JP2000124708A - Variable attenuator and mobile communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the impedance of a coupler and also attain the control of attenuation by connecting a diode between every coupling port of a sub- transmission line of the coupler and the ground and controlling the voltage applied to the diode to vary the resistance of the diode. SOLUTION: A positive voltage is applied to the control terminals Vc1 and Vc2 of diodes D1 and D2 which are connected to both ends of a sub-transmission line 13. When the positive voltage is increased from 0 V, the resistance of diodes D1 and D2 are reduced. Thus, the high frequency signal value that is sent from an input port Pi of a coupler 11 to an output port Po via a main transmission line 12 is reduced and the attenuation of a variable attenuator 10 is increased. Thereby the variable control is possible to the voltage applied to the terminals Vc1 and Vc2 and the resistance of diodes D1 and D2 are variable. Then the variable control is possible to the high frequency signal value that is sent to the port Po from the port Pi via the line 12. As a result, the variable control is possible to the attenuation of the attenuator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a variable attenuator and a mobile communication device.

[0002]

2. Description of the Related Art In general, a mobile communication device such as a portable telephone uses a variable attenuator in which a plurality of attenuators having different attenuations are switched by a switch in order to variably attenuate a high-frequency signal.

FIG. 9 shows a conventional variable attenuator used in a microwave band. The variable attenuator 50 has an input port 51, an output port 52, field effect transistors (hereinafter referred to as FETs) 531 to 533, 541 to 543 for switching conduction or cutoff between input and output, and the attenuation of each is A ( dB), B (dB), and C (dB). T-type resistance attenuators 551 to 553 are included. The drain electrodes D of the FETs 531 to 533, which are input-side switching devices, each have a capacitor C51. FET5 which is connected to the input port 51 via the
The drain electrodes 41 to 543 are connected to the capacitors C, respectively.
It is connected to the output port 52 via 52. Also, FE
The source electrode S of T531-533 is connected to the capacitor C53-
The resistance R of the T-type resistance attenuators 551 to 553 via C55
Source electrodes S of the FETs 541 to 543 are connected to one ends of the resistors R54 to R56 of the T-type resistor attenuators 551 to 553 via capacitors C56 to C58, respectively. Further, R5 of the T-type resistance attenuators 551 to 553
The other ends of R1 to R53 are connected to the other ends of R54 to R56, respectively, and their connection points are grounded via resistors R57 to R59. Further, FETs 531-533, 541
To 543 are grounded via capacitors C59 to C64 and connected to control terminals Vc51 to Vc56 via inductors L51 to L56 for blocking high frequency.

[0004] From the control terminals Vc51 to Vc56, for example, a negative voltage or 0V voltage which is substantially the same as the pinch-off voltage of the FET to be controlled is selectively applied. That is, 0V is applied to the control terminals Vc51 and Vc54 included in the first path,
Control terminals Vc52 and Vc included in the second and third paths
FETs to be controlled to 55, Vc53 and Vc56 respectively
When the same negative voltage as the pinch-off voltage of 532, 542, 533, 543 is applied, the channel resistance between the drain and the source of the FETs 531, 541 is reduced by the T-type attenuator 5.
51 is sufficiently smaller than the characteristic impedance. On the other hand, the channel resistance between the drain and the source of each of the FETs 532, 542, 533, and 543 is extremely large because a depletion layer extends in the channel. As a result, input port 5
1 passes through only the first path including the T-type resistance attenuator 551, and the T-type resistance attenuators 552, 5
The second and third paths including 53 are in a cutoff state. Therefore, the amount of attenuation between the input port 51 and the output port 52 is A (dB).

When the amount of attenuation between the input port 51 and the output port 52 is switched to B (dB), 0 V is applied to the control terminals Vc 52 and Vc 55 included in the second path,
And control terminals Vc51 and Vc5 included in the third path.
4, FET5 to be controlled to Vc53 and Vc56, respectively
A second voltage including a T-type resistor attenuator 552 by applying a negative voltage substantially equal to the pinch-off voltage of
Make only the route pass. The same operation can be used to switch the attenuation amount to C (dB). By the above operation, a plurality of attenuation amounts can be variably controlled discontinuously.

[0006]

However, in the above-mentioned conventional variable attenuator, a plurality of attenuators having different attenuations are switched by a switch, so that the attenuation is continuously variably controlled. There was a problem that can not be.

Further, since the FETs constituting the switch included in each path need to be a multiple of the number of variable attenuations, the number of components is increased, and the configuration of the switch and the variable attenuator itself are further increased. There has been a problem that the configuration becomes complicated, the variable attenuator becomes large, and the manufacturing cost increases.

The present invention has been made to solve such a problem, and has as its object to provide a small variable attenuator capable of continuously variably controlling the amount of attenuation.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a variable attenuator according to the present invention comprises a coupler comprising a main transmission line having an input / output port and a sub transmission line having a coupling port; And a diode connected between each coupling port of the sub transmission line and the ground.

In addition, a plurality of the couplers are used, and a first transmission line of a main transmission line of an adjacent coupler among the plurality of couplers is used.
The plurality of couplers are connected in tandem by connecting a second port to a second port.

[0011] Further, among the plurality of couplers connected in cascade, the first coupling port and the second coupling port of the sub-transmission line of the adjacent coupler are connected and shared. .

A ceramic substrate formed by laminating a plurality of ceramic sheet layers; a main transmission line and a sub transmission line forming the coupler are formed on at least one of the inside and the main surface of the ceramic substrate; The diode is mounted on a main surface of a ceramic substrate.

A mobile communication device according to the present invention is characterized by using the above-described variable attenuator.

According to the variable attenuator of the present invention, since the diodes are connected between the respective coupling ports of the sub-transmission lines of the coupler and the ground, the applied voltages applied to the diodes can be variably controlled. Thus, the resistance of these diodes can be variably controlled, and as a result, the impedance of the coupler can be variably controlled.

According to the mobile communication device of the present invention, since a small variable attenuator is used, a small mobile communication device can be realized while maintaining the reception balance of the receiving system.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a first embodiment of a variable attenuator according to the present invention. The variable attenuator 10 includes a coupler 11 and diodes D1 and D2.

The coupler 11 has a main transmission line 12 having input and output ports Pi and Po having first and second ports at both ends, and a secondary transmission line 131 and 132 having both ends at first and second coupling ports 131 and 132. It has a transmission line 13.

The diodes D 1 and D 2 are connected to the first and second coupling ports 13 of the sub-transmission line 13 of the coupler 11.
The first and second coupling ports 131 and 132 are connected between the first and second grounds and the ground so that the first and second coupling ports 131 and 132 serve as anodes. The control terminals Vc1 and Vc2 are connected to the anodes of the diodes D1 and D2 via the resistors R1 and R2.

The operation of the variable attenuator 10 having the above-described circuit configuration will be described. The control terminal Vc is connected to the diodes D1 and D2.
By applying a positive voltage from 1 and Vc2 as an applied voltage, the resistance of the diodes D1 and D2 decreases, and the characteristic impedance of the coupler 11 decreases. As a result, the amount of the high-frequency signal sent from the input port Pi of the coupler 11 to the output port Po via the main transmission line 12 decreases, and the attenuation of the variable attenuator 10 increases.

That is, when the positive voltage applied from the control terminals Vc1 and Vc2 to the diodes D1 and D2 is gradually increased from 0 V, the diode D
The resistances of D1 and D2 gradually decrease. As a result, the amount of the high-frequency signal transmitted from the input port Pi of the coupler 11 to the output port Po via the main transmission line 12 gradually decreases, and the attenuation of the variable attenuator 10 gradually increases.

Therefore, by variably controlling the voltage applied from the control terminals Vc1 and Vc2, the resistance of the diodes D1 and D2 can be variably controlled, and the impedance of the coupler 11 can be variably controlled. As a result, the amount of the high-frequency signal transmitted from the input port Pi of the coupler 11 to the output port Po via the main transmission line 12 can be variably controlled, so that the attenuation of the variable attenuator 10 can be variably controlled. .

FIG. 2 is an exploded perspective view of a variable attenuator provided with the circuit of FIG. The variable attenuator 10 includes barium oxide,
A ceramic substrate 14 is formed by laminating sheet layers 14a to 14c made of ceramics containing aluminum oxide and silica as main components. Diodes D1 and D2 and resistors R1 and R2 are mounted on the ceramic substrate 14, , An input port Pi and an output port Po of the coupler 11, control terminals Vc1 and Vc2 for applying a control voltage to the diodes D1 and D2, and a ground terminal G.

On the sheet layer 14a constituting the ceramic substrate 14, diodes D1 and D2 and a resistor R
1, a land La made of copper for mounting R2, a main transmission line 12 and a sub-transmission line 13 made of copper forming the coupler 11 on the sheet layer 14b, and made of copper on the sheet layer 14c. The ground electrodes 15 are respectively formed by screen printing or the like.

The connection between the coupling ports 131 and 132 at both ends of the sub transmission line 13 forming the coupler 11 and the diodes D1 and D2, and the connection between the diodes D1 and D2 and the ground electrode 15 are provided on the sheet layers 14a and 14b. This is performed by the formed via hole electrode VH, which is a connecting means.

According to the variable attenuator of the first embodiment, since the diodes are connected between the respective coupling ports of the sub-transmission lines of the coupler and the ground, the applied voltages applied to the diodes are connected. , The resistance of these diodes can be variably controlled, and as a result, the impedance of the coupler can be variably controlled. Therefore, since the amount of the high-frequency signal sent from the input port to the output port of the coupler can be variably controlled, the attenuation of the variable attenuator can be variably controlled, and the return loss when the VSWR is 1.5 or less is obtained. Can be set to −13 (dB) or less.

Further, since the variable attenuator is composed of a coupler and a diode, the configuration of the variable attenuator is simplified.
As a result, the size of the variable attenuator can be reduced, and the manufacturing cost can be reduced.

Furthermore, a ceramic substrate formed by laminating a plurality of sheet layers made of ceramics is provided, and the main transmission line and the sub transmission line made of copper, which form a coupler, are built into the ceramic substrate. It is possible to cope with a high frequency band of 1 GHz or more by a shortening effect and a reduction in loss due to copper.

FIG. 3 is a circuit diagram of a variable attenuator according to a second embodiment of the present invention. The variable attenuator 20 is different from the variable attenuator 10 of the first embodiment (FIG. 1) in that three couplers 21 to 23 are connected in cascade.

That is, the cascaded couplers 21 and 2
3, the second port 242 of the main transmission line 24 of the adjacent coupler 21, the first port 251 of the main transmission line 25 of the coupler 22, and the second port 242 of the main transmission line 25 of the adjacent coupler 22. The second port 252 and the first port 261 of the main transmission line 26 of the coupler 23 are connected.

The first transmission line 24 of the coupler 21
Is the input port Pi, and the second port 262 of the main transmission line 26 of the coupler 23 is the output port Po.

The sub transmission line 2 of the couplers 21 to 23
7 to 29 first and second coupling ports 271 to 27
First and second coupling ports 271-291, 272-2 between 291, 272-292 and the ground
Diodes D1 to D6 are connected such that the 92 side becomes the anode. Control terminals Vc1 to Vc6 are connected to anodes of the diodes D1 to D6 via resistors R1 to R6, respectively.

FIG. 4 is a graph showing changes in the attenuation and return loss of the variable attenuator shown in FIG. In this case, the voltage applied from the control terminals Vc1 to Vc6 to the diodes D1 to D6 is changed to change the resistance values of the diodes D1 to D6 in the range of 200 to 50 (Ω).

The horizontal axis of FIG. 4 shows the resistance values of these diodes D1 to D6. The return loss is
The case where VSWR (voltage standing wave ratio) is 1.5 or less is shown.

From the above, as is apparent from FIG. 4, the diodes D1 to D6 are connected from the control terminals Vc1 to Vc6.
By controlling the applied voltage to be applied to the diodes D1 to D6.
Is controlled within the range of 200 to 50 (Ω), so that the attenuation of the variable attenuator 20 is -3.8 to -10.1.
(DB), and the VSWR is 1.
It can be seen that the reflection loss at 5 or less can be made -15 (dB) or less.

FIG. 5 is another diagram showing changes in the attenuation and return loss of the variable attenuator shown in FIG. In this case, the voltages applied from the control terminals Vc1 to Vc6 to the diodes D1 to D6 are changed, and the diodes D1, D3, D3
4, D6 has a constant resistance of 150 (Ω), and the diode D
2, the resistance value of D5 is changed in the range of 50 to 4 (Ω).

The horizontal axis of FIG. 5 shows the resistance values of these diodes D2 and D5. The return loss is
The case where VSWR (voltage standing wave ratio) is 1.5 or less is shown.

From the above, as is apparent from FIG. 5, the diodes D1 to D6 are connected from the control terminals Vc1 to Vc6.
Is controlled by controlling the applied voltage to be applied to the diodes D1 and D1.
3, the resistance of D4 and D6 is fixed at 150 (Ω), and the resistance of diodes D2 and D5 is controlled in the range of 50 to 4 (Ω), so that the attenuation of variable attenuator 20 is -5.5.
-15.1 (dB).
The reflection loss when the SWR is 1.5 or less is -13 (dB).
You can see below.

According to the variable attenuator of the second embodiment, since a plurality of couplers are connected in cascade, the range in which the amount of attenuation can be variably controlled can be increased. Therefore,
The number of components of a mobile communication device equipped with the variable attenuator can be reduced, and as a result, the size of the mobile communication device can be reduced.

FIG. 6 is a circuit diagram of a third embodiment of the variable attenuator according to the present invention. The variable attenuator 30 is different from the variable attenuator 20 of the second embodiment (FIG. 3) in that the second coupling port 372 of the sub-transmission line 37 of the adjacent coupler 31 and the sub-transmission of the The first coupling port 381 of the line 38 is connected to the second coupling port 38 of the sub transmission line 38 of the adjacent coupler 32.
2 is connected to the first coupling port 391 of the sub transmission line 39 of the coupler 33.

That is, between the first coupling port 371 of the sub transmission line 37 of the coupler 31 and the ground,
The diode D1 is connected so that the first coupling port 371 side becomes an anode. Further, the second coupling port 372 of the sub transmission line 37 of the coupler 31 connected and shared and the first coupling port 372 of the sub transmission line 38 of the coupler 32 are connected.
Between the connection point with the coupling port 381 and the ground so that the connection point side becomes the anode.
Is connected.

Further, the connected and shared coupler 32
Between the connection point between the second coupling port 382 of the sub transmission line 38 of the second transmission line 38 and the first coupling port 391 of the sub transmission line 39 of the coupler 33 and the ground, so that the connection point side becomes an anode. Is connected. A diode D4 is connected between the second coupling port 392 of the auxiliary transmission line 39 of the coupler 33 and the ground so that the second coupling port 392 side becomes an anode.
Is connected.

The control terminals Vc1 to Vc4 are connected to the anodes of the diodes D1 to D4 via resistors R1 to R4.
Are respectively connected.

FIG. 7 is a graph showing changes in attenuation and return loss of the variable attenuator shown in FIG. In this case, the voltage applied from the control terminals Vc1 to Vc6 to the diodes D1 to D6 is changed so that the resistance values of the diodes D1 and D4 are constant at 150 (Ω), and the resistance values of the diodes D2 and D3 are 150 to 10 (Ω).

The horizontal axis in FIG. 7 shows the resistance values of these diodes D2 and D3. The return loss is
The case where VSWR (voltage standing wave ratio) is 1.5 or less is shown.

From the above, as is apparent from FIG. 7, the diodes D1 to D6 are connected from the control terminals Vc1 to Vc6.
By controlling the applied voltage to be applied to the diodes D1 and D4.
Are fixed at 150 (Ω), and diodes D2 and D2
3 is controlled in the range of 150 to 10 (Ω), so that the attenuation of the variable attenuator 30 is set to −4.9 to −15.
It can be seen that the control can be performed in the range of 3 (dB) and the reflection loss when the VSWR is 1.5 or less can be made -15 (dB) or less.

According to the variable attenuator of the third embodiment, since the first and second coupling ports of the sub-transmission lines of the adjacent couplers are connected and shared, First of the cascaded coupler sub-transmission lines
The same attenuation can be obtained even if the number of diodes connected between the second coupling port and the ground is reduced.

Therefore, the variable control range of the attenuation of the variable attenuator can be increased, and the number of components constituting the variable attenuator can be reduced. Can be realized.

FIG. 8 shows a PC which is one of the mobile communication devices.
It is a block diagram of the portable telephone for S (Personal Cellular System). The mobile phone 40 includes a receiving antenna 41, a first receiving system 42 corresponding to the antenna 41, a transmitting / receiving antenna 43, a duplexer 44 connected to the antenna 43, and a transmitting system 4 corresponding to the antenna 43.
5, a second receiving system 46 is provided.

The first and second receiving systems 42 and 46 include low-noise amplifiers LNA1 and LNA2 and a band-pass filter BP.
F1, BPF2, attenuators Att1, Att2, and mixers MIX1, MIX2. The transmission system 45 includes a high-output amplifier PA, a band-pass filter BPF3, and a mixer MI.
X3 is included. At this time, the attenuators Att1 and Att2 are used to keep the reception balance constant.

In this configuration, the first and second
Attenuators Att1 and Att included in the receiving systems 42 and 46 of FIG.
2, the small variable attenuator 1 shown in FIGS. 1, 3, and 6
If 0, 20, and 30 are used, a small-sized mobile phone can be realized while keeping the reception balance of the reception system constant.

In the first to third embodiments described above,
Although the case where the main transmission line and the sub transmission line forming the coupler are formed inside the ceramic substrate has been described, the same effect can be obtained by forming the main transmission line and the sub transmission line forming the coupler on the main surface of the ceramic substrate. be able to.

In the second and third embodiments described above,
Although the case where three couplers are connected in tandem has been described,
It may be two or four or more. In this case, as the number of couplers increases, the range in which the attenuation can be variably controlled can be increased.

[0053]

According to the variable attenuator of the first aspect, since diodes are connected between the coupling ports of the sub-transmission lines of the coupler and the ground, the voltages applied to these diodes can be varied. By controlling, the resistance of those diodes can be variably controlled, and as a result, the impedance of the coupler can be variably controlled.

Therefore, since the amount of the high-frequency signal sent from the input port to the output port of the coupler can be variably controlled, the amount of attenuation of the variable attenuator can be variably controlled, and when the VSWR is 1.5 or less. Can be reduced to -13 (dB) or less.

Since the variable attenuator is composed of a coupler and a diode, the configuration of the variable attenuator is simplified.
As a result, the size of the variable attenuator can be reduced, and the manufacturing cost can be reduced.

According to the variable attenuator of the second aspect, since a plurality of couplers are connected in cascade, the range in which the amount of attenuation can be variably controlled can be increased. Therefore, the number of components of a mobile communication device equipped with the variable attenuator can be reduced, and as a result, the size of the mobile communication device can be reduced.

According to the variable attenuator of the third aspect, the first coupling port and the second coupling port of the sub-transmission lines of the adjacent couplers are connected and shared.
Similar attenuation can be obtained even if the number of diodes connected between the first and second coupling ports of the sub-transmission lines of the cascaded couplers and the ground is reduced.

Therefore, the variable control range of the attenuation of the variable attenuator can be increased, and the number of components constituting the variable attenuator can be reduced. Can be realized.

According to a fourth aspect of the present invention, there is provided a variable attenuator comprising: a ceramic substrate formed by laminating a plurality of ceramic sheet layers; a main transmission line forming a coupler on at least one of the inside and the main surface of the ceramic substrate; Since the sub transmission line is formed, it is possible to cope with a high frequency band of 1 GHz or more due to the wavelength shortening effect of the ceramic substrate.

According to the mobile communication device of the fifth aspect, since a small variable attenuator is used, a small mobile communication device can be realized while maintaining the reception balance of the receiving system.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment according to a variable attenuator of the present invention.

FIG. 2 is an exploded perspective view of the variable attenuator of FIG.

FIG. 3 is a circuit diagram of a second embodiment according to the variable attenuator of the present invention.

FIG. 4 is a diagram showing attenuation and return loss of the variable attenuator of FIG. 3;

FIG. 5 is another diagram showing attenuation and return loss of the variable attenuator of FIG. 3;

FIG. 6 is a circuit diagram of a third embodiment according to the variable attenuator of the present invention.

FIG. 7 is a diagram illustrating attenuation and return loss of the variable attenuator of FIG. 5;

FIG. 8 is a block diagram of a mobile phone as one of the mobile communication devices.

FIG. 9 is a circuit diagram showing a conventional variable attenuator.

[Explanation of symbols]

10,20,30 Variable attenuator 11,21-23,31-33 Coupler 12,24-26,34-36 Main transmission line 121,241-261,341-361 First port 122,242-262,342 362 Second port 13, 27-29, 37-39 Secondary transmission line 131, 271-291, 371-391 First coupling port 132, 272-292, 372-392 Second coupling port 40 Move Body communication equipment (mobile phone) D1-D6 Diode

Claims (5)

[Claims] 1. A coupler comprising a main transmission line having a first port and a second port at both ends, a sub-transmission line having first and second coupling ports at both ends, and a sub-transmission of the coupler. A variable attenuator comprising: a diode connected between first and second coupling ports of a line and a ground. 2. A method of connecting a plurality of couplers by connecting a first port and a second port of a main transmission line of an adjacent coupler among the plurality of couplers. The variable attenuator according to claim 1, wherein the variable attenuator is connected in cascade. 3. The plurality of cascade-connected couplers.
The variable attenuator according to claim 2, wherein the first coupling port and the second coupling port of the auxiliary transmission line of the adjacent coupler are connected and shared. 4. A ceramic substrate formed by laminating a plurality of sheet layers made of ceramic, wherein a main transmission line and a sub transmission line forming the coupler are formed on at least one of the inside and the main surface of the ceramic substrate, 4. The variable attenuator according to claim 1, wherein the diode is mounted on a main surface of a ceramic substrate. 5. A mobile communication device using the variable attenuator according to claim 1.