JP2805542B2 - Spread spectrum signal demodulation method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spread spectrum signal demodulation method in a CSK (Code Shift Keying) method and an improvement of an apparatus therefor.

(Prior art) Conventionally, in a local area network system, a home control system, and the like, in which a transmission line is laid in a building to transmit an information signal or a control signal, the cost of laying the transmission line is reduced. In order to do so, it has been considered to use a power line or the like already laid in a building as a transmission line.

Conventionally, impedance characteristics and the like have not been taken into account as such originally communication lines, and as a modulation and demodulation method suitable for use on various noisy electrical circuits, NEC Technical Report vol.42
No. 9/1989: A spread-spectrum signal modulation / demodulation system called CSK system as described in "High-performance SS power line modem" has been developed.

In this modulation and demodulation method, as shown in FIG. 4, the modulation side T prepares PN sequences PN ₀ and PN ₁ having the same period length and a small correlation value, respectively, and the state value of the information data to be transmitted is “0”. In this case, the PN sequence PN ₀ is transmitted to the power line 1, and when the state value of the information data to be transmitted is “1”, the PN sequence PN ₁ is transmitted to the power line 1.

Meanwhile, the In correlator H ₀ the demodulation side R PN sequence PN ₀
And a correlation value with the received signal is calculated, and a voltage corresponding to the calculated value is output. This voltage is a predetermined reference voltage V _a [v]
A comparator M ₀ to the reset state "0" to the RS flip-flop 2 when exceeded. Further, the In Similarly correlator H ₁
A PN sequence PN _1, the correlation value between the received signal, the RS flip-flop by this comparator M ₁ when exceeding the predetermined reference voltage V _a is the set state "1" to RS flip-flop 2 2 obtains original information data from the output terminal of the second information terminal.

That is, information data having _a bit length T _a [s] from the modulation side T,
For example, when "110 ..." is transmitted, the correlator H on the demodulation side R
₀ The third cycle, as shown in Figure 5 outputs the correlation peak waveform at the first and second periods, respectively (a), the addition correlator H ₁ is FIG. 5 (b) since outputs the correlation peak waveform at the correlator by H ₀ and H _1, respectively either side of the output voltage level is detected whether exceeds the reference voltage V _a, demodulates the original information data "110 ..." Is what you do.

Therefore, according to this modulation / demodulation method, even if the output waveform of each of the correlators H ₀ and H ₁ is distorted based on the transmission characteristics of the power line or the like, the correlation peak is detected from the output waveform of each correlator. If this is possible, the demodulation side R can obtain the original information data, so that a power line or the like that is not originally intended for communication can be used as a transmission line.

However, in this modulation and demodulation method, large delay deviation and amplitude deviation occur in the transmission characteristics of the transmission line, and the correlators H ₀ and H ₁
If each output waveform is distorted as shown in FIGS. 6 (a) and 6 (b) and the existence of the correlation peak is not clear, the correlation peak cannot be detected from the output waveform of each correlator. There was a problem that the original information data could not be obtained.

(Object of the Invention) The present invention has been made to solve the above-mentioned problem of the spread spectrum signal modulation and demodulation method, in which a large delay deviation and amplitude deviation occur in the transmission characteristics of a transmission line, and the output waveform of a correlator is reduced. It is an object of the present invention to provide a spread spectrum signal demodulation method capable of obtaining original information data on a demodulation side even if the existence of a correlation peak is not clear, and an apparatus therefor.

(Summary of the Invention) In order to achieve the above object, the present invention is configured as follows.

For example, when the status value of the information data to be transmitted is "0", the first PN sequence is used. When the status value of the information data is "1", the second PN sequence having the same cycle length as the first PN sequence is used. Means for demodulating a spread spectrum signal modulated so as to output a PN sequence of: a correlation means for obtaining a correlation value between the spread spectrum signal and each of the two PN sequences; and a correlation value for each correlation means. Means for generating an absolute value signal, means for generating a signal obtained by adding all of the absolute value signals generated for each correlation means, means for extracting the signal speed period signal of the information data from the added signal, Means for outputting a level difference of the absolute value signal generated for each correlation means at a timing based on the periodic signal. Alternatively, demodulation is performed by such a method.

(Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of a modulation / demodulation device according to the spread spectrum signal demodulation method of the present invention.

Here, in order to facilitate understanding of the operation, description will be given including the modulation side.

In the figure, T is a modulator, which comprises two PN sequences PN ₀ and PN ₁ having a small correlation value and a period length of 31 bits, corresponding to the bit values of the information data SD to be transmitted. PN
It is intended to spread spectrum modulation by outputting one of the sequences PN ₀ or PN _1. If the modulator T information data SD bit rate to be transmitted is 600b / s, with inputting the imagewise signal to the control terminal of the switch S ₁ via the synchronization circuit 3 the information data SD, clocks 18.6 [kHz] The clock signal output terminal of 600 [Hz] of the timing generator 4 for generating a signal and a clock signal of 600 [Hz] is connected to the input terminal of the synchronization circuit 3. Further, the timing generator 4 for connecting its output and inputs a transmission request signal RS to the control terminal of the switch S _2. G ₀ and G ₁ is a PN sequence generator for each generating the PN sequence PN ₀ and PN _1, both
Connect the input terminals of the PN sequence generator to one of the timing generators 4
Connect to 8.6 [kHz] clock signal output terminal and PN
The output terminal of the sequence generator G ₀ is connected to the terminal a of the switch S _1, which connects the output terminals of the PN sequence generator G ₁ to the terminal b of the switch S _1. Furthermore, by connecting the terminal c of the switch S ₁ to one terminal of the power line 1 to terminal e of the switch S ₂ as a transmission line through a band pass filter 5 with connected to the terminal d of the switch S _2, the It is configured to supply a spread spectrum signal from a terminal e.

On the other hand, R is a demodulation device according to the present invention, which converts a signal received via the power line 1 into an amplifier 6 and a pass band of 0.
The correlator H ₀ passes through a band pass filter 7 of 1 to 18.6 [kHz].
And supplying respectively to the input terminal of the H _1. The correlator H ₀ is a PN sequence generator G ₀ ′ that generates the same PN sequence as the PN sequence PN ₀ of the modulator T, and the correlator H ₁ is a PN sequence PN _{1 of the} modulator T.
And a PN sequence generator G ₁ ′ for generating the same PN sequence, which are connected so as to be controlled by the output of the clock oscillator 8. Here, the clock oscillator 8 is 18.6
A clock signal of [kHz] is output, and the phase of this clock signal is synchronized with the clock signal sent from the timing generator 4 of the modulation device T by means not shown. The output signals of the correlators H ₀ and H ₁ are 2
The multiplier circuits B ₀ , B ₁ and the low-pass filters L ₀ , L ₁ whose cut-off frequency is higher than 600 [Hz] are both connected to be supplied to the adder 9 and the comparator 10, respectively. Adder 9
Output signal is timing extraction filter 11, waveform shaping circuit
The signal is supplied to one input terminal of a processing circuit 14 via a phase shift adjusting circuit 13 and an output signal of the comparator 10 and a signal from the phase shift adjusting circuit 13. It is configured to output information data SD. Further, if necessary, the demodulation device R supplies the output signals of the timing extraction filter 11 and the waveform shaping circuit 12 to the carrier detection circuit 15 and obtains the carrier detection signal CD from the output terminal.

The spread spectrum signal modulator / demodulator configured as described above operates as follows.

First, before supplying the information data SD to be transmitted to the synchronization circuit 3, the modulation side T supplies the transmission request signal RS to the timing generator 4 to operate the timing generator 4,
The switch S ₂ and on, based on the clock signal of the PN sequence generator G ₀ and G ₁ each timing generator 4 1/18600
[S] PN sequences PN ₀ and PN ₁ of 1 bit occurs in each, one of the PN sequence (the In Figure 1 terminal c of the switch S1
Is connected to the terminal a, so that the PN sequence PN ₀ ) is transmitted to the power line 1 via the band-pass filter 5 for a predetermined time K [s]. This signal is for extracting a timing signal, and is generally sent continuously for a predetermined time prior to sending the information data SD.

After that, the modulation side T supplies the information data SD to be transmitted to the synchronization circuit 3, and the synchronization circuit 3
And outputs 1-bit information data SD every 1/600 [s] based on the clock signal. That is, the synchronization circuit 3 outputs one bit of the information data SD each time the PN sequence generators G ₀ and G ₁ generate the 31-bit PN sequences PN ₀ and PN ₁ . Therefore, the clock of the PN sequence is 600 × 31 = 18.6 [kHz].
Connects the terminal c of the switch S ₁ in the case of the state value of the synchronization circuit 3 of the output signal is "0" to the terminal a, in the case of state value "1" also in respectively connected to the terminal b PN The series PN ₀ or PN ₁ is transmitted to the power line 1 via the band pass filter 5.

On the other hand, as described above, after transmitting the PN sequence PN ₀ for a predetermined time K [s] for extracting a timing signal from the modulator T as shown in FIG. For example, the PN sequence PN1, PN1, PN0,
.. Are sequentially transmitted as spread spectrum signals.

The demodulator R which receives the signal first amplifies the signal transmitted from the modulator T to a required level by the amplifier 6 and outputs the output signal of the amplifier 6 by the noise removal band-pass filter 7 outside the commercial power frequency and the signal transmission band. From which unnecessary signal components are removed. Correlator H ₀ is a band pass filter 7
Low-pass filter with the output signal and the signal amplitude changes as shown by the solid line in FIG. 2 when calculating a correlation value between the PN sequence PN ₀ (b) is generated, squaring by squaring circuit B ₀ the signal When smoothing is performed at L _0, a signal having a waveform corresponding to the envelope of the output waveform of correlator H ₀ is output as shown by the solid line in FIG. 2C. Give the signal shown in solid lines in Figure 2 by calculating a correlation value between the output signal and the PN sequence PN ₁ similarly correlator H ₁ In the band-pass filter 7 (d), 2 square circuit B ₁ and the low-pass filter L and outputs a signal of the waveform shown by the solid line in Figure 2 through _one and (e). Here, the reason why the correlation value is squared is to increase the amplitude level difference and to obtain the absolute value. The adder 9 outputs a signal shown by the solid line in Figure 2 by adding the output signals of the L ₁ of the low-pass filter L ₀ (f). As described above, the timing extraction filter 11 is a filter having a center frequency of 600 [Hz] (corresponding to 600 b / s). Therefore, as shown by a solid line in FIG. Signal components of the same data rate are extracted. The waveform shaping circuit 12 is, for example, a timing extraction filter.
A pulse signal having the same cycle as this signal is generated based on the zero crossing point of the output signal of 11 or based on a rectangular wave signal generated by shaping the waveform of the signal. The phase shift adjusting circuit 13 is shifted in synchronization with the correlation peak point to one of the output waveform of the correlator H ₀ or H _1, as shown in Figure 2 to compensate for the phase deviation caused by the timing extraction filters 11 (h) The phase is adjusted so that the output pulse signal of the phase adjustment circuit 13 rises and is output.

When the demodulation device R receives a timing extraction signal transmitted prior to the transmission of the information data SD, the demodulation device R in the carrier detection circuit 15 outputs the timing extraction filter 11.
Is determined to be a carrier signal transmitted from the modulator T by outputting a predetermined value for a predetermined time K [s] or more, and a carrier detection signal CD is output. still,
The carrier detection signal is used, for example, when it is determined that a signal to be received or currently received is information data SD.

Then, the transmission request signal RS followed by information data SD and the demodulator second view in R sent (h) to the low-pass filter L ₀ In comparator 10, as shown with the output signal of the L ₁ detects the level magnitude of outputs state values of when the level of the output signal of the low-pass filter L ₀ is larger than the output signal level low-pass filter L ₁ from the comparator 10 is "0", a low-pass filter L in the opposite comparator 10 when the level of the _first output signal is greater than the output signal level of the low-pass filter L ₀
Outputs a state value of "1". As a result, signals from the processing circuit 14 waveform as shown in example FIG. 2 (i) is obtained, which is "0" or "1" by the magnitude of the rectified output of the correlator H ₀ and H ₁ Although they are output, near either of the central peaks, one of the levels is clearly increased and becomes a relatively long-term pulse, but on both sides thereof, short-term random pulses are generated because there is no clear magnitude relation between both. This waveform (i) and the output (h) of the timing extraction filter 11
From this, the signal shown in (j), that is, (j), becomes a transmitted information data SD when a signal output as a state value with the comparator output value at the time of generation of the timing signal is obtained.

As described above, the present invention compares the correlation value output regarding each of the PN sequences PN ₀ and PN ₁ and determines the bit value. Therefore, when a clear peak value is obtained for each correlation value, Even if a clear peak value cannot be obtained, accurate demodulation can be performed. That is, the case where the clear correlation peak in the output waveform of the correlator H ₀ and H ₁ are present, the amplitude value of the output waveform of the low-pass filter L ₀ and L ₁ of the case where no waveform as shown in Figure 2 differs from 2 (g), the output signal of the timing extraction filter 11 has the same phase except for the amplitude value, as shown by the dotted line in FIG. 2 (g). j)
It can be positively correlated peak output the same output signal as when present in the output waveform of the correlator H ₀ and H ₁ as shown in.

Therefore, according to this spread spectrum signal modulation / demodulation device, even if a large delay deviation and amplitude deviation occur in the transmission characteristics of the transmission line and the output waveform of each correlator is distorted and the existence of the correlation peak is not clear, the demodulation side is As shown in FIG. 2 (i), the original information data can be obtained from the output terminal of the processing circuit.

The transmission rate of 600b / s of information data to be transmitted in the embodiment described above, the bit length of the PN sequence PN ₀ and PN ₁ showed the case of 31 bits, the present invention is not necessarily limited thereto.

In the above-described embodiment, the comparator 10 outputs “0” or “1” depending on the magnitude of the rectified output between the correlators H ₀ and H _1. However, the present invention is not limited to this. vessels H ₀ and depending on the polarity of the level difference of the rectified output of the H ₁ "0" or may be output to "1".

Further, in the above-described embodiment, the case where the information data SD to be transmitted is binary data having a state value of “0” or “1” is described. The present invention is also applicable to the case of data (where n is a positive number). For example, when the information data SD to be transmitted is ternary data, the modulators T have a periodic length as shown in FIG. the PN sequence in accordance with the state value of the information data to be transmitted PN sequence generator G ₀ to G ₂ each provided equal correlation value is small three PN sequences PN _0, the PN ₁ and PN ₂ respectively generated and it sends to the transmission line either PN ₀ to PN _2. On the other hand, the demodulation device R correlator H ₀ to H ₂ corresponding to the PN sequence PN ₀ to PN ₂ each as shown in FIG. 3 (b), also square circuit B ₀ through B ₂ and the low-pass filter L _{0 to} L ₂ are provided and the adder 9 is a low-pass filter
A low-pass filter that combines the output signals of L _{0 to} L ₂ , and the comparator 10 determines whether the level of any of the output signals of the low-pass filters L _{0 to} L ₂ is the maximum and outputs the output signal of the maximum level If the configuration is such that the state value corresponding to the correlator that has output the signal is output, the original information data could be obtained from the output terminal of the processing circuit 14 as described above.

In the above-described embodiment, the output signal of each correlator is squared by the squaring circuit and supplied to the low-pass filter. However, in the present invention, for example, the absolute value of the output signal of each correlator is obtained and supplied to the low-pass filter. It is obvious that the same effect as in the above-described embodiment can be obtained.

Further, in the above-described embodiment, each component is shown in the functional block diagram. However, according to the present invention, if the output signal of the amplifier 6 or the band-pass filter 7 on the demodulation side is A / D converted, all the subsequent processing is performed Digital signal processing is possible, and those skilled in the art can generally replace these with digital devices such as digital signal processors (DSPs).

The principle of this device is not limited to this embodiment,
It will be obvious that the configuration can be extended and modified in various ways.

(Effects of the Invention) As described above, the present invention compares the levels of the output signals of the correlators with each other when demodulating the spread spectrum signal, and obtains the original information data based on the result. A correlator output signal in the presence of a correlation peak even if the presence of a correlation peak cannot be clearly detected from the output signal of the correlator due to a large delay deviation and amplitude deviation in the transmission characteristics of the transmission path; If there is a difference between the level of the correlation output signal and the level of the correlation output signal when there is no correlation peak, it is possible to determine which correlator output signal has the maximum level and obtain the original information data. The present invention is particularly effective in providing a spread spectrum signal demodulation method capable of utilizing a path and a device therefor.

[Brief description of the drawings]

FIG. 1 is a block diagram of a spread-spectrum signal modulation / demodulation apparatus showing one embodiment of the present invention, FIGS. 2 (a) to (j) are timing charts for explaining the operation of the embodiment, FIG. a) and (b) are block diagrams of a spread-spectrum signal modulation / demodulation device showing a modified embodiment of the present invention, FIG. 4 is a block diagram of a conventional spread-spectrum signal modulation / demodulation device, and FIG. FIG. 6 is a diagram showing the waveform of the output signal of the correlator in the case. FIG. 6 is a diagram showing the waveform of the output signal of the correlator when the correlation peak does not clearly exist. 1 ... power line, 3 ... synchronization circuit, 4 ... timing generator, 5 ... band-pass filter, 6 ... amplifier, 7 ...
... bandpass filter, 8 ... clock oscillator, 9 ...
Adder, 10 Comparator, 11 Timing extraction filter, 12 Waveform shaping circuit, 13 Phase shift adjustment circuit, 14
Processing circuitry, T ...... modulator, R ...... demodulator, G ₀ and G ₁
...... PN sequence generator, S ₁ and S ₂ ...... switches, H ₀ and H ₁ ...
... Correlator, B ₀ and B ₁ ... Square circuit, L ₀ and L ₁ .

──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Umeda Inventor 2-1-1 Kotani, Samukawa-cho, Koza-gun, Kanagawa Prefecture Examiner, Kenichi Ishii, Toyo Tsushinki Co., Ltd. (56) References JP-A-60-5637 (JP) JP-A-2-114431 (JP, A) JP-A-2-246540 (JP, A) JP-A-2-24639 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB Name) H04J 13/00

Claims (11)

(57) [Claims] 1. A means for demodulating a spread spectrum signal modulated so as to output one of a plurality of PN sequences having the same period length and a small correlation value in accordance with the state value of information data to be transmitted. A correlation means for calculating a correlation value between the spread spectrum signal and each of the PN sequences, generating an absolute value signal of the correlation value for each correlation means, and based on a signal obtained by adding all of the absolute value signals. A periodic signal corresponding to the signal speed of the information data is extracted, and the level value of the absolute value signal generated for each of the correlating means is compared with each other to generate a maximum level signal. The spread spectrum signal demodulation method, wherein the information data is demodulated by outputting the information data at a timing based on the periodic signal. 2. A means for demodulating a spread spectrum signal modulated so as to output one of a plurality of PN sequences having the same period length and a small correlation value in accordance with the state value of information data to be transmitted. A correlation means for obtaining a correlation value between the spread spectrum signal and each of the PN sequences, generating a signal obtained by smoothing an absolute value signal of the correlation value for each correlation means, and generating a signal for each correlation means. A periodic signal corresponding to the signal speed of the information data is extracted based on a signal obtained by adding all of the signals, and a level of a signal generated for each of the correlating means is compared with each other to generate a signal having a maximum level. A spread spectrum signal demodulation method, wherein the information data is demodulated by outputting a state value related to the means at a timing based on the periodic signal. 3. The first PN sequence when the status value of the information data to be transmitted is "0", and the same cycle length as the first PN sequence when the status value of the information data is "1". Means for demodulating a spread-spectrum signal modulated to output a second PN sequence of
A correlation means for obtaining a correlation value with each of the series, generating an absolute value signal of the correlation value for each correlation means, and adding the absolute value signal generated for each correlation means to a signal obtained by adding all of the absolute value signals. A signal component having a cycle related to the signal speed is extracted, and “0” or “1” is output at a timing based on the signal component in accordance with the polarity of the level difference of the absolute value signal generated for each correlation unit. A spread spectrum signal demodulation method characterized in that the information data is demodulated by the method. 4. The first PN sequence when the status value of the information data to be transmitted is "0", and the same cycle length as the first PN sequence when the status value of the information data is "1". Means for demodulating a spread-spectrum signal modulated to output a second PN sequence of
Correlation means for obtaining a correlation value with each of the series, a signal obtained by smoothing an absolute value signal of the correlation value for each correlation means, and a signal obtained by adding all of the signals generated for each correlation means from the signal A periodic signal related to the signal speed of the information data is extracted, and “0” or “1” is set at a timing based on the periodic signal in accordance with the polarity of the level difference of the smoothed signal generated for each correlation means. A spread spectrum signal demodulation method, wherein the information data is demodulated by outputting. 5. A means for demodulating a spread spectrum signal modulated so as to output one of a plurality of PN sequences having the same period length and a small correlation value corresponding to the state value of information data to be transmitted. A correlation means for obtaining a correlation value between the spread spectrum signal and each of the PN sequences; a means for generating an absolute value signal of the correlation value for each correlation means; and a means for generating an absolute value signal for each correlation means. Means for generating a signal obtained by adding all the signals, means for extracting the signal speed period signal of the information data from the added signal, and comparing the levels of the absolute value signals generated for each of the correlation means with each other to the maximum level Means for outputting a corresponding state value at a timing based on said periodic signal. 6. A means for demodulating a spread spectrum signal modulated so as to output any one of a plurality of PN sequences having the same period length and a small correlation value in accordance with the state value of information data to be transmitted. A correlation means for calculating a correlation value between the spread spectrum signal and each of the PN sequences; a means for generating a signal obtained by smoothing an absolute value signal of the correlation value for each correlation means; and a means for generating a signal for each correlation means. Means for generating a signal obtained by adding all of the smoothed signals, and means for extracting a signal speed period signal of the information data from the added signal,
Means for comparing the levels of the smoothed signals generated for each of the correlation means with each other and outputting a state value related to the signal of the maximum level at a timing based on the periodic signal. apparatus. 7. The first PN sequence when the status value of the information data to be transmitted is "0", and the same cycle length as that of the first PN sequence when the status value of the information data is "1". Means for demodulating a spread-spectrum signal modulated to output a second PN sequence of
Correlation means for obtaining a correlation value with each of the series, means for generating an absolute value signal of the correlation value for each correlation means, and means for generating a signal obtained by adding all the absolute value signals generated for each correlation means Means for extracting a signal speed periodic signal of the information data from the added signal, and means for outputting a difference in level of an absolute value signal generated for each of the correlation means at a timing based on the periodic signal. A spread spectrum signal demodulator characterized by the above-mentioned. 8. The first PN sequence when the status value of the information data to be transmitted is "0", and the same period length as the first PN sequence when the status value of the information data is "1". Means for demodulating a spread-spectrum signal modulated to output a second PN sequence of
Correlation means for obtaining a correlation value with each sequence, means for generating a signal obtained by smoothing an absolute value signal of the correlation value for each correlation means, and a signal obtained by adding all of the smoothed signals generated for each correlation means Means for extracting the signal speed periodic signal component of the information data from the added signal, and means for outputting the level difference of the smoothed signal generated for each correlation means at a timing based on the periodic signal. A spread spectrum signal demodulator characterized by comprising: 9. Claims 1, 2 and 3,
5. The spread spectrum signal demodulation method according to claim 4, wherein a square signal is used in place of said absolute value signal. 10. A spread-spectrum signal demodulator according to claim 5, 6, 7, or 8, wherein a square signal is used instead of the means for generating the absolute value signal. A spread spectrum signal demodulation device characterized by using a generating means. 11. A spread-spectrum signal demodulator and system according to claim 5, wherein it is detected that the level of said periodic signal continuously exceeds a predetermined value for a predetermined time. And a method for determining the presence or absence of a carrier signal by using a spread spectrum signal demodulation apparatus and method.