JPH05176013A - Transmission speed variable demodulator - Google Patents

Abstract

PURPOSE:To automatically alter transmission speed in a demodulator to appropriate transmission speed matched with the speed of reception speed. CONSTITUTION:This demodulator is provided with means 3-8 converting the reception signal into a base band signal, means (a both waves detectors 20, an A/D converter 21 and a high speed Fourier transformer 22) extracting a transmission speed component from the converted base band signal and recognizing transmission speed and a means (controller 13) for outputting a parameter alteration control signal for varying transmission speed in accordance with the transmission speed. A parameter for outputting the parameter alteration control signal based on recognized transmission speed and altering transmission speed is controlled and transmission speed is automatically altered in accordance with the reception signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable transmission rate demodulator, and more particularly to a demodulator which automatically changes its transmission rate according to a received signal.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional variable transmission rate demodulator. The received signal 1 that has been subjected to the four-phase modulation is distributed to the distributor 2
Is branched into two and input to mixers 3 and 4, respectively. On the other hand, a frequency signal that is close to the carrier frequency of the received signal is output from the oscillator 6, and this frequency signal is used as it is and the signal that is shifted by the 90 ° phase shifter 5 is input to the mixer 3, respectively.
Input to 4. As a result, the received signal 1 becomes the mixer 3,
Quasi-synchronous detection is performed on the baseband signal by 4.

The quasi-coherently detected signal is noise-compressed by the variable low-pass filters 7 and 8. This filter 7,
The output of 8 is an analog-digital (A / D) converter 9,
A digital signal of arbitrary bits is converted by 10 and further synchronously detected by a digital demodulator 11 to obtain demodulated data 15a and 15b. Also, the A / D converters 9 and 10
The sampling clock for is supplied from the clock extractor 12.

Here, when changing the transmission rate, the bands of the variable low-pass filters 7 and 8 are changed, the parameters in the digital demodulator 11 are changed, and the clock extractor 12 is used. It is necessary to change the time constant of the loop filter of. These changes are performed by outputting the control signals 16a, 16b, 16c for changing each parameter through the controller 13 by the transmission rate switching device 14 that is manually operated.

[0005]

In such a conventional variable transmission rate demodulator, when changing the transmission rate,
It is necessary to manually switch the transmission rate switch 14. Therefore, there is a problem that the change of the transmission rate becomes troublesome and it is difficult to set an appropriate transmission rate corresponding to the rate of the received signal in order to perform suitable demodulation. It is an object of the present invention to provide a variable transmission rate demodulator capable of automatically changing to an appropriate transmission rate suitable for the speed of a received signal.

[0006]

According to the present invention, there is provided means for converting a received signal into a baseband, means for recognizing a transmission rate by extracting a transmission rate component from the converted baseband signal, and the transmission rate. And means for outputting a control signal for changing the parameter for varying the transmission rate accordingly. Here, a means for extracting the transmission rate component from the baseband signal and recognizing the transmission rate is a dual-wave detector for detecting both waves of the baseband signal and an A / D conversion for performing analog-digital conversion on the detected output. And a fast Fourier transformer for Fourier transforming the converted digital signal.

[0007]

[Function] By detecting the baseband signal with the double-wave detector, the output spectrum has a velocity component (clock component).
Therefore, the detected output is A / D converted into a digital signal of arbitrary bits, and the clock component is detected by Fourier transforming this digital signal, and the clock frequency that matches the transmission speed of the received signal from this clock component. Decode and recognize the transmission speed. A control signal for changing the parameter for setting the transmission rate based on the transmission rate is output.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram of an embodiment of the present invention.
The same parts as those of the conventional configuration shown in FIG. 2 are designated by the same reference numerals. That is, the reception signal 1 that has been subjected to the four-phase modulation is split into two by the distributor 2 and input to the mixers 3 and 4, respectively. On the other hand, a frequency signal that is close to the carrier frequency of the received signal is output from the oscillator 6, and this frequency signal is used as it is and the signal that is shifted by the 90 ° phase shifter 5 is input to the mixer 3, respectively.
Input to 4. As a result, the received signal 1 becomes the mixer 3,
Quasi-synchronous detection is performed on the baseband signal by 4.

The quasi-coherently detected signal is noise-compressed by the variable low-pass filters 7 and 8. This filter 7,
The output of 8 is an analog-digital (A / D) converter 9,
A digital signal of arbitrary bits is converted by 10 and further synchronously detected by a digital demodulator 11 to obtain demodulated data 15a and 15b. Also, the A / D converters 9 and 10
The sampling clock for is supplied from the clock extractor 12.

Further, the output of the variable low-pass filter 8 is input to a double-wave rectifier 20 and double-wave rectified. In this double-wave rectifier 20, as shown in FIG. 3, a clock component appears in its output spectrum, and this clock frequency matches the transmission rate (symbol rate) frequency. The rectified output is converted into a digital signal of arbitrary bits by the A / D converter 21, and is input to the fast Fourier transformer 22. The fast Fourier transformer 22 detects the clock component, decodes the clock frequency, and outputs it to the controller 13. The controller 13 recognizes the transmission rate of the received signal from the decoded clock frequency, and changes the parameter control signals 16 of the variable low-pass filters 7 and 8, the digital demodulator 11 and the clock extractor 12.
a, 16b, 16c are output.

Therefore, in this configuration, the double-wave rectifier 2
0, the A / D converter 21 and the fast Fourier transformer 22 automatically decode the clock frequency in the received signal,
Based on this clock frequency, the controller 13 sends the parameter signals 16a, 16b, 16 of the variable low-pass filters 7, 8, the digital demodulator 11, and the clock extractor 12, respectively.
Since "c" is output and the transmission rate is changed, it is not necessary to manually change the transmission rate, and the transmission rate is automatically converted to an appropriate transmission rate corresponding to the received signal.

[0012]

As described above, according to the present invention, the transmission rate component is detected from the baseband signal and the control signal for changing the parameter for setting the transmission rate is output based on the detected transmission rate component, so that the transmission is performed manually. Even if the speed is not changed, there is an effect that it is automatically converted into an appropriate transmission speed corresponding to the received signal and normal digital demodulation is performed.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of a variable transmission rate demodulator of the present invention.

FIG. 2 is a block circuit diagram of an example of a conventional variable transmission rate demodulator.

FIG. 3 is a spectrum diagram of an output of a double-wave detector.

[Explanation of symbols]

 1 Received Signal 3,4 Mixer 6 Oscillator 7,8 Variable Low Pass Filter 11 Digital Demodulator 12 Clock Extractor 13 Controller 20 Double Wave Detector 21 A / D Converter 22 Fast Fourier Transformer

Claims (2)

[Claims] 1. A means for converting a received signal into a baseband signal, a means for recognizing a transmission rate by extracting a transmission rate component from the converted baseband signal, and a transmission rate variable according to the transmission rate. And a means for outputting a control signal for changing parameters for the transmission rate variable demodulation device. 2. A means for extracting a transmission rate component from a baseband signal and recognizing the transmission rate, a dual wave detector for detecting both waves of the baseband signal, and an A / A for performing analog-digital conversion on the detected output. 2. The variable transmission rate demodulator according to claim 1, comprising a D converter and a fast Fourier transformer for Fourier transforming the converted digital signal.