JPH0336446B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a single sideband signal generation circuit.

(Prior art) Telecommunications systems using single sideband signals were first applied to wired carrier telephones in 1918, and have since been widely used in multiplex communications using unarmored cables, coaxial cables, and wireless frequency division multiplex communications. It is well known that in addition to being put into practical use, it is also used for secret communications, and various types of single sideband signal generation circuits have been proposed.

A common way to obtain a single sideband signal is to obtain a double sideband signal with the carrier wave suppressed, for example by using a balanced modulator, and then convert the sideband signal on one side of the signal to Either the carrier wave and the signal can be selectively separated by a filter to generate a single sideband signal, or the carrier wave and the signal can be phase-shifted by 90 degrees and supplied to two balanced modulators. A known method is to generate a single sideband signal without using a filter by adding the output signals of (See "Electronic Circuits" by Masamitsu, pp. 136-138).

(Problems to be Solved by the Invention) In a single sideband signal generation circuit configured to generate a single sideband signal by the conventional single sideband signal generation means described above, , not only when the circuit is configured using a filter, but even when it is configured without using a filter, the use of many capacitors is necessary when configuring these circuits. Although it is necessary, the necessity to use a large number of capacitors as circuit components poses a major hindrance to the monolithic integration of the above-described circuits.

In other words, in monolithic integrated circuits, the capacitors are externally attached, so the number of pins in monolithic integrated circuits increases in proportion to the number of capacitors used in the integrated circuit, but From the perspective of cost reduction,
In order to obtain a monolithic integrated circuit with a small number of pins, it is desirable that the single sideband signal generation circuit to be monolithically integrated has a circuit configuration with as few capacitors as possible.

Now, if the conventional single sideband signal generation circuit described above were to be made into a monolithic integrated circuit, it would be possible to use the filter mentioned above as an example of the conventional single sideband signal generation circuit. Compared to
A single sideband signal can be generated without using a filter by supplying the carrier wave and the signal with a phase shift of 90 degrees to two balanced modulators, and adding the output signals from the two balanced modulators. The third
The conventional single-sideband signal generation circuit shown in the figure is advantageous for monolithic integration because it uses fewer capacitors.

In the single sideband signal generation circuit shown in Fig. 3, 1 is an input terminal for a modulation signal (for example, an audio signal), and 2 and 11 are 90 degree phase shifters that give a 90 degree phase shift to the input signal. 6 is a low-pass filter, 7 is an output terminal for a single sideband signal, 8 is an input terminal for a carrier wave, 9 and 10 are analog multipliers, and 12 is an adder.

Now, the modulation signal sinPt is supplied to the input terminal 1 of the single sideband signal generation circuit shown in FIG.
Also, carrier wave sinCt is applied to carrier wave input terminal 8.
is supplied, the analog multiplier 9 multiplies the modulation signal sinPt and the carrier wave sinCt,
Further, in the analog multiplier 10, the modulation signal cosPt and the carrier wave whose phase is shifted by 90 degrees by a 90 degree phase shifter are used.
Multiplication with cosCt is performed.

If the amplitude of the output signal from the analog multiplier 9 is A, the output signal from the analog multiplier 9 is as follows.
It becomes as shown in equation (1).

2AsinPt・sinCt=Acos(P-C)t-Acos(P+
C)t...(1) Furthermore, if the amplitude of the output signal from the analog multiplier 10 is B, the output signal from the analog multiplier 10 will be as shown by the following equation (2).

2BcosPt・cosCt =Bcos(P-C)t+Bcos(P+C)t...(2) Now, assuming that A and B are in the relationship A=B, the output signal from the analog multiplier 9 and When the output signal from the analog multiplier 10 is added by the adder 12, the output signal from the adder 12 becomes a single sideband signal as shown by the following equation (3).

{Acos(P-C)t-Acos(P+C)t} +{Acos(P-C)t+Acos(P+C)t} =2Acos(P-C)t...(3) Figure 4 shows the above-mentioned 3 This figure shows the operating waveforms of each part in the conventional single sideband signal generation circuit shown in the figure. ,Also,
Modulation signal sinPt supplied to input terminal 1 in Figure 3
The signal cosPt which is phase-shifted by 90 degrees by the 90-degree phase shifter 2 and supplied to the analog multiplier 10 is shown in FIG. 4a, and so on.
The signal shown in FIG. 3 corresponds to the signal shown in the part a in FIG. 3, and the signal shown in b in FIG. Similarly, the signals indicated by c to h in FIG. 4 correspond to the signals of the parts indicated by c to h in FIG. 3, respectively. In addition,
Reference numeral 6 in FIG. 3 indicates a circuit having a function of removing harmonic components from the output signal of the adder 12, such as a low-pass filter. Further, in the operational waveform diagram shown in FIG. 4, the waveform of the carrier wave is shown as a square wave to facilitate understanding of the circuit operation of the single sideband signal generation circuit. This point also applies to FIG. 2, which will be described later.

Now, the conventional single-sideband signal generation circuit that has been explained with reference to FIGS. 3 and 4 does not use a filter, so the single-sideband signal generation circuit that uses a filter Although the number of capacitors used in the circuit is small compared to the waveband signal generation circuit, the conventional single sideband signal generation circuit shown in Figure 3 uses two 90 degree phase shifters 2. , 11, the number of capacitors used in the circuit becomes an obstacle to monolithic integration of the single sideband signal generation circuit, and the number of capacitors used in the circuit It was desired that a circuit for generating a single sideband signal with even fewer sidebands be developed.

(Means for Solving the Problems) The present invention provides a 90° phase shift that gives an input signal a 90° phase shift.
means for supplying the output signal from the 90 degree phase shifting means to the first analog switch; means for inverting the phase of the input signal; and means for inverting the phase of the input signal; means for supplying the second analog switch; the output signal from the first analog switch is used as a minuend signal; and the output signal from the second analog switch is used as a subtract signal; subtraction of the two signals; a first subtraction circuit for performing the above-mentioned first subtraction circuit; means for supplying the output signal from the first subtraction circuit to a third analog switch and a fourth analog switch; and an output signal from the third analog switch. is used as the minuend signal, and the output signal from the fourth analog switch described above is used as the subtraction signal, and a second subtraction circuit performs subtraction between the two signals, and a signal with a period of 1/2 of the period of the carrier wave is switched. The means for controlling the opening and closing of the second analog switch described above as a control signal and the switching control signal having a period of 1/2 of the period of the carrier wave used to control the opening and closing of the second analog switch described above have a switching polarity opposite to that of the control signal. means for controlling opening/closing of the first analog switch by means of a control signal; means for obtaining a carrier wave by dividing the signal having a period of 1/2 of the period of the carrier wave by 1/2; means for controlling the opening and closing of the fourth analog switch described above as a switching control signal, and means for controlling opening and closing of the third analog switch described above using a signal obtained by inverting the phase of the carrier wave as a switching control signal. The present invention provides a single sideband signal generation circuit consisting of the following.

(Example) Hereinafter, the specific contents of the single sideband signal generation circuit of the present invention will be explained in detail. FIG. 1 is a block diagram of an embodiment of the single sideband signal generation circuit of the present invention, in which 1 is an input terminal for a modulation signal (for example, an audio signal), and 2 is a 90 Phase shifter, 3 is an input terminal for a signal having a period of 1/2 that of the carrier wave, 4 and 5 are inverters, 6 is a low-pass filter, 7 is an output terminal for a single sideband signal, PIA
is an inverting amplifier, SW1 is a first analog switch, SW2 is a second analog switch, SW3 is a third analog switch, and SW4 is a fourth analog switch (for example, electronic switches are used as the analog switches SW1 to SW4). However, in order to simplify the explanation, each analog switch SW1 to SW4 is shown in the drawing as a type of mechanical switch, and the following explanation will also be based on the drawing. ), SUB1 is the first subtracter, SUB2 is the second subtracter, and Div is the 1/2 frequency divider.

In the single sideband signal generation circuit of the present invention shown in FIG. 1, the modulated signal S1 {a in FIG. 2} supplied to the input terminal 1 is transmitted through the 90 degree phase shifter 2 and the inverting amplifier PIA. is given to. And as mentioned above
Output signal S2 from 90 degree phase shifter 2 {b in Figure 2}
is given to the first analog switch SW1,
Further, the output signal S3 of the inverting amplifier PIA mentioned above is supplied to the second analog switch SW2.

The second analog switch SW2 receives a signal as shown in e of FIG. Frequency signal}C1 is given as the switching control signal C1 to perform the opening/closing control operation and output the signal S5 as shown in g in Fig. 2, which is sent to the first subtractor.
Supplies SUB1 as a subtraction signal.

In addition, the first analog switch SW1
is the signal in FIG. 2 obtained by inverting the polarity of a signal C1 (signal with a frequency twice the frequency of the carrier wave) having a period half that of the carrier wave supplied to the input terminal 3 using the inverter 4. The signal C2 shown in d is applied as the switching control signal C2 to perform the opening/closing control operation, outputting the signal S4 shown in f in FIG. The subtractor SUB1 is supplied as the minuend signal.

The first subtracter SUB1 performs a subtraction operation on the two signals S4 and S5 supplied thereto, and the output signal S6=(S4-S5) is shown in h of FIG. It outputs a signal S6 like this, and sends it to the third analog switch SW3 and the fourth analog switch SW3.
It is supplied to the analog switch SW4.

The fourth analog switch SW4 receives a signal as shown in e of FIG. Frequency signal}j in Figure 2, where C1 is divided into 1/2 by 1/2 frequency divider Div
The signal Cr1 shown in is the switching control signal.
Cr1 performs the opening/closing control operation and outputs a signal S8 as shown at 1 in FIG. 2, which is supplied to the second subtracter SUB2 as a subtraction signal.

In addition, the third analog switch SW3
is a signal C1 having a period half the period of the carrier wave supplied to the signal input terminal 3 {a signal with a frequency twice the frequency of the carrier wave} C1, and the 1/2 frequency divider Div
The signal Cr1 as shown in j in FIG. 2 is divided into 1/2 by the inverter 5, and the polarity is inverted by the inverter 5, and the signal Cr1 as shown in i in FIG.
Cr1 is given as the switching control signal Cr2 to perform the opening/closing control operation, output the signal S7 as shown in k in FIG. 2, and send it to the second switch.
is supplied to the subtractor SUB2 as the minuend signal.

The second subtracter SUB2 performs a subtraction operation on the two signals S7 and S8 supplied thereto, and the output signal S9=(S7-S8) is shown in m in FIG. If a signal S9 such as
A single sideband signal S10 as shown at n in the figure
is sent.

(Effects) As is clear from the detailed explanation above, the single sideband signal generation circuit of the present invention includes a 90 degree phase shifter that provides a 90 degree phase shift to an input signal, and a 90 degree phase shifter as described above. means for supplying the output signal from the phase means to the first analog switch; means for phase inverting the input signal; and means for supplying the output signal from the phase inversion means to the second analog switch; a first subtraction circuit that performs subtraction between the two signals by using the output signal from the first analog switch as the minuend signal and using the output signal from the second analog switch as the subtrahend signal; means for supplying the output signal from the first subtraction circuit to a third analog switch and a fourth analog switch; and a means for supplying the output signal from the third analog switch as a minuend signal;
a second subtraction circuit that subtracts the two signals by using the output signal from the fourth analog switch as a subtraction signal; means for controlling the opening and closing of the second analog switch, and a switching control signal having a polarity opposite to that of the switching control signal having a period of 1/2 of the period of the carrier wave used to control the opening and closing of the second analog switch. means for controlling the opening and closing of the first analog switch; means for obtaining a carrier wave by dividing the frequency of a signal having a period of 1/2 of the period of the carrier wave to 1/2; It is constructed by including means for controlling the opening and closing of the fourth analog switch, and means for controlling the opening and closing of the third analog switch, using a signal obtained by inverting the phase of the carrier wave as a switching control signal. The single sideband signal generation circuit of the present invention requires a 90 degree phase shift circuit compared to the conventional single sideband signal generation circuit already described with reference to FIGS. 3 and 4. Therefore, a single sideband signal generation circuit with the same performance can be configured with a reduced number of external capacitors. The generation circuit can be easily and inexpensively provided as a monolithic integrated circuit with a small number of pins. In addition, in the single sideband signal generation circuit of the present invention, only one 90-degree phase shifter is required, which reduces the number of man-hours for adjusting the amount of phase shift of the 90-degree phase shifter. Even if the amount of phase shift in the single-sideband signal generation circuit is slightly different, the sidebands that should be removed will not be removed. The fact that there is only one phase shifter is extremely advantageous compared to the case where multiple 90 degree phase shifters are used as in the conventional single sideband signal generation circuit described above. This greatly contributes to improving the performance of the sideband signal generation circuit, and furthermore, the fewer number of circuit components compared to the conventional single sideband signal generation circuit improves the stability of the circuit. , which helps reduce the cost of the single sideband signal generation circuit. Furthermore, in the single sideband signal generation circuit of the present invention, a DC drift component that occurs in the signal due to the temperature characteristics of a switching circuit such as an analog switch is subtracted from the output signals from two analog switches using a subtraction circuit. As a result, a highly stable single sideband signal can be generated.In this way, the single sideband signal generation circuit of the present invention has excellent temperature characteristics as well. Since the circuit has high performance, it can be said to be a single sideband signal generation circuit that is optimal for integration into an integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the single sideband signal generation circuit of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the single sideband signal generation circuit of the present invention, and FIG.
FIG. 4 is a block diagram of a conventional single sideband signal generation circuit, and FIG. 4 is a waveform diagram for explaining the operation of the conventional single sideband signal generation circuit. 1... Input terminal for a modulation signal (for example, audio signal), 2, 11... 90 degree phase shifter, 3... Input terminal for a signal having a period of 1/2 of the period of the carrier wave, 4,
5... Inverter, 6... Circuit having a function of removing high frequency components (e.g., low-pass filter), 7...
...Single sideband signal output terminal, 9, 10...Analog multiplier, 12...Adder, SW1 to SW4...
First to fourth analog switches, PIA...inverting amplifier, SUB1, SUB2...first and second subtracters.

Claims (1)

[Claims] 1. 90 degree phase shifting means for imparting a 90 degree phase shift to the input signal, means for supplying the output signal from the 90 degree phase shifting means to the first analog switch, and means for inverting the phase of the input signal. and means for supplying the output signal from the above-mentioned phase inverting means to the second analog switch; the output signal from the above-mentioned first analog switch is used as the minuend signal; a first subtraction circuit that subtracts the two signals by using the output signal as a subtraction signal; and means for supplying the output signal from the first subtraction circuit to a third analog switch and a fourth analog switch. , a second subtraction circuit that subtracts the two signals by using the output signal from the third analog switch as the minuend signal and the output signal from the fourth analog switch as the subtrahend signal, and a carrier wave. means for controlling the opening/closing of the second analog switch by using a signal with a cycle of 1/2 of the cycle as a switching control signal;
Means for controlling the opening/closing of the first analog switch using a switching control signal having a polarity opposite to that of the switching control signal having a period of 1/2 of the period of the carrier wave used to control the opening/closing of the second analog switch. , means for obtaining a carrier wave by frequency-dividing a signal having a period of 1/2 of the period of the carrier wave, and means for controlling the opening/closing of the fourth analog switch using the carrier wave as a switching control signal. and means for controlling the opening and closing of the third analog switch by using a signal obtained by inverting the phase of the carrier wave as a switching control signal.