JPS60165150A - Double side band modulating system using exclusive or circuit - Google Patents

Abstract

PURPOSE:To attain simply double side band (DSB) modulation for one signal by the other signal by using an exclusive OR circuit when the amplitude of the signal is constant. CONSTITUTION:A modulated signal V2 is given to one input of an exclusive OR circuit (it is desirable to use an integrated circuit EX OR gate) XOR and a carrier signal V1 is given to other input. The frequency of the carrier signal V1 is f1 and the frequency of the signal V2 to be modulated is f2. The carrier signal V1 (Fig. A) is subject to phase inversion as shown in Fig. C by the signal V2 to be modulated as shown in Fig. B. A DSB modulator is realized by using a very inexpensive exclusive OR gate in this way, no externally mounted component is required at all and it is not required to care about the level because a digital signal is employed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field 1 of the Invention] The present invention relates to a double sideband modulation system, and particularly to a system in which modulation is performed using an exclusive OR circuit.

[Prior art 1] Conventionally, double sideband modulation (hereinafter abbreviated as DSB modulation) has been performed, but when performing such modulation, a coil and diode bridge called a balanced modulator (ring modulator) are combined. Figure 1 shows an example of a conventional DSB modulator in the former case, where the modulated signal @V2 input via the transformer T1 is a carrier wave signal. It is guided to 1~ lance T2 through diodes D1~D4 which are forward and reverse biased by the excitation of V+, and this 1~
A DSB modulated signal v3 is obtained from the intermediate tap on the primary side of the lance T2.

However, it has disadvantages in terms of cost and increased power consumption due to each input/output terminal being driven with an impedance of 50Ω.

Moreover, in the latter modulator, the input/output level is lVp
The disadvantages are that it is low (less than p) and that there are many IC parts.

[Object of R, Light] In view of the above, the object of the present invention is to provide a case in which the amplitude of a signal may be constant, and to easily convert one signal to DSB by another signal using an exclusive OR circuit. The object of the present invention is to provide a modulation method for modulation.

[Summary of the Invention] In order to achieve such an object, the present invention is provided with an exclusive OR circuit, and a modulated signal and a predetermined constant amplitude modulated signal are connected to two input horns of the exclusive OR circuit. A carrier signal is applied, and a double sideband modulation signal is obtained from the output end of this exclusive OR circuit.

[Example] The present invention will be described in detail below with reference to the drawings. As shown in Fig. 2, the modulated signal V2 is applied to one input of the exclusive OR circuit (it is preferable to use an exclusive OR gate integrated into an IC), and the carrier signal @V1 is applied to the other input. give.

The operation of such a configuration will be explained next.

Here, the frequency of the carrier signal V1 is fl, and the modulated signal V2
Let the frequency of be f2. As shown in FIG. 3, the carrier signal V+ ((a) in the same figure) undergoes phase inversion as shown in (c) in the figure by the modulated signal V2 as shown in (b).

Now, the signals of Vl and V2 are expressed by Fourier series as follows.

However, ω1. ω2 are the angular frequencies of f, , f2, respectively. Also, for the sake of simplicity, both signals are L1
It is assumed that there is no DC component in the positive direction like a sick signal.

On the other hand, this exclusive or gate is converted into a logical formula % formula % (
3) <1), substituting equation (2) into equation (3) gives V-, "-
Vl X V2 X2 = hachin u+t 9'lh (j)
)2 T: Embryo', A = -1 3z Sui'3jll '゛B = -, z 0JitSlt'13ωzt+H'J
nu;t 5ihcl, cit (4) formula is V3-AS'In((dl+(,1)z)lL+h'I
It can be seen that n((JJI Uz) also becomes (''-), indicating that D 313 modulation was achieved.

FIG. 4 is a diagram showing the frequency spectrum of a DSB-modulated output signal, with the frequency on the horizontal axis and the intensity (level) of the spectrum on the vertical axis. As shown in the figure, there are frequency components of f1+f2 and 1-f2, which are the frequency of the carrier signal - the same as in the conventional case, but they can be easily removed by passing them through a filter.

[Effects of the Invention] As explained above, according to the present invention, a DSB modulator can be realized using an extremely inexpensive exclusive or goo. It also has the advantage of not requiring any parts (outer A), and since it is a digital signal, there is no need to consider the level.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional DSB modulator, FIG. 2 is a block diagram for implementing the method of the present invention, FIG. 3 is a waveform diagram for explaining the present invention in detail, and FIG. FIG. 4 is a diagram showing DSB modulation modulation output signal wave number spectra 1 to ram. XOR, exclusive or gate. Consultation 1 Intori 2 Figure 3? P, 4 tl-/12 fl+n t2

Claims (1)

[Claims] A rectangular wave-shaped modulated signal and a carrier signal having a predetermined constant amplitude are applied to the two inputs of the exclusive OR circuit, and the exclusive OR circuit A double sideband modulation method using a υ1 other music OR circuit, characterized in that a double sideband modulation signal is output from the output end.