JPS6016761B2 - Detection device for all carrier single sideband signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for reproducing a single sideband amplitude modulated signal that transmits a full carrier wave.

Single sideband amplitude modulation signal (hereinafter referred to as SSB-AM signal)
The synchronous detection method is well known as a detection method for this. That is, as shown in FIG. 1, in principle, on the transmitting side, input information Si is frequency-converted by a frequency converter 1 using a local carrier wave from a local frequency source 3, and one of the sidebands is transmitted. The received signal is frequency-mixed by the frequency converter 2 with a local carrier wave from a local frequency source 4 having an oscillation frequency very close to the oscillation frequency of the transmitting local frequency source 3, and is reproduced as an information signal power So. Conventionally, the received signal is converted into an information signal by frequency conversion, so fluctuations in the received electric field strength due to the effects of fading during atmospheric propagation of the SSB-AM signal directly affect the information signal. The problem was that it caused noise. The present invention is characterized in that an information signal is detected from a phase modulation component that is less susceptible to fading in the atmospheric propagation of an SSB-AM signal that transmits a carrier wave, a so-called all-carrier SSB-AM signal. The objective is to improve the transmission quality of wireless communication systems.

First, the principle of the all-carrier SSB-AM signal detection device according to the present invention will be explained.

Generally, the total carrier upper sideband SSB-AM signal es(t) is eS(t)=Re[(C0S(t)1iH[S(t)]
) ej ct] ,. ．． (1)
=R(t)Re[ejwqei○(t)] ...■.

However, C: positive constant, S(t): information signal, C+S(t
) > 0, day [S(t)]: Hilbert transform of S(t),
c: angular frequency of carrier wave, R(t) = {(C+S(t
))2 10 days 2 [S(t)]}1'2, ◇(t)=ne n
-・[Bible name], Re: Each means a real number component.

Information signal S(t), envelope R(t) and phase modulation component? The relationship with (t) is given by the following equation.

C+S(t)=R(t)COS? (t) …(31
It is also known that the following relationship holds between the envelope R(t) and the phase modulation component 0(t). t) = day [l
n(R(t)/C]...[4,R(t)/C=e-
Day [tsu (t)] ...■Using this relationship, the formula [3} is: Ten Symphony = e - day [small] x COS◇ (t).・
・[Can be replaced with 6'.

This formula is the phase modulation component of the total carrier SSB-AM signal (
This shows that the information signal S(t) can be reproduced from t). FIG. 2 shows an embodiment of the present invention constructed according to the principles described above.

The envelope component R(t) of the received full carrier SSB-AM signal is removed by the amplitude limiter 5, resulting in e,(t). e, (t) = K, Re [CteJ○(t) of ej]
...[7} However, K is a constant.

A carrier wave frequency is extracted by a carrier wave extracting circuit 6 from these e, (t), and the carrier wave is phase-shifted by 90 degrees by a 90 degree phase shifter 7 and supplied to the frequency converter 2, and the output of the amplitude limiter 5 is e, (t) is subjected to orthogonal synchronous detection to obtain e2(t). e2(t)=K,K2Sin○(t)
...■ However, K2 is a constant. After adjusting K, K2=1, e2(t) is input to the arc sine function unit 8 and becomes e2(t
) is converted into an inverse sine function to obtain a phase modulation component (t). In other words, this raw force e3(t) is e3(t)=sin
-1[e2(t)]=◇(t) ...■. The phase modulation component ◇(t) extracted in this way is divided into two,
One of them is phase-shifted by a wideband 900 phase shifter and 900 degrees, and is converted into an exponential function by an exponential function unit 11 and converted into an envelope component R(t). That is, e4(t) = e-day [
The = science. ．． ．． (,.

) is obtained. Another bisected phase modulation component? The other of (t) is given a string function by the cosine function unit 9, and becomes e5(t).
is obtained. e5(t)=K3cos t)
...(11) e4(t) and e5(t) are multiplier 1
2 to reproduce the information signal S(t).

In other words, e6(t) = e4(t) xe5(t) = K3 palm C
OSo(t):Sa(C+S(t)) ---(12
) is bound.

Figure 3 shows that the phase modulation component is zero due to the frequency discriminator and integrator.
A configuration for detecting (t) is shown.

The output e,(t) of the amplitude limiter 5 is subjected to frequency discrimination by a frequency discriminator 13 using c as a reference, and its output becomes a time differential signal e7(t) of the phase modulation component g(t). e7(
t) = K4'(t) ...(13 but K
4 is a constant. e7(t) is converted to e8 by the integrator 14.
(t)=K4&◇(t) 10KB...(Converted to 1 core.

Here, by setting K4&:1, K6=0, e
8(t)=◇(t)...(15)
is obtained.

From the signal S(t) thus obtained, the information signal S(t) is reproduced in the same manner as shown in FIG. As described above, in the present invention, since the received signal is first subjected to amplitude limiting processing, it is possible to reduce noise caused by fluctuations in received electric field strength such as fading.

As explained above, the present invention can use an amplitude limiter at the front stage of the receiving system to reproduce information signals from the phase modulation components of all carrier SSB-AM signals, thereby reducing noise caused by level fluctuations during propagation such as fading. There are advantages that can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle of a single sideband communication system using a synchronous detection method, FIG. 2 is a block diagram showing an embodiment of an SSB-AM signal detection device according to the present invention, and FIG. 3 is a block diagram showing an embodiment of an SSB-AM signal detection device according to the present invention - It is a block diagram showing another example of the AM signal detection device. . 1, 2: Frequency converter, 3, 4: Local frequency source, 5:
Amplitude limiter, 6: Carrier extraction circuit, 7: Phase shifter, 8
: Arcsine function unit, 9: Cosine function unit, 10: Wideband 90o
Phase shifter, 11: Exponential function unit, 12: Multiplier, 13: Frequency discriminator, 14: Integrator. Hair diagram Figure 2 Recruitment diagram

Claims (1)

[Claims] 1. An amplitude limiter for amplitude limiting a received all-carrier single sideband amplitude modulated signal, means for extracting a phase component of the amplitude-limited output, and a 90° phase shifter for shifting the extracted phase component by 90°. an exponential function generator that takes the exponential function of its phase shift output to reproduce the envelope component, a cosine function function that takes the cosine function of the phase component extracted above, the cosine function output, and the above reproduced 1. A detection device for an all-carrier single sideband signal, comprising a multiplier that obtains a reproduced output of an information signal by multiplication with an envelope component.