JPS62231549A - Phase synchronization detecting and demodulating device - Google Patents

Abstract

PURPOSE:To extract and reproduce a carrier without developing a phase jitter by detecting the phase error of converted carriers based on two detection signals that orthogonally intersect and are outputted from a phase detector and controlling the partially oscillating frequency of a frequency converter so as to minimize said phase error. CONSTITUTION:The two detection signals e1 and e2 that are outputted by the phase detector l and orthogonally intersect are inputted to a carrier extractor 2. Receiving the two detection signals e1 and e2 that the phase detector outputs, a control circuit 10 detects the phase error DELTAtheta between the carriers of outputs a' converted by the frequency converter 9, forms a phase error signal (ec) corresponding to said error, and outputs it to a voltage controlled oscillator 8. It generates the partially oscillating frequency (d) with the prescribed frequency to make the phase errorDELTAtheta into zero. Accordingly, if a reception signal (a) has the fluctuation of ites frequency, the frequency converter 9 absorbs the fluctuation, and supplies a signal PSK with a fixed carrier frequency the same as the central frequency of a band-pass filter 4 to the carrier extractor 2 and the phase detector 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a phase synchronized detection demodulator, and particularly to a technique for suppressing phase jitter occurring in a recovered carrier wave.

(Prior Art) FIG. 5 shows a configuration example of a conventional phase-locked detection demodulator. This phase-locked detection demodulator includes a phase detector 1, a carrier extractor 2, a first frequency converter 3, A bandpass filter 4 and a second
, a frequency converter 5 , a phase comparator 6 , a low-pass filter 7 , and a voltage-controlled oscillator 8 .

The received signal a is a PSK signal, and this received signal a is input to the phase detector 1 and a part thereof is input to the carrier extractor 2.

The phase detector 1 detects the received signal a using the phase of the reproduced carrier wave b' outputted by the second frequency converter 5 as described later as a reference phase, and outputs a baseband demodulated signal e.

The carrier wave extractor 2 extracts a carrier wave from the received signal a and outputs it to the first frequency converter 3.

This carrier extractor 2 has various configurations depending on the carrier extraction method, and an example thereof is shown in FIG. 6. FIG. 6 shows the case where the received signal a is a 2-PSK signal. In FIG. 6(A), the frequency multiplication carrier extractor 2 includes a multiplier 21 that doubles the frequency of the received signal a, and a band that limits the output signal of the multiplier 21 and removes unnecessary signal components. Filter 22 and bandpass filter 22
The frequency divider 23 divides the frequency of the output signal h' by 1/2 to form a carrier wave.

In addition, in FIG. 6(B), the inverse modulation type carrier wave extractor 2 includes a delay circuit 24 that delays the received signal a addressed to the phase detector 1 by the delay time, and a received signal a delayed by the delay circuit 24. The demodulated signal (received digital signal)
A modulator 25 that performs phase modulation by e to form a carrier wave.
It consists of

The first frequency converter 3 converts the frequency of the carrier wave to a predetermined frequency based on the frequency of the control signal C from the voltage controlled oscillator 8, and sends the converted frequency signal d to the bandpass filter 4 and the phase comparator 6. Output each.

The bandpass filter 4 is a narrowband filter having filtering characteristics as described later, and performs necessary wave processing on the frequency signal d, and sends the resulting frequency signal d' to the second frequency converter. 5 and the phase comparator 6, respectively.

The second frequency converter 5 forms a regenerated carrier wave b' of a predetermined frequency based on the frequency signal d' and the frequency of the control signal C from the voltage controlled oscillator 8, and outputs it to the phase detector 1.

Here, if the phase of the recovered carrier wave b' is not stable and fluctuates, the phase detector 1 cannot stably demodulate the received signal a by synchronous detection.

Therefore, the voltage controlled oscillator 8 generates a control signal C that makes the phase difference between the input frequency signal d and the output frequency signal d' of the bandpass filter 4 zero, with reference to the frequency of the carrier wave S.
This ensures that the reproduced carrier wave b' is stably equal to the carrier wave.

That is, the filtering characteristics of the bandpass filter 4 are as shown in FIG.
Since it has amplitude frequency characteristic A and phase frequency characteristic B, the input frequency varies from the center frequency fB of the bandpass filter 4 to Δf.
When shifted by Δθ, the output phase of the bandpass filter 4 changes by Δθ.

Furthermore, even if the input frequency is constant, the output phase also changes when the center frequency fB changes due to temperature changes, aging, etc. in the bandpass filter 4.

Therefore, it is necessary to control the phase difference between the input frequency signal d and the output frequency signal d' of the bandpass filter 4 to zero, and this is done as follows.

The phase comparator 6 detects the phase difference between the frequency signals d and d', and generates a detected voltage e proportional to the phase difference. This detected voltage e is suitably band-limited by a low-pass filter 7 to become a control signal f, which is input to a voltage controlled oscillator 8. The voltage controlled oscillator 8 sets the frequency of the control signal C to a predetermined frequency based on the control signal f in order to make the input/output phase difference of the bandpass filter 4 zero. Here, the relationship between the frequency fv of the control signal C of the voltage controlled oscillator 8, the center frequency 8 of the bandpass filter 4, and the frequency fC of the carrier wave is expressed by the following equation (1).

f v + f c ” f a ---
--- (1) (Problem to be solved by the invention) By the way, in the conventional phase-locked detection demodulator mentioned above, as is clear from the above-mentioned equation (1), the carrier extraction Frequency control is performed based on the extracted carrier wave S, which is the output of the device 2, but if there is a frequency fluctuation in the received signal a, for example, in the frequency multiplication method shown in Fig. 6(A), a bandpass filter 2
A phase error due to the phase characteristics of 2 is expected, and Fig. 6 (
In the inverse modulation method shown in B), a phase error caused by the delay circuit 24 is expected, and phase jitter will occur in the carrier wave. Then, with the conventional frequency control method, there is a problem that the phase of the reproduced carrier wave b' cannot always be kept constant, and stable synchronous detection demodulation cannot be performed.

The present invention has been devised in view of these conventional problems, and an object of the present invention is to provide a phase synchronized detection demodulator that can stably perform coherent detection demodulation even if there is a frequency fluctuation in a received signal.

(Means for Solving the Problems) The phase synchronized detection demodulator of the present invention has the following configuration in order to achieve the above object.

That is, the phase synchronized detection demodulator of the present invention includes: a frequency converter that receives a predetermined local oscillation frequency signal and converts the carrier frequency of the received PSK signal to a predetermined frequency; a carrier wave extractor that extracts the converted carrier wave; a bandpass filter that performs band filtration processing on the extracted converted carrier wave; and a bandpass filter that uses the phase of the converted carrier wave that has passed through the bandpass filter as a reference phase. a phase detector that performs no detection processing on the PSK signal outputted by the PSK signal and forms at least two detected signals that are orthogonal to each other; P that the frequency converter converts and outputs;
The control is performed so that the frequency fluctuation of the converted carrier wave of the SK signal is minimized, and a signal indicating the phase error of the carrier wave is formed by receiving the two detection signals, and a signal indicating the phase error of the carrier wave is controlled based on this phase error signal. A frequency control means for generating the local oscillation frequency signal; and a frequency control means for generating the local oscillation frequency signal.

(Function) Next, the function of the phase locked detection demodulator of the present invention having the above-mentioned configuration will be explained.

The frequency converter receives a predetermined local oscillation frequency signal, converts the carrier frequency of the received PSK signal to a predetermined frequency, and outputs the same to a carrier extractor and a phase detector, respectively.

The carrier wave extractor receives the PSK signal converted and outputted by the frequency converter using a frequency multiplication method, an inverse modulation method, etc., extracts the converted carrier wave, and outputs it to the bandpass filter.

The phase detector uses the phase of the converted carrier wave that has passed through the bandpass filter as a reference phase, and detects the PSK output from the frequency converter.
Detection processing is performed on the signal to form at least two detected signals that are orthogonal to each other. Here, if the PSK signal is binary phase modulation, two detection signals having an orthogonal relationship are particularly formed.

The frequency control means receives the two detection signals and forms a signal indicating a phase error of the converted carrier wave, generates the local oscillation frequency signal of a predetermined frequency based on this phase error signal, and the frequency converter generates the local oscillation frequency signal of a predetermined frequency. Control is performed so that the frequency fluctuation of the converted carrier wave of the output PSK signal is minimized.

As a result, even if there is a fluctuation in the received signal frequency, all of the fluctuation is absorbed by the frequency converter, and the carrier extractor can extract and reproduce the carrier wave without generating phase jitter, allowing coherent detection demodulation operation. It can be done stably. In addition, as a frequency control method, a frequency converter is installed on the input side of the phase detector, and this is done by controlling the local oscillation frequency of this frequency converter.The local oscillation frequency is variable, so that it is within the range that allows frequency conversion. If so, a bandpass filter with the same filtering characteristics can be used regardless of the frequency band of the received signal frequency, and there is an advantage that a wideband phase-locked detection demodulator can be obtained.

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

FIG. 1 shows a phase synchronized detection demodulator according to an embodiment of the present invention, and parts with the same names as those shown in FIG. 5 are given the same reference numerals.

The phase synchronized detection demodulator according to the first embodiment includes a frequency converter, a phase detector 1, a carrier extractor 2, a bandpass filter 4, and a control circuit 10 that forms a frequency control means by t/4.
and a voltage controlled oscillator 8.

The received signal a consists of a PSK signal, and this received signal a is input to the frequency converter 9.

The frequency converter 9 receives a predetermined local oscillation frequency signal d generated under the control of the voltage controlled oscillator 8 as described later, and converts the carrier frequency of the received PSK signal a to a predetermined frequency which is the center frequency of the bandpass filter 4. Convert to frequency and its conversion output a
' is sent to the phase detector 1 and the carrier extractor 2, respectively.

The carrier extractor 2 converts and outputs P from the frequency converter 9.
After receiving the SK signal a', the converted carrier wave is extracted, and it is passed through the bandpass filter 4 to the phase detector 1 as the extracted carrier wave.
Output to.

In this first embodiment, the carrier extractor 2 is of an inverse modulation type, and the carrier wave extractor 2 is of an inverse modulation type, and the carrier wave extractor 2 is of an inverse modulation type, and the carrier wave extractor 2 is of an inverse modulation type.
Two detection signals el and e2 are input.

As a result, the phase detector 1 uses the phase of the recovered carrier wave b' (which is equal to the frequency of the extracted carrier) as a reference phase, which is equal to the center frequency of the bandpass filter 4, and the P S K output by the frequency converter. Detection processing is performed on the signal a', and two detected signals e1 and e which are orthogonal to each other are obtained.
form 2.

By the way, the carrier wave angular frequency of the received signal a is ω0, its variation is Δω, the phase of the recovered carrier wave b' is θ, its variation is Δθ, and the carrier wave extractor 2 and the bandpass filter 4 are
If the delay time that occurs until input to the phase detector 1 via τ is τ, then θ+Δθ=(ω0+Δω)τ
・−−−１−−・・−・・−(2>) Here, regarding the phase θ, from the relationship θ=ω0τ, ω0 is a constant angular frequency, so from the carrier extractor 2 to the phase detector 1
A variable phase shifter for adjustment (not shown) is provided at an appropriate position on the route leading to the carrier wave b', and by adjusting and setting the delay time τ to an appropriate value, the phase θ of the reproduced carrier wave b' can be set to a desired value. I can do it. However, the variable phase component Δθ=Δω・τ generated by the variable angular frequency Δω cannot be adjusted by such means, and this becomes a phase error and leads to deterioration of the demodulation characteristics, so it is desirable that its value be zero. Therefore, the present invention focuses on the fact that when a PSK signal of four-phase phase modulation or higher is subjected to synchronous detection demodulation, the detected signal has mutually orthogonal components.

That is, the control circuit 10 receives the two detection signals el and e2 output from the phase detector 1, detects the phase error Δθ of the carrier wave of the conversion output a' of the frequency converter 9, and calculates a signal corresponding to this phase error Δθ. A phase error signal ec is formed and outputted to the voltage controlled oscillator 8.
is designed to generate the local oscillation frequency signal d of a predetermined frequency that should make the phase error Δθ zero.

Therefore, even if there is a frequency fluctuation in the received signal a, the frequency converter 9 absorbs the fluctuation and converts the PSK signal with a constant carrier frequency equal to the center frequency of the bandpass filter 4 into the carrier extractor 2 and the phase detector. It will be supplied to the vessel. In other words, since the carrier wave extractor 2 is not affected by the frequency fluctuation of the received signal a, the carrier wave can be extracted without causing phase jitter.

Next, the specific contents of the above-mentioned frequency control operation of the present invention will be explained with reference to FIG. In Figure 2, the received signal a is 4-
This is a concrete example of the structure of the phase detector 1 and the control circuit 10 in the case of a PSK signal, and mainly shows the parts related to the present invention.

First, the phase detector 1 includes two mixers 100 and 110.
and a π/2 phase shifter 120, the mixer 100 and the same 110
The conversion output a' of the frequency converter 9 is input to one input of each of the frequency converters 9 and 9, respectively.

Further, a π/2 phase shifter 1 is connected to the other input terminal of the mixer 100.
The regenerated carrier wave b' is inputted via the mixer 11
The regenerated carrier wave b' is directly inputted to the other input terminal of the carrier.

As a result, the mixers 100 and 110 output mutually orthogonal detection signals el and e2, respectively. Here, the detected signals el and e2 are expressed by the following equations (3) and (4).
) is expressed by the formula.

el=sin(Δθ+at 10) ---m-・-
=-=(3)-knee e2 =cos (Δθ+at)...
−・−・−・−・・−・・・・・・(4) Then, Δθ:
Carrier phase error aI: ±1. A modulation phase code that arbitrarily takes ±3 Next, the control circuit 10 includes an adder 130, a subtractor 2S 140, a multiplier 160, 170, 150, and an inverting amplifier 180.
and a low pass filter (LPF) 190.

The adder 130 and the subtracter 140 each receive the detection signal C1 at one input terminal and the detection signal e2 at the other input terminal, and perform addition 1a (e++e2) and subtraction 1a of both signals.
(e+ -83) are output to the multiplier 160, respectively.

The multiplier 160 outputs an addition value (e++e2) and a subtraction value (e+
ez) and sends it to one input terminal of the multiplier 170.

A= (et+ez)X (e+-ez)
-・---・---(5) On the other hand, the multiplier 150 receives the input of the detection signals el and e2, calculates the product value B of both signals, and sends it to the other input terminal of the multiplier 170. Send.

B = e IX e 2 =--
1---(6) As a result, the multiplier 170 inputs A,
The product value C of both 4B is determined. This is shown by the following equation (7).

C=AXB = (sin 2Aθsin a, L) 1si on X
n(2Δθ+a, prediction) )−・・−・・−−−1−・
(7) Here, considering that a+=±1, ±3, C=''-s in 2ΔθXcos2ΔθAya'-s
i n 4Δθ−−−−−−・−−−(8) This is input to the inverting amplifier 180, so the output of the inverting amplifier 180 is D=−KX”−5in4Δθ−−1− ---
−−−−(9) However, since Δθ is minute, D=−KX−1−s i n4Δθ−, Δθ −
----(10), this D becomes the phase error signal e through the low-pass filter 190, and the voltage controlled oscillator 8
It is output to.

As described above, since the frequency control method of the present invention extracts the phase error Δθ from two orthogonal detected signals, the received signal is a modulated signal of 4-PSK signal or higher (for example,
(8-PSK, 16QAM, etc.) basically includes orthogonal detection signals, so the configuration of the control circuit 10 can extract the phase error Δθ. Also, the received signal is 2-PS
In the case of K signals, if the detected signals are made orthogonal to each other in the phase detector, the multiplier 16 of the control circuit 10
The phase error Δθ can be extracted from the zero output.

Note that FIG. 3 shows the output signal waveform of the multiplier 170, that is, each four-value signal corresponds to one of the four-phase signals shown by the broken line, and the range A of the upward-sloping curve shown by the solid line in the figure, Same B,
Control is performed to make the phase error Δθ of the corresponding signal zero in C1, that is, in ranges A, B, and C1, the phase is pulled to the point where the solid curve intersects 0.

Next, FIG. 4 shows a phase locked detection demodulator according to another embodiment of the present invention.

The phase synchronized detection demodulator according to the second embodiment is provided with a multiplier 41 and a frequency divider 42 in place of the carrier extractor 2 of the inverse modulation method, and the frequency multiplier as a whole including the bandpass filter 4 is multiplied. This is a carrier wave extractor of the system. That is, if the received signal a is an N-PS■ (signal), then the multiplier 4
1 multiplies the conversion output of the frequency converter 9 by N to remove the modulation component to form a frequency signal f of a constant frequency (frequency equal to the center frequency of the bandpass filter 4), and sends it to the bandpass filter 4. Send. Further, the frequency divider 42 divides the frequency signal f that has passed through the bandpass filter 4 by 1/N, and sends a recovered carrier wave b' of a desired frequency to the phase detector 1.

Therefore, this phase synchronized detection demodulator operates in the same manner as the first embodiment and can obtain the same effects.

(Effects of the Invention) As detailed above, according to the phase locked detection demodulator of the present invention, the received signal (PSK signal) is input to the phase detector and carrier extractor via the frequency converter, The phase error of the converted carrier wave is detected based on two orthogonal detected signals output by the phase detector, and the local oscillation frequency of the frequency converter is controlled to minimize this phase error. Even if there is a fluctuation in the signal frequency, all of the fluctuation is absorbed by the frequency converter, and the carrier extractor can extract and reproduce the carrier wave without generating phase jitter, allowing stable synchronous detection demodulation operation. be able to. In addition, a bandpass filter with the same filtering characteristics can be used to handle any frequency band of the received signal as long as it is within the frequency conversion range, making it possible to use a wideband phase-locked detection demodulator. There are advantages that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of a phase synchronized detector 1-adjuster according to an embodiment of the present invention, and FIG. 2 is a block diagram of the configuration of a phase detector and a control circuit when the received signal is a 4-PSK signal. 3 is a diagram of the output signal waveform of the multiplier 170, FIG. 4 is a block diagram of the configuration of an embodiment of the present invention, FIG. 5 is a block diagram of the configuration of a conventional phase-locked detection demodulator, and FIG. 6 is a diagram of the carrier waveform FIG. 7 is a configuration block diagram of various configuration examples of the extractor, and FIG. 7 is an amplitude phase characteristic diagram of a bandpass filter. 1...Phase detector, 2...Carrier extractor, 4...Band filter, 8...Voltage controlled oscillator, 9...・Frequency converter, 10・
... Control circuit, 41 ... Multiplier, 42
・・・・・・Frequency divider. Agent: Yoshihiro Yahata, Patent Attorney.
r) Figure 1! , ne, the example of Mr. Kou of the season of invention, the creation of the invention, the sailing of the ship, and the example of the tg (IIJ No. 4 Zushinkanshi liquid chiang and the poem of the control circuit 2 diagram purge A/70/) Tomogata diagram Figure 3 Figure 5 (fs) Conventional example of West Liang Yami Xiang Sokui 1 Sword installation class Figure 5 (fs) Band width (m-width term υa material of oak) is supported Figure 7

Claims (1)

[Claims] a frequency converter that receives a predetermined local oscillation frequency signal and converts the carrier frequency of the received PSK signal to a predetermined frequency; a carrier extractor that receives the PSK signal converted and outputted by the frequency converter and extracts the converted carrier wave; a bandpass filter that performs a bandpass filtering process on the extracted converted carrier wave; and a bandpass filter that performs a bandpass filtering process on the extracted converted carrier wave; and performs a detection process on the PSK signal outputted by the frequency converter using the phase of the converted carrier wave that has passed through the bandpass filter as a reference phase; a phase detector that forms two detection signals that are orthogonal to each other; a phase detector that controls so that the frequency fluctuation of a converted carrier wave of a PSK signal converted and output by the frequency converter is minimized; a frequency control means for receiving a signal to form a signal indicating a phase error of the converted carrier wave, and generating the local oscillation frequency signal of a predetermined frequency based on the phase error signal; Demodulator.