JPS61179605A - Circuit of generating single side band signal - Google Patents

Abstract

PURPOSE:To attain ease of monolithic circuit integration by providing a means applying an output signal from a 90 deg. phase shift means to an analog switch and a means inverting the phase of an input signal and applying subtraction and switching control to an output signal from the analog switch sequentially so as to decrease number of externally mounted capacitors. CONSTITUTION:A modulation signal S1 fed to an input terminal 1 is given to the 90 deg. phase shifter 2 and an inverse amplifier PIA, and an output signal S2 from the 90 deg. phase shifter 2 is given to the 1st analog switch SW1 and an output signal S3 of the inverse amplifier PIA is fed to the 2nd analog switch SW2. The 2nd analog switch SW2 outputs a signal S5, which is fed to the 1st subtractor SUB1 as a decrement signal. Similarly, the 2nd subtractor SUB2 applies subtraction to two signals S7, S8, a signal S9 is sent via a circuit 6 having a function rejecting a high frequency component and a single side band signal S10 is sent to an output terminal 7.

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 unmounted 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.
Various types of single sideband signal generation circuits have been proposed in the past.

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 Alternatively, the carrier wave and the signal may be selectively separated using a filter to generate a single sideband signal, or the carrier wave and the signal may be
For example, by supplying the phase-shifted signal by 0 degrees to two balanced modulators and adding the output signals from the two balanced modulators, a single sideband signal is generated without using a filter. (See, for example, "Electronic Circuit ■" by Masamitsu Kawakami, pages 136 to 138, published by Kyoritsu Shuppan Co., Ltd., May 25, 1955).

(Problems to be Solved by the Invention) In the single sideband signal generation circuit configured to generate a single sideband signal by the conventional single sideband signal generation means described above, Of course, if the circuit is constructed using a filter, even if it is constructed without using a filter, the use of many capacitors is necessary when configuring these circuits. However, the necessity to use a large number of capacitors as circuit components poses a major hindrance to monolithically integrated circuits.

In other words, in a monolithic integrated circuit, the capacitors are externally attached, so the number of pins in a monolithic integrated circuit increases in proportion to the number of capacitors used in the integrated circuit, but it is necessary for integrated circuits. From the perspective of cost reduction.

In order to obtain a monolithic integrated circuit with a small number of bins, 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 , the carrier wave and the signal are
A signal shifted by 0 degrees is supplied to two balanced modulators, and the output signals from the two balanced modulators are added to generate a single sideband signal without using a filter. The conventional single-sideband signal generation circuit shown in FIG. 3 is more 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);
11 is a 90 degree phase shifter that gives a 90 degree phase shift to the input signal, 6 is a low pass filter, 7 is a single sideband signal output terminal, 8 is a carrier wave input terminal, 9.10 is an analog multiplication vessel,
12 is an adder.

Now, the modulation signal sin P t is supplied to the input terminal 1 of the single sideband signal generation circuit shown in FIG.
If a carrier wave of 5 inCt is supplied to the carrier wave input terminal 8, the analog multiplier 9 inputs the modulated signal sin
Multiplication of P t and carrier wave gin Ct is performed.

In addition, the analog multiplier 10 uses a 90 degree phase shifter to
Modulated signal cos P t and carrier wave c phase-shifted by 0 degrees
Multiplication with oset is performed.

If the amplitude of the output signal from the analog multiplier 9 is A, then
The output signal from the analog multiplier 9 is expressed by the following equation (1).

2AsinPt−sinCt, =Acos(P−
C) t - Acos (P + C) t - (1) Also, if the amplitude of the output signal from the analog multiplier 1o is B, then
The output signal from the analog multiplier 10 is expressed by the following equation (2).

2BcosPicosCt, =Bcos(P-C)70Bcos(P+C)t-(2) Now, assuming that the above-mentioned A and B are in the relationship A=B, the output signal from the above-mentioned 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)7+Acos(P+C)t
) =2Acos(P−C)t−・=(3) FIG. 4 shows the operating waveforms of each part in the conventional single sideband signal generation circuit shown in FIG. The modulated signal 5inPt supplied to the input terminal l in FIG. 3 is shown in FIG. 4(b), and the modulated signal 5inP7 supplied to the input terminal 1 in FIG. The signal c supplied to the analog multiplier 10 with a phase shift of 90 degrees by
osPt is shown in FIG. 4(a). As such, the signal shown in (a) of FIG.
Corresponds to the signal in the part shown in (
The signal shown in b) corresponds to the signal in the part b in FIG.
The signals shown in h) are respectively shown in c” in Fig. 3.
These are the signals of the portions indicated by h. Note that 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 one circuit is small compared to a 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 a hindrance 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 degree phase shifter that provides a 90 degree phase shift to an input signal, and supplies an output signal from the 90 degree phase shifter to a first analog switch. With means.

means for inverting the phase of the input signal, means for supplying the output signal from the phase inversion means to the second analog switch, and the output signal from the first analog switch being the minuend signal; A first subtraction circuit subtracts the two signals by using the output signal from the second analog switch as a subtraction signal, and a third analog switch and a fourth
means for supplying the analog switch to the analog switch;
Let the output signal from the analog switch be the minuend signal,
Further, a second subtraction circuit is provided which performs subtraction between the two signals by using the output signal from the fourth analog switch as a subtraction signal, and a second subtraction circuit which uses the output signal from the fourth analog switch as a subtraction signal, and a second subtraction circuit which uses a signal having a period of 1/2 of the period of the carrier wave as a switching control signal. and means for controlling opening and closing of the second analog switch.

means for controlling the opening and closing of the first analog switch by means of a switching control signal having a polarity opposite to that of the switching control signal having a cycle of 172 carrier waves used to control the opening and closing of the second analog switch; 1 of the period of the carrier wave
means for obtaining a carrier wave by dividing a signal with a period of /2 into 1/2; means for controlling the opening and closing of the fourth analog switch described above using the carrier wave as a switching control signal; and means for controlling the opening and closing of the fourth analog switch described above using the carrier wave as a switching control signal; The present invention provides a single sideband signal generation circuit including means for controlling the opening and closing of the third analog switch described above using the signal as a switching control signal.

(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 a single sideband signal generation circuit of the present invention, in which l is an input terminal for a modulation signal (for example, an audio signal), and 2 is a 90 degree Phase shifter, 3 is 1/2 of the period 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, 5lll is the first analog switch, SW2 is the second analog switch, SW3 is the third
The analog switch 514 is a fourth analog switch (for example, 1 is used as the analog switches 5l11 to 5114).

Although electronic switches are used, in order to simplify the explanation, each analog switch SWI~51 is shown in the drawing.
14 is shown in the form of a mechanical switch, and the following explanation is also based on that drawing), 5UBI is the first subtractor, 5UBI is the first subtractor,
2 is a second subtracter, and Div is a 1/2 frequency divider.

In the single sideband signal generation circuit of the present invention shown in FIG. 1, the modulated signal Si (a) in FIG. It is given to PIA. The output signal S2 ((b) in FIG. 2) from the 90-degree phase shifter 2 is applied to the first analog switch 5ll, and the inverting amplifier P
The output signal S3 of the IA is supplied to the second analog switch Sw2.

The second analog switch 5112 is connected to the input terminal 3
A signal CI (a signal with a frequency twice that of the carrier wave) as shown in FIG. It performs an opening/closing control operation based on the input signal and outputs a signal S5 as shown in FIG. 2(g),
It is supplied to the first subtractor SυB1 as a subtraction signal.

Further, the first analog switch 511 receives a signal (a signal with a frequency twice the frequency of the carrier wave) CI having a period of 172 times the period of the carrier wave supplied to the input terminal 3.
is obtained by inverting the polarity using the inverter 4 (d
) is applied as the switching control signal C2 to perform the opening/closing control operation, and output the signal S4 as shown in (f) of FIG.
It is supplied to the first subtractor 5UBI as a minuend signal.

The first subtracter SOB t receives the two signals S4 . The subtraction operation for S5 is performed, and the output signal 56=(S4-35) is obtained as (h in FIG. 2).
) and sends it to the third
analog switch SW3 and fourth analog switch 5
14.

The fourth analog switch 5w4 receives a signal (half the frequency of the carrier wave) as shown in FIG. The opening/closing control operation is performed by giving the signal Crl as shown in FIG. 2 (j), which is obtained by dividing the frequency of CI (signal with double frequency) to 172 by the 172 frequency divider Div, as the switching control signal Crl. , (Q) in Figure 2
The third analog switch SW3 outputs a signal S8 as shown in and supplies it to the second subtracter 5UB2 as a subtraction signal. The signal C1, which has a period that is 1/2 of the period of the carrier wave (a signal with a frequency twice that of the carrier wave), is divided into 172 by a 1/2 frequency divider Div, as shown in (j) in Fig. 2. The opening/closing control operation is performed by applying the signal Crl as shown in FIG.
A signal S7 as shown in (k) of the figure is outputted and supplied to the second subtractor 5UB2 as a minuend signal.

The second subtracter 5UB2 receives the two signals S7. After performing the subtraction operation for S8, the output signal 59=(S7-88) is obtained as (m) in FIG.
Outputs a signal S9 as shown in .

When the signal S9 is sent to the output terminal 7 through the circuit (for example, a low-pass filter) 6 having a function of removing high frequency components, the output terminal 7 receives the signal shown in (n) in FIG. A single sideband signal SlO is sent out.

(effect) As is clear from the detailed explanation above.

The single sideband signal generation circuit of the present invention includes a 90 degree phase shift means for giving a 90 degree phase shift to an input signal, and a means for supplying an output signal from the 90 degree phase shift means to a first analog switch. and means for inverting the phase of the input signal,
means for supplying the output signal from the phase inverting means to the second analog switch, the output signal from the first analog switch as a minuend signal, and the output signal from the second analog switch; a first subtraction circuit that subtracts the two signals by using the 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; means for controlling the opening and closing of the second analog switch by using a signal with a period of 1/2 of the period as a switching control signal; means for controlling the opening/closing of the first analog switch by a switching control signal having a polarity opposite to that of the period switching control signal;
means for dividing the frequency into a carrier wave to obtain a carrier wave; means for controlling the opening and closing of the fourth analog switch described above using the carrier wave as a switching control signal; and means for controlling the opening and closing of the fourth analog switch described above using the carrier wave as a switching control signal; Since the single sideband signal generation circuit of the present invention includes means for controlling the opening and closing of analog switches, the single sideband signal generation circuit of the present invention does not require the conventional method described above with reference to FIGS. 3 and 4. The number of 90 degree phase shift circuits required can be halved compared to a single sideband signal generation circuit, and therefore a single sideband signal generation circuit with the same performance can be replaced with an external capacitor. Since the single sideband signal generating circuit of the present invention can be configured with a reduced number of pins, it is possible to easily and inexpensively provide the single sideband signal generating circuit 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 steps required to adjust the amount of phase shift of the 90-degree phase shifter. The 90 degree phase shifter used in the single sideband signal generation circuit is also used to deal with the fact that sidebands that should be removed are not removed even if the phase shift amount in the single sideband signal shifter is slightly shifted. 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. Also,
In the single sideband signal generation circuit of the present invention, the DC drift component that occurs in the signal due to the temperature characteristics of switching circuits such as analog switches is canceled out by subtracting the output signals from two analog switches using a subtraction circuit. Therefore, it is possible to generate a highly stable single sideband signal, and as described above, the single sideband signal generation circuit of the present invention is a circuit that has high performance in terms of temperature characteristics as well. Therefore, it can be said that it is an optimal single sideband signal generation circuit for integration into an integrated circuit.

[Brief explanation of drawings]

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. 3 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 modulated 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 carrier wave period, 4.5...Inverter, 6...Has a high frequency component removal function circuit (for example, low-pass filter), 7... output terminal for single sideband signal, 9.10... analog multiplier, 12...
Adder, SW1 to SW4...first to fourth analog switches, PIA...inverting amplifier, 5UBI, 5UB
2...1st degree second subtractor. Many 2 (2

Claims (1)

[Claims] 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. , 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 as a minuend signal, and the output from the above-mentioned second analog switch; a first subtraction circuit that subtracts the two signals by using the 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; means for controlling the opening and closing of the second analog switch by using a signal with a period of 1/2 of the period as a switching control signal; means for controlling the opening and closing of the first analog switch by a switching control signal having a polarity opposite to that of the period switching control signal; means for obtaining a carrier wave, means for controlling the opening and closing of the fourth analog switch described above using the carrier wave as a switching control signal, and means for opening and closing the third analog switch described above using a signal obtained by inverting the phase of the carrier wave as a switching control signal. A single sideband signal generation circuit comprising control means.