JPH0823235A - Signal reproduction device - Google Patents

Abstract

PURPOSE:To demodulate a digital signal from a signal that contains many noises by processing a modulation signal component and a clock signal component in different systems and reproducing the modulation signal digital data by a demodulation means based on a clock signal. CONSTITUTION:The radiation electromagnetic waves received by an antenna 1A are amplified by a wide band amplifier 2A and inputted to a receiver 3A. Then these amplified waves are selectively amplified by the receiver 3A and undergo the AM detection. The noises of the AM detected waves are eliminated by a BPF 4A, and a modulation signal is outputted to a modulation signal output terminal 11. In a clock signal reproduction system, the radiated electromagnetic waves received by an antenna 1B are amplified by a wide band amplifier 2B and inputted to a receiver 3B. These amplified waves are selectively amplified by the receiver 3B and undergoes the AM detection. The noises of the AM detected waves are eliminated by a BPF 4B, and a clock is outputted to a synchronizing clock output terminal. Then the modulation signal outputted to a PS from the terminal 11 is demodulated by a demodulation circuit 13 based on the clock outputted from an output terminal 12. Thus the digital data are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal reproducing device for demodulating a digital modulation signal.

[0002]

2. Description of the Related Art Conventionally, there is no technique for reproducing digital data from radiated electromagnetic waves from a modem of communication equipment such as FAX, but as applicable techniques, there is a PSK differential detection system which is a demodulation system of a digital modulation wave and There is a PSK synchronous detection method.

A conventional signal reproducing apparatus will be described with reference to FIG. FIG. 7 is a block diagram showing the configuration of a conventional PSK differential detection type signal reproducing apparatus disclosed in, for example, “Graphic Communication System”, pages 246 to 248, published by Kogyo Tosho Co., Ltd., by Nobuo Araki.

In FIG. 7, 1 is an antenna for receiving radiated electromagnetic waves, 2 is a wide band amplifier for amplifying received signals, 3 is a receiver, 4 is a band pass filter (BPF),
5 is a synchronous detection circuit, 6 is a low pass filter (LPF),
Reference numeral 7 is a code determination circuit, 8 is a 1-symbol delay circuit, 9 is a clock recovery circuit, and 10 is a digital data output terminal.

A differential PSK signal is input from the receiver 3,
The input differential PSK signal is set to 1 in the 1-symbol delay circuit 8.
The symbol is delayed and the input differential P is input in the synchronous detection circuit 5.
Synchronous detection is performed using the phase difference from the SK signal. Further, the clock reproducing circuit 9 reproduces the clock, the code judging circuit 7 uses the clock to judge the sign, and the reproduced digital signal is obtained from the digital data output terminal 10.

[0006]

Since the conventional signal reproducing apparatus as described above is constructed as described above,
There is a problem that it is not suitable for reproducing a signal including much noise such as a radiated electromagnetic wave.

The present invention has been made to solve the above problems, and an object thereof is to obtain a signal reproducing apparatus capable of demodulating a digital signal from a noisy signal such as an electromagnetic wave radiated from a modem. And

[0008]

A signal reproducing apparatus according to claim 1 of the present invention comprises a first antenna for receiving a radiated electromagnetic wave containing a modulated signal component and a second antenna for receiving a radiated electromagnetic wave containing a clock signal component. Antenna, modulated signal extracting means for extracting a modulated signal from the signal received by the first antenna, clock extracting means for extracting a clock signal from the signal received by the second antenna, and the extracted clock signal And demodulation means for reproducing digital data from the extracted modulated signal based on the above.

In the signal reproducing apparatus according to the second aspect of the present invention, the first and second antennas are the same.

According to a third aspect of the present invention, there is provided a signal reproducing device, wherein the demodulating means is an identifying device for identifying a modulation system,
It is composed of a plurality of demodulation circuits having different demodulation methods.

[0011]

In the signal reproducing apparatus according to the first aspect of the present invention, the radiated electromagnetic wave containing the modulated signal component is received by the first antenna, and the radiated electromagnetic wave containing the clock signal component is received by the second antenna. It Further, the modulated signal extraction means extracts a modulated signal from the signal received by the first antenna, and the clock extraction means extracts a clock signal from the signal received by the second antenna. Then, the demodulation means reproduces digital data from the extracted modulated signal based on the extracted clock signal. Therefore, although the radiated electromagnetic wave has high noise, the characteristic that the clock signal component and the modulated signal component are radiated at different frequencies can be used, and even from a signal under high noise such as radiated electromagnetic wave that could not be demodulated in the past. The clock can be recovered and the digital data can be recovered.

In the signal reproducing apparatus according to the second aspect of the present invention, since the first and second antennas are the same, it is not necessary to provide separate antennas.

In the signal reproducing apparatus according to the third aspect of the present invention, since the demodulating means is composed of an identifying device for identifying a modulation system and a plurality of demodulation circuits having different demodulation systems, the communication modulation system. Even if is unknown, the modulated signal can be identified and the digital data can be reproduced.

[0014]

【Example】

Example 1. The configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In each figure, the same reference numerals indicate the same or corresponding parts.

In FIG. 1, reference numeral 1A is a biconical antenna for receiving a radiated electromagnetic wave having a center frequency of, for example, about 50 MHz, and 1B is a log-periodic antenna for receiving a radiated electromagnetic wave having a center frequency of, for example, about 150 MHz. 2A and 2B are wide band amplifiers, 3A and 3B are receivers, and 4A is, for example, 300 Hz to 3.4 KHz.
Band pass filter (BPF) of 4B is, for example, 120
Bandpass filter (BP that passes 0 Hz signal)
F). Further, 11 is a modulation signal output terminal, 12 is a synchronous clock output terminal, and 13 is a phase shift (PSK: Pha
se shift keying) demodulation circuit.

The radiated electromagnetic wave of the modem has a characteristic that the clock signal component and the modulation signal component are radiated at different frequencies. Utilizing this characteristic, the clock signal component and the modulation signal component are separated into separate receivers 3A, 3B. To receive and play.

FIG. 2 shows an example in which the clock signal component contained in the radiated electromagnetic wave is selectively extracted, and 14 shows the frequency component (1200 Hz) of the clock. High-level signals other than the clock frequency component 14 (2400 Hz
Indicates the harmonics of the clock. FIG. 3 is an example in which the modulation signal component is selectively extracted, and 15 indicates the center frequency (1700 Hz) of the modulation signal.

Next, the operation of the first embodiment will be described. In order to reproduce the digital data from the electromagnetic wave radiated from the modem, in the modulated signal reproducing system of the first embodiment, the radiated electromagnetic wave received by the antenna 1A is amplified by the wide band amplifier 2A and input to the receiver 3A. After being selectively amplified and AM-detected in the receiver 3A, noise is removed by the bandpass filter 4A, and a modulation signal is output at the modulation signal output terminal 11. The bandpass filter 4A uses, for example, a filter having a frequency band of 300 Hz to 3.4 kHz on the telephone line.

Further, in the clock signal reproducing system, the radiated electromagnetic wave received by the antenna 1B is the wide band amplifier 2B.
Is amplified by and input to the receiver 3B. Receiver 3B
In the same manner as in the modulation signal reproduction system,
After M detection, noise is removed by the bandpass filter 4B and a clock is output at the synchronous clock output terminal 12.

Then, in the PSK demodulation circuit 13, the modulated signal output from the modulated signal output terminal 11 is demodulated using the clock output from the synchronous clock output terminal 12, whereby digital data can be obtained.

The first embodiment utilizes the characteristic that the electromagnetic wave radiated from the modem is high noise, but the clock signal component and the modulation signal component are radiated at different frequencies.
The clock signal component and the modulation signal component are received by separate receivers 3A and 3B. As a result, the clock can be regenerated even from a signal under high noise such as a radiated electromagnetic wave of a modem, which could not be demodulated conventionally, and digital data can be obtained. Also, the conventional clock recovery circuit can be omitted.

Example 2. In the above-mentioned first embodiment, P
Although the SK demodulation circuit 13 is used, as shown in FIG. 4, even if a frequency shift (FSK) frequency demodulation circuit 13A is used, the same effect as that of the first embodiment can be obtained.

Example 3. Further, in the above-described first embodiment, P
Although the SK demodulation circuit 13 is used, as shown in FIG. 5, a quadrature amplitude (QAM: Quadrature Amplitude Modulatio) is used.
n) Even if the demodulation circuit 13B is used, the same effect as that of the first embodiment can be obtained.

Example 4. In each of the above embodiments, the modulation method used for communication is known. However, the fourth embodiment can be applied when the modulation method is unknown.

A fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the fourth embodiment of the present invention, and the portion preceding the vector modulation analyzer 16 is the same as that of the first embodiment described above.

As shown in FIG. 6, the synchronous clock output from the synchronous clock output terminal 12 is input to the vector modulation analyzer 16 as a coherent carrier to display and recognize the constellation pattern. Since the modulation system can be identified by this pattern, the demodulation circuits 13 and 13 in the subsequent stages can be identified by the modulation system.
The modulated signal and the clock are transmitted to either A or 13B.

According to the fourth embodiment, the clock can be regenerated from the radiated electromagnetic waves of the modem, which cannot be demodulated by the conventional method, and the digital data can be regenerated. Also, the conventional clock recovery circuit can be omitted. Moreover, even if the modulation method of communication is unknown, it is possible to identify the modulated signal and demodulate the digital data.

In each of the above embodiments, the antennas 1A, 1
Although B is provided separately, the radiated electromagnetic wave may be received by one antenna capable of receiving the modulation signal component and the clock signal component. In this case, if a diversity function in the plane of polarization (horizontal polarization and vertical polarization) is provided, horizontal polarization and vertical polarization can be compared and reception can be performed considering the level strength.

[0029]

As described above, the signal reproducing apparatus according to the first aspect of the present invention receives the radiating electromagnetic wave containing the modulated signal component and the radiating electromagnetic wave containing the clock signal component. Two antennas, a modulation signal extraction means for extracting a modulation signal from the signal received by the first antenna, a clock extraction means for extracting a clock signal from the signal received by the second antenna, and the extracted clock Since it has demodulation means for reproducing digital data from the extracted modulated signal based on a signal,
It is possible to reproduce a clock from a signal under high noise such as a radiated electromagnetic wave that cannot be demodulated in the past and to reproduce digital data.

As described above, in the signal reproducing apparatus according to the second aspect of the present invention, since the first and second antennas are the same, there is an effect that it is not necessary to provide separate antennas.

As described above, in the signal reproducing apparatus according to the third aspect of the present invention, since the demodulating means is composed of the identifying device for identifying the modulation system and the plurality of demodulating circuits having different demodulation systems, the communication is performed. Even if the modulation method is unknown, it is possible to identify the modulated signal and reproduce the digital data.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram showing the operation of the first embodiment of the present invention.

FIG. 3 is a signal waveform diagram showing the operation of the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a conventional signal reproducing device.

[Explanation of symbols]

1A, 1B antenna, 2A, 2B wide band amplifier, 3
A, 3B receiver, 4A, 4B bandpass filter,
13 PSK demodulation circuit, 13A FSK demodulation circuit, 13
B QAM demodulator, 16 vector modulation analyzer.

Claims (3)

[Claims] 1. A first antenna for receiving a radiated electromagnetic wave containing a modulated signal component, a second antenna for receiving a radiated electromagnetic wave containing a clock signal component, and a modulated signal extracted from a signal received by the first antenna. Modulation signal extraction means, clock extraction means for extracting a clock signal from the signal received by the second antenna, and demodulation means for reproducing digital data from the extracted modulation signal based on the extracted clock signal. A signal reproducing device characterized by. 2. The signal reproducing apparatus according to claim 1, wherein the first and second antennas are the same. 3. The signal reproducing device according to claim 1, wherein the demodulating means is composed of an identifying device for identifying a modulation system and a plurality of demodulating circuits having different demodulation systems.