JPH08331185A - Demodulation method and device for fdm-fsk/psk modulation wave - Google Patents

Abstract

PURPOSE: To allow a receiver side only to discriminate transmission by a transmitter side without addition of a synchronizing signal by the transmitter side by sending all or part of individual multi-tones modulated by a required pattern at the transmitter side prior to transmission and discriminating the required pattern and demodulating the received tone signal by a measurement/ discriminating function of the receiver side provided to each individual demodulator for each tone. CONSTITUTION: A signal presence discrimination circuit 29 receives outputs from level measurement, devices 22, 23,..., 28 to measure the presence of tone signals. The signal presence discrimination circuit 29 uses any one of various methods such as a method that a total number of the presence of output levels of full band filters 11-18, for example, is obtained and total number of the presence of a reception level of each tone is obtained to discriminate it as a fact of transmission from the transmitter side when the number of presence of a reception level of each tone is within 1/8±α of the total number, or a method of majority decision that e.g. 5 tones or over in, 8 tones have a specified level or over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data transmission, and more particularly to a demodulation method for demodulating an FDM (frequency division modulation) -FSK (frequency shift modulation) / PSK (phase shift modulation) modulated wave.

[0002]

2. Description of the Related Art Conventionally, in data communication using wireless such as HF band, compared with wired transmission, radio wave propagation becomes non-uniform within the frequency band due to effects of fading, multipath, etc. Was deteriorated, causing distortion and noise, and the fluctuation range of the line quality and characteristics became large, making it impossible to perform high-speed data communication. The fluctuation range as described above is rarely a fixed value due to factors such as the place and distance between communications, and the time of use.
In addition, the level deviation within the band is non-uniform depending on the characteristics of the wireless device used (combination of transmitter and receiver), and also changes depending on the combination of transceiver.

FIGS. 4 and 6 show a conventional FDM system for solving this kind of problem and increasing the modulation speed. Further, FIG. 5 is an explanatory diagram showing frequency arrangement of transmission tones and data examples in the above case, and FIG. 7 shows a circuit example for determining demodulated data on the receiving side in FIG. This FDM system divides a communication band (for example, 300 Hz to 2700 Hz) into a plurality of sub-channels, arranges a tone for each sub-channel, and disperses information in each tone in order to perform high-speed data communication. It is then transmitted. In FIG. 4, 101 is an FDM-FSK modulator that modulates transmission data for each subchannel, 102 is a transmitter that transmits a modulated signal, and 103 is an antenna.

In this system, as shown in the figure, the transmission data includes sub-channels CH0 having frequency bands of b0 to b7.
The signal tones of level "0" and "1" are arranged in CH7 to CH7 and transmitted.

The transmission data is demodulated by the receiving side demodulation device shown in FIG. In FIG. 6, 104 is an antenna,
105 is a receiver for receiving the modulated signal, and 106 is an FDM-
This is an FSK demodulator. Further, in FIG. 7, 107 is a band-pass filter BPF1, 108 centered at 350 Hz.
Is a band-pass filter BPF2, 10 centered at 450 Hz
Reference numeral 9 is a level comparator for comparing signal levels. The transmission data from the transmission side is transmitted to the receiver 105 via the antenna 104.
And is input to the FDM-FSK demodulation device 106.

In the FDM-FSK demodulator 106, for CH0, for example, as shown in FIG.
Of the level A and the level B after passing through the band-pass filter BPF 117 of No. 1 and the band-pass filter BPF 128 of 450 Hz (the characteristic is shown in the lower side of FIG. 7).
The comparison is made at 09, and if level A> level B, it is determined to be data “0”, and if level A <level B, it is determined to be data “1” and b0 is transmitted. Similarly, CH1, C
H2 ,. ． ． Compare the levels for CH7,
Finally, b0, b1 ,. ． ． b7 is output.

Incidentally, such a conventional method also has the following problems. That is, in HF band communication, compared to other communication systems (wired, UHF band wireless, satellite communication, etc.), it is unavoidable that some degree of data error will occur due to the large line fluctuation, but in addition to this, In the data communication using the FSK modulated wave, even if the transmitting side is not actually transmitting, the demodulator as shown in FIG. 7 has irregular data (“0”) due to the influence of noise on the receiving side. Alternatively, "1") is output. Also, the demodulator of each channel determines whether the data is "1" or "0" only by comparing the level at the mark ("1") side frequency and the level at the space ("0") side frequency. , It is not judged including the reception tone. Comparison of very small levels,
Even when the noise levels are compared, either "0" or "1" is output. From the above points, in the demodulation device in which the FSK demodulation device as shown in FIG. 6 is arranged corresponding to the transmission frequency, synchronization between transmission and reception should be ensured in advance when transmitting the transmission data, and the transmission signal at the reception side should be ensured. It is necessary to capture the data only when it is determined that is determined and can be detected.

Therefore, for example, the transmitting side adds a synchronizing signal and the transmitting side receives the transmitted data as information only when the receiving side detects this, or establishes a time between transmission and reception to perform communication (determined). It was necessary to introduce auxiliary means such as (except for time, which is not recognized as reception). FIG. 8 shows, as an example, a method in which a synchronization signal is added to the transmission sequence. As shown in the figure, the transmission side adds a synchronization signal to the transmission (modulation) data and transmits it to the reception side. The receiving side detects the synchronization signal from the received (demodulated) data and confirms the signal transmission on the transmitting side. However,
Even in this conventional method, when the number of characters to be transmitted is small, the ratio of the synchronization time to the entire transmission time increases, which is inconvenient, and the transmitting side transmits a specific character, and the receiving side detects the specific character, Even if an attempt is made to realize an information transmission method that determines that there is a transmission, there is a problem that the possibility of erroneous determination increases as a result.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a synchronization signal is added in advance to the transmission sequence on the transmitting side in order to synchronize with the receiving device, or synchronization is previously established between transmission and reception. Level measurement / measurement is performed for each channel (subcarrier) of the FDM-FSK system and for each individual FSK demodulator without using other control means (such as time synchronization).
FDM-FSK / PSK modulated wave demodulation, in which the transmitting side transmits a specific pattern, and when the receiving side detects the specific pattern, it is possible to determine that the transmitting side has transmitted data by adding a determination function. It is an object to provide an apparatus and method.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, a method of demodulating an FDM-FSK / PSK modulated wave according to the present invention is a frequency shift keying (FSK) / phase shift keying (PSK) method (using multi-frequency multitone). FDM-FSK / ps
In the wireless communication using the modulator / demodulator in k), the transmitting side modulates all or part of the individual multitones with the required pattern prior to data transmission, and then transmits and the receiving side separates each tone individually. Each demodulator has a function of measuring / determining the received tone signal level, and determines the required pattern for demodulation.

An FDM-FSK / PSK modulated wave demodulator according to the present invention is a frequency demodulator (FSK) / phase shift keying (PSK) system (FDM-FSK / PSK) modulator / demodulator using multi-frequency multitone. In wireless line communication using, the transmitting side modulates all or part of individual multitones with the required pattern prior to data transmission, and when transmitting, the received tones for each individual demodulator for each tone The receiving side is provided with a signal level measuring / determining means that has a signal level measuring / determining function and determines the required pattern to be used for demodulation.

[0012]

In the present invention, the transmitting side modulates each tone for data transmission with a predetermined pattern and transmits it, prior to data transmission, irrespective of the synchronizing signal and time synchronization. On the receiving side, the signal level measurement / judgment means measures the level of the received tone signal, judges the presence / absence of tones, detects the signal on the transmitting side by the majority judgment function for the total number of tones, and demodulates in accordance with this detection. Capture data.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of an FDM-FSK / PSK modulated wave demodulator according to the present invention. In FIG. 1, 11-18 are 350 Hz-
Bandpass filter centered at 2550 Hz, 21, 2
3 ,. ． ． 27 are bandpass filters 11 and 12, 1 respectively
3 and 14 ,. ． ． , 17 and 18 for comparing the levels of the received signals, level comparators 22, 24 ,. ． ． , 28 are bandpass filters 11 and 12, 13 and 1 respectively.
4,. ． ． , 17 and 18 for measuring the levels of the received signals. Further, 29 is a level measuring device 22, 23 ,. ． ． , 28, and a signal presence / absence determining circuit for measuring the presence / absence of a tone. In the signal presence / absence determination circuit 29, for example, all bandpass filters 11 to 18 are used.
The total number of output levels of each tone is calculated, and when the number of reception levels of each tone is within 1/8 + -α of the total, it is determined that there is transmission from the transmitting side, or Various determination methods are used, such as a method based on a majority decision as to whether or not 5 or more tones have a level higher than a specified level. Next, the demodulation device according to the present invention is applied to FDM-PSK using multitone.
A second embodiment applied to a demodulation device for modulated signals will be described.

FIG. 2 shows an FDM-FSK / P according to the present invention.
FD that uses multi-tone for demodulator of SK modulated wave
It is a block diagram which shows the structure of the 2nd Example applied to the demodulation apparatus of the M-PSK modulation signal. In the figure, 31, 3
2 ,. ． ． , 38 are band filters for channel 0 (CH0), band filters for channel 1 (CH1) ,. ． ． , A bandpass filter for channel 7 (CH7),
39, 41 ,. ． ． , 53 are PSK demodulators, 40, 4
2 ,. ． ． , 54 is a level measuring device, 55 is a signal presence / absence determining device for determining the presence / absence of a signal, and 56 is a synchronizing signal detector for detecting a synchronizing signal.

A part of the received signal from the receiver is the band-pass filters 31, 32 ,. ． ． , 38, and the other part is input to the synchronization signal detector 56. Bandpass filter 3
1 ,. ． ． , 38, the received signals of the respective bands extracted by the PSK demodulators 39, 41 ,. ． ． , 53 and level measuring devices 40, 42 ,. ． ． , 54 respectively. The PSK demodulated received signals are b0, b
1 ,. ． ． , B7, and the level measuring device 4
0 ,. ． ． , 54, a level determination is performed and the signal is input to the signal presence / absence determining unit 55. On the other hand, in the sync signal detection circuit 56, the sync signal added prior to the information (data) is detected on the transmission side. The detected synchronizing signal is sent to the signal presence / absence determining circuit 55. As a result, the possibility of fetching erroneous data caused by erroneous determination by the synchronization signal portion is greatly reduced, and the reliability of the transmission system is improved.

Next, a third embodiment in which the demodulation device according to the present invention is applied to a demodulation device for demodulating data by FFT (Fast Fourier Transform) by digital signal processing will be described. FIG. 3 shows an FDM-FSK according to the present invention.
It is a block diagram which shows the structure of the 3rd Example which applied the demodulation apparatus of the / PSK modulation wave to the demodulation apparatus which demodulates data by FFT (Fast Fourier Transform) by digital signal processing. In the figure, 61 is an A / D converter for converting an analog signal into a digital signal, 62 is a fast Fourier transformer (FFT), and 63 is a data demodulation & signal presence / absence judging device having the features of the present invention.

The received signal from the receiver is an A / D converter 61.
Is converted into a digital signal by the fast Fourier transformer 62
Fourier transform is performed by the data demodulator & signal presence / absence determiner 63
Is input to In the data demodulation & signal presence / absence determiner 63,
In case of FDM-FSK modulated wave, each tone (each channel)
The level of the mark frequency and that of the space frequency are compared. With such a configuration, the presence or absence of transmission on the transmitting side can be determined on the receiving side without additional circuits such as a synchronization signal and time control by simply performing level distribution / level comparison for each channel.

[0018]

As described in detail above, according to the present invention,
Prior to data transmission on the transmission side, all or part of the individual multitone is modulated and transmitted in the required pattern, and each individual demodulator for each tone has a measurement / judgment function for the received tone signal level. By determining the required pattern and using it for demodulation, the transmitting side can determine the presence or absence of transmission on the transmitting side without adding a synchronization signal on the transmitting side, which has the effect of shortening the communication time. .

Further, as shown in the second embodiment, by using the present invention in combination with the conventional transmission system in which a synchronization signal is added, transmission due to noise or interference on the receiving side is caused. Even if the data is not transmitted on the side, there is an effect that the risk of accidentally capturing it as received data can be significantly reduced.

Further, even in the transmission system in which the transmission time is determined between the transmission and the reception, the data can be taken in correctly by using the present invention, an accurate time device becomes unnecessary, and the cost can be reduced. There is an effect that can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an FDM-FSK / PSK modulated wave demodulator according to the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment in which an FDM-FSK / PSK modulated wave demodulation device according to the present invention is applied to an FDM-PSK modulated signal demodulation device using multitone.

FIG. 3 is a block diagram showing a configuration of a third embodiment in which an FDM-FSK / PSK modulated wave demodulating device according to the present invention is applied to a demodulating device for demodulating data by FFT (fast Fourier transform) by digital signal processing. It is a figure.

FIG. 4 is a block diagram showing a configuration of a conventional FDM system.

5 is an explanatory diagram showing frequency allocation of transmission tones and data examples in the conventional example of FIG.

FIG. 6 is a block diagram showing a configuration of a conventional FDM system.

FIG. 7 is a block diagram showing an example of a circuit that determines demodulated data on the receiving side in FIG.

FIG. 8 is an explanatory diagram showing a conventional method in which a synchronization signal is added to a transmission sequence.

[Explanation of symbols]

11-18 band-pass filters, 21, 23 ,. ． ． , 27
Level comparators 22, 22 ,. ． ． , 28 level measuring device, 29 signal presence / absence determining circuit, 31 ,. ． ． , 38
The bandpass filters 39, 41 ,. ． ． , 53 PSK demodulators, 40, 42 ,. ． ． , 54 level measuring instrument, 55
Signal presence / absence determiner, 56 sync signal detector, 61 A / D
Converter, 62 FFT, 63 data demodulation & signal presence / absence determiner, 101 FDM-FSK modulator, 102 transmitter, 103 antenna, 104 antenna, 105 receiver, 106 FDM-FSK demodulator, 107, 108
Band-pass filter, 109 level comparator

Claims (2)

[Claims] 1. In a communication of a wireless line using a modulator / demodulator of a frequency shift keying (FSK) / phase shift keying (PSK) method (FDM-FSK / PSK) using multi-frequency multi-tone, data is transmitted at a transmission side. Prior to transmission, all or part of the individual multitone is modulated with the required pattern and transmitted, and the receiving side has a function to measure / determine the received tone signal level for each individual demodulator for each tone. A demodulation method of an FDM-FSK / PSK modulated wave, characterized by determining the required pattern and using it for demodulation. 2. A frequency shift keying (FSK) / phase keying (PSK) system (FDM) using multi-frequency multi-tone.
In a wireless communication using a FSK / PSK modulator / demodulator, the transmitting side modulates all or part of individual multitones with a required pattern prior to data transmission,
When transmitted, the receiving side is provided with a signal level measuring / judging means for measuring / judging the received tone signal level for each individual demodulator for each tone and judging the required pattern for demodulation. FDM-FSK / characterized by
Demodulator for PSK modulated wave.