JP4641388B2 - High frequency switch circuit - Google Patents

Description

The present invention relates to a high-frequency switch circuits, in particular, it relates to a high-frequency switch circuits using PIN diodes as switching elements.

  In recent years, high-frequency switch circuits using PIN diodes are frequently used in communication devices that handle high frequency bands. FIG. 19A is a circuit diagram showing this type of conventional high-frequency switch, and FIG. 19B is an equivalent circuit diagram of the high-frequency switch of FIG. 19A in the OFF state. FIG. 20 is a frequency characteristic diagram of the high frequency switch of FIG. 19 in the on state and the off state.

  As shown in FIG. 19A, this high frequency switch is interposed between an input terminal IN for inputting a predetermined high frequency signal and an output terminal OUT for outputting it, and responds to a predetermined bias voltage in the forward direction. A PIN diode D that changes from the off state to the on state or from the on state to the off state. DC blocking capacitors C1 and C2 are connected in series between the input terminal IN and the PIN diode D and between the PIN diode D and the output terminal OUT, respectively.

  Inductors L1 and L2 are connected in series between the control terminal to which the on / off bias voltage + V is applied and the PIN diode D, and between the PIN diode D and the ground terminal, respectively. The PIN diode D can be equivalently represented by a parasitic capacitance Cv ′ and a resistance Rv ′ as shown by D ′ in FIG. 19B when the bias voltage + V is not applied, that is, in the OFF state. it can. An inductor Lv for resonating in parallel with the capacitance Cv ′ is connected in parallel to the PIN diode D in order to positively utilize the parasitic capacitance Cv ′ to increase isolation in a specific frequency band f1. Cv is a DC blocking capacitor.

In such a configuration, when a predetermined bias voltage + V is applied to the PIN diode D, the PIN diode D is turned on, and exhibits frequency characteristics as shown by a thick line in FIG. On the other hand, when the bias voltage + V is not applied to the PIN diode D, the PIN diode D is turned off and exhibits frequency characteristics as indicated by a thin line in FIG. That is, in the specific frequency band f1, the parasitic capacitance Cv ′ included in D ′ of FIG. 19B and the inductor Lv resonate, so that the isolation (the output in the ON state) in this frequency band f1 The ratio of the output in the off state) is ensured. Such a conventional high-frequency switch is also shown in Patent Document 1 below.
JP 63-13418 A Japanese Patent Application No. 2002-83085

  The conventional high-frequency switch is suitable for switching control of a communication device or the like that uses only one frequency band. Incidentally, in recent years, as will be described later with reference to FIG. 6 in addition to one frequency band, a high-frequency switch using a PIN diode is also used for switching control in a communication device or the like that uses multiple frequency bands of two or more frequency bands. It has been tried. However, in the conventional high frequency switch, although isolation in the frequency band f1 can be secured, a PIN diode is used in a specific frequency band other than the frequency band f1, for example, the 1.6 GHz band and the 2.5 Hz G band in FIG. There is no difference in passage loss between the on state and the off state, that is, sufficient isolation cannot be ensured.

  Therefore, in a device or system that uses these 1.6 GHz band, 2.5 HzG band, and the like in addition to the frequency band f1, there arises a problem that signals in these frequency bands are mixed in unexpected parts.

  In recent years, such high-frequency switches are often used for mass-produced products such as communication devices, and it is necessary to mass-produce high-frequency switches for multiple frequencies. For this reason, each high-frequency switch has uniform frequency band characteristics and suitable isolation characteristics with no variation, easy bandwidth adjustment according to specifications, easy design and adjustment, etc. , Tend to be more demanded.

Thus, the present invention is, in view of the situation described above, Xiu is the isolation characteristic for the multi-frequency band, and an object of the invention to provide a suitable high-frequency switch circuits to the frequency switching control in mass production, such as communications equipment.

The high-frequency switch circuit according to claim 1, wherein the high-frequency switch circuit is provided between an input terminal and an output terminal, and is turned on in response to a predetermined bias voltage, and the PIN diode. to be connected in parallel, a first resonant element which resonates at a parasitic capacitance and a first frequency band of the PIN diode in the off state, the connected in parallel to both the PIN diode and the first resonance element, in the off-state A parasitic capacitance of a certain PIN diode and a second resonant element that resonates in a second frequency band different from the first frequency band; a parallel connection to the PIN diode and a serial connection to the first resonant element; A second frequency band blocking filter for blocking signals of two frequency bands from passing through the first resonant element; and the PIN diode. A resonance circuit including a first frequency band rejection filter connected in series and connected in series to the second resonance element and blocking a signal of the first frequency band from passing through the second resonance element; It is characterized by having.

According to the first aspect of the present invention, the resonant circuit includes a first resonant element that resonates in the first frequency band with the parasitic capacitance of the PIN diode, a second resonant element that resonates with the parasitic capacitance and the second frequency band, A second frequency band rejection filter that blocks passage of the second frequency band to the first resonance element, and a first frequency band rejection filter that blocks passage of the first frequency band to the second resonance element. Is done. Thus, when a signal in the first frequency band is input in the OFF state of the PIN diode, the first resonant element resonates with the parasitic capacitance of the PIN diode without being affected by the second resonant element, and the second frequency band. When the above signal is input, the second resonant element resonates with the parasitic capacitance of the PIN diode without being affected by the first resonant element. Thereby, suitable isolation is ensured in both the first frequency band and the second frequency band.

According to the first aspect of the present invention, the resonant circuit includes a first resonant element that resonates in the first frequency band with the parasitic capacitance of the PIN diode, a second resonant element that resonates with the parasitic capacitance and the second frequency band, A second frequency band rejection filter that blocks passage of the second frequency band to the first resonance element, and a first frequency band rejection filter that blocks passage of the first frequency band to the second resonance element. Is done. Thus, when a signal in the first frequency band is input in the OFF state of the PIN diode, the first resonant element resonates with the parasitic capacitance of the PIN diode without being affected by the second resonant element, and the second frequency band. When the above signal is input, the second resonant element resonates with the parasitic capacitance of the PIN diode without being affected by the first resonant element. As a result, it is possible to secure suitable isolation in both the first frequency band and the second frequency band, and switching control in communication devices and the like that are increasing in recent years is very useful. Become.

[First embodiment]
FIG. 1 is a circuit diagram showing a high-frequency switch according to a first embodiment of the present invention. FIG. 2 is a frequency characteristic diagram of the high-frequency switch of FIG. 1 in an on state and an off state. Here, this high-frequency switch is used in, for example, a communication device or communication system that uses the 5.8 GHz band and the 1.6 GHz band, and passes both frequency band signals input to the input terminal IN side to the output terminal OUT side. It is assumed that it is used for switching control whether to pass or block passage.

  As shown in FIG. 1, the high frequency switch according to the first embodiment is interposed between an input terminal IN for inputting signals of 5.8 GHz band and 1.6 GHz band and an output terminal OUT for outputting the signals, for example. And a PIN diode D that changes from an off state to an on state or from an on state to an off state in response to a predetermined bias voltage in the forward direction. DC blocking capacitors C1 and C2 are connected in series between the input terminal IN and the PIN diode D and between the PIN diode D and the output terminal OUT, respectively.

  Inductors L1 and L2 are connected in series between the control terminal to which the on / off bias voltage + V is applied and the PIN diode D, and between the PIN diode D and the ground terminal, respectively. The PIN diode D can be represented by an equivalent circuit as indicated by D ′ in FIG. 19B when the bias voltage + V is not applied, that is, in the OFF state.

  Further, a parasitic capacitance Cv of the PIN diode D in the OFF state and a resonance circuit 11 that resonates in the 5.8 GHz band and the 1.6 GHz band are connected in parallel to the PIN diode D. The resonance circuit 11 includes a 5.8 GHz band resonance inductor L11a and a 1.6 GHz band resonance inductor L11b connected in parallel. This 5.8 GHz band resonance inductor L11a is connected in series with a 1.6 GHz band resonance filter BRF11b, and the 1.6 GHz band resonance inductor L11b is connected in series with a 5.8 GHz band resonance filter BRF11a. . C3 is a DC blocking capacitor.

  The 5.8 GHz band resonance inductor L11a resonates in the 5.8 GHz band with the parasitic capacitance of the PIN diode D in the off state, and the 1.6 GHz band resonance inductor L11b has the parasitic capacitance of the PIN diode D in the off state. Resonates at 1.6 GHz band. Further, the 5.8 GHz band device filter BRF11a prevents a 5.8 GHz band signal from passing through the 1.6 GHz band resonance inductor L11b, and the 1.6 GHz band device filter BRF11b The signal is prevented from passing through the 5.8 GHz band resonance inductor L11a.

  As is well known, the 5.8 GHz band device filter BRF11a is composed of an inductor L113 and a capacitor C113 connected in parallel, and has a value that prevents passage of a 5.8 GHz band signal as described above. As is well known, the 1.6 GHz band device filter BRF11b is also composed of an inductor L111 and a capacitor C111 connected in parallel, and has a value that prevents passage of a 1.6 GHz band signal as described above.

  In such a configuration, when a predetermined bias voltage + V is applied to the PIN diode D, the PIN diode D is turned on and exhibits a frequency characteristic as shown by a thick line in FIG. At this time, both 5.8 GHz band and 1.6 GHz band signals input to the input terminal IN can pass through to the output terminal OUT side with almost no loss.

  On the other hand, when the bias voltage + V is not applied to the PIN diode D, the PIN diode D is turned off and exhibits frequency characteristics as indicated by a thin line in FIG. That is, the 5.8 GHz band signal is blocked from passing to the 1.6 GHz band resonance inductor L11b by the 5.8 GHz band rejection filter BRF11a, and therefore the PIN diode D is in the 1.6 GHz band resonance in the OFF state. The parasitic capacitance of the PIN diode D and the 5.8 GHz band resonance inductor L11a resonate without being affected by the inductor L11b. As a result, as indicated by f1 in FIG. 2, a pass loss of about −25 dB to −20 dB occurs for a signal of 5.8 GHz band. As is clear from comparison with the on-state passage loss in the 5.8 GHz band, it can be seen that sufficient isolation is ensured.

  Since the 1.6 GHz band signal is blocked from passing to the 5.8 GHz band resonance inductor L11a by the 1.6 GHz band blocking filter BRF11b, the PIN diode D is 5.8 GHz band resonance in the off state. The parasitic capacitance of the PIN diode D and the 1.6 GHz band resonance inductor L11b resonate without being affected by the inductor L11a. As a result, as indicated by f2 in FIG. 2, a loss of about −25 dB to −20 dB occurs even for a 1.6 GHz band signal. As is clear from comparison with the on-state passage loss in the 1.6 GHz band, it can be seen that sufficient isolation is ensured in the two frequency bands.

  Thus, according to the first embodiment, the present invention is similarly applied to communication devices and communication systems that use three or more frequency bands by combining the resonance inductance corresponding to the frequency band to be used and the band rejection filter. It becomes possible. As illustrated in the above embodiment, the band rejection filter may be connected in series not only to one end of the resonance inductor but also to both ends. In the above embodiment, application to the 5.8 GHz band and the 1.6 GHz band is exemplified, but the same applies to combinations of other frequency bands.

  This first embodiment corresponds to claims 1 and 2. Specifically, the 5.8 GHz band and the 1.6 GHz band of the first embodiment correspond to the first frequency band and the second frequency band of claim 2, respectively, and the 5.8 GHz band resonance inductor L11a and the 1.6 GHz band. The resonance inductor L11b corresponds to the first resonance element and the second resonance element of claim 2, respectively, and the 5.8 GHz band rejection filter BRF11a and the 1.6 GHz band rejection filter BRF11b are respectively the first frequency band of claim 2. It corresponds to a band rejection filter and a second frequency band band rejection filter.

[ First Reference Example ]
FIG. 3 is a circuit diagram showing the high-frequency switch of the first reference example . Again, this high frequency switch is used, for example, in a communication device or communication system that uses the 5.8 GHz band and the 1.6 GHz band, and passes both frequency band signals input to the input terminal IN side to the output terminal OUT side. It is assumed that it is used for switching control whether to pass or block passage.

As shown in FIG. 3, the high-frequency switch of the first reference example has a configuration in which the resonance circuit 11 in the high-frequency switch of the first embodiment of FIG. Therefore, here, the same reference numerals are given to the parts common to FIG.

In the high frequency switch of the first reference example , the resonance circuit 12 is configured by an LC ladder type circuit connected in parallel to the PIN diode D. That is, the resonance circuit 12 is configured by connecting in series a circuit in which a capacitor C12b and an inductor L12b are connected in parallel to the inductor L12a. C12a is a DC blocking capacitor.

In such an LC ladder type circuit, by appropriately adjusting the values of the capacitors and the inductor, the parasitic capacitance in the OFF state of the PIN diode D can be used to resonate in the 5.8 GHz band and the 1.6 GHz band. it can. In this reference example , the resonance circuit 12 composed of such an LC ladder circuit is used for improving the isolation characteristics.

  In such a configuration, when a predetermined bias voltage + V is applied to the PIN diode D, the PIN diode D is turned on, and the frequency characteristic as shown by the thick line in FIG. 2 is obtained as in the first embodiment. Present. At this time, both 5.8 GHz band and 1.6 GHz band signals input to the input terminal IN can pass through to the output terminal OUT side with almost no loss.

  On the other hand, when the bias voltage + V is not applied to the PIN diode D, the PIN diode D is turned off and exhibits frequency characteristics as shown by the thin line in FIG. 2 as in the first embodiment. That is, the parasitic capacitance of the PIN diode D and the resonance circuit 12 constituted by the LC ladder type circuit resonate in the 5.8 GHz band and the 1.6 GHz band. As a result, as indicated by f1 and f2 in FIG. 2, a pass loss of about −25 dB to −20 dB occurs for signals in the 5.8 GHz band and the 1.6 GHz band. As is apparent from comparison with the on-state passage loss in these frequency bands, it can be seen that sufficient isolation is ensured in the two frequency bands.

As described above, according to the first reference example , by using the resonance circuit 12 configured by the LC ladder type circuit, it is preferable in the 5.8 GHz band and the 1.6 GHz band while having a simple configuration. Isolation can be secured. In the above reference example , application to the 5.8 GHz band and the 1.6 GHz band is illustrated, but the same applies to combinations of other frequency bands. Such a high frequency switch of the first reference example can be applied to, for example, a communication device or a communication system using two frequency bands .

[ Second Reference Example ]
FIG. 4 is a circuit diagram showing a high frequency switch of a second reference example of the present invention. FIG. 5 is a frequency characteristic diagram of the high-frequency switch of FIG. 4 in an on state and an off state. Here, this high frequency switch is used for a communication device or a communication system using, for example, a 5.8 GHz band, a 2.5 GHz band, and a 1.6 GHz band, and outputs signals in both frequency bands that are input to the input terminal IN side. It is assumed that it is used for switching control whether to pass to the end OUT side or to prevent passage.

As shown in FIG. 4, the high frequency switch of the second reference example is an LC ladder type corresponding to three frequency bands, in which the resonance circuit 12 composed of an LC ladder type circuit in the high frequency switch of the first reference example of FIG. The configuration is replaced with a resonance circuit 13 constituted by a circuit. Therefore, the description which overlaps here is also abbreviate | omitted.

In the high frequency switch of the second reference example , the resonance circuit 13 is configured by an LC ladder type circuit corresponding to three frequency bands connected in parallel to the PIN diode D. That is, the resonance circuit 13 is configured by an LC ladder type circuit in which a parallel connection circuit of a capacitor C13c and an inductor L13c is added by one stage to the LC ladder type circuit of the resonance circuit 12 of FIG. C13a and C13b indicate capacitors (C13a is a DC blocking capacitor), and L13a and L13b indicate inductors.

In such an LC ladder type circuit, by appropriately adjusting the values of the capacitors and the inductor, the parasitic capacitance in the OFF state of the PIN diode D is used to make use of the 5.8 GHz band, 2.5 GHz band, and 1.6 GHz band. Can be made to resonate. In this reference example , the resonance circuit 13 composed of such an LC ladder circuit is used for improving the isolation characteristics.

In such a configuration, when a predetermined bias voltage + V is applied to the PIN diode D, the PIN diode D is turned on, as shown by the thick line in FIG. 5, as in the first embodiment and the first reference example . Exhibits frequency characteristics. At this time, 5.8 GHz band, 2.5 GHz band, and 1.6 GHz band signals input to the input terminal IN can pass to the output terminal OUT side with almost no loss.

  On the other hand, when the bias voltage + V is not applied to the PIN diode D, the PIN diode D is turned off and exhibits frequency characteristics as indicated by a thin line in FIG. That is, the parasitic capacitance of the PIN diode D and the resonance circuit 13 constituted by the LC ladder type circuit resonate in the 5.8 GHz band, 2.5 GHz band, and 1.6 GHz band. As a result, as indicated by f1 and f2 in FIG. 5, a pass loss of about −25 dB to −20 dB occurs for signals in the 5.8 GHz band and 1.6 GHz band, and as indicated by f3, Even for a 2.5 GHz band signal, a pass loss of about −15 dB occurs. As is apparent from comparison with the on-state passage loss in these frequency bands, it can be seen that sufficient isolation is ensured in the three frequency bands.

Thus, according to the second reference example , the 5.8 GHz band, the 2.5 GHz band, and the 1.6 GHz band are obtained by using the resonance circuit 13 including the LC ladder type circuit, although the configuration is simple. Suitable isolation can be secured in the band. In the above reference example , application to the 5.8 GHz band, 2.5 GHz band, and 1.6 GHz band is exemplified, but the same applies to combinations of other frequency bands. Such a high frequency switch of the second reference example can be applied to, for example, a communication device or a communication system using three frequency bands as shown in FIG.

[ Third reference example ]
FIG. 6 is a block diagram showing an in-vehicle communication system using the high frequency switch of the second reference example . FIG. 7 is a circuit diagram showing a high-frequency switch circuit unit in the in-vehicle communication system of FIG.

  As shown in FIG. 6, this in-vehicle communication system includes a three-frequency antenna (antenna corresponding to three frequency bands) 2 via a high-frequency switch circuit unit 1, a 1.6 GHz band receiver 3, and a 2.5 GHz band receiver. 4 and 5.8 GHz band receiver 5a and 5.8 GHz band transmitter 5b. Note that the antenna duplexer and the like are omitted. Here, the 1.6 GHz band receiver 3 is assumed to be a GPS (Global Positioning System) receiver, and the 2.5 GHz band receiver 4 is assumed to be a VICS (Road Traffic Information Communication System) receiver, and the 5.8 GHz band. The receiver 5a and the 5.8 GHz band transmitter 5b are assumed to be DSRC (narrow band communication) / ETC (automatic toll collection system) transceivers.

  The GPS receiver as the 1.6 GHz band receiver 3 is a 1.6 GHz band dedicated reception device, and demodulates the received signal in this frequency band to extract information and time information necessary for positioning. The VICS receiver as the 2.5 GHz band receiver 4 is a dedicated receiver for 2.5 GHz band, and demodulates the received signal in this frequency band to obtain traffic information such as traffic jams, accidents, traffic regulations, and parking lots. Extract. The DSRC / ETC transmitter / receiver as the 5.8 GHz band receiver 5a and the 5.8 GHz band transmitter 5b is a 5.8 GHz band transmitter / receiver, and using this frequency band, various control signals related to toll collection, etc. Modulation / demodulation of. These transceivers are well known.

  The three-frequency antenna 2 is, for example, the antenna described in Patent Document 2 and can transmit and receive 1.6 GHz band radio waves, 2.5 GHz band radio waves, and 5.8 GHz band radio waves at a practical level. . The 1.6 GHz band radio wave includes a positioning GPS signal transmitted from a GPS satellite. The 2.5 GHz band radio wave includes traffic information such as traffic jams, accidents, traffic regulations, and parking lots transmitted using beacons from roadside devices, FM multiplex broadcasting, or the like. The 5.8 GHz band radio wave includes signals used in narrow area communication with a radio wave reach of several meters assumed by ITS (Intelligent Transport System), etc. The control signal for communicating between the roadside machine on the gate side and the vehicle-mounted apparatus on the vehicle side is included.

As shown in FIG. 7, the high-frequency switch circuit unit 1 includes a pair of high-frequency switches. In the figure, the high-frequency switch on the left is composed of the high-frequency switch of the second reference example of FIG. 4, and capacitors C1a and C2a, inductors L1a and L2a, and PIN diode Da are capacitors C1 and C2 and inductor L1 of FIG. , L2, and PIN diode D. Therefore, although repeated explanation is omitted, each capacitor and inductor constituting the resonance circuit 13 have values corresponding to the 5.8 GHz band, 2.5 GHz band, and 1.6 GHz band as described with reference to FIG. It has become.

  In addition, the right-side high-frequency switch in the figure is also composed of the high-frequency switch shown in FIG. 4, and the capacitors C1b and C2b, the inductors L1b and L2b, and the PIN diode Db are respectively the capacitors C1 and C2, and the inductors L1 and L2 shown in FIG. , Equivalent to the PIN diode D. However, the high-frequency switch on the right side is related to the transmission portion, that is, the 5.8 GHz band transmitter 5b, and therefore may not have the resonance circuit 13. This is because even if a weak reception signal is mixed in a transmission portion that outputs a high power signal, it does not matter so much. However, since this may vary from system to system depending on the design of the transmission part, it is more preferable to connect the resonant circuit 13 here as well.

  The bias voltages + Va and + Vb are used to control whether the terminal 1c is connected to the terminal 1a or the terminal 1b.

  In the in-vehicle communication system having such a configuration, the received signal in the 1.6 GHz band, 2.5 GHz band and / or 5.8 GHz band received by the three-frequency antenna 2 is a high frequency switch circuit as indicated by a solid arrow. The data is input to the 1.6 GHz band receiver 3, the 2.5 GHz band receiver 4, and the 5.8 GHz band receiver 5 a via the unit 1, and each processing is performed.

  Specifically, at this time, only the bias voltage + Va is applied, and the bias voltage + Vb is 0V. For this reason, the received signal from the three-frequency antenna 2 is transmitted to the terminal 1a with almost no loss, but is hardly transmitted to the terminal 1b.

  On the other hand, the 5.8 GHz band transmission signal from the 5.8 GHz band transmitter 5b reaches the three-frequency antenna 2 via the high-frequency switch circuit unit 1 as shown by a dotted arrow, and passes to a predetermined roadside device or the like. Sent.

  Specifically, at this time, only the bias voltage + Vb is applied, and the bias voltage + Va is 0V. For this reason, the transmission signal from the terminal 1b is transmitted to the three-frequency antenna 2 with almost no loss, but is hardly transmitted to the terminal 1a.

As described above, according to the third reference example , in the in-vehicle communication system configured to include a GPS receiver, a VICS receiver, and a DSRC / ETC transmitter / receiver, which has been frequently installed in the vehicle in recent years, Suitable isolation can be ensured in the frequency band used by the device. In particular, it is possible to effectively prevent a transmission signal from a DSRC / ETC transceiver having a transmission function from being mixed into another receiver such as a GPS receiver.

[ Fourth Reference Example ]
FIG. 8 is a plan circuit diagram showing a high-frequency switch according to a fourth reference example of the present invention. FIGS. 9A and 9B are graphs showing an example of variation improvement in the 1.6 GHz band. FIG. 10A and FIG. 10B are graphs showing an example of variation improvement in the 2.5 GHz band. FIG. 11A and FIG. 11B are graphs showing an example of variation improvement in the 5.8 GHz band. FIG. 12 is a plan circuit diagram showing a modification of the high-frequency switch of the fourth reference example of the present invention.

  The high frequency switch as shown in FIG. 4 has a suitable isolation characteristic in each of a plurality of desired frequency bands, and the inductor and the capacitor constituting the LC ladder circuit are all lumped constants. There remains an improvement in that the resonance frequency varies during production. Usually, it is known that variations of ± 10% and ± 5% occur in lumped constant inductors and capacitors, respectively.

  According to 10 prototypes of the high-frequency switch as shown in FIG. 4 using such a lumped constant inductor and capacitor, for example, in the 1.6 GHz band, as shown in FIG. In the 2.5 GHz band, as shown in FIG. 10 (B), there is a 230 MHz variation, and in the 5.8 GHz band, there is a 220 MHz variation as shown in FIG. 11 (B). I understand.

In order to reduce such variation, in the fourth reference example , only the inductor constituting the LC ladder circuit is configured as a planar circuit having a microstrip structure. That is, as shown in FIG. 8, for example, only the inductor of the high-frequency switch as shown in FIG. 4 is formed as a planar circuit having a microstrip structure on the back surface of the substrate, for example. The reason why only the inductor is a planar circuit having a microstrip structure is to reduce the variation and not to be disadvantageous from the viewpoint of miniaturization.

  For example, if both the inductor and the capacitor are formed as a microstrip structure planar circuit, the substrate will inevitably increase in size. However, as described above, only the inductor having a large variation compared to the capacitor is used as the microstrip structure planar circuit. Thus, the variation is reduced and the increase in the size of the substrate is moderately suppressed. Supplementally, if the capacitor has a microstrip structure planar circuit when the dielectric constant of the substrate dielectric is low, it will be necessary to enlarge the substrate, but only the inductor will be a microstrip structure planar circuit. This avoids this.

  In FIG. 8, if the equivalent inductance of the planar circuit having the microstrip structure is LE, the value can be approximated by the following equation.

_{L E = Z 0 × L /} v g

In the above equation, Z ₀ is the characteristic impedance of the planar circuit microstrip structure, L is the length of the planar circuit microstrip structure, v _g is the group velocity in the plane circuit microstrip structure.

  According to ten prototypes of the high-frequency switch as shown in FIG. 8, for example, in the 1.6 GHz band, as shown in FIG. 9A, in the variation of 30 MHz, in the 2.5 GHz band, FIG. As shown in FIG. 11A, it can be seen that in the 60 MHz variation and 5.8 GHz band, as shown in FIG. 11A, the variation is reduced to 50 MHz. That is, in any frequency band, it can be seen that the variation is reduced to about 25%.

  As shown in the modification of FIG. 12, both the inductor and the capacitor constituting the LC ladder circuit can be configured as a planar circuit having a microstrip structure. However, in this case, in order to prevent the substrate from becoming larger than necessary, the inductor and the capacitor are formed separately on the back surface and the front surface of the substrate, respectively. Note that the relationship between the inductor and the capacitor and the back surface and front surface of the substrate may be reversed.

In FIG. 12, the equivalent inductance of the planar circuit of microstrip When L _E, the value can be approximated by the following equation.

_{L E = Z 0 × L /} v g

In the above equation, Z ₀ is the characteristic impedance of the planar circuit microstrip structure, L is the length of the planar circuit microstrip structure, v _g is the group velocity in the plane circuit microstrip structure.

If the equivalent capacitance of a planar circuit having a microstrip structure is _CE , the value can be approximated by the following equation.

C _E = ε _r × A / d

In the above equation, ε _r is the relative dielectric constant of the dielectric of the substrate, A is the area of the capacitance, and d is the thickness of the substrate.

  According to the 10 prototypes of the high-frequency switch as shown in FIG. 12, the variation of both the inductor and the capacitor can be reduced. Therefore, the 1.6 GHz band, the 2.5 GHz band, and the 5.8 GHz band are all shown in FIG. ), The variation can be reduced more than that shown in FIGS. 10 (A) and 11 (A).

As described above, according to the fourth reference example , it is possible to reduce the variation in the resonance frequency of each high-frequency switch circuit during mass production. Accordingly, it is possible to ensure suitable isolation in a uniform frequency band, which is advantageous for mass production of a high-frequency switch circuit and a product using the same. In addition, by making only the inductor a microstrip structure planar circuit, or by forming the microstrip structure planar circuit inductor and capacitor separately on either the front surface or the back surface of the substrate, it is also disadvantageous in terms of miniaturization. Must not. Similarly, the high frequency switch as shown in FIG. 3 can be similarly configured as a planar circuit having a microstrip structure of an inductor and / or a capacitor, thereby obtaining the same effect as described above .

[ Fifth Reference Example ]
13 and 14 are diagrams for explaining a fifth reference example of the present invention. 15 and 16 are graphs for explaining a fifth reference example of the present invention. In addition, in order to understand a 5th reference example more concisely, FIG.13 and FIG.14 attaches another code | symbol with respect to the circuit diagram shown in FIG.3 and FIG.4, respectively.

  The high-frequency switch as shown in FIG. 4 has suitable isolation characteristics in a plurality of desired frequency bands, but there has been no established method for adjusting the bandwidth in each frequency band. For example, in the in-vehicle communication system as shown in FIG. 6 and FIG. 7, the 1.6 GHz band corresponding to the GPS receiver is narrowed and the 2.5 GHz band corresponding to the DSRC / ETC transceiver is widened according to the specifications. You may want to In such a case, conventionally, since it has been necessary to adjust the bandwidth of each frequency band by changing the values of the inductor, the capacitor, and the like by trial and error, a long time has been required. The fifth reference example solves this problem.

As shown in FIGS. 13 and 14, included in the high-frequency switch circuit, the impedance Z _N of N frequency bands corresponding LC ladder circuit can generally represented by the following formula (1). Here, in FIGS. 13 and 14, the convenience of the _{C P} is calculated and denoted as _{C 1.}

As shown respectively in FIGS. 13 and 14, respectively the impedance Z ₃ of the impedance Z ₂ and 3 the frequency band corresponding LC ladder circuit 2 frequency bands corresponding LC ladder circuit, as a special case of the above formula (1), the following It can represent like Formula (2) and Formula (3).

Here, it can be seen that the denominators of the equations (2) and (3) are a quadratic equation and a cubic equation with respect to ω ² , respectively. From this, there are two and three frequencies at which the denominator of Equations (2) and (3) is 0, that is, the impedance is infinite (isolation at OFF is increased), respectively. It can be seen that a high frequency switch using such an LC ladder circuit has high isolation characteristics at a plurality of frequencies. Also, of the formula (2) and parameters included in the denominator of equation (3) (the value of each element), but the parameters C _{1 =} C _P is the eigenvalues determined by the PIN diode, freely adjusted to Other It can be seen that there are three possible parameters in the denominator of equation (2) and five in the denominator of equation (3), respectively. Accordingly, since the number of parameters is larger than the number of solutions to be obtained, when the isolation frequency (corresponding to the resonance frequency) is fixed, there is a degree of freedom in taking parameters.

A specific calculation method will be described with reference to FIGS. FIG. 15 corresponds to the circuit of FIG. 13 and shows calculation results for two frequency bands. In FIG. 15, the calculation was performed with the isolation frequency fixed at 1.6 GHz band and 5.8 GHz band. Three parameters _{C 2,} L 1, the parameter _{C 2} of the _{L 2} is varied, the figures to secure the isolation frequency, the other two parameters _L 1, was adjusted _{L 2,} the three calculation examples Shown above 15 graphs.

As can be seen from Figure 15, reducing the parameter _{C 2,} 1.6GHz band becomes wide, 5.8 GHz band is narrowed. Increasing the parameter _{C 2,} conversely, 1.6GHz band is narrowed, 5.8 GHz band is widened. Thus, since the bandwidth of each frequency band has a trade-off relationship, it can be understood that the allocation of the bandwidth of each frequency can be easily designed according to the specification.

FIG. 16 corresponds to the circuit of FIG. 14 and shows calculation results for three frequency bands. In FIG. 16, the calculation was performed with the isolation frequency fixed at 1.6 GHz band, 2.5 GHz band, and 5.8 GHz band. Five parameters _{C 2,} C _3, L _1, the L 2, the parameter _{C 2} of the _{L 3} is varied, in order to secure the isolation frequency, the other four parameters _{C 3,} L _{1, L} 2, _Three calculation examples in which L3 is adjusted are shown on the graph of FIG.

As it can be seen from FIG. 16, reducing the parameter _{C 2,} 1.6GHz band is narrowed, 5.8 GHz band is widened. Increasing the parameter _{C 2,} conversely, 1.6GHz band becomes wide, 5.8 GHz band is narrowed. Thus, since the bandwidth of each frequency band has a trade-off relationship, it can be understood that the allocation of the bandwidth of each frequency can be easily designed according to the specification. Here, the adjustment between the 1.6 GHz band and the 5.8 GHz band is shown as an example, but the same adjustment is possible for any two of the three frequency bands.

As described above, according to the fifth reference example , the bandwidth of each frequency band is adjusted by controlling the value of any one of the inductor and the capacitor constituting the LC ladder type circuit corresponding to the multi-frequency band. Therefore, it is possible to easily adjust the bandwidth according to the specifications. In addition, in order to adjust the bandwidth of the multi-frequency band, it is only necessary to control one value of the inductor and the capacitor, which is useful for switching control in a communication device using a multi-frequency band. Become .

[ Sixth reference example ]
FIG. 17 is a circuit diagram showing a high-frequency switch according to a sixth reference example of the present invention. FIG. 18 is a frequency characteristic diagram of the high frequency switch of FIG. 17 in the on state and the off state. Here, this high-frequency switch is used in, for example, a communication device or communication system that uses the 5.8 GHz band and the 1.6 GHz band, and passes both frequency band signals input to the input terminal IN side to the output terminal OUT side. It is assumed that it is used for switching control whether to pass or block passage.

As shown in FIG. 17, the high frequency switch of the sixth reference example is interposed, for example, between an input terminal IN for inputting a signal of 5.8 GHz band and 1.6 GHz band and an output terminal OUT for outputting the signal. The first PIN diode D21 and the second PIN diode D22 change from an off state to an on state or from an on state to an off state in response to a predetermined bias voltage in the forward direction. DC blocking capacitors C21 and C22 are connected in series between the input terminal IN and the first PIN diode D21 and between the second PIN diode D22 and the output terminal OUT, respectively.

  Inductors L21 and L22 are connected in series between the control terminal to which the on / off bias voltage + V is applied and the first PIN diode D21, and between the second PIN diode D22 and the ground terminal, respectively. The first PIN diode D21 and the second PIN diode D22 can be represented by an equivalent circuit as indicated by D 'in FIG. 19B when the bias voltage + V is not applied, that is, in the off state.

  In addition, the first PIN diode D21 includes a parasitic capacitance of the first PIN diode D21 in the off state and a 1.6 GHz band in order to increase isolation in the 1.6 GHz band (corresponding to the first frequency band in the claims). A resonating inductor L21v (corresponding to the first resonance element in the claims) is connected in parallel. C21v is a DC blocking capacitor.

  Further, the second PIN diode D22 includes a parasitic capacitance of the second PIN diode D22 in the off state and a 5.8 GHz band in order to increase isolation in the 5.8 GHz band (corresponding to the second frequency band in the claims). A resonating inductor L22v (corresponding to the second resonant element in the claims) is connected in parallel. C22v is a DC blocking capacitor.

  That is, it can be seen that a circuit that resonates in the 1.6 GHz band and a circuit that resonates in the 5.8 GHz band are cascade-connected.

  In such a configuration, when a predetermined bias voltage + V is applied to the PIN diode D, the PIN diode D is turned on and exhibits a frequency characteristic as shown by a thick line in FIG. At this time, both 5.8 GHz band and 1.6 GHz band signals input to the input terminal IN can pass through to the output terminal OUT side with almost no loss.

  On the other hand, when the bias voltage + V is not applied to the first PIN diode D21 and the second PIN diode D22, both the first PIN diode D21 and the second PIN diode D22 are turned off, and the frequency shown by the thin line in FIG. It exhibits characteristics.

  That is, the parasitic capacitance of the first PIN diode D21 in the off state and the inductor L21v resonate in the 1.6 GHz band, and the passage of the 1.6 GHz band signal from the input terminal IN to the output terminal OUT at the time of off is prevented. The In addition, the parasitic capacitance of the second PIN diode D22 in the off state and the inductor L22v resonate in the 5.8 GHz band, and the passage of the signal in the 5.8 GHz band from the input terminal IN to the output terminal OUT at the time of off is blocked. The As shown in FIG. 18, it can be seen that the isolation characteristics in both frequency bands are wider.

Thus, according to the sixth reference example , it is possible to ensure isolation in a multi-frequency band with a simple configuration. Moreover, since it is a simple structure, design and adjustment are easy. Furthermore, the isolation characteristic becomes wider. Therefore, it is very useful for switching control in a communication device or the like using a multi-frequency band that has been increasing in recent years. In the above reference example , the application to the 5.8 GHz band and the 1.6 GHz band is illustrated, but the same effect can be obtained even when other frequency bands are combined. The same effect can be obtained even when applied to three frequency bands .

  As described above, according to the above-described embodiment of the present invention, in a high-frequency switch corresponding to a multi-frequency band, it is possible to ensure suitable isolation with little variation, and further, it is easy to adjust the bandwidth. Therefore, it is very useful for switching control in a communication device or the like using a multi-frequency band that has been increasing in recent years.

The high-frequency switch circuit of the present invention is particularly useful when applied to the in-vehicle communication system as described above, but it is not necessarily required to be mounted on the vehicle. In addition, the high frequency switch circuit of the present invention can be applied to frequency bands other than the illustrated frequency band . The present invention includes those modified without departing from the gist of the present invention.

It is a circuit diagram showing the high frequency switch of a 1st embodiment of the present invention. It is a frequency characteristic figure in the ON state and OFF state of the high frequency switch of FIG. It is a circuit diagram which shows the high frequency switch of the 1st reference example of this invention. It is a circuit diagram which shows the high frequency switch of the 2nd reference example of this invention. It is a frequency characteristic figure in the ON state and OFF state of the high frequency switch of FIG. It is a block diagram which shows the vehicle-mounted communication system using the high frequency switch of the 2nd reference example . It is a circuit diagram which shows the high frequency switch circuit part in the vehicle-mounted communication system of FIG. It is a plane circuit diagram which shows the high frequency switch of the 4th reference example of this invention. FIGS. 9A and 9B are graphs showing an example of variation improvement in the 1.6 GHz band. FIG. 10A and FIG. 10B are graphs showing an example of variation improvement in the 2.5 GHz band. FIG. 11A and FIG. 11B are graphs showing an example of variation improvement in the 5.8 GHz band. It is a plane circuit diagram which shows the modification of the high frequency switch of the 4th reference example of this invention. It is a figure for demonstrating the 5th reference example of this invention. It is a figure for demonstrating the 5th reference example of this invention. It is a graph for demonstrating the 5th reference example of this invention. It is a graph for demonstrating the 5th reference example of this invention. It is a circuit diagram which shows the high frequency switch of the 6th reference example of this invention. It is a frequency characteristic figure in the ON state and OFF state of the high frequency switch of FIG. FIG. 19A is a circuit diagram showing this type of conventional high-frequency switch, and FIG. 19B is an equivalent circuit diagram of the high-frequency switch of FIG. 19A in the OFF state. FIG. 20 is a frequency characteristic diagram of the high-frequency switch of FIG. 19 in an on state and an off state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency switch circuit part 2 3 Frequency antenna 3 1.6 GHz band receiver 4 2.5 GHz band receiver 5a 5.8 GHz band receiver 5b 5.8 GHz band transmitter 11, 12, 13 Resonant circuit

Claims (1)

A PIN diode interposed between the input terminal and the output terminal and turned on in response to a predetermined bias voltage;
Wherein connected in parallel to the PIN diode, a first resonator element that resonates with the parasitic capacitance and the first frequency band of the PIN diode in the off state, the are PIN diode and connected in parallel with both the first resonator element, said A parasitic capacitance of the PIN diode in the off state and a second resonant element that resonates in a second frequency band different from the first frequency band, and a parallel connection to the PIN diode and a serial connection to the first resonant element. A second frequency band blocking filter for blocking the signal of the second frequency band from passing through the first resonant element; and a parallel connection to the PIN diode and a series connection to the second resonant element; A first frequency band rejection filter that prevents a signal in the first frequency band from passing through the second resonant element. And circuit vibration,
A high-frequency switch circuit comprising:

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