JPH0799463A - Communication equipment - Google Patents

Abstract

PURPOSE:To provide a communication equipment in which the characteristic impedance is matched depending on each of plural transmission reception circuits in use without incurring the increase in the circuit scale. CONSTITUTION:The communication equipment is an equipment having at least 22 transmission reception circuits 12-15, and is provided with a filter 1 eliminating spurious radiation, matching circuits 4, 5 located at the input and / or output side and varying the impedance in response to an input control voltage, a control voltage generating circuit 16 generating a predetermined control voltage to the matching circuits in response to the transmission reception circuit in use, 1st changeover switches 10, 11 switching the connection between one of the transmission reception circuits and the filter, 2nd changeover switches 21, 22 switching the control voltage outputted from a control voltage generating circuit to the matching circuits, and a switch control means linking the 2nd changeover switches 21, 22 with the 1st changeover switches 10, 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided on the input side and / or output side of a filter for removing unnecessary spurious,
The present invention relates to a communication device including a matching circuit for matching the characteristic impedance of a high frequency transmission circuit including a transmission / reception circuit.

[0002]

2. Description of the Related Art Generally, in a high frequency transmission circuit of a communication device including a transmission / reception circuit, it is necessary to match a load impedance connected to a terminal of a transmission line with a characteristic impedance of a used circuit. In this way, the transmission line has the same effect as if it were extended infinitely, the propagating radio wave can move forward without any obstruction, and the generation of reflected waves and standing waves can be prevented. It Therefore, in the high frequency transmission circuit of the communication device,
An impedance matching circuit, which is usually a matching circuit, is provided on the input side and / or output side of the filter used to remove spurious in the transmission signal, and the characteristic impedance of the circuit is matched to reduce power loss. I am trying.

By the way, when the filter itself to be used has the characteristic impedance of the circuit, it is not necessary to purposely provide the matching circuit, and the filter having the characteristic impedance is directly inserted into the circuit for use. Is possible. However, if the filter to be used does not have the characteristic impedance, or if the impedance characteristic seen from the input side or the output side of the filter inserted in the circuit does not have the characteristic impedance of the circuit, it is inevitable. It is necessary to provide a matching circuit. Then, by using such a matching circuit, generation of reflected waves is suppressed, damage to the circuit is prevented, and electric power is efficiently transmitted. Note that the matching circuit is often formed of fixed reactance elements.

FIG. 4 is a block diagram showing a conventional example of installing a matching circuit in a communication device. In this example, a high frequency signal transmission / reception circuit 41 (including an RF transmission circuit, an RF reception circuit, and a transmission / reception signal changeover switch) and an intermediate frequency signal transmission / reception circuit 42 (an IF transmission circuit and an IF reception circuit, and And a transmission / reception signal changeover switch) are respectively formed as monolithic IC elements. When taking such a form,
A matching circuit cannot be provided for each of the transmission circuit and the reception circuit. Therefore, as shown in the figure, the filter 43 is inserted at a position between the high-frequency transmission lines that connect the high-frequency signal transmission / reception circuit 41 and the intermediate-frequency signal transmission / reception circuit 42, and the matching circuits 44 and 45 respectively The filter 43 is provided at a position sandwiching the filter 43.

FIG. 5 is a block diagram showing another conventional example of installation of a matching circuit in a communication device. In this example, matching circuits 52 and 54 are provided for each of the two high-frequency signal transmission circuits 51 and 53 (both shown as RF transmission circuits in the figure), and further two high-frequency signal transmission circuits are provided. Each of the receiving circuits 55 and 57 (in the figure, both are RF
(Shown as the receiving circuit), the matching circuit 5
6 and 58 are provided. Similarly, matching circuits 62 and 64 are provided for each of the intermediate frequency signal transmission circuits 61 and 63 (both shown as IF transmission circuits in the figure), and two intermediate frequency signal transmission circuits are provided. Matching circuits 66 and 68 are provided for the receiving circuits 55 and 57 (both shown as IF receiving circuits in the figure).

The high frequency signal transmitting circuit 51 and the matching circuit 52, the high frequency signal transmitting circuit 53 and the matching circuit 54, the high frequency signal receiving circuit 55 and the matching circuit 56, the high frequency signal receiving circuit 57 and the matching circuit 58, It is adapted to be selected by the transmission / reception signal changeover switch 59. Similarly, the intermediate frequency signal transmitting circuit 61 and the matching circuit 62, the intermediate frequency signal transmitting circuit 63 and the matching circuit 64, the intermediate frequency signal receiving circuit 65 and the matching circuit 66, the intermediate frequency signal receiving circuit 67 and the matching circuit 68, Is selected by the transmission / reception signal changeover switch 69.

Further, transmission / reception signal changeover switches 59 and 69
High frequency signal transmitting / receiving circuit group 50 connected by
A filter 70 for removing spurious is inserted at a position between the high-frequency transmission line which connects the intermediate frequency signal transmitting / receiving circuit group 60 and the intermediate frequency signal transmitting / receiving circuit group 60. The example shown here is an example of installation of a matching circuit in the case where all of the plurality of transmitting / receiving circuits 50 and 60 to be connected have unique impedance characteristics, and as shown in the figure, for each transmitting / receiving circuit, Matching circuits are individually provided.

[0008]

However, in the installation example of the matching circuit shown in FIG. 4 described above, the high frequency signal transmission / reception circuit 41 and the intermediate frequency signal transmission / reception circuit 42 are internally formed as a monolithic IC element together with the transmission / reception signal changeover switch. Therefore, impedance matching cannot be achieved for each circuit. That is, if the impedance characteristics of both circuits are not the same, optimum impedance matching cannot be achieved only by the installed matching circuit, and the amplitude characteristics of the filter (that is, the power level value at a certain frequency The characteristics represented by the abscissa, specifically, the characteristics representing the amount of attenuation) and the group delay characteristics (differentiating the phase with frequency, of the characteristics represented by the frequency on the abscissa). That is, in terms of waveform reproducibility, flatness is required within a predetermined band).

For this reason, at present, either the impedance characteristic of one of the transmitting and receiving circuits is sacrificed, or the compromise point of the impedance characteristic of each circuit is found, and after a slight deterioration of the filter characteristic is recognized. The only way is to use a communication device. Further, in the above-mentioned example of installation of the matching circuit shown in FIG. 5, there are a plurality of transmitting / receiving circuits to be used, and a matching circuit is provided for each circuit. Therefore, there is a great possibility that the impedance matching state is changed when there is performance variation or when the performance is changed due to temperature change or the like during use. In such a case, the group delay characteristic and the amplitude characteristic of the filter with respect to a certain frequency are destabilized, and the transmission characteristic of the transmission system deteriorates. Furthermore,
In this example, since many matching circuits are used, the circuit scale is obviously increased.

The present invention has been made in view of the above circumstances, and communication in which characteristic impedances can be matched according to a plurality of individual transmission / reception circuits to be used without causing an increase in circuit scale. The purpose is to provide a machine.

[0011]

In order to achieve the above object, the invention according to claim 1 is a communication device having at least two transmission / reception circuits, wherein unnecessary spurious signals are transmitted from the transmitted / received signals. Is provided on the input side and / or the output side of the filter in order to match the characteristic impedance of the filter for removing the noise and the characteristic impedance of the high frequency transmission circuit including the transmission / reception circuit and the filter, and changes the impedance according to the input control voltage. A matching circuit, a control voltage generation circuit for generating a predetermined control voltage to be input to the matching circuit according to the transmission / reception circuit used, and a first switching connection between one of the transmission / reception circuits and the filter. The changeover switch and the input of the control voltage output from the control voltage generation circuit to the matching circuit are switched. When the one of the transmission / reception circuits and the matching circuit are connected by the second changeover switch and the first changeover switch, a predetermined control voltage output from the control voltage generation circuit is supplied to the matching circuit. The second changeover switch to the first
Switch control means for performing control in conjunction with the change-over switch.

According to a second aspect of the present invention, the control voltage generating circuit is provided with a predetermined number of different power sources for generating a predetermined control voltage to be input to the matching circuit, and the second changeover switch is provided. It is characterized in that a predetermined power source to be used is selected by the switching operation.

[0013]

According to the above structure, the communication device according to the invention of claim 1 is provided with at least two transmitting / receiving circuits. Further, a filter is inserted in a high-frequency transmission circuit including the transmission / reception circuit to remove unnecessary spurious from the transmission / reception signal to be transmitted. Further, on the input side and / or the output side of such a filter, a matching circuit that changes the impedance according to the input control voltage is provided in order to match the characteristic impedance of the high frequency transmission circuit. In addition, a control voltage generating circuit for generating a predetermined control voltage to be applied to the matching circuit is provided in order to achieve impedance matching between the transmitting / receiving circuit and the filter used.

On the other hand, the connection between one of the transmitting and receiving circuits and the filter is switched by the first changeover switch. Further, the connection between the matching circuit and the control voltage generating circuit is switched by the second changeover switch. The switch operation of the first and second changeover switches is controlled by the switch control means. In this case, the switch control means
The second changeover switch is used so that the predetermined control voltage output from the control voltage generation circuit is input to the matching circuit when one of the transmission / reception circuits and the matching circuit are connected by the first changeover switch. The switch is adapted to interlock with the first changeover switch.

According to the second aspect of the present invention, the control voltage generating circuit is provided with the predetermined number of different power sources for generating the predetermined control voltage to be input to the matching circuit. Then, the required predetermined power source among them is selected and used by the switching operation of the second changeover switch. As a result, in the present communication device, since the predetermined control voltage is input to the matching circuit according to the transmitting / receiving circuit used, it is possible to match the characteristic impedance in the high frequency transmission circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration for characteristic impedance matching in a high frequency transmission circuit of a communication device according to the present invention. Here, as the filter 1, a surface acoustic wave filter (also referred to as a SAW filter) used in an intermediate frequency band is realized by simultaneously extracting and adding the amplitude and phase of a surface wave propagating on a solid surface. Is what you are trying to do)
Is used. The input / output terminals 2 and 3 of the filter 1 are connected to the input / output terminals 6 of the variable matching circuits 4 and 5, respectively.
And 7 are connected (the configuration and operation of the variable matching circuit will be described in detail with reference to FIG. 2). The input / output terminals 8 and 9 of the variable matching circuits 4 and 5 are connected to the RF transmission circuit 12 and the RF reception circuit 13 via the signal change-over switches 10 and 11, respectively.
The F transmission circuit 14 and the IF reception circuit 15 are connected.

The signal change-over switches 10 and 11 are controlled to be switched so that the IF signal is transmitted during signal transmission.
A high-frequency transmission circuit extending from the transmission / reception circuit 14 to the RF transmission circuit 12 is formed. Similarly, at the time of signal reception, the high-frequency transmission circuit to the RF reception circuit 13 → A transmission circuit will be formed. On the other hand, a control voltage generator 16 is provided to generate a control voltage for the variable matching circuits 4 and 5 provided to match the characteristic impedance of the high frequency transmission circuit formed during signal transmission or signal reception. ing. The output terminals 17 and 18 of the control voltage generator 16 are connected to the control input terminal 23 of the variable matching circuit 4 via the matching changeover switch 21, and the output terminals 19 and 20 of the control voltage generator 16 are It is connected to the control input terminal 24 of the variable matching circuit 5 via the matching changeover switch 22. Further, the matching changeover switch 21, the signal changeover switch 10, and
The matching changeover switch 22 and the signal changeover switch 11 are interlocked with each other to perform the changeover operation. (Note that the configuration and operation of the control voltage generator 16 will be described in detail with reference to FIG. 3).

As described above, during signal transmission and signal reception, a predetermined control voltage is applied to the matching circuits 4 and 5 provided at the positions sandwiching the filter 1. Then, impedance matching is performed between the RF transmitting circuit 12 and the filter 1, the IF transmitting circuit 14 and the filter 1, the RF receiving circuit 13 and the filter 1, and the IF receiving circuit 15 and the filter 1 to perform high frequency transmission of the communication device. Matching of characteristic impedance in the circuit is achieved.

FIG. 2 shows the variable matching circuit 4 shown in FIG.
3 is a circuit diagram showing the configuration of FIG. This variable matching circuit 4
1, the input / output terminal 8 is connected to the signal changeover switch 10, the input / output terminal 6 is connected to the filter 2, and the control input terminal 23 is further connected via the matching changeover switch 21. Are connected to the control voltage generator 16.

The circuit configuration of the variable matching circuit 4 (internal configuration surrounded by a chain line in the figure) is as follows. A coupling capacitor C ₁ is provided in series between the input / output terminals 6-8. A coil L is connected between the coupling capacitor C ₁ and the input / output terminal 6 with the other end grounded. Similarly, between the coupling capacitor C ₁ and the input / output terminal 6, a varicap diode (also referred to as a varistor) C _V whose capacity is changed by a DC voltage has its anode side grounded and its coupling side C ₂ connected to its cathode side. Connected through. Further, the above-mentioned control input terminal 23 is connected between the varicap diode C _V and the coupling capacitor C ₂ .

According to the above configuration, when a DC voltage is applied to the control input terminal 23 from the control voltage generator 16, the capacitance of the varicap diode C _V changes and the input / output terminal 8 side is changed. Variable matching circuit 4 from the side of impedance Z ₁ and input / output terminal 6 looking at matching circuit
The impedance Z ₂ seen changes and impedance matching is performed.

Now, the coupling capacitor C₁Capacity of C₁,
Inductance of coil L is L, coupling capacitor C₂of
Capacity is C₂, Varicap diode C_VChange the capacity of
If ΔC, impedance Z₁And impedance Z
₂Is calculated by the following equation [Equation 1]. [Equation 1] Z₁= [1 / jωC₁+ JωL (C₂+ ΔC) / {(C₂+ ΔC) -ω²LC ₂ ΔC}] // Z_Four....

Z ₂ = [jωL (C ₂ + ΔC) / {(C ₂ + ΔC) −ω ² LC ₂ ΔC}] // (Z ₃ + 1 / jωC ₁ ) ... However, Z ₄ in the above equation is the impedance when the circuit in the subsequent stage following the filter 1 is seen from the input / output terminal 6, and Z ₃ in the above equation is the circuit in the stage preceding the signal changeover switch 10 from the input / output terminal 8. Is the impedance when looking at. In addition, ω in the above equations and is the angular frequency, and the calculation symbol “//” is for calculating A // B = A · B / A + B. That is, [1 / jωC ₁ + jω
L (C ₂ + ΔC) / {(C ₂ + ΔC) −ω ² LC ₂ Δ
If C}] _{= Zx, Z 1 = Zx ·} Z 4 / Zx + Z 4
Becomes

Here, when the variable matching circuit 4 is in the impedance matching state, at the input / output terminal 8, Z
The conjugate impedance of ₁ becomes equal to Z ₃ , and at the input / output terminal 6, the conjugate impedance of Z ₂ becomes equal to Z ₄ . Therefore, it is possible to match the impedance of the high frequency transmission circuit by changing the value of ΔC in the above equation and in order to realize such a relationship. As a result, the amplitude characteristic and the group delay characteristic of the filter 1 change, and the ideal transfer characteristic of the high frequency transmission circuit is realized.

FIG. 3 is a circuit diagram showing a configuration of control voltage generator 16 shown in FIG. In the control voltage generator 16, a power supply V _RFTX that generates a voltage applied to the control input terminal 23 of the variable matching circuit 4 so that the RF transmission circuit 12 and the filter 1 are impedance-matched,
Similarly, a power supply V _RFRX for generating an applied voltage for impedance matching between the RF receiving circuit 13 and the filter 1 and I
A power supply V _IFTX that generates a voltage applied to the control input terminal 24 of the variable matching circuit 5 so that the F transmission circuit 14 and the filter 1 are impedance-matched, as well as the IF reception circuit 15 and the filter 1. And a power supply V _IFRX for generating an applied voltage for impedance matching of the.

[0026] Then, the constant voltage generated by the power supply V _RFTX from the output terminal 17, a constant voltage generated by the power supply V _RFRX is from the output terminal 18, is inputted to the matching selector switch 21. Similarly, the constant voltage generated by the power supply V _IFTX is output terminal 2
From 0, the constant voltage generated by the power supply V _IFRX is input from the output terminal 19 to the matching changeover switch 22. Also,
The matching changeover switch 21 and the signal changeover switch 10 are interlocked by a control means (not shown) (indicated by an alternate long and short dash line in the figure to indicate interlocking state) so that they can be simultaneously switched during signal transmission and signal reception. ing. Similarly, the matching changeover switch 22 and the signal changeover switch 11 are adapted to be interlocked by the control means, and are simultaneously changed over at the time of signal transmission and at the time of signal reception.

As a result, the required control voltage is applied from the control voltage generator 16 to the variable matching circuit 4 and the variable matching circuit 5 depending on the signal transmission and the signal reception, respectively. Therefore, the impedance matching between the transmitting and receiving circuits is achieved. In order to determine the control voltage to be applied to the variable matching circuit 4 and the variable matching circuit 5 described above, the reference control voltage value is determined as a design specification at the time of manufacturing each matching circuit.

Further, in the above embodiment, the four power supplies constituting the control voltage generator 16 are all constant voltage generating power supplies, but in some cases, the generated voltage may be variable. It is possible, and if you do this,
It covers fluctuation factors in high-frequency transmission circuits (for example, there are fluctuation factors such as the impedance characteristics of each matching circuit composed of fixed reactance elements fluctuating due to temperature changes, etc.) to ensure impedance matching more reliably. It is possible to plan.

[0029]

As described above, according to the present invention, even when a plurality of transmission / reception circuits used in a communication device are integrated together with a signal changeover switch as a monolithic IC, the input side of the filter and the / Since a predetermined control voltage according to the transmitter / receiver circuit used is applied to the matching circuit provided on the output side, variations in impedance characteristics in the high frequency transmission circuit can be absorbed and the characteristic impedance of the circuit can be matched. Becomes as a result,
The amplitude characteristic and group delay characteristic of the filter are stabilized, and the transfer characteristic of the transmission system becomes extremely good.

Further, the first changeover switch is controlled to connect the necessary transmitting / receiving circuit and the matching circuit, and at the same time, the second changeover switch is controlled to change the control voltage to be applied to the matching circuit. Since the switching is performed, it is not necessary to provide a matching circuit for each of the plurality of transmission / reception circuits as in the related art, and the characteristic impedance of the circuits can be matched without increasing the circuit scale.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration for characteristic impedance matching in a high frequency transmission circuit of a communication device according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a variable matching circuit 4 shown in FIG.

3 is a circuit diagram showing a configuration of a control voltage generator 16 shown in FIG.

FIG. 4 is a block diagram showing a conventional example of installation of a matching circuit in a communication device.

FIG. 5 is a block diagram showing another conventional example of installation of a matching circuit in a communication device.

[Explanation of symbols]

 1 Filter 4, 5 Variable Matching Circuit 10, 11 Signal Changeover Switch 12 RF Transmission Circuit 13 RF Reception Circuit 14 IF Transmission Circuit 15 IF Reception Circuit 16 Control Voltage Generator 21, 22 Matching Changeover Switch

Claims (2)

[Claims] 1. A communication device having at least two transmitting / receiving circuits, wherein a filter for removing unnecessary spurious from a transmitted / received signal and a characteristic impedance of a high-frequency transmission circuit including the transmitting / receiving circuit and the filter are set. For matching, a matching circuit provided on the input side and / or output side of the filter for changing impedance according to an input control voltage, and to the matching circuit according to the transmitting / receiving circuit used A control voltage generation circuit that generates a predetermined control voltage, a first changeover switch that switches connection between one of the transmission / reception circuits and the filter, and a control voltage output from the control voltage generation circuit to the matching circuit. A second changeover switch for changing the input of the When one of the circuits and the matching circuit are connected, the second changeover switch is set to the first switch so that a predetermined control voltage output from the control voltage generation circuit is input to the matching circuit. And a switch control means for performing control for interlocking with the changeover switch of. 2. The control voltage generating circuit includes a predetermined number of different power sources for generating a predetermined control voltage to be input to the matching circuit, and a predetermined operation to be performed by a switching operation of the second changeover switch. The communication device according to claim 1, wherein a power source is selected.