JPH0443740A - Demodulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a demodulator for use in digital radio or digital wired equipment.

(Prior Art) In recent years, systems using digital transmission methods such as FSK (Frequency Shift Keying) have been put into practical use in wireless communication devices such as hoodless telephones in order to improve voice quality and ensure confidentiality.

A conventional demodulator will be described below.

As shown in Figure 3, a demodulator for wireless communication equipment using a digital transmission system converts the received intermediate frequency signal (hereinafter referred to as IF multiplied signal) into an analog detected signal (fibutter) by synchronous detection, delay detection, discrete detection, etc. After that, the demodulated data is obtained by converting it into a 1 or 0 digital signal using voltage comparison means.In this demodulator, the comparison voltage Vref of the voltage comparison means is detected as shown in FIG. 4(a). Correct demodulated data is obtained by matching the center voltages of the signals (demodulated eye butter/).However, in the case of FSK discrete detection, for example, when the IF multiplied signal frequency of the detection means input is shifted by Δf from the center, the 454th (b) As shown in FIG. 1, the direct current level of the co-detection signal shifts, and the comparison voltage Vref of the voltage comparison means does not match the center voltage of the detection signal, causing an error in the demodulated data.

To solve this problem, a demodulator shown in FIG. 5 is generally used. In FIG. 5, the detection signal (demodulated eye pattern) is input to the voltage comparison means (14) and simultaneously input to the low-pass filter (13). The detection signal (demodulated eye pattern) is integrated by this low-pass filter (13), and the output DC voltage is used as the comparison voltage Vref of the voltage comparison means (14).

According to this method, even if the IF multiplied signal frequency input to the detection means deviates and the DC voltage of the detection signal (demodulated eye pattern) shifts, the comparison voltage Vre of the voltage comparison means (14)
f is always the center of the detected signal (demodulated eye pattern), and demodulated data can always be reproduced without error.

(Problem to be Solved by the Invention) However, in the above conventional configuration, the cutoff frequency of the low-pass filter that integrates the detection signal (demodulated eye pattern) is set low in order to reduce fluctuations in the comparison voltage of the voltage comparison means due to the received data pattern. The problem is that it takes a long time for the low-pass filter output voltage to match the center voltage of the detected signal (demodulated eye butter) after reception starts, and as a result, it takes a long time to obtain strong demodulated data. be. An object of the present invention is to provide a demodulator that can solve the conventional problems and obtain accurate demodulated data in a short time.

(Means for Solving the Problem) The gist of the present invention that solves the problem is to provide a plurality of voltage comparison means for comparing a detected signal of a received intermediate frequency signal using different comparison voltages, and each of the plurality of voltage comparison means. A plurality of band pass filters having a center frequency of 1/2 of the transmission speed of the data carried by the received intermediate frequency signal are input, and the output level of the output signal of each band pass filter is compared to determine the maximum level. The demodulating device comprises a comparing means for selecting the voltage comparing means, and a selecting means for selecting the output signal of the voltage comparing means having the maximum output level selected by the comparing means as the demodulated signal.

(Operation) The detected signal of the received intermediate frequency signal is compared with a plurality of different comparison voltages by the voltage comparing means, and the detected signal of 7spg is converted into a digital signal. The digital signal is inputted to a bandpass filter having a center frequency of 1/2 of the data transmission rate and subjected to waveform shaping, and the output signal of each bandpass filter whose waveform is IE-shaped is inputted to a comparison means to compare the output signal. The output levels are compared and the output signal with the highest output level is selected. The selection means inputs the selection signal and selects and outputs the output digital signal of the voltage comparison means, which is the output signal with the highest output level, as demodulated data.

By rubbing in this way, the comparison voltage closest to the center voltage t of the detection signal (demodulated eye pattern) is selected, and the output digital signal of the voltage comparison means of that comparison voltage is selected as the demodulation data. be.

(Embodiment) FIG. 1 shows a block diagram of a demodulator in an embodiment of the present invention in which the comparison voltage is binary. The comparison means (30) for selecting the one with the highest output level includes two systems of rectification means (5) and (6), a p-bus filter (7),
(81 and one! pressure comparison means (9).

In FIG. 1, (1) and (2> are voltage comparison means for converting the detected signal of the received intermediate station wave number signal into digital data, and (3) and (4) are voltage comparison means (1), respectively. ,
(2) A bandpass filter for extracting a frequency component of 1/2Tb ('rb: data bit period) from the output, (5), (6) + i sole bandpass filter (3
), (4) rectifying means for rectifying the output, (7), (8)
is a low-pass filter for integrating the outputs of the rectifying means (5) and (6), (9) is a voltage comparison means for comparing the voltages of the output of the low-pass filter (7) and the output of the low-pass filter (8), and (10) is a low-pass filter for integrating the outputs of the rectifying means (5) and (6). This is a switch that selects and outputs the output of the voltage comparison means (1) or the output of the voltage comparison means (2) according to the output of the voltage comparison means (9). Also, (R1) to (R
3) is the comparison voltage V1. of the voltage comparison means (1) and (2).
This is a resistor for determining V2.

The demodulator configured as described above will be explained using FIG. 2. First, the detection signal of the received intermediate frequency signal (
The demodulated eye pattern 7) is converted into two digital data by a voltage comparison means (1) whose comparison voltage is Vl and a voltage comparison means (2) whose comparison voltage is V2. Now, the relationship between the detection signal (demodulated eye pattern) and the comparison voltages Vl and V2 is as shown in FIG. For slightly lower voltages, voltage comparison means (1).

(2) The output digital data signal is as shown in number (b) of the same figure.
This is 2Tb NRZ data, and the output of the voltage comparison means (2) is NRZ data with a data ratio exceeding 50%.

The outputs of the voltage comparison means (1) and (2) are input to band pass filters (3) and (4) with a center and frequency of 1/2Tb (Tb: bit period), respectively. Since the 1/2Tb component contains more 1/2Tb component, a bandpass filter (3
) Output level becomes larger than hand bus filter (4) output. The outputs of the band-pass filter (3) and the band-pass filter (4) are rectified by the rectifying means (5) and (6), and the low-pass filters (7) and (8), respectively, as shown in FIG. )): more integrated. p-bus filter (7).

The outputs of (8) are compared in voltage comparison means (9),
The voltage comparator (9) outputs a control signal so that the output of the voltage comparator (1) becomes a demodulated output.

Next, when the frequency of the IF multiplied signal to be detected changes and the comparison voltage V2 becomes a late number with the center voltage of the detection signal (demodulated eye pattern), the output of the voltage comparison means (2) is 1/2
It now contains a large amount of Tb component, and a bandpass filter (
The output level of 4) becomes higher than the output level of bad pass filter (3). As a result, the voltage comparison means (9) for comparing the rectified and integrated signals of these two signals is connected to the selection means (
A control signal is output to select the output of the voltage comparator (2) as the demodulated output for the demodulated output.

Here, the low-pass filters (7) and (8) that integrate the rectifying means (5) and (6) do not need to completely remove the received data pattern, and can operate even if they have a relatively high cutoff frequency. , the voltage comparison means (1) and (2) having the optimum comparison voltage can be selected and correct demodulated data can be output in a relatively short time after the start of reception.

In the embodiment described above, the comparison voltage of the voltage comparison means is set to two levels, but by setting this level to three or more, it is possible to further expand the control range and improve control accuracy.

(Effects of the Invention) As described above, the present invention provides a plurality of voltage comparison means having different comparison voltages, and a plurality of voltage comparison means each having a center frequency of 1/2 of the data transmission rate by inputting each output of the plurality of voltage comparison means. , a comparison means for comparing the output levels of the plurality of bandpass filters, and a selection means for selecting one of the voltage comparison means according to the output of the comparison means. It is possible to provide a demodulator that can demodulate correct data even when the IF multiplied signal frequency changes and the DC voltage of the output signal of the detection means fluctuates, and can operate in a relatively short time from the start of reception.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a demodulator according to an embodiment of the present invention, FIG. 2 is a time chart diagram of the demodulator of this embodiment,
FIG. 3 is a block diagram of a conventional demodulator, FIG. 4 is a time chart of a conventional demodulator, and FIG. 5 is a block diagram of an improved conventional demodulator. (6): (7) = (8): (9) = (10): (11): (12): (13) + (14): (30): Rectification means low-pass filter low-pass filter voltage comparison means selection Means Detection means Voltage comparison means Low-pass filter Voltage comparison means Comparison means (1): Voltage comparison means (2): Voltage comparison means (3): Bandpass filter (4): Bandpass filter (5): Rectification means Patent application Matsushita Electric Industrial Co., Ltd. jl 1 Fig. 2 Fig. (L) Te light/Cb) fIF Fuku-f Fig. 3 Fig.

Claims (1)

[Claims] 1) A plurality of voltage comparison means for comparing detected signals of the received intermediate frequency signal using different comparison voltages, and a method that inputs each output of the plurality of voltage comparison means and determines the transmission rate of data carried by the received intermediate frequency signal. a plurality of band-pass filters having a center frequency of /2, a comparison means for comparing the output levels of the output signals of each band-pass filter and selecting the highest level, and a comparison means for selecting the maximum output level selected by the comparison means. A demodulating device comprising: selecting means for selecting an output signal of the voltage comparing means as a demodulated signal.