JPH02280552A - Phase modulation signal demodulator - Google Patents

Abstract

PURPOSE:To improve the characteristic of a capture range by using an adaptive luminance line emphasis device so as to extract only a carrier signal from an output of a frequency multiplier eliminating a modulation component from an M-phase modulation signal, applying product detection from the carrier signal and a phase modulation signal and eliminating a phase shift from a signal point unable to be eliminated with a phase shifter. CONSTITUTION:A phase modulation signal inputted from a terminal 10 is multiplied by M at a multiplier 1 and a modulation component is eliminated. The output of the multiplier 1 is inputted to an adaptive luminance line emphasis device 2, noise is suppressed and only the carrier component with a frequency of a multiple of M is extracted. A frequency divider 3 reproduces the frequency of the original carrier from the carrier component multiplied by M. The reproduced original carrier signal is subject to multiplication detection with a phase modulation signal at a terminal 10 by a multiple detector 4. The carrier frequency is eliminated from the output of the detector 4 and the phase modulation signal with a fixed phase error from the signal point is obtained, Then the phase shifter 5 is used after the detector 4 to eliminate a fixed phase error thereby demodulating the phase modulation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to carrier wave demodulation of phase modulated signals.

(Prior art) Conventionally, there are many types of phase modulation signal demodulators.
Most of them are phase-locked loops (Reference: Floyd,
“Phaselock Te” by M. Gardner.
chniques”, Jhon Wiley & 5o
ns, Inc., New York, 1966).

(Problem to be solved by the invention) In the conventional technology, noise (N) is added to the signal (S) and the S/N
If the carrier wave frequency offset amount was extremely low or the amount of carrier frequency offset was large, the characteristics would deteriorate. Generally, it is known that problems such as narrow capture range and long pull-in time are caused by characteristic deterioration due to carrier frequency offset. The present invention seeks to ameliorate these problems.

(Means for Solving the Problems) A phase modulation signal demodulator of the present invention includes a frequency multiplier that removes a modulation component from an M-phase phase modulation signal, and a frequency multiplier that removes only a carrier wave signal multiplied from the output signal of the frequency multiplier. an adaptive bright line enhancer for extracting; a frequency divider for extracting the frequency of the original Ω carrier signal from the signal obtained by the adaptive bright line enhancer;
a product detector that performs product detection on the output of the frequency divider and the phase modulation signal; and a phase shifter that removes, from the output of the product detector, a phase shift from a signal point that cannot be removed by the product detector. It consists of:

(Operation) The present invention will be described in detail with reference to FIG. The phase modulation signal inputted from the terminal 10 is multiplied by M by the multiplier 1, and the modulation component is removed. Therefore, the output of the multiplier 1 is a carrier wave component with a frequency M times that of the phase modulation signal and noise. The output of this multiplier 1 is input to an adaptive bright line emphasizing device 2, which suppresses noise and extracts only the carrier wave component of M times the frequency. The adaptive bright line enhancer 2 is a very high Q narrowband filter that adaptively enhances the line spectrum contained in the input signal and suppresses white noise, and is a type of adaptive filter. The characteristics of this adaptive narrowband filter are adapted by linear operation, so they do not change regardless of the frequency of the line spectrum within the Nyquist band. For example, if the capture range is fb, which is the signal transmission rate, it can be expressed as 'cap'±fb/2M (1), and its characteristics are not affected by the carrier frequency offset.In the frequency divider 3, this M The frequency of the original carrier wave is reproduced from the multiplied carrier component.The reproduced original carrier wave signal is subjected to product detection with the phase modulated signal at the terminal 10 in the product detector 4.

The carrier wave frequency is removed from the output of the on-board detector 4, and it becomes a phase modulated signal with a fixed phase error remaining from the signal point. Therefore, by removing this fixed phase error using a phase shifter 5 after the product detector 4, the phase modulated signal is demodulated. The phase shifter 5 is realized by a phase synchronization system, but since the input signal of the phase shifter has no carrier frequency offset, it does not affect the characteristics of the capture range. Therefore, the capture range of the phase modulation signal demodulator of the present invention is expressed by equation (1). The same can be said about other characteristics.

(Example) FIG. 2 shows an example of the present invention. The phase modulated signal is input to a multiplier 1, and its output is input to an adaptive bright line enhancer 2. The adaptive bright line enhancer 2 is Bunju (B).

Widrow, et al.
ve No.1se Canceling:Pr1nc
iples and Applications”,
Proc, IEEE, VOL, 63°No, 1
2. It is composed of a correlation separator 20 composed of a delay operator, an adaptive filter 21, and an adder 22, as described in J. Dec., 1975). This adaptive filter is an optimal solution of a discrete Wiener filter, and the transfer function H(ω) of the filter is the cross-correlation spectrum of the multiplier output signal ri and the correlation separator output signal Xi. , and if the autocorrelation spectrum of Xi is Sx, it is expressed as H(ω)=S,/sm (2). Here, the signals ri and Xi are respectively ri=ai
+nH(3) Xi = a'kenn2ffi where a is defined as a carrier wave component and n as a noise component. Substituting these equations (3) into equation (2), the transmission function of the filter is H(ω)=Saa/(Saa +5nn)nTb (n
: integer) (4) where nTb (=fb) is the correlation separator 20
Equation (4), which is the delay amount, means that the transfer function (ω) is a filter that inputs the delayed multiplier output signal Xi and extracts only the carrier wave component ai in the signal Xi. The signal obtained here is a carrier wave signal multiplied by M with noise suppressed. In order to demodulate the phase modulated signal, the frequency divider 3 determines the original frequency of this M-multiplied carrier wave. For example, as shown in FIG. 2, the frequency divider 3 first includes a differentiator 30
, a phase detector 31, and an integrator 32, a complex signal-to-phase change converter extracts only the phase change of the signal. Next, the value obtained by multiplying this phase change by 17M using the multiplier 33 is set as the phase value φi, and the complex signal conversion 34 converts zH=exp (jφi),
(5) where j represents a complex operator. When a complex signal Zi is obtained, the signal becomes the frequency estimation signal of the original carrier signal. Further, the phase change output from the integrator 32 is multiplied by 1/M by a multiplier 35, and the product detector 4
Then, a conjugate circuit 41 takes the complex conjugate of this frequency estimation signal, and a multiplier 42 multiplies it by the input phase modulation signal. In the multiplicative detector 4, the carrier frequency is removed. In actual received signals, not only does a carrier frequency offset occur due to deviations from the transmitting/receiving stations, but also frequency drift occurs in the transmitting/receiving stations due to temperature changes. This phenomenon leaves an adaption tracking error in the adaptive bright line enhancer 2. This tracking error leaves a fixed fixed phase error in the output signal if the drift is a constant change. The phase shifter 5 is for removing fixed phase errors from the remaining signal points. This is multiplier 5
1. Correction is performed by a primary loop composed of a phase detector 52, a perfect integrator 53, a complex signal converter 54, and a conjugate circuit 55. This first-order loop multiplies the conjugate signal Pi of the complex signal corresponding to the estimated fixed phase error Φ by the output of the multiplicative product detector to obtain an estimated error. Subsequently, the estimated value of the fixed phase error is updated using the estimation error.

By this operation, a demodulated phase modulation signal without a fixed phase error is output from the multiplier output 51.

(Effects of the Invention) According to the present invention, there is an effect that characteristics such as capture range are improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the operation of the present invention, and FIG. 2 is a diagram showing one embodiment of the present invention. In the figure, 1...multiplier, 2...adaptive bright line enhancer, 3...frequency divider, 4...product detector, 5...phase shifter.

Claims (1)

[Claims] A demodulator that demodulates an M-phase phase modulation signal includes a frequency multiplier that removes modulation components from the M-phase phase modulation signal, and an adaptive bright line enhancement that extracts only the multiplied carrier signal from the output signal of the frequency multiplier. a frequency divider that extracts the frequency of the original carrier signal from the signal obtained by the adaptive bright line enhancer; and a product detector that performs product detection of the output of the frequency divider and the phase modulation signal. , a phase shifter that removes a phase shift from a signal point that cannot be removed by the product detector from the output of the product detector, and a phase modulation signal demodulator that demodulates the carrier phase and frequency.