JPS61293006A - Two-dimensional vestigial side-band wave modulator - Google Patents

Abstract

PURPOSE:To transmit information by twice as much as a linear vestigial side- band wave modulator by providing two vestigial side-band wave modulators and adding their vestigial side band wave modulated signals together. CONSTITUTION:A signal f(t) is inputted to an input terminal 1 and a phase difference branching filter 21 sends out an in-phase output and an orthogonal output which is 90 deg. advanced in phase. Those outputs are supplied to an orthogonal modulator 31, which multiplies the in-phase output by a carrier cosomegact and the orthogonal output by a carrier sinomegact and inputs the results to a subtracting circuit, obtaining the 1st vestigial side-band wave modulated signal. Similarly, a signal g(t) from an input terminal 12 is supplied to an orthogonal modulator 32 through a phase branching filter 22 to obtain the 2nd vestigial side-band wave modulated signal. Then, the 1st and the 2nd vestigial side-band wave modulated signals are summed up by an adding circuit 50. Consequently, information is transmitted by twice as much as one linear vestigial side-band wave modulator.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a two-dimensional vestigial sideband modulator using a vestigial sideband modulation method.

〔overview〕

The present invention provides a two-dimensional vestigial sideband modulator using a vestigial sideband modulation method, which includes: a 90' phase difference splitter that splits and outputs an input signal into an in-phase signal and an orthogonal signal whose phase is advanced by 90'; and a quadrature modulator that complexly multiplies the signal and the orthogonal signal by the orthogonal carrier to obtain a residual sideband modulation signal, and adds each residual sideband modulation signal to send out a two-dimensional residual sideband modulation signalζ This makes it possible to transmit twice the amount of information in the same band compared to conventional methods.

[Conventional technology]

Spectrum 1 of modulated signals such as data signals and image information
~ If the signal contains DC components or low frequency components, 1
Because these components reside near the general transmission wave, single sideband modulated signals (SSB
It is difficult to perform transmission by means of signals).

Therefore, a residual sideband modulation method is used to compress the band by making the sum of the amplitudes of the residual sideband and deleted sideband equal to the amplitude of the original signal and having an odd phase symmetry with respect to the general transmission wave. (VSB method) is used.

In other words, one of the two sideband waves of the modulated output and a part of the other sideband are sent out to the transmission path, and on the receiving side, a gentle wave generator (V S
B-shaped filter).

When a carrier wave with the same frequency and same phase as the general transmission wave used for modulation is regenerated on the receiving side and combined with this shaped output, the - part of the band wave is folded back and returned to the original signal 8 times. .

FIG. 2 is a block diagram showing a conventional one-dimensional residual sideband modulator.

The input signal of the input terminal 10 is outputted by the 90° phase difference wave circuit 20 as two orthogonal signals f ftl, f (tl). These two orthogonal signals f it), f (
tl is an angular frequency gauze ω generated by the orthogonal modulation circuit 30. The carrier waves cosωCt and 5jn(JJcj of
sinωCt is obtained at output terminal 40.

FIG. 3 is a diagram showing the process of creating a residual sideband signal. If the spectra of each signal f (tl, f (tl, p(t)) are respectively F(ω), F(ω), and P(ω), then the residual sideband modulation signal spectrum P(ω) is shown in Figure 3. The residual sideband characteristics are shown in Figure 3(a), where f
(The spectrum F(ω) of tl, +b+bf (The spectrum F(ω) of tl, (C) is f (t)cos ω
c The shuector of L is expressed as [dl is f (tlsinωc
1, and (e) shows the p (tl (7) spectrum P(ω)).

[Problem that the invention seeks to solve]

However, such a conventional one-dimensional residual sideband modulator has the disadvantage that the amount of information that can be transmitted is limited because the carrier waves cos ω, t, and sin ω ct carry only f(tl).

SUMMARY OF THE INVENTION The present invention aims to improve these conventional drawbacks and provides a two-dimensional vestigial sideband modulator that has twice the information transmission capacity as compared to the conventional system.

(Means for Solving the Problems) ° The present invention provides an input signal with its in-phase signal and 9
A 90° phase difference duplexer that outputs two orthogonal signals with a 0° phase difference, and an orthogonal waveform that subtracts the complex multiplication output of each output signal of the 90° phase difference duplexer and the orthogonal carrier. Equipped with two sets of residual sideband modulators including a modulator,
The present invention is characterized by comprising arithmetic means for adding the outputs of the respective vestigial sideband modulators and sending the result to the vestigial sideband modulation signal output terminal.

[For production]

In the present invention, two sets of one-dimensional residual sideband modulators each consisting of a 90° phase difference modulator and a quadrature modulator are prepared, and each 90°
Different signals are input to each phase difference waver, and in the first quadrature modulator, for example, the in-phase output of the 90° phase difference waver is complex multiplied by a cosine wave carrier, the orthogonal output is multiplied by a sine wave carrier, and the second For example, in a quadrature modulator, the in-phase output is complex multiplied by a sine wave carrier, the orthogonal output is multiplied by a cosine wave carrier, and the one-dimensional residual sideband modulation signals of each quadrature modulator are added to create a two-dimensional residual sideband modulation signal. By outputting
It can carry twice as much information as a conventional one-dimensional vestigial sideband modulator.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The basic configuration of this embodiment is such that two conventional vestigial sideband modulators are prepared, and their respective vestigial sideband modulation signals are added and taken out to an output terminal.

That is, the signal f (t) is input to the input terminal 11 of the first residual sideband modulator, and the in-phase output f (11) and the quadrature output f (11 whose phase advances by 90 degrees) are input to the input terminal 11 of the first residual sideband modulator. Each of the outputs is output as a carrier wave cosωCt to an in-phase output f (t) in a quadrature modulator 31.
The multiplications are combined and the orthogonal output f (t) is given by the carrier wave sinω
ct are multiplied together and input to the subtraction circuit, and the first residual sideband modulation signal p (t) (-f 1lcosωc t
-f(t)sinωct) is obtained.

On the other hand, the signal g(1) is input to the input terminal 12 of the second vestigial sideband modulator, and similarly, the in-phase output g (tl) and the quadrature output g (tl) are output from the 90° phase difference modulator 2. Each output is obtained by multiplying the in-phase output g (t) by the carrier wave sinωゎt in the quadrature modulator 32, and
The orthogonal output g (1+ and carrier wave CO5ωct are combined 11-+ and input to the subtraction circuit, and the second residual sideband modulation signal q(t)(-g (tlsinωct-g ft1c
osωct). Each residual sideband modulated signal p(11,
q tt) is added by the adder circuit 50 to obtain a two-dimensional residual sideband modulation signal p(11+Q (tl −(f (tl−g(tll cosωct+ (g(
t) -f fill sinωet is taken out to the output terminal 41.

〔Effect of the invention〕

As explained above, the present invention enables two signals to be transmitted by adding two residual sideband modulation signals, and doubles the information transmission in the same band compared to the conventional method. This has the effect of reducing transmission costs.

4. Detailed description of the invention FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional residual sideband modulator.

FIG. 3 is a diagram showing the process of creating a residual sideband signal.

10.11.12...Input terminal, 20.21.22.
90° phase difference waveform generator, 30.31.32 Quadrature modulator, 40.41 Output terminal, 50 Adder circuit.

Claims (1)

[Claims] (1) A 90° phase difference duplexer that outputs two signals for an input signal, an in-phase signal and a quadrature signal with a 90° phase difference, and each output signal of this 90° phase difference duplexer and a quadrature carrier. Two sets of vestigial sideband modulators including a quadrature modulator that subtracts and outputs the complex multiplication output of each are provided, and the outputs of each vestigial sideband modulator are added and sent to the vestigial sideband modulation signal output terminal. A two-dimensional residual sideband modulator characterized by comprising a calculation means.