JPH0337334B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to correlation between a received signal and an M-sequence code generated on the receiving side, which is performed to demodulate a received signal that is transmitted after being spread spectrum modulated, and particularly relates to a method for obtaining the correlation. M contained in the received signal for
The present invention relates to a correlator synchronization control method and apparatus for performing synchronization control between a sequence code and an M-sequence code for reception without being affected by noise contained in a received signal. [Prior Art] Recently, research has been underway to actively utilize spread spectrum communication systems in various fields, and an explanation of its principles and application fields can be found in 956 of the September 1983 issue of the Journal of the Institute of Electronics and Communication Engineers. Page and page 1053 of the October issue. This spread spectrum communication system is characterized by wideband spectrum and correlation demodulation, and when used for data transmission using power lines as transmission lines, it is less susceptible to noise and transmission characteristics.
High-speed data transmission can be performed with high reliability. In other words, this spread spectrum power line carrier communication system modulates transmission data having a narrow band spectrum distribution with an M-sequence code, thereby spreading the spectrum evenly over a wide band and transmitting the data. Then, on the receiving side, an M-sequence code for reception having the same code pattern as the M-sequence code used for spread spectrum modulation on the transmitting side is generated, and this M-sequence code for reception is generated.
Received data is extracted by finding the correlation between the sequence code and the received signal. Here, when calculating the correlation between the received signal and the receiving M-sequence code, the M-sequence code included in the received signal and the receiving M-sequence code are
It is necessary to completely synchronize the sequence code. For this reason, on the receiving side, the correlation output level that changes depending on the correlation state output from the correlator is
Synchronization control is performed by controlling the generation phase of the receiving M-sequence code using the output of this correlator so that it is always equal to or higher than a predetermined set value. Therefore, in the spread spectrum power line carrier communication system configured in this way, even if a zero point occurs in part of the transmission characteristics due to the load condition of the power line, it will be less affected, and the received signal will not be affected by noise. Even if it is mixed in, the receiving side extracts the received data by finding the correlation between the received signal and the M-sequence code for reception, so the S/N ratio becomes extremely large. [Problems to be Solved by the Invention] However, in the above-mentioned spread spectrum power line carrier communication system, the output of the correlator is used to generate the M-sequence code for reception so that the output level of the correlator is equal to or higher than the set value. Since the M-sequence code for reception generated on the receiving side is controlled to be synchronized with the M-sequence code included in the received signal by controlling the generation phase of If the output level of the receiver fluctuates, the synchronization control will be disrupted, making it impossible to synchronize the M-sequence code for reception with the M-sequence code included in the received signal, resulting in the problem that demodulation of the received data cannot be performed. ing. [Means for Solving the Problems] Therefore, the correlator synchronization control method and device according to the present invention generates three types of first to third M-sequence codes whose phases are sequentially shifted from each other from an M-sequence code generator for reception. The first to third correlation outputs are extracted by generating the signals and determining the correlation with the received signal, and when the second correlation output from which the received data is extracted is below the synchronization determination level, the M-sequence code generator is clocked. By controlling the supplied clock generating section to the search mode, the phase of the M-sequence code generated from the M-sequence generating section is continuously moved in a predetermined direction (advanced direction or delayed direction), and the second When the correlation output exceeds the synchronization determination level, it is determined that synchronization has been acquired and the mode shifts to synchronization fine adjustment mode. The clock generator is controlled so that the phase of the received M-sequence code to be generated is advanced or delayed by generating an advanced or delayed phase state, and when the second correlation output is equal to or higher than the synchronization determination level and If both the first and third correlation outputs are determined to be lower than the first correlation output, it is determined that a synchronized state is established and the phase of the clock generated from the clock generation section is controlled to be fixed. . [Operation] Therefore, in such correlator synchronous control,
Since the synchronization state is determined based on the magnitude relationship between the three types of correlation outputs obtained by calculating the correlation between the three types of receiving M-sequence codes and the received signal, which are out of phase with each other, the noise contained in the received signal is determined. Since each correlation output is also affected by noise under the same conditions, the effects of noise cancel each other out during comparison, and the effects of noise no longer appear in the comparison results. As a result, the synchronization control performed using the above comparison results becomes stable, and reliable demodulation operation is always obtained. It is valid. [Embodiment] FIG. 1 is a circuit diagram for explaining an embodiment of a correlator synchronization control method and apparatus according to the present invention. In the figure, reference numeral 1 indicates a clock generating section 4, which will be described later.
Depending on the clock pulse CP supplied from M
Three types of receiving M-sequence codes whose phases are shifted within 1 bit of sequence code M ₀ and M-sequence code M ₀
This is an M-sequence code generation unit that generates M ₁ , M ₂ , and M ₃ . The M-sequence code generator 1 includes a frequency divider 1a which divides the clock pulse CP by eight and outputs it as a clock pulse _CP8 , and an M-sequence code generator which generates a sequence code _M0 in response to the supply of the clock pulse _CP8 . Code generator 1b and clock pulse
By sequentially shifting the M-sequence code M0 generated from _the M-sequence code generator 1b in accordance with the supply of CP, the M-sequence code _M0 for reception is shifted in phase within 1 bit of the M-sequence code M0. ₁ , _M2 , _M3
and a shift register 1c that outputs. 2 is a correlation unit in which the received data is M
Received data A that is spread spectrum modulated and sent using a sequence code and each of the M sequence codes for reception.
It is constituted by first to third correlators 2a to _2c which output correlation output signals _B1 , _B2 , _B3, respectively, by determining the correlation with M1 _, M2, M3 _, respectively. The correlation output signal _B2 output from the second correlator 2b is supplied as received data to a data processing section (not shown). 3 determines the synchronization state between the M-sequence code included in the received signal _A and each of the receiving M-sequence codes M ₁ to M ₃ by determining the correlation output signals B 1 and B ₃ . This is a synchronization control unit that executes control for synchronizing the M-sequence code M ₂ with the M-sequence code included in the received signal A. The synchronization control unit 3 includes a comparator 3b that compares the correlation output signal _B2 , which changes depending on the correlation state, with a synchronization determination level V _R set by a variable resistor 3a, and a comparator 3c that generates _an "H" output only when the level of B1 is higher than the correlation output signal _B2 ;
A comparator 3d that generates an "H" output only when the correlation output signal _B2 is higher in level than the correlation output signal _B3 , and output signals C, D, and E of the comparators 3b, 3c, and 3d are input. , and a logic operation unit 3e for determining synchronization deviation, complete synchronization, synchronization delay, and synchronization advance. The logic operation unit 3e receives the output signals C, D, and E of each of the comparators 3b, 3c, and 3d, and uses the logic operation unit 3e to determine synchronization deviation, complete synchronization, synchronization delay, and synchronization advance. It is structured as follows. and,
The theoretical calculation section 3e inputs the output signals C, D, and E of each of the comparators 3b to 3d, and performs an AND operation that sets the output signal F to "H" only in a completely synchronized state.
NOA which inputs the gate 3f and the output signals C and D of the comparators 3b and 3c and outputs the output signal G.
It is composed of game and 3g. Here, the output signals C, D, E of each comparator 3b to 3d in the synchronization control section 3 and the output signals F, G of the logic operation section 3e
Table 1 summarizes the relationship between

〔Effect of the invention〕

As explained above, the correlator synchronization control method and apparatus according to the present invention calculates the correlation between at least three types of receiving M-sequence codes whose phases are shifted from each other and the received signal, and compares the respective correlation outputs. Therefore, even if the correlation output fluctuates due to noise contained in the received signal, the influence of noise will cancel each other out when determining the synchronization state by mutual comparison of each correlation output. Therefore, the determination of the synchronization state and the accompanying synchronization control become extremely resistant to noise, which has an excellent effect of allowing stable synchronization control to be performed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the correlator synchronization control method and apparatus according to the present invention;
Figure 2 is a circuit diagram showing a specific example of the phase control circuit shown in Figure 1, Figures 3 a to n, Figures 4 and 5.
FIGS. a to n, FIGS. 6 a to c, FIGS. 7 a to n, and FIGS. 8 a to n are waveform diagrams for explaining the operation of the circuit shown in FIGS. 1 and 2. 1...M-sequence code generator, 1a...Frequency divider, 1
b...M sequence code generation circuit, 1c...shift register, 2...correlation unit, 2a to 2c...first to third
Correlator, 3...Synchronization control section, 3b to 3d...Comparator, 3e...Logic operation section, 4...Clock generation section, 4a...Clock generator, 4b...Phase control circuit.

Claims (1)

[Claims] 1. At least three types of receiving M-sequence codes whose phases are shifted from each other are generated and their correlations with the received signals are obtained in respective correlators, thereby extracting a correlation output signal, and When the correlation output signal used for extraction is below a predetermined synchronization determination level, a synchronization search is performed by shifting the generation phase of each receiving M-sequence code, and the signal is used for extraction of the received data. If the correlation output signal becomes equal to or higher than the synchronization determination level, the receiving M-sequence code is in an advanced phase and a delayed phase with respect to this correlation output signal and the reception M-sequence code used to obtain this correlation output signal. A level comparison is performed with the correlation output signal extracted using the M-sequence code, and based on the comparison results, the receiving M used for demodulating the received data is determined.
By determining the phase relationship between the sequence code and the M-sequence code included in the received signal, and controlling the generation phase of each received M-sequence code generated according to the determination result, the system is used for demodulating the received signal. A correlator synchronization control method characterized in that the received M-sequence code is synchronized with the M-sequence code included in the received signal. 2. A clock generating section in which the phase of the clock pulses generated varies in accordance with an external command; and at least a clock generating section in which the phases of the clock pulses generated by the clock generating section vary depending on the clock pulses generated from the clock generating section.
an M-sequence code generation unit that generates a third receiving M-sequence code; and first to third correlators that respectively calculate correlations between the first to third receiving M-sequence codes and the M-sequence code included in the received signal. When the correlation output signal of the second correlator that demodulates the received signal and extracts the received data is below a predetermined synchronization determination level, the phase of the clock pulse generated from the clock generator is shifted as an out-of-synchronization state. When the correlation output signal of the second correlator is equal to or higher than the synchronization determination level, the second correlator
The second receiving M-sequence code and the M included in the received signal are determined according to the magnitude relationship of the correlation output signals of the first and third correlators with respect to the correlation output signals of the correlators.
The phase of the clock pulse generated from the clock generator is controlled in a direction in which synchronization is obtained by determining the phase lead and lag relationship with the sequence code, and the correlation output signals of the first and third correlators are both The clock is generated from the clock generator by detecting that the correlation output signal of the second correlator is lower than that of the second correlator and determining synchronization between the second receiving M-sequence code and the M-sequence code included in the received signal. 1. A correlator synchronization control device comprising: a synchronization control section that executes control to fix the generation phase of a clock pulse to a predetermined state.