JPH0336445B2 - - 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), 2 and 11 are 90 degree phase shifters, and 7 is a single sideband signal. , 8 is the carrier wave input terminal, 9 is the output terminal of
10 is an analog multiplier, 12 is an adder 13 is a low-pass filter.

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) Also, if the amplitude of the output signal from the analog multiplier 10 is B, the output signal from the analog multiplier 10 is as follows. It becomes as shown in equation (2).

2BocosPt・cosCt =Bcos(P-C)t+Bcos(P+C)t...(2) Now, assuming that the above-mentioned A and B are in the relationship of 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)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 shift circuit 2 and supplied to the analog multiplier 10, is the fourth
The signal shown in a of FIG. 4 corresponds to the signal of the part a in FIG. 3, and the signal shown in b of FIG. The signals shown in FIG. 3 correspond to the signals shown in the part b in FIG.
The signals shown in are c to h in Fig. 3, respectively.
These are the signals of the parts shown respectively. Note that the block 13 indicated by 13 in FIG.
1 shows 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 means for obtaining two signals having a relative phase difference of 90 degrees from one signal, and a means for obtaining two signals having a relative phase difference of 90 degrees as described above. and means for multiplying the output signal from the signal switching means by the carrier wave. The present invention provides a single sideband signal generation circuit.

(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 3 is a change-over switch (for example, an alternate type electronic switch is used as the change-over switch 3, but to simplify the explanation, this change-over switch 3 is shown as a mechanical change-over switch). It is shown as a switch-like format,
In addition, the following explanation is based on the drawing), 4 is an input terminal for a signal having a period of 1/2 of the carrier wave period, 5 is a 1/2 frequency divider, and 6 is an analog multiplier. 7 is a single sideband signal output terminal, and 13 is a circuit (for example, a low-pass filter) having a function of removing high frequency components.

In the single sideband signal generating circuit of the present invention shown in FIG. 1, the modulated signal {b in FIG. 2} supplied to the input terminal 1 is applied to the fixed contact b in the changeover switch 3, and It is also given to 90 degree phase shifter 2. The output signal {a in FIG. 2} from the 90-degree phase shifter 2 described above is supplied to the fixed contact a of the changeover switch 3 described above.

The movable contact v of the changeover switch 3 receives a signal having a period half the period of the carrier wave supplied to the input terminal 4 {as shown in c in FIG. A signal with a frequency of )6.

The analog multiplier (or balanced modulator) 6 has an output signal from the 1/2 frequency divider 5, that is, a period that is 1/2 of the period of the carrier wave supplied to the input terminal 4. A signal obtained by dividing a signal {a signal with a frequency twice the frequency of the carrier wave as shown in c in Fig. 2} by 1/2 {a signal shown in e in Fig. 2, This signal is also supplied with a signal having the same frequency as the carrier wave, and the analog multiplier (or balanced modulator) 6 uses a changeover switch as shown in FIG. 3 and the output signal from the 1/2 frequency divider 5 as shown in e of FIG. Outputs a signal.

The output signal from the analog multiplier (or balanced modulator) 6 is passed through a circuit (for example, a low-pass filter) 13 having a function of removing high frequency components.
2 to the output terminal 7, a single sideband signal as shown at g in FIG. 2 is sent to the output terminal 7.

(Effects) As is clear from the detailed explanation above, the single sideband signal generation circuit of the present invention generates two signals having a relative phase difference of 90 degrees from one signal.
A means for obtaining a signal, and two signals having a phase difference of 90 degrees relative to each other as described above are divided into two signals having a phase difference of 1/2 of the period of the carrier wave.
The single sideband signal of the present invention is constituted by a signal switching means that sequentially and alternately switches at a switching period of , and a means for multiplying the output signal from the signal switching means by a carrier wave. This generation circuit requires 90 MHz compared to the conventional single sideband signal generation circuit described above with reference to FIGS. 3 and 4.
The number of phase shift circuits can be halved, and therefore a single sideband signal generation circuit with the same performance can be configured with a reduced number of external capacitors. A single sideband signal 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.

[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 modulation signal (for example, audio signal), 2, 11... 90 degree phase shifter, 3... Selector switch, 4... Input for signal having a period half the period of the carrier wave. Terminal, 5... 1/2 frequency divider, 6... Analog multiplier (or balanced modulator), 7... Single sideband signal output terminal, 8... Carrier wave input terminal,
9, 10...analog multiplier, 12...adder,
13 is a circuit (for example, a low-pass filter) having a function of removing high frequency components;

Claims (1)

[Claims] 1. Means for obtaining two signals having a relative phase difference of 90 degrees from one signal, and two signals having a relative phase difference of 90 degrees as described above. A single sideband signal comprising: a signal switching means for sequentially and alternately switching the signal at a switching period of 1/2 of the carrier wave period; and a means for multiplying the output signal from the signal switching means by the carrier wave. generation circuit. 2. The single sideband signal generation circuit according to claim 1, which uses a balanced modulator as means for multiplying the output signal from the signal switching means and the carrier wave.