JPS61140260A - Carrier wave recovery circuit - Google Patents

Abstract

PURPOSE:To obtain very stable recovered carrier wave by using an oscillation signal of a frequency fixed reference oscillator as a reference signal, applying correlation processing with an input signal by a complex correlation device, applying complex number multiplication by a complex 4 quadrant multiplier so as to recover a carrier wave. CONSTITUTION:An output of a phase modulator 6 is a signal obtained by remodulating a reference signal sin(omega0t+alpha) by a demodulation signal from a discriminator 5 and goes to sin[omega0t+theta(t)+alpha]. A complex number correlation device 10 applies correlation between the said remodulation signal and a modulated input signal sin[omega1t+theta(t)]. A part of the modulated input signal inputted to a signal input terminal 1 is inputted to a hybrid 21 of the complex number correlation device after being subject to time adjustment by a delay circuit 8, a real part output R is fed to a 4 quadrant multiplier 23 of a complex number 4 quadrant multiplier 9 and an imaginary part output I is fed to a 4 quadrant multiplier 23'. Then the output signal of the 4 quadrant multiplier 23 and the output signal of the 4 quadrant multiplier 23' are synthesized by a hybrid 26' and the result is fed to a phase detector 3 as a recovered carrier wave C.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is based on PSK (Phaae 5hift Ke
eing) relates to improvements in carrier regeneration circuits required for phase demodulation circuits.

(Prior art and problems) Conventionally, most of the carrier wave regeneration circuits of PSK phase demodulation circuits using synchronous detection use voltage controlled oscillators (VCOs), but they tend to cause phase errors due to poor stability. Since it constitutes a phase-locked loop (phaseLook Loop), if synchronization occurs, it takes time to pull in, so there is a drawback that there is a large amount of dross.

(Means for Solving the Problems) An object of the present invention is to provide a carrier wave regeneration circuit that can obtain a stable regenerated carrier wave synchronized with an input signal using a relatively simple circuit.

The present invention has the following configuration to achieve the above object.

That is, in a synchronous detection type PSK phase demodulation circuit, a reference oscillator that generates a reference signal, a phase modulator that receives the reference signal and modulates the reference signal again with a demodulated signal of a modulated input signal, and the phase modulator a complex correlator that takes a complex correlation between the output signal of the output signal and the modulated input signal, a low-pass filter that extracts low frequency components of the real part output and the imaginary part output of the complex correlator, and each of the low-pass filters. This carrier wave regeneration circuit includes a complex four-quadrant multiplier that performs complex multiplication of the output of the wave generator and the reference signal.

(Function) The function of the carrier wave regeneration circuit of the present invention will be explained below. For ease of explanation, a KPSK two-phase demodulation circuit will be explained.

Figure 1 shows its basic circuit.

In FIG. 1, 1 is a signal input terminal, 2 is a demodulated signal output terminal, 3 is a phase detector, 4 is a low-pass filter, 5 is a determiner,
6 is a phase modulator, 7 is a reference oscillator, and 8 is a delay circuit, which performs time adjustment for correlating the input signal and the re-modulated signal.

Numeral 9 is a complex four-quadrant multiplier, 10 is a complex correlator, and 11 is a gate circuit which functions to gate the best point of the signal to be correlated.

Moreover, the complex four-quadrant multiplier 9 includes hybrid, de 26, and d2
6', a π/2 phase shifter 22', a four-quadrant multiplier 23, and a four-quadrant multiplier 23'. The complex correlator 10 is composed of a hybrid 21 and a hybrid 21', a '/2 phase shifter 22, a correlator (mixer) 24, and a hybrid 24'. 25 and 25' are low-pass filters that serve to remove high frequency components from the output of the complex correlator IO.

Now, assume that the signal of the reference oscillator 7 is 5in (- is 70, and the modulated input signal is sin (cho 1 + I (1)).

where is the angular frequency of the signal, and α and σ(1) are the phase of the signal.

Further, the output of the phase modulator 6 is a signal obtained by re-modulating the reference signal 5in (*.t+α), which is the output signal of the reference oscillator 7, with the demodulation signal from the determiner 5.
(tl+α).

In the complex correlator 10, this re-modulated signal and the modulated input signal 5
in(Town 1-)-# (Take the correlation of the first item. This point will be explained in detail.

A part of the modulated input signal input to the signal input terminal 1 is time-adjusted by the delay circuit 8, and then input to the hybrid 21 of the complex correlator 10, where it is distributed into two parts and sent to the correlator (
mixers) 24 and 24', respectively.

On the other hand, the output of the phase modulator 6 is applied via the gate circuit 11 to the high voltage 21' of the complex correlator 10.

Here, it is divided into two parts, one being directly applied to the correlator 24, and the other being applied to the correlator 2 through the jI/2 phase shifter 22.
Added to 4'.

Correlators 24 and 24' each perform multiplication of the added signals. If the respective outputs are expressed in complex terms, the output of the correlator 24 will be the real part, and the output of the correlator 24' will be the imaginary part. This can be expressed as a formula as follows.

First, regarding the real part output R of the correlator 24, R=si
n (town t+θ(tJ) sin (set+'(tl
+a)+2θ(tl+α)...(1).

Next, regarding the imaginary part output I of the 1 correlator 24', ■=si
n(*,t+'(t)) cos(a+o t
+θ(1)+-)+2#(t)+α)...(2).

Next, the real part output R is applied to the 4-quadrant multiplier 23 of the complex 4-quadrant multiplier 9 via the low-pass filter 25f, and the imaginary part output Quadrant multiplier 23'
added to.

Here, since both the real part signal R and the imaginary part signal pass through the low-pass filters 25 and 25', the equation (1) and the equation (
The second term of 2), that is, the higher frequency signal is blocked,
Only the signals of the first terms of equations (1) and (2) are applied to the four-quadrant multipliers 23 and 23'.

On the other hand, the reference signal which is the output of the reference oscillator 7 is applied to the hybrid 26 of the complex 4-quadrant multiplier 9, where it is divided into two parts, one of which is applied to the 4-quadrant multiplier 23, and the other one of which is applied to the 4-quadrant multiplier 23. 4-quadrant multiplier 2 via phase shifter 22'
3' is added. Four-quadrant multiplier 23 and four-quadrant multiplier 23
', respectively, performs multiplication of the two added signals and outputs the product R' and the product R'. This can be expressed as a formula as follows.

First, for the real part output system, multiplication is performed in the four-quadrant multiplier 23, and the output R' is = -! -(5ins1
t+sin ((2se-at) t-#(t)-
2g)) ...(3).

Next, for the imaginary part ratio crab system, the four-quadrant multiplier 23'
Multiplication is performed and the output is = 1 (sin #,
t-5in((2#@-at)t-#(t)-2g
) ) ・(4) becomes.

Then, the output signal of the four-quadrant multiplier 23 expressed by equation (3) and the output signal of the four-quadrant multiplier 23' expressed by equation (4) are combined by the hybrid 26' and phase-detected as a recovered carrier wave C. Add to vessel 3.

Since both signals are added in Hypuri and Do26', the reproduced carrier wave C is C=R'+I' = ain town t ・・・・・・・・・・・・・・・(5)
Therefore, it can be seen that the output of the complex four-quadrant multiplier 9, that is, the reproduced carrier wave signal input to the phase detector 3 becomes a signal synchronized with the input signal, and the carrier wave is correctly reproduced.

The above explained two-phase PSK demodulation, but N-phase (N=2
It is clear that carrier wave regeneration can be similarly performed for "n: a positive integer" by simply increasing the number of phase detectors and changing the modulation circuit 6.

(Effects of the Invention) As explained above, the carrier wave recovery circuit of the present invention performs correlation processing using a complex correlator between the oscillation signal of the reference oscillator with a fixed frequency as the reference signal and the input signal, and then performs complex four-quadrant multiplication. Since the carrier wave is regenerated by performing complex multiplication on the device, it is said that unlike conventional carrier wave regeneration circuits using voltage controlled oscillators, it compensates for unstable factors caused by temperature and aging of the voltage controlled oscillator. This method has the advantage that there is no need for this, and a very stable regenerated carrier wave can be obtained with a relatively simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a carrier recovery circuit according to the present invention in a PSK two-phase demodulation circuit. l... Signal input terminal, 2... Demodulated signal output terminal, 3... Phase detector, 4... Low pass filter, 5
...Determiner, 6...Phase modulator, 7...
Reference oscillator, 8...Delay circuit, 9...Complex four-quadrant multiplier, 10...Complex correlator, 11...Gate circuit, 21.21'...Hybrid (distributor or combiner), 22.22'...'/2 phase shifter, 23.2
3'... Four-quadrant multiplier, 24.24'... Correlator (mixer), 25.25'... Low-pass filter,
26.26'...Hai-Furi, Do Agent Patent Attorney Yoshihiro Yahata No. l Figure zt, z(,z5.w;'...Hai-Furi, Soto 22
, d..."/z transfer S ticket 23.23...4 elephants Tomoaki de To.

Claims (1)

[Claims] A synchronous detection PSK phase demodulation circuit includes a reference oscillator that generates a reference signal, a phase modulator that receives the reference signal and modulates the reference signal again with a demodulated signal of a modulated input signal, and an output of the phase modulator. A complex correlator that takes a complex correlation between a signal and a modulated input signal, a low-pass filter that extracts low frequency components of a real part output and an imaginary part output of the complex correlator, and each of the low-pass filters. A carrier wave regeneration circuit comprising a complex four-quadrant multiplier that performs complex multiplication by the output of the reference signal and the reference signal.