonant network and a capacitive network having a capacitive reactance that resonates in parallel with the inductive reactance at the required frequency, respectively, and further includes a capacitor between the other terminal and ground. The capacitance value of the capacitive reactance is larger than the capacitance value of the capacitor, and the transmission line has a line length at the required frequency. High frequency switch circuit, characterized in that less than one wavelength of the frequency.   3. The high frequency switch circuit according to claim 1, wherein a transistor, a diode, or a combination of a transistor and a diode is used as the variable capacitance element for switching.   4. The high frequency switch circuit according to claim 3, wherein a transistor used as the variable capacitance element, a transistor having the same gate width as the diode, and a diode are used as the capacitive reactance.   The radio frequency switch circuit according to any one of claims 1 to 4 is used as the radio frequency switch circuit in a wireless device that transmits and receives signals by switching between an antenna, a transmission circuit, and a reception circuit by a radio frequency switch circuit. Wireless equipment characterized by   5. A signal path switching device for selectively switching a plurality of signal paths, wherein the high frequency switch circuit according to claim 1 is used as a signal path selective switching means. .

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