JPH02241250A - Demodulation device - Google Patents

Abstract

PURPOSE:To realize the stable demodulation device of high performance by measuring difference between the expected value vector of an ideal state or a reference signal vector end an actual received vector, and deciding a receiving state according to the magnitude of this difference, and adjusting a feedback coefficient to a carrier wave reproducing device. CONSTITUTION:A received signal is multiplied by a receiving side carrier wave by a multiplier 31, and a high frequency noise is removed by a low pass filter 32. This signal is corrected in the difference between a carrier wave and the receiving side carrier wave by the carrier wave reproducing device 34. Corrected data is inputted to a phase determining device 33, and the phase of the received signal is determined. Besides, at that time, a differential vector between the ideal reference signal and the received signal is calculated, and is inputted to a feedback coefficient adjusting device 35. Here, the feedback coefficient is adjusted from the differential vector, and the corrected differential vector is inputted to the carrier wave reproducing device 34.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a demodulation device for a broad phase modulation (including quadrature amplitude phase modulation) method for data transmission using a telephone line.

Prior Art A conventional system configuration is shown in FIGS. 5 and 6. 11.
21 is a multiplier, 12.22 is a low pass filter 13
．． 23 is a phase determining device, and 14.degree. 24 is a carrier wave reproducing device. The following algorithm is known for reproducing the carrier frequency from the receiving side demodulated signal using this device.

(a) Multiplier 11.21 multiplies the received signal by the receiving side carrier frequency and the frequency obtained by softening it.

(b) The outputs obtained in (a) above are passed through low-pass filters 12 and 22, respectively.

(C) The phase difference between the phases of the two orthogonal outputs obtained in the above (b) and the expected value in the ideal state is detected by the phase determining device 13°23.

In addition, in phase difference detection, the concept of the following mathematical formula is introduced.

The expected value vector or reference signal vector of the ideal state is i
−(il, i2), the actual received vector is r−(r+
+ r2), then the phase difference θ is θ2s inθ−(i+−r2 i2・r+)/1i
llr... (1). In reality, this approximation can be further changed to θ2sinθ
α1/1it2・(i bir2−i2・rt)・・・・・・
・It is often approximated by (2). This is because these processes commonly use devices called digital signal processors.

ω) Using each of the approximate expressions (1) and (2) above, calculate the phase difference between the carrier wave and the receiving side (demodulation side) carrier wave, convert it to a frequency difference, and use the carrier wave reproduction device 14.24 to Reproduce the carrier wave.

Problems to be Solved by the Invention When the above-mentioned technology is used, there are the following three problems.

First, unreliable data due to poor reception conditions also ends up being fed back to the carrier wave reproduction device.

Second, each approximate expression (L) and (2) mentioned above is
The larger θ becomes, the larger the error becomes.

Thirdly, in the aforementioned approximation formula c2, the error increases as the difference between the amplitude of the reception vector of the reception signal and the amplitude of the expected value vector (or reference signal vector) in the ideal state increases.

Due to these problems, the receiving performance of the demodulator deteriorates,
This is a cause of unstable operation.

In order to solve these problems, the present invention uses the approximate formula (1)
, When the results obtained in (2) are fed back to the carrier wave reproduction device, the feedback coefficient is adjusted depending on the receiving condition.

Means for Solving the Problems In order to solve the above problems, the present invention measures the difference between the expected value vector or reference signal vector in the ideal state and the actual received vector, and determines the difference depending on the magnitude of this difference. Determines the reception condition and adjusts the feedback coefficient to the carrier wave reproduction device.

■Depending on the magnitude of calculation result θ of approximate formulas (1) and (2),
Adjust the feedback coefficient to the carrier reproduction device.

(2) Measure the difference between the amplitude of the expected value vector or reference vector in the ideal state and the amplitude of the actual received vector, and adjust the feedback coefficient to the carrier wave reproduction device depending on the magnitude.

We aim to solve the problems by using a device equipped with each of the above functions T to (2).

Operation: In the demodulator of the present invention, the feedback adjustment device feeds back phase difference information, which takes into account the state of the received signal, to the carrier wave reproduction device. This results in
After correcting unreliable data when reception conditions are poor and data when approximation errors are large, the data is fed back as phase difference information, so a stable and high-performance demodulation device can be obtained.

Embodiment FIGS. 1 and 2 show a system configuration for embodying the present invention. 31.32 is a multiplier, 32°42 is a low-pass filter, 33.43 is a phase determining device, 34.44
35.45 is a carrier wave reproduction device, and 35.45 is a feedback coefficient adjustment device that adjusts the feedback coefficient according to the receiving condition. A received signal, which explains the signal flow in FIG. 1, is multiplied by a receiving side carrier wave by a multiplier 31, and harmonic noise is removed by a low-pass filter 32. The carrier wave reproducing device 34 corrects the difference between the carrier wave and the receiving side carrier wave. The corrected data is input to a phase determining device 33 to determine the phase of the received signal. Also, at this time, a difference vector between the ideal reference signal and the received signal is calculated and input to the feedback coefficient adjustment device 35. Here, the feedback coefficient is adjusted from the difference vector, and the corrected difference vector is input to the carrier wave reproduction device 34. The same applies to FIG. The difference is that in FIG. 1, the carrier wave reproduction device and the receiving side carrier generation section are separate, whereas in FIG. 2, the carrier wave reproduction device includes the generation section.

FIG. 3 shows a conceptual diagram of an example of an adjustment method for adjusting a feedback coefficient of phase difference information in a demodulator that implements the present invention. In the figure, area 51 is an area where the reception condition is good and the phase difference is small, and correct phase information can be obtained, area 52 is an area where the phase difference is large and approximation error is large, and area 53 is an area where some signal transmission path This is an area where the amplitude of the received vector has become abnormal due to the influence of , and the reception condition is poor. In each of these areas, 1:0
．． 9: Set a feedback coefficient of 0.3.

Now, here in Fig. 4, these are signal vectors 62, 63.
64. Assuming that each reception vector is input, the phase difference between the carrier signal and the reception side (demodulation) at this time can be expressed as (α + 0.9β + 0.37)/3. This is more stable than (α+β+γ)/3 when treating highly reliable phase wave information like vector 61 and less reliable phase wave information like vector 62.63 equally. There are few errors.

In this way, the feedback coefficient to the carrier signal reproduction device is adjusted, and a stable and high-performance demodulation device is obtained. The method of determining the feedback coefficient will be explained using FIG. 6 as an example. In the case of the received signal vector 62, there is a phase difference of about π/4 from the ideal reference signal vector, and the value of β obtained from the approximate equation (1) is about 10% larger than the actual phase difference. Therefore, by multiplying the value obtained by the approximation formula (1) by a feedback coefficient of 0.9, a value close to the actual phase difference is obtained. Further, in the case of the received signal vector 63, the amplitude is only about 1/2 that of the ideal reference signal vector.

When γ is calculated using approximation formula (2), it is calculated as a value approximately twice the actual phase difference. Taking this into account and the reliability of the received signal, multiplying the result obtained by approximation formula (2) by a feedback coefficient of about 0.5 to 0.3 gives a result close to the actual phase difference. Becomes a value.

Effects of the Invention As described above, according to the present invention, corrected phase difference information can be fed back to the carrier reproduction device, and a stable and high-performance demodulation device can be obtained.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of the demodulator of the present invention, FIG. 3 is a conceptual diagram of an embodiment of the determination region of the feedback coefficient, and FIG.
The figure is a vector diagram showing an example of an actual received signal, and FIGS. 5 and 6 are schematic diagrams of a general demodulator. 11.21.31.41... Multiplier, 12.2
2゜32.42・・・Low pass filter, 13
．． 23゜33.43... phase determining device, 14,
24, 34°44... Carrier wave reproduction device, 35.
45... Feedback coefficient adjustment device. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 Figure 2

Claims (1)

[Claims] comprising a phase determining device that determines the phase of a received signal, and calculates a phase difference between the phase of the received signal and the phase of a reference signal;
A demodulation device comprising a feedback coefficient adjustment device that adjusts the amount of feedback of the phase difference from the phase determination device to the carrier wave reproduction device using a weighting coefficient depending on the state and characteristics of the received signal.