JP4193873B2 - High frequency switch - Google Patents

Description

  The present invention relates to a high-frequency switch, and more particularly to a high-frequency switch used by being incorporated in a mobile communication device or the like.

  The high frequency switch is generally used for switching between a transmission circuit and a reception circuit in a digital cellular phone or the like. FIG. 6 is an electric circuit diagram showing a conventional high-frequency switch 1. The anode of the diode D1 is connected to the transmission terminal Tx. The anode of the diode D1 is grounded via the series circuit of the transmission line 2 and the capacitor C1. A voltage control terminal Vc1 is connected to an intermediate connection point between the transmission line 2 and the capacitor C1 via a resistor Ra. The cathode of the diode D1 is connected to the antenna terminal ANT.

  A reception terminal Rx is connected to the antenna terminal ANT via the transmission line 3. Furthermore, the anode of the diode D2 is connected to the receiving terminal Rx. The cathode of the diode D2 is grounded. Here, the bias-cut capacitor C1 connected between the transmission line 2 and the ground has a large capacity (about 47 pF near 1 GHz and about 22 pF near 2 GHz).

  Since the conventional high frequency switch 1 requires a large capacity capacitor as the bias cut capacitor C1 connected between the transmission line 2 and the ground, the size of the capacitor C1 is large and the high frequency switch 1 can be downsized. It was hindering.

  Moreover, in the high frequency switch 1, when the transmission terminal Tx and the antenna terminal ANT are connected, it is necessary to ensure isolation between the antenna terminal ANT and the reception terminal Rx. This is because if this isolation is poor, the insertion loss between the transmission terminal Tx and the antenna terminal ANT increases.

  Accordingly, an object of the present invention is to provide a high-frequency switch that is small and has excellent performance.

In order to achieve the above object, the present invention provides:
(A) a transmission terminal, an antenna terminal, a reception terminal, and a voltage control terminal;
(B) a first diode having a cathode electrically connected to the transmission terminal and an anode electrically connected to the antenna terminal;
(C) a first transmission line electrically connected between the antenna terminal and the receiving terminal;
(D) a second diode having a cathode electrically connected to the receiving terminal and an anode electrically connected to the voltage control terminal;
(E) a second transmission line having one end electrically connected to the transmission terminal and the other end directly grounded;
(F) a capacitor electrically connected between the voltage control terminal and the ground, and connected in series to the second diode;
A high-frequency switch comprising (g),
(H) one end of the second transmission line and the cathode of the first diode are directly connected;
(I) By controlling the voltage control terminal to a predetermined potential, the first and second diodes are simultaneously controlled to be in an ON state or an OFF state;
(J) In the ON state, the inductance of the second diode and the capacitance of the capacitor resonate at the transmission frequency,
(K) Laminating a plurality of dielectric layers, the first and second transmission lines, a capacitor electrode of the capacitor, and a ground electrode that is disposed directly opposite the capacitor electrode to form the capacitor. The transmission terminal, the reception terminal, the antenna terminal, and the voltage control terminal are provided on the surface of the laminated body configured as described above, and the first and second diodes are mounted, respectively.
It is characterized by.

  With the above configuration, when a positive potential is applied to the voltage control terminal, the first and second diodes are turned on, and the transmission signal that has entered the transmission terminal is transmitted to the antenna terminal. At this time, the transmission signal is hardly transmitted to the reception terminal. This is because when the second diode is in the ON state, the inductance and the capacitance of the capacitor resonate in series at the transmission frequency, and the impedance becomes zero. That is, since the first and second transmission lines operate as λ / 4 short stubs, the transmission terminal and the antenna terminal are connected, and the reception terminal is grounded.

  Further, when the voltage control terminal is set to the ground potential, the first and second diodes are turned off, and the transmission terminal and the antenna terminal are cut off, and the reception terminal and the ground are also cut off. As a result, the reception signal that has entered the antenna terminal is transmitted to the reception terminal and hardly transmitted to the transmission terminal. As described above, the high-frequency switch can switch the transmission path of the transmission / reception signal by controlling the bias voltage applied to the voltage control terminal.

  Furthermore, the conventional large-capacitance capacitor connected to the transmission terminal side becomes unnecessary, and only a small-capacitance capacitor connected to the reception terminal side is required.

Further , a high-frequency switch having a laminated structure in which necessary circuits are built in one component can be obtained.

  According to the present invention, the direction of the cathode and anode of the diode is reversed from that of the conventional high-frequency switch, thereby eliminating the need for the conventional large-capacity and large bias-cut capacitor connected to the transmission terminal side. Only a small capacitor and a small bias-cut capacitor connected to the receiving terminal can be used. Therefore, the high frequency switch can be reduced in size.

  Also, by adjusting the capacitance of this small capacitor, the isolation between the antenna terminal and the reception terminal when the transmission terminal and the antenna terminal are connected can be made larger than that of the conventional high-frequency switch. . Therefore, the insertion loss between the transmission terminal and the antenna terminal can be reduced. Furthermore, since the voltage control terminal is short-circuited to the ground during transmission and is blocked from the high-frequency signal by the high impedance of the second diode during reception, the control circuit connected to the voltage control terminal is isolated from the high-frequency signal. Can be secured greatly. As a result, a high-frequency switch with excellent performance can be obtained.

  Embodiments of a high frequency switch according to the present invention will be described below with reference to the accompanying drawings.

[First embodiment, FIGS. 1 to 3]
FIG. 1 is an electric circuit diagram showing an example of a high-frequency switch according to the present invention. The cathode of a diode D11 that is a switching element is connected to the transmission terminal Tx. The cathode of the diode D11 is grounded to the ground via the transmission line 12. The transmission line 12 is
Functions as a choke element. Furthermore, the anode of the diode D11 is connected to the antenna terminal ANT.

  A reception terminal Rx is connected to the antenna terminal ANT via the transmission line 13. Furthermore, the cathode of the diode D12 is connected to the receiving terminal Rx. The anode of the diode D12 is grounded via the bias cut capacitor C12. A voltage control terminal Vc is connected to an intermediate connection point between the diode D12 and the capacitor C12 via a resistor R11. A control circuit for switching the transmission path of the high frequency switch 21 is connected to the voltage control terminal Vc.

  A series circuit of a transmission line 14 and a capacitor C13 is connected to both ends (between the anode and cathode) of the diode D11. The transmission line 14 and the capacitor C13 are for improving isolation when the diode D11 is in the OFF state.

  Here, as the transmission lines 12 and 13, a distributed constant line having a characteristic impedance of 40Ω or more, or a high-frequency inductor is used. In the case of a distributed constant line, the line lengths of the transmission lines 12 and 13 are set in a range of λ / 12 to λ / 4 (λ: wavelength of a desired frequency). The transmission line 14 is also a distributed constant line or a high frequency inductor. Further, the stray capacitances Cf1, Cf2, and Cf3 generated between the terminals Tx, ANT, and Rx and the ground can function as bypass capacitors for impedance matching.

  Next, transmission / reception using the high-frequency switch 21 will be described. When a positive potential is applied to the voltage control terminal Vc, this voltage acts as a forward bias voltage for the diodes D11 and D12. Accordingly, the diodes D11 and D12 are turned on. At this time, the DC component is cut by the capacitor C12, and the voltage supplied to the voltage control terminal Vc is applied to the circuit including the diodes D11 and D12.

  As a result, the transmission signal that has entered the transmission terminal Tx is transmitted to the antenna terminal ANT via the diode D11. At this time, the transmission signal is hardly transmitted to the reception terminal Rx. This is because when the diode D12 is in the ON state, the inductance of the diode D12 and the capacitance of the capacitor C12 resonate in series at the transmission frequency, and the impedance becomes zero. That is, since the transmission lines 12 and 13 operate as a λ / 4 short stub, the transmission terminal Tx and the antenna terminal ANT are connected, and the reception terminal Rx is grounded.

  Further, when the voltage control terminal Vc is set to the ground potential, the diodes D11 and D12 are turned off. Accordingly, the transmission terminal Tx and the antenna terminal ANT are blocked, and the reception terminal Rx and the ground are also blocked. As a result, the reception signal that has entered the antenna terminal ANT is transmitted to the reception terminal Rx via the transmission line 13 and hardly transmitted to the transmission terminal Tx. Thus, the high frequency switch 21 can switch the transmission path of the transmission / reception signal by controlling the bias voltage applied to the voltage control terminal Vc.

  Furthermore, the high frequency switch 21 connects the cathodes and anodes of the diodes D11 and D12 in the opposite direction to the cathodes and anodes of the diodes D1 and D2 of the conventional high frequency switch 1 shown in FIG. The large-capacity and large bias-cutting capacitor C1, the voltage control terminal Vc1, and the resistor Ra that the switch 1 has can be eliminated. That is, the high-frequency switch 21 requires only a small capacitor C12 having a small capacity connected between the diode D12 and the ground on the receiving terminal Rx side. The capacitance of the capacitor C12 is, for example, 10 pF near 1 GHz and 3 pF near 2 GHz. Therefore, the high-frequency switch 21 can be reduced in size.

  Further, by adjusting the capacitance of the capacitor C12, the isolation between the antenna terminal ANT and the reception terminal Rx when the transmission terminal Tx and the antenna terminal ANT are connected is made larger than that of the conventional high-frequency switch. Can do. As a result, the insertion loss between the transmission terminal Tx and the antenna terminal ANT can be reduced.

  Furthermore, the voltage control terminal Vc is short-circuited to the ground during transmission (when the diode D12 is in an ON state), and is blocked from a high-frequency signal due to the high impedance of the diode D12 during reception (when the diode D12 is in an OFF state). A large isolation between the control circuit connected to the control terminal Vc and the high frequency signal can be secured.

  Next, an example of a multilayer high-frequency switch having the electric circuit shown in FIG. 1 will be described with reference to FIGS. As shown in FIG. 2, the high-frequency switch 31 includes a dielectric sheet 45 provided with distributed constant lines 32a and 32b, a dielectric sheet 45 provided with large-area ground electrodes 35 and 36, a distributed constant line 33a, The dielectric sheet 45 is provided with 33b, 34a, 34b, the dielectric sheet 45 provided with pads 50a to 54b with via holes, and the like.

  The distributed constant lines 33 a and 33 b have, for example, a spiral shape and are provided on the left side of the sheet 45. The lead portion 42 a of the distributed constant line 33 a is exposed on the left side of the back side of the sheet 45, and the lead portion 42 b of the distributed constant line 33 b is exposed on the left side of the sheet 45. The distributed constant lines 33 a and 33 b are electrically connected in series via via holes 58 provided in the sheet 45 to form the transmission line 12.

  The distributed constant lines 34 a and 34 b are generally meandered and are provided on the right side of the sheet 45. The lead-out portion 43a of the distributed constant line 34a is exposed at the center of the front side of the sheet 45, and the lead-out portion 43b of the distributed constant line 34b is exposed at the right side of the back side of the sheet 45. The distributed constant lines 34 a and 34 b are electrically connected in series via via holes 59 provided in the sheet 45 to form the transmission line 13.

  The distributed constant lines 32 a and 32 b have a spiral shape and are provided on the right side of the sheet 45. The distributed constant lines 32 a and 32 b are electrically connected in series via via holes 57 provided in the sheet 45 to form the transmission line 14. As described above, the transmission lines 12 to 14 having a constant characteristic impedance are formed of two layers of distributed constant lines 33a, 33b, 34a, 34b, 32a, and 32b, respectively, so that the length of the transmission line per layer is increased. This is shorter than before. Therefore, the size of the sheet 45 can be reduced, and the high frequency switch 31 having a small occupation area with respect to a printed circuit board or the like can be obtained.

  The ground electrodes 35 and 36 are each provided in a large area on the surface of the sheet 45. The lead portions 35a and 36a of the ground electrodes 35 and 36 are exposed on the left side of the sheet 45, the lead portions 35b and 36b are exposed on the right side of the sheet 45, and the lead portions 35c and 36c are in the center of the back side of the sheet 45. The drawers 35d and 36d are exposed on the right side of the front side of the sheet 45. Transmission lines 12 and 13 are arranged in parallel between these two ground electrodes 35 and 36.

Furthermore, extraction electrodes 37, 38, 39 and a relay electrode 40 are provided on the surface of the sheet 45 on which the distributed constant line 32a is provided. One end of each of the extraction electrodes 37 and 38 is exposed on the left and right sides of the back side of the sheet 45, and one end of the extraction electrode 39 is exposed on the left side of the front side of the sheet 45. The distributed constant line 32a is electrically connected to the pad 52b with via hole, the extraction electrode 37 is electrically connected to the pads 50a, 52a with via hole, the extraction electrode 38 is electrically connected to the pad 51a with via hole, The relay electrode 40 is electrically connected to pads 53b, 54b, 51b with via holes.

  An extraction electrode 41 is provided on the surface of the sheet 45 on which the distributed constant line 32b is provided. One end of the extraction electrode 41 is exposed at the center of the front side of the sheet 45. The lead electrode 41 is electrically connected to the distributed constant line 32 b and is also electrically connected to the pad 50 b with via hole via the via hole 55. Further, the via-holed pad 53 a is electrically connected to the ground electrode 35 via via holes 56 a and 56 b provided in the sheet 45.

  Each sheet 45 having the above configuration is stacked and integrally fired to form a laminate 60 as shown in FIG. A transmission terminal Tx, a ground terminal G3, and a reception terminal Rx are formed on the left side, the center, and the right side of the side surface portion on the back side of the multilayer body 60, respectively. A voltage control terminal Vc, an antenna terminal ANT, and a ground terminal G4 are formed on the left side, the center, and the right side of the side surface portion on the near side of the multilayer body 60, respectively. Ground terminals G <b> 1 and G <b> 2 are formed on the left and right side portions of the multilayer body 60, respectively.

  The transmission terminal Tx is electrically connected to one end portion of the transmission line 12 (specifically, the lead portion 42a of the distributed constant line 33a) and the lead electrode 37. The receiving terminal Rx is electrically connected to one end portion of the transmission line 13 (specifically, the lead portion 43b of the distributed constant line 34b) and the lead electrode 38. The antenna terminal ANT is electrically connected to the other end portion of the transmission line 13 (specifically, the lead portion 43a of the distributed constant line 34a) and the lead electrode 41. The voltage control terminal Vc is electrically connected to the extraction electrode 39. The ground terminal G1 is electrically connected to the other end portion of the transmission line 12 (specifically, the lead portion 42b of the distributed constant line 33b) and the lead portions 35a and 36a of the ground electrodes 35 and 36. . The ground terminals G2, G3, G4 are electrically connected to the lead portions 35b, 36b, 35c, 36c, 35d, 36d of the ground electrodes 35, 36, respectively.

  Furthermore, the cathode and anode electrodes of the diode D11 are soldered to the pads 50a and 50b on the upper surface of the multilayer body 60, respectively, and the cathode and anode electrodes of the diode D12 are soldered to the pads 51a and 51b, respectively. , 52b is soldered with the terminal electrode of the capacitor C13, the pads 53a and 53b are soldered with the terminal electrode of the capacitor C12, and the pads 54a and 54b are soldered with the terminal electrodes of the resistor R11.

  In this way, the surface mount type multilayer high frequency switch 31 having the electric circuit shown in FIG. 1 is obtained. Since the multilayer high-frequency switch 31 does not need to incorporate or mount the large-capacity bias cut capacitor C1 included in the conventional high-frequency switch 1 shown in FIG. However, the number of layers of the stacked body 60 can be reduced. Further, the size of the sheet 45 can be reduced, and the area occupied by the high-frequency switch 31 on the printed circuit board can be reduced.

  Further, the conventional high-frequency switch 1 shown in FIG. 6 has a complicated wiring because the resistor Ra (mounted component) is electrically connected to the intermediate connection point between the transmission line 2 and the capacitor C1. On the other hand, in the high frequency switch 31, one end of the transmission line 12 is connected to the ground terminal G1, so that the wiring is simplified, and the insertion loss due to the reduction in the number of layers of the stacked body 60 and the reduction in unnecessary coupling. Can be improved.

[Second Embodiment, FIGS. 4 and 5]
Another example of the multilayer high-frequency switch having the electric circuit shown in FIG. 1 will be described with reference to FIGS. In the high frequency switch 61 of the second embodiment, a bias cut capacitor C12 is built in the laminate. 4 and 5, the same parts and portions as those in FIGS. 2 and 3 are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the high frequency switch 61 includes a dielectric sheet 45 provided with a distributed constant line 62 and a capacitor electrode 70, a dielectric sheet 45 provided with large-area ground electrodes 35 and 36, and a distributed constant line 63. , 64, a dielectric sheet 45 provided with lead-out electrodes 37, 38, etc., a dielectric sheet 45 provided with pads 50a, 50b with via holes, and the like.

  The distributed constant line 62 has, for example, a meander shape, and forms the transmission line 14. One end of the distributed constant line 62 is electrically connected to the extraction electrode 41, and the other end is electrically connected to a pad 52 b with a via hole via a via hole 67 provided in the sheet 45. The distributed constant lines 63 and 64 are also generally meandered, and form transmission lines 12 and 13, respectively. One lead portion 63 a of the distributed constant line 63 is exposed on the left side of the back side of the sheet 45, and the other lead portion 63 b is exposed on the left side of the sheet 45. One lead portion 64 a of the distributed constant line 64 is exposed at the center of the front side of the sheet 45, and the other lead portion 64 b is exposed at the right side of the back side of the sheet 45. Thus, the number of layers of the laminated body 80 (described later) can be further suppressed by configuring the transmission lines 12 to 14 with one layer of the distributed constant lines 63, 64, and 62, respectively.

  The capacitor electrode 70 faces the ground electrode 35 with the sheet 45 interposed therebetween, and forms a capacitor C12 together with the ground electrode 35. The capacitor electrode 70 is electrically connected to the relay electrode 65 provided on the sheet 45 through the via hole 66. Further, the relay electrode 65 is electrically connected to the pads 51b and 54b with via holes.

  Each sheet 45 having the above configuration is stacked and fired integrally to form a laminate 80 as shown in FIG. A transmission terminal Tx, a ground terminal G3, and a reception terminal Rx are formed on the side surface portion on the back side of the stacked body 80, respectively. A voltage control terminal Vc, an antenna terminal ANT, and a ground terminal G4 are formed on the side surface portion on the near side of the stacked body 80, respectively. Ground terminals G <b> 1 and G <b> 2 are formed on the left and right side portions of the laminate 80, respectively.

  The transmission terminal Tx is electrically connected to the extraction portion 63 a of the distributed constant line 63 and the extraction electrode 37. The receiving terminal Rx is electrically connected to the lead portion 64 b of the distributed constant line 64 and the lead electrode 38. The antenna terminal ANT is electrically connected to the lead portion 64 a of the distributed constant line 64 and the lead electrode 41. The voltage control terminal Vc is electrically connected to the extraction electrode 39. The ground terminal G1 is electrically connected to the lead portion 63b of the distributed constant line 63 and the lead portions 35a and 36a of the ground electrodes 35 and 36. The ground terminals G2, G3, G4 are electrically connected to the lead portions 35b, 36b, 35c, 36c, 35d, 36d of the ground electrodes 35, 36, respectively.

  Further, the cathode and anode electrodes of the diode D11 are soldered to the pads 50a and 50b on the upper surface of the multilayer body 80, respectively, and the cathode and anode electrodes of the diode D12 are soldered to the pads 51a and 51b, respectively. , 52b is soldered to the terminal electrode of the capacitor C13, and the pads 54a, 54b are soldered to the terminal electrode of the resistor R11.

  In this way, the surface mount type laminated high frequency switch 61 having the electric circuit shown in FIG. 1 is obtained. Since the capacitor C12 has a small capacity, the area of the capacitor electrode 70 is small, and the occupied area is small even if the capacitor C12 is built in the multilayer body 80. Therefore, the high frequency switch 61 can be made smaller than before.

  Further, since the high-frequency switch 61 includes the capacitor C12 in the multilayer body 80, the length of the wiring path from the capacitor C12 to the ground is shorter than when the capacitor C12 is mounted on the multilayer body as a mounting component. Becomes shorter. Accordingly, the residual inductance is reduced and the bias cut function is improved. Further, the value of the capacitor C12 can be finely adjusted by changing the size of the capacitor electrode 70, and the antenna terminal ANT and the reception terminal Rx when the transmission terminal Tx and the antenna terminal ANT are connected. Can be made larger than that of the conventional high-frequency switch, and the effect of reducing the insertion loss between the transmission terminal Tx and the antenna terminal ANT can be enjoyed efficiently.

[Other embodiments]
The high-frequency switch according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the gist.

  For example, in the high-frequency switch 21 shown in FIG. 1, a series circuit of a transmission line and a capacitor may be connected to both ends (between the anode and cathode) of the diode D12. Alternatively, a capacitor is connected in parallel to both ends of the diodes D11 and D12 (between the anode and the cathode) in parallel with the series circuit of the transmission line and the capacitor, so that the isolation when the diodes D11 and D12 are in the OFF state is improved. May be. Further, a resistor (10 KΩ or more) for voltage stabilization at the time of applying a reverse bias may be connected in parallel to both ends of the diodes D11 and D12.

  In the above embodiment, since a DC bias is applied to the terminals Tx, Rx, and ANT, a separate coupling capacitor for bias cutting is separately applied to these terminals Tx to ANT as necessary. You may connect.

1 is an electric circuit diagram showing a first embodiment of a high-frequency switch according to the present invention. FIG. 2 is an exploded perspective view of a multilayer high-frequency switch having the electric circuit shown in FIG. The perspective view which shows the external appearance of the high frequency switch shown in FIG. The disassembled perspective view which shows 2nd Example of the high frequency switch which concerns on this invention. The external appearance perspective view of the high frequency switch shown in FIG. The electric circuit diagram which shows the conventional high frequency switch.

Explanation of symbols

21, 31, 61 ... high frequency switch D11, D12 ... diode C12 ... capacitor 12, 13 ... transmission line
53 ... Ground electrodes 60, 80 ... Laminated body
70: Capacitor electrode Tx: Transmission terminal ANT: Antenna terminal Rx: Reception terminal Vc: Voltage control terminal G1, G2, G3, G4 ... Ground terminal

Claims (1)

A transmission terminal, an antenna terminal, a reception terminal, and a voltage control terminal;
A first diode having a cathode electrically connected to the transmitting terminal and an anode electrically connected to the antenna terminal;
A first transmission line electrically connected between the antenna terminal and the receiving terminal;
A second diode having a cathode electrically connected to the receiving terminal and an anode electrically connected to the voltage control terminal;
A second transmission line having one end electrically connected to the transmission terminal and the other end directly grounded;
A capacitor electrically connected between the voltage control terminal and ground, and connected in series to the second diode;
A high frequency switch comprising:
One end of the second transmission line and the cathode of the first diode are directly connected;
By setting the voltage control terminal to a predetermined potential, the first and second diodes are simultaneously controlled to be in an ON state or an OFF state,
In the ON state, the inductance of the second diode and the capacitance of the capacitor resonate at the transmission frequency,
A structure in which a plurality of dielectric layers, the first and second transmission lines, the capacitor electrode of the capacitor, and a ground electrode that is disposed directly opposite to the capacitor electrode to form the capacitor are stacked. On the surface of the laminated body, the transmission terminal, the reception terminal, the antenna terminal, and the voltage control terminal are provided, and the first and second diodes are respectively mounted.
High frequency switch characterized by

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