JPH02246541A - Manchester m sequence code modulating device - Google Patents

Abstract

PURPOSE:To obtain the modulating device of simple constitution which suits to a CSK communication system by determining one circuit corresponding to sent data between two Manchester M sequence generators at each constant period and sending a CKSmodulated sent signal from an exclusive OR circuit. CONSTITUTION:Two feedback circuits 31a and 31b which are connected to shift registers FF1-FF3 used as two Manchester M sequence generators 31 and 32 and correspond to the Manchester M sequence generators are switched selectively by a switching circuit 33 according to sent data to provide feedback to the inputs of the shift registers FF1-FF3, thereby determining one circuit corresponding to the sent data between the two Manchester M sequence generators 31 and 32. Then the exclusive OR circuit 39 sends out a CSK- modulated sent signal TXO to a transmission line or transmission medium. Consequently, the modulating device of simple constitution for the CSK communication system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a modulation device for spread spectrum (SS) communications, particularly for code e-shift keying (Code e-shift keying).
The present invention relates to a modulation device using a 5hlft Keying-CSK) modulation method.

The conventional SS communication method has been widely applied to power line communication as well as satellite communication and mobile communication. The conventional SS communication system will be explained with reference to FIGS. 4 and 5. On the transmitting side, the output a of the PN (pseudo-noise) code sequence generator 1
After performing an EX-OR operation on the transmission data b and the EX-OR circuit 2 (signal c), the amplifier 3 sends the signal to the transmission line as a transmission signal. On the receiving side, the received signal is amplified by an amplifier 4, then correlated with the output d of the synchronous PN code sequence generator 5 by a correlator 6, and the correlation value (signal e) is compared with a predetermined threshold value by a comparator 7. Demodulate the received data f.

The transmission path may be wireless, wired, or other transmission media. Therefore, the transmission signal is not only sent directly to the transmission medium, but also often converted into a signal suitable for transmission through the transmission medium and sent. Also, power line communication requires an interface that separates it from commercial power. The connection portion with the transmission medium that performs such signal conversion and separation is hereinafter referred to as a reception interface and a transmission interface.

Problems to be Solved by the Invention In conventional communication systems, it is necessary to synchronize the PN sequence generated by the synchronous PN code sequence generator 5 on the receiving side with the PN sequence on the transmitting side. There is a need to. If there is no problem with the transmission characteristics of the transmission path, a peak is detected in the correlation waveform at the synchronization point. However, in power line communications, where the transmission characteristics are extremely poor and there are dip points within the transmission band, the correlation waveform deteriorates and the relationship between positive and negative correlation values becomes reversed.

This may result in a data error of 1 or 0. Another drawback was that synchronization could not be maintained due to waveform deterioration.

The present invention provides a modulation device for a novel CSK communication system that overcomes the drawbacks of the conventional SS communication system described above.

Means for solving the problem, a Manchester M-sequence code modulation device according to the present invention, has the following features:
first and second Manchester M-sequence generators each generating two Manchester M-sequences of the same code length with low cross-correlation at a constant cycle, and at each constant cycle,
The first or second
A switching circuit is provided for selecting the output signal of either one of the Manchester M-sequence generators.

The first and second Manchester M-series generators each include a clock generation circuit that generates a commonly used clock signal, a commonly used multi-stage shift register, and an output from a predetermined stage of the shift register as input. a first feedback circuit for the first Manchester M-sequence generator, which feeds back to its input the output of a stage different from the first feedback circuit of the shift register; It is composed of a second feedback circuit for the sequence generator and an exclusive OR circuit which is used in common and which receives the output of the final stage of the shift register and the clock signal as input, and which is connected to the first and second feedback circuits. The output of the feedback circuit No. 2 is given as an input to the switching circuit, and the output of the switching circuit is fed back to the input of the shift register,
The output signal of the exclusive OR circuit is sent out as a transmission signal.

Preferably, the device further includes a circuit that detects a specific phase of the shift register, and a timing circuit that takes in transmission data in response to a detection signal from the detection circuit and controls switching of the switching circuit.

CS K (Code 5hift Keyling)
means that two binary PN code sequences (including M sequence and Manchester M sequence) of the same code length with low cross-correlation are made to correspond to transmission data 1 and O, respectively, and one of them is assigned depending on the transmission data. A modulation method for transmitting a PN code sequence. This concept of CSK will become clearer from the entire specification.

The M sequence refers to a code sequence with the largest period among various code sequences that can be generated using a multi-stage shift register and a linear arithmetic circuit. When an n-stage shift register is used, the length of the M sequence generated is given by 2n-1 bits.

The Manchester code is a code format in which one cycle of a rectangular wave having a specific phase is assigned to a 1 of an input binary signal, and one cycle of an opposite phase is assigned to a 0 of the input binary signal.

Function: The two feedback circuits connected to the shift register that is shared by the two Manchester M-sequence generators and corresponding to each Manchester M-series generator are selectively switched by the switching circuit in accordance with the transmitted data, and the shift register is connected to the shift register. As a result, one circuit of the two Manchester M-sequence generators corresponding to the transmission data is established at each predetermined period. As a result, from the exclusive OR circuit connected to the output of the shift register,
A CSK-modulated transmission signal is sent out to a transmission path or transmission medium.

Embodiment FIG. 1 shows the overall configuration of a C5K communication system using the Manchester code M sequence.

On the transmitting side, a modulating device (transmitting device) 11 uses a Manchester code M having a low cross-correlation and the same code length.
Two Manchester M's each generated by synchronizing the series.
Sequence generators 31 and 32 are provided, and their code outputs are provided to a switching circuit 33. This switching circuit 33 is controlled according to the binary transmission data (1 or O). For example, when the transmission data is 0, the code output of the generator 31 is 1.
When , the code output of the generator 32 is selected. The code output signal selected by this switching circuit 33 becomes the transmission signal TXO. Switching control in the switching circuit 33 is performed in synchronization with the cycle of the Manchester code M series that is generated, and one piece of binary data (1 or 0) is expressed by one cycle of the Manchester code M series.

Since the switching or selection of two different Manchester code M sequences is performed according to the code (1 or 0) of the data to be transmitted, this modulation method is called code-subordinate shift keying (CSK).

The transmission signal TXO is sent out to the transmission line or transmission medium via the transmission interface 12A. As described in the "Prior Art" section, the transmission interface 12A is a connection section in a broad sense, and is a section that performs carrier modulation, mixing processing into a power line, and the like.

The receiving interface 12B also demodulates the carrier.

It performs separation from the power line, A/D conversion, etc., and converts the signal input from the transmission line or transmission medium into a digital reception signal RXr and outputs the signal.

The receiving device on the receiving side includes two correlators 21, 22° demodulator f 23. Carrier detection circuit 24. Synchronous control circuit 2
5th grade is included. The digital reception signal RXI output from the reception interface 12B is branched into two and input into correlators 21 and 22, respectively. One correlator 21
A Manchester code M sequence generated from one Manchester M sequence generator 31 is set in , and the correlation between this set sequence and the received signal RXI is taken. Similarly, the other Manchester M-sequence generator 3 is connected to the other correlator 22.
2 is set, and the correlation between this set sequence and the received signal RXI is taken. The correlation outputs obtained from these correlators 21 and 22 are given to a demodulator 23, in which a demodulated signal 1 or 0 is assigned according to the correlation value and output as received data RXD. That is, if the correlator 21 shows a larger correlation peak value among the correlation outputs of the correlators 21 and 22, the received data is 0, and conversely, if the correlator 22 shows a larger correlation peak value. If there are, l received data are generated respectively.

The correlation output is also input to carrier detection circuit 24 and synchronization control circuit 25. The carrier detection circuit 24 detects the presence or absence of a carrier based on the correlation output, and provides the detection signal to the synchronization control circuit 25. The presence or absence of a carrier is determined by the received signal RX.
This is used to determine whether or not I is being received. The synchronous control circuit 25 is.

When a carrier is being detected, a timing signal for demodulation and carrier detection is created based on the correlation output and is provided to the demodulator 23 and the carrier detection circuit 24.

As described above, in the C5K communication system, two correlation outputs are compared on the receiving side, and depending on the magnitude, 0 of the received data is
Since the Manchester M sequence on the receiving side does not need to be strictly synchronized with that on the transmitting side, data demodulation errors do not occur. Furthermore, if the absolute value is taken as the output of the correlator, no error will occur even in the case of a transmission line with degraded characteristics such that the transmission peak value becomes negative. Furthermore, by using the Manchester code M sequence, it is possible to reduce the low-frequency components of the received signal and suppress the coupling loss with the transmission path.

FIG. 2 shows a specific configuration example of the C8K modulation device 11. Further, output signal waveforms of each part of this circuit are shown in FIG.

The Manchester M-sequence generator includes a multi-stage shift register, a feedback circuit provided in the shift register, and an EX-OR circuit for generating a Manchester code that takes the exclusive OR of the output of the shift register and a clock signal. It can be composed of C3K modulation device 11 shown in FIG.
In this case, one Manchester M-sequence generator 31 has shift registers FF1-FF3 . EX-OR as a feedback circuit
Circuit 31a and EX- for Manchester code generation
The other Manchester M-sequence generator 32 is comprised of shift registers FF1 to FF, an EX-OR circuit 31b as a feedback circuit, and an EX-OR circuit 39 for Manchester code generation. That is, the shift register FF-FF3 (in this embodiment, 3 stages; n-3) is also used as the two Manchester M-sequence generators 31 and 32, and similarly, the EX-OR circuit 39 for Manchester code generation. is also used.

Shift register FF ~ FF3 and EX-OR circuit 31
a first M-sequence generator (PN code generator, PN
It may be considered that the shift registers FF-FF3 and the EX-OR circuit atb constitute a second M-sequence generator. Then, the Manchester M-sequence generator 31 is generated by the first M-sequence generator and the EX-OR circuit 39, and the Manchester M-sequence generator 31 is generated by the first M-sequence generator and the EX-OR circuit 39.
The Manchester M-sequence generator 32 is configured as follows.

The EX-OR circuit 31a serving as a feedback circuit feeds back the codes of the second and third stage cells of the shift registers FF-FF3 to its input.

The EX-OR circuit 31b feeds back the codes of the first and second stage cells. In this way, two Manchester M
The feedback circuits of series generators 531 and 32 are different from each other. A switching circuit 33 is provided in this feedback loop. That is, the outputs D and D2 of the EX-OR circuits 31m and 31b are input to the switching circuit 33, and the output of the switching circuit 33 is given to the inputs of the shift registers FF and FF3.

The switching circuit 33 is controlled by the Q output (SW multiplication signal) of the D flip-flop 30 for each period T (data period) of the Manchester code M series in accordance with the transmission data TXD. The clock signal CK given to the shift registers FF-FF3 controls the shift operation timing thereof, and
It is input to the D flip-flop 30. On the other hand, when the sign of all stages of shift register FF-FF3 is 1, (this state occurs once in the period T mentioned above) NAND
The output of the circuit 3B becomes L level, which is applied to the D flip-flop 30 as an enable signal EN. Therefore, when the enable signal EN is at the L level, the D flip-flop takes in the manually input transmission data TXD at the falling timing of the clock signal CK, and provides it to the switching circuit 33 as the switching control SW. Manchester M sequence generator 31 or 32 depending on switching of switching circuit 33
Since either the feedback circuit (first or second M-sequence generator) is established, the output of the M-sequence generator established by the feedback circuit (the output of the final stage cell of shift registers FF1 to F Fa) will be input to the EX-OR circuit 39. The EX-OR circuit 39 is also supplied with a clock signal CK, and the output of the 1M sequence generator is Manchester encoded and output as a transmission signal TXO.

If necessary, the output of the NAND circuit 36 can be applied as a transmission request signal to the transmission data processing section (for example, a microprocessor), and in response, the transmission data processing section can generate the next 1 bit worth of transmission data TXD. good. Furthermore, a one-clock latch circuit may be provided on the output side of the EX-OR circuit 39 to shape the waveform of the transmission signal TXO.

Effects of the Invention The Manchester M-sequence code modulation device according to the present invention is applied to a CSK communication system using Manchester codes. In the C3K communication system.

Since the two correlation outputs are compared on the receiving side and 0 or 1 is assigned to the received data depending on the magnitude, the Manchester M sequence on the receiving side does not need to be strictly synchronized with that on the transmitting side.

Data demodulation errors also no longer occur. Furthermore, if the absolute value is taken as the output of the correlator, no error will occur even in the case of a transmission line with degraded characteristics such that the transmission peak value becomes negative. Furthermore, by using the Manchester code M sequence,
This has the effect of reducing the low-frequency components of the received signal and suppressing the coupling loss with the transmission path.

The present invention also provides the above-mentioned method in which two feedback circuits connected to a shift register that is shared by two Manchester M-sequence generators and corresponding to each Manchester M-series generator are selectively switched by a switching circuit in accordance with transmitted data. By being fed back to the input of the shift register, one circuit of the two Manchester M-sequence generators corresponding to the transmission data is established at each constant cycle. As a result, the CSK-modulated transmission signal is sent out to the transmission path or transmission medium from the exclusive OR circuit connected to the output of the shift register, so it is a relatively simple configuration and can be applied to the C3K modulation method. A suitable modulation device is realized. In particular, in this invention, the clock generation circuit, shift register, and exclusive OR circuit are commonly used in the two Manchester M-sequence generators, so that the circuit configuration can be simplified.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of a CSK communication system. FIG. 2 is a circuit diagram showing an embodiment of the modulation device according to the present invention, and FIG. 3 is a time chart showing its operation. 4 and 5 show a conventional SS communication system, FIG. 4 is a circuit diagram showing the configuration, and FIG. 5 is a time chart showing its operation. 34...Clock generator. 36...NAND circuit. 39...EX-OR circuit. FF-FF3...Shift register. that's all

Claims (2)

[Claims] (1) First and second Manchester M-sequence generators each generate two Manchester M-sequences of the same code length with low cross-correlation at a constant cycle, and each of the above-mentioned constant cycles generates 1 or 0 of the transmission data. a switching circuit that selects the output signal of either the first or second Manchester M-sequence generator according to the clock signal that is commonly used by the first and second Manchester M-sequence generators; a clock generation circuit that generates a clock, a commonly used multi-stage shift register, and a first feedback circuit for the first Manchester M-series generator that feeds back the output of a predetermined stage of the shift register to its input. and the second Manchester M that feeds back the output of a stage different from the first feedback circuit of the shift register to its input.
It consists of a second feedback circuit for the sequence generator, and an exclusive OR circuit that is used in common and receives the output of the final stage of the shift register and the clock signal as input, and The output of the feedback circuit No. 2 is given as an input to the switching circuit, the output of the switching circuit is fed back to the input of the shift register, and the output signal of the exclusive OR circuit is sent out as a transmission signal. A Manchester M-sequence code modulation device. (2) A circuit that detects a specific phase of the shift register; and a timing circuit that takes in transmission data in response to a detection signal of the detection circuit and controls switching of the switching circuit. 1) The Manchester M-sequence code modulation device according to item 1).