JPH01305647A - Phase jump erase device - Google Patents

Abstract

PURPOSE:To exactly execute the correction of phase jump due to a decision error by providing a smoothing circuit, a deciding circuit and a corrector. CONSTITUTION:In the demodulator of a K-phase modulating signal, difference between a value Xi of a signal point and a value Xi-1 of preceding signal point in a complex signal, for which the phase synchronization of a carrier is not established, is obtained. Then, real phase quantity Ai, for which phase shift due to modulation is removed, a phase angle is successively obtained until a time Ti and a sum is obtained, is inputted to a smoothing circuit 1 and a moving average value Bi of this quantity Ai is obtained. In a deciding circuit 2, it is decided whether the absolute value of difference between this moving average value Bi and a moving average value Bi-n before an (n)-number of phases satisfies a deciding condition or not. Then, when the value does not stiafy the deciding condition, it is judged that there is the decision error. After that, the phase correction of + or -2pi/K is added to the phase quantity A by a corrector 3. Thus, the correction of the phase jump due to the decision error can be exactly executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase jump canceling device, and more particularly to a phase jump canceling device that cancels phase jumps by estimating the carrier phase in a phase modulated signal.

[Conventional technology]

Conventionally, the least squares method has been used to estimate the carrier phase of a phase modulated signal. This is the value obtained by removing the phase shift due to modulation from the value XI of each signal point for which carrier phase synchronization has not been established, and the value X of the previous signal point
Using the fact that the net phase amount A, which is obtained by taking the difference from the value after removing the phase shift due to modulation and calculating the sum up to time T1, is distributed on a certain straight line, at each point of the distribution, When the straight line with the least error is estimated using the least squares method, the slope of the straight line is the carrier offset,
Further, the point of contact of the straight line with the Y-axis is the initial phase offset 1~. However, when the noise level is high,
A phase fluctuation due to noise is added to the phase shift due to the carrier wave offset, and this is mistakenly removed as a phase shift l- due to modulation, so that an incorrect phase jump occurs in the distribution of the phase amount A1. Several methods have been described in the past to improve this phase jump (Namiki: ``Storage-Bulk Demodulation Method for Wireless Anti-Packet'', IEICE Theory (B), J67-Bi],
.

] pp54-611 1982-01, or Higashida et al.

“'PSK Signal Accumulation - Timing Extraction and Carrier Estimation in Bulk Demodulation Method’” 2 Tsukata Kenkai, C386-169,
p+) 31-38, 1986). In the conventional technology for improving this incorrect phase jump, the net phase amount A1 is used to determine that an incorrect phase jump has occurred when the difference between the phase amount A+ and A1-11 exceeds a predetermined threshold. He made a judgment and made corrections.

[Problem to be solved by the invention]

FIG. 2 is a diagram showing an example of a temporal change in the net phase amount A1. In the conventional phase jump cancellation method, the phase amount AI is used as the evaluation signal, and the phase amount difference, Al Al-7
Since an incorrect phase jump was determined from 201 in the figure, it was erroneously determined that an incorrect phase jump occurred in a portion where thick noise was temporarily added, as shown by 201 in the figure. This is for correcting incorrect phase jumps.
There is a problem in that the incorrect correction causes further incorrect phase jumps and deteriorates the characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a phase jump canceling device that is more effective than the conventional incorrect phase jump canceling method, which has been insufficient.

[Means to solve the problem]

In the phase jump canceling device of the present invention, in a demodulator for a K phase modulation signal, the value XI of a signal point of a complex signal for which carrier phase synchronization has not been established and the value x of the previous signal point x + -, The net phase amount A is obtained by taking the difference between , removing the phase shift due to modulation), finding the phase angle sequentially up to time TI, and summing the sum.
1 is input, and the smoothing circuit calculates the moving average value B1 of this phase amount AI, and checks whether the absolute value of the difference between the moving average value Bi and the moving average value Bi−n n times before satisfies the determination condition. The present invention is characterized by comprising a determination circuit that makes a determination, and a corrector that determines that a decision error has occurred when the determination circuit does not satisfy a determination condition, and adds a phase correction of ±2π/K to the phase amount A+.

[Effect]

The principle of the present invention will be explained using FIGS. 1 to 3.

FIG. 1 is a block diagram showing an embodiment of the phase jump canceling device of the present invention, and FIG. 3 is a diagram showing the state of the phase amount B1 after the smoothing circuit for the phase amount A1 shown in FIG. 2.

In the conventional example, when an incorrect phase jump is erased using the phase amounts AI and Al-0 shown in FIG. 2, the determination circuit determines that a decision error has occurred at the points indicated by 201 and 202 in the diagram. Although the phase jump is corrected, a decision error actually occurs only at point 202.

In this embodiment, the moving average value Bi of this phase amount A1 is determined. Here, as shown at 301 in FIG. 3, the determination circuit 2 does not recognize the phase jump at the point shown at 201 in FIG. This takes advantage of the fact that the noise component has a high peak value but an average value, and it eliminates what appears to be a short phase jump, allowing for more accurate phase jump correction. becomes. For points where the determining circuit 2 determines that there is a phase jump, the corrector 3 applies a correction of ±2π/K to the phase amount A.

〔Example〕

Next, the present invention will be specifically explained with reference to FIG.

FIG. 4 is a block diagram of a phase modulation demodulator showing an example of application of the present invention.

In FIG. 4, the phase modulation signal is converted into a complex baseband signal by a frequency converter 4. This complex baseband signal is band-limited by a filter 6, and converted into a complex digital signal by an A/D converter 7 at synchronized symbol rate timing. The net phase amount A of this complex digital signal is determined by the phase difference detection circuit 8 and is stored in the memory 9. The net phase amount A obtained by the phase difference detection circuit 8 is inputted to a phase jump canceller, and is sent to a smoothing circuit 11 and a determination circuit 2. The corrector 3 performs phase jump correction due to a decision error, and the net phase amount without any incorrect phase jump is input to the carrier phase estimator 10. For example, assuming that there is a phase jump when lBi B1-51>π/K is satisfied as a judgment condition, the following correction is made.

A+=A+ 2π/K ; BI B1-5>π/K AI = A.

: −π / ■gu ＜ B +
BI-5<π/KAl=A,
→−2π/K; Bi −Bi 5 <
-π/K Carrier phase estimator 10 is carrier frequency offset I~Δ
ω and carrier initial phase θ. is estimated, a correction value for each complex digital signal is obtained in the phase difference correction circuit 11, and the multiplication is combined with the complex digital signal stored in the memory 9 in the complex multiplier 12, and the demodulated phase modulation signal is obtained. Output.

〔Effect of the invention〕

As explained above, in the present invention, in a demodulator for a K-phase modulated signal, the value x1 of a signal point of a complex signal for which carrier phase synchronization has not been established and the value X1 to 1 of the previous signal point , remove the phase shift due to modulation, calculate the phase angle sequentially up to time T1, and calculate the sum by inputting the net phase amount At, and calculate the moving average value Bi of this phase amount A. , it is determined whether the absolute value of the difference between this moving average value B1 and the moving average value Bi−n n times before satisfies the determination condition, and when the determination condition is not satisfied, it is determined that a decision error has occurred. By adding a phase correction of ±2π/K to the phase amount A, there is an effect that phase jump correction due to a decision error can be performed more accurately than the conventional device.

[Brief explanation of the drawing]

FIG. 1 is a basic block diagram showing an embodiment of the phase jump canceling device of the present invention, FIG. 2 is a diagram showing an example of a temporal change in the net phase amount, and FIG. FIG. 4 is a block diagram of a phase modulation demodulator showing an example of application of the present invention. 1... Smoothing circuit, 2... Judgment circuit, 3... Corrector, 4
- Frequency converter, 6 Filter, 7... A/D converter, 8... Phase difference detection circuit, 9... Memory, 10
-Carrier phase estimator, 11...phase difference correction circuit, 12
...Complex multiplier.

Claims (1)

[Claims] In the demodulator of the K phase modulation signal, the difference between the value X_i of the signal point of the complex signal for which carrier phase synchronization has not been established and the value X_i_−_1 of the previous signal point is taken, and the phase shift due to modulation is calculated. Input the net phase amount A_1 obtained by sequentially calculating and summing the phase angles until time T_i, and calculate this phase amount A_1.
a smoothing circuit that calculates the moving average value B_i of _1; a determination circuit that determines whether the absolute value of the difference between the moving average value B_i and the n-th previous moving average value B_i_−_n satisfies a determination condition; When the judgment condition is not satisfied in the circuit, it is determined that a decision error has occurred and the phase amount A_
1. A phase jump canceling device comprising: a corrector for adding a phase correction of ±2π/K to 1.