JP2839973B2 - Spread spectrum communication equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication apparatus for converting information into a signal having a much larger bandwidth than an information band when transmitting information by wire or wirelessly.

[0002]

2. Description of the Related Art A spread spectrum communication system is a system for transmitting a signal having a much wider bandwidth than information data, and there are two conventional systems for realizing this.

The first method is direct diffusion (Direct Sequenc).
e: DS) method. This involves multiplying a digitized baseband signal by a spreading code such as a high-speed pseudo-noise code to generate a baseband signal having an extremely wide bandwidth compared to the original data, and furthermore, phase shift keying (PSK), Frequency shift keying (FS
K) or the like, and converts the signal into an RF (radio frequency) signal for transmission. On the other hand, the receiving side demodulates the original data by performing despreading to obtain a correlation with the received signal using the same spreading code as that of the transmitting side.

A second method is frequency hopping (Freque
In a method called an ncy hopping (FH) method, the frequency of a carrier wave modulated by a baseband signal is switched according to a spreading code at a time interval of one bit of data, or a fraction of the data, or an integral multiple of the data. The receiving side performs despreading by demodulating the original data by performing a correlation operation of tuning the carrier at the receiver side to the transmitting side using the same spreading code as the transmitting side.

[0005] In these systems, in order to obtain a correct correlation on the receiving side, the spreading codes need to be accurately synchronized on the transmitting side and the receiving side. Conventionally, a synchronization circuit called a sliding correlation loop has been used for a synchronization circuit for realizing this.

FIG. 4 is a block diagram showing a sliding correlation loop for the DS method.

In the figure, a received spread signal is supplied to a mixer 401.
Is multiplied by the spreading code sequence generated from the spreading code generator 406. The output of the mixer 401 is a band-pass filter (BPF) having a bandwidth corresponding to the original data.
It is input to 402. Further, the output of the BPF 402 is subjected to envelope detection by a detection circuit 403 and smoothed by a low-pass filter (LPF) 404.

If the autocorrelation is obtained, the mixer 40
1, the despread signal is obtained, and the BPF 402
And the envelope is detected by the detection circuit 403.
Further, it is smoothed by the LPF 404 to obtain a DC level.

On the other hand, if the autocorrelation cannot be obtained, no despread signal is obtained at the output of mixer 401, and most of the received spread signal power is blocked by BPF 402.
Subsequently, the envelope is detected by the detection circuit 403 and the LPF 4 is detected.
04, the obtained DC level is sufficiently smaller than that obtained when the autocorrelation is obtained.

The DC level output of the LPF 404 is supplied to a voltage controlled oscillator (VCO) 405. If the autocorrelation cannot be obtained, the DC level of the output of the LPF 404 is sufficiently small, and the VCO 405 obtains an output of a frequency slightly different from the frequency of the spread code included in the received spread signal. This is supplied to the spread code generator 406 as a clock. Since the clock speed of the spread code generated by the spread code generator 406 is slightly different from the clock speed of the received spread signal, the phases of the two are gradually shifted. As a result, by the time the two phases are shifted by one synchronization of the spreading code, synchronization is established and the autocorrelation is obtained. Then, the DC output level of the LPF 404 increases, and V
Lock the oscillation frequency of CO405 to the current frequency,
Synchronization between the received spread code and the spread code generated by the spread code generator 406 is obtained. The synchronization acquisition time of this method generally becomes extremely long because the phase of the receiving-side spread code is gradually shifted.

FIG. 5 is a block diagram showing a sliding correlation loop for the FH method.

FIG. 5 is a block diagram of the frequency synthesizer 5 shown in FIG.
It has the same configuration except that 07 is added. The overall operation is the same as in the case of the DS method.

[0013]

As described above, in the conventional spread spectrum communication system, since the spread code is changed on the time axis, a spread code synchronizing circuit is required. There is a disadvantage that the time required is extremely long.

The present invention eliminates the need for a spread code synchronization acquisition circuit for changing the spread code on the time axis by expanding the spread code on the frequency axis, thereby reducing the time required for synchronization acquisition. The purpose is to provide.

[0015]

SUMMARY OF THE INVENTION The present invention is directed to a predetermined
Sample each of the waveforms of multiple analog signals
Memory means for storing the extracted data;
Waveform of analog signal according to transmission data of
Is read from the memory means.
Reading means and data read from the memory means.
Transmission signal generation means for generating a transmission signal according to the data.
And each of the plurality of analog signals has a plurality of
Each of the wave number components represents a plurality of values constituting a spreading code.
Are modulated according to each of the above.

Also, the present invention provides a method for controlling a predetermined analog signal.
Memory means for storing data obtained by sampling a signal
Read the data stored in the memory means.
Output means, and sampled the analog signal.
The received data is converted to an intermediate frequency signal using the above data.
Conversion means for recovering a clock from the intermediate frequency signal.
Clock recovery means and an address to be supplied to the memory means.
The dress signal is reproduced by the clock reproducing means.
Means for generating an address signal generated from the lock;
Above according to the clock generated by the clock generation means.
And a demodulated signal for demodulating an inter-frequency signal.
Each of the plurality of frequency components has a spreading code.
A signal modulated according to each of the constituent values
There is a feature.

With the above configuration, the spread code can be developed on the frequency axis, and multiple access can be made without using a circuit for changing the spread code on the time axis to acquire synchronization.

[0018]

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

In the figure, a clock source 11 is a memory 1
3 is output to the address generation circuit 12 as an address clock at a frequency twice or more of the highest frequency of the signal data stored in the signal generator 3, and a frequency obtained by appropriately dividing this frequency is supplied to an information source as a data clock.

The address generation circuit 12 includes a clock source 11
An address is generated from an address clock and data input from the memory and output to the memory 13.

The memory 13 is a memory that outputs previously stored signal data based on an address signal input from the address generation circuit 12.

The D / A converter 14 performs D / A conversion of the output of the memory 13 and includes a low-pass filter (LPF).
Reference numeral 15 denotes an anti-aliasing output of the D / A converter 14.

The mixer 16 and the local oscillator 17 are LP
The baseband signal output from the F15 is converted into a transmission band, and the bandpass filter (BPF) 18 removes signals outside the transmission band.

The BPF 110 is for removing out-of-band signals mixed in the transmission line 19, and the BPF 112 is for removing signals other than a predetermined data bandwidth from the output of the mixer 111.

The clock recovery circuit 113 includes a BPF 112
The demodulator 114 reproduces data from the output of the BPF 112 and the output of the clock reproducing circuit 113.

The address generation circuit 115 generates an address based on the address clock from the clock recovery circuit 113.
A signal data stored in advance is output based on the address signal input from the control unit 15.

The D / A converter 117 has a memory 116
The D / A conversion of the output of
The output of the D / A converter 117 is anti-aliased. Mixer 119 and local oscillator 120
Converts a baseband signal output from the LPF 118 into a predetermined frequency band signal.
Is to remove signals other than the predetermined frequency band signal.

Next, prior to the description of the operation, the data stored in the memory 13 and the memory 116 will be described in detail.

The signal in the memory 116 is composed of n frequency components. Then, for each frequency component, the reception spread codes C0 ', C1', C2 ',.
1 'is given and has a value of 0 or 1, respectively.

Here, assuming that the data clock frequency is fd, each frequency component is (4p + 2C0 ') fd, {4 (p + 1) + 2C1'}.
fd, ｛4 (p + 2) + 2C2 '｝ fd,... ｛4 (p
+ N-1) + 2Cn-1 '｝ fd. Here, p is a positive integer.

The address clock is mfd (m ≧ m)
8 (p + n-1) +1). The data in the memory 116 is as shown in FIG.

On the other hand, in the memory 13, P
The most significant bit of the address is assigned to data to perform SK modulation. That is, the data in the memory 13 is as shown in FIG. Note that C0 in FIG.
C1, C2,... Cn-1 are transmission spreading codes, each having a value of 0 or 1.

FIG . 10 is a schematic diagram showing a list of arithmetic expressions used in the description of this embodiment.

[0034] In the above configuration, the output of the memory 13 through the D / A converter 14, LPF 15 Figure
It becomes an analog signal shown in Expression 1 of 10 .

FIG. 2 is a waveform diagram showing the waveform of this analog signal.

This analog signal is frequency-converted by the mixer 16 and only the transmission band signal is extracted by the BPF 18 and sent out to the transmission line. The frequency of the local oscillator 17 is fc
Then, the transmitted signal is as shown in Equation 2 in FIG .

On the receiving side, unnecessary signals mixed in the transmission path are removed by the BPF 110 and input to the mixer 111. The output of the LPF 118 is in the form of Equation 3 in FIG. 10 and passes through the BPF 121 via the mixer 119 to become a predetermined frequency band signal. Local oscillator 1
Assuming that the frequency of 20 is fc ′, the output of the BPF 121 is
Equation 4 in FIG . Therefore, the output of mixer 111 is
Assuming that fc−fc ′ = f _IF , Equation 5 in FIG. 10 is obtained.

If the BPF 112 has a center frequency f _IF and a bandwidth of 2 fd, the signal passing through the BPF 112 is
Equation 6 in FIG. 10 is obtained. That is, if the spreading code on the transmitting side and the spreading code on the receiving side are the same, Ci-Cj ′ = 0, and all signals passing through the BPF 112 are added in phase, so that the signal voltage becomes n times.

On the other hand, assuming additive white Gaussian noise, the noise voltage is all uncorrelated, so that the average addition voltage is at most n1 ^{/ 2} times, so the BPF 112
The signal-to-noise power ratio (S / N) after passing is n ² / (n
^1/2 ) ² = n times.

If the spreading code {Ci} is selected from a set having a small cross-correlation, the receiver using different codes does not increase the signal after passing through the BPF 112 by n times. Electric power cannot be obtained.
Therefore, multiple access by code division becomes possible.

From the output of the BPF 112, a data clock and an address clock are reproduced by a clock regeneration circuit 113 and supplied to a demodulator 114 and an address generation circuit 115, respectively. The demodulator 114 performs PSK demodulation based on the data clock and the output of the BPF 112.

Next, a second embodiment of the present invention will be described.

The second embodiment is the same as the first embodiment except for the data stored in the memory 13.
Therefore, here, the data stored in the memory 13 will be described.

In the first embodiment, the data stored in the memory 13 is a PSK modulated wave that is not band-limited for each frequency slot. Act as
There is a disadvantage that the demodulation performance is adversely affected.

Therefore, in the second embodiment, in order to suppress the out-of-band component of the signal corresponding to each frequency slot, the envelope of the signal corresponding to each frequency slot of the data stored in the memory 13 in the first embodiment is described. The result of the waveform shaping is the data stored in the memory 13. FIG. 3 schematically shows an example in which the weighting of the amplitude level is used as one example of the band limitation. Thereby, it is possible to obtain better demodulation performance as compared with the first embodiment.

Next, a third embodiment of the present invention will be described.

The third embodiment is the same as the first embodiment except that the data stored in the memory 13 and the memory 116 are replaced. The other configuration is the same as that of the first embodiment. Therefore, first, the memory 13 and the memory 1
16 will be described in detail.

The signal in the memory 116 is composed of n frequency components. If the data clock frequency is fd, the respective frequency components are 2pfd, 2 (p + 1) fd, 2 (p + 2) fd,.
2 (p + n-1) fd. Here, p is a positive integer.

The address clock is mfd (m ≧
8 (p + n-1) +1). Further, the reception spread codes C0 ', C1', C2
', ... Cn-1' are given, each having a value of 0 or 1.

The data in the memory 116 is shown in FIG.
It is shown as follows.

On the other hand, in the memory 13, P
The most significant bit of the address is assigned to data to perform SK modulation. That is, the data in the memory 13, FIG.
9 . Note that C0 in FIG.
C1, C2, ...... Cn-1 is Ri transmission spread codes der, each with a value of 0 or 1.

FIG. 11 is a schematic diagram showing a list of arithmetic expressions used in the description of this embodiment.

In this embodiment, the output of the memory 13 is
The signal passes through the D / A converter 14 and the LPF 15 and becomes an analog signal shown in Expression 11 in FIG.

FIG. 12 is a waveform diagram showing the waveform of this analog signal.

The analog signal is frequency-converted by the mixer 16 and only the transmission band signal is extracted by the BPF 18 and sent out to the transmission line. The frequency of the local oscillator 17 is fc
Then, the transmitted signal is as shown in Expression 12 in FIG.

On the receiving side, the BPF 110 controls the transmission path.
Unnecessary mixed signals are removed and input to the mixer 111.
It is. The output of LPF 118 is in the form of equation 13 in FIG.
Through the BPF 121 via the mixer 119.
Thus, a predetermined frequency band signal is obtained. Local oscillator 1
If the frequency of 20 is fc ′, the output of the BPF 121 is
Equation 14 in FIG. 11 is obtained. Therefore, the mixer 111output
Is fc−fc ′ = f_IFThen, Equation 15 in FIG.
Swell.

If the BPF 112 has a center frequency f _IF and a bandwidth of 2 fd, the signal passing through the BPF 112 is
Equation 16 in FIG. 11 is obtained. That is, if the spreading code on the transmitting side and the spreading code on the receiving side are the same, Ci−Cj ′ = 1
Since all signals passing through the BPF 112 are added in phase, the signal voltage becomes n times.

On the other hand, assuming additive white Gaussian noise, the noise voltage is all uncorrelated, so that the average added voltage is at most n1 ^{/ 2} times, so the BPF 112
The signal-to-noise power ratio (S / N) after passing is n ² / (n
^1/2 ) ² = n times.

If the spreading code {Ci} is selected from a set having a small cross-correlation, the receiver using different codes does not increase the signal after passing through the BPF 112 by n times. Electric power cannot be obtained.
Therefore, multiple access by code division becomes possible.

From the output of the BPF 112, a data clock and an address clock are reproduced by a clock regeneration circuit 113 and supplied to a demodulator 114 and an address generation circuit 115, respectively. The demodulator 114 performs PSK demodulation based on the data clock and the output of the BPF 112.

Next, a fourth embodiment of the present invention will be described.

The fourth embodiment has the same configuration as the third embodiment except for the data stored in the memory 13.
Therefore, here, the data stored in the memory 13 will be described.

In the third embodiment, the data stored in the memory 13 is a PSK modulated wave that is not band-limited for each frequency slot. Act as
There is a disadvantage that the demodulation performance is adversely affected.

Therefore, in the fourth embodiment, as in the second embodiment, in order to suppress out-of-band components of the signal corresponding to each frequency slot, each frequency slot of the data stored in the memory 13 in the third embodiment is reduced. Is obtained by shaping the waveform of the envelope of the signal corresponding to the data stored in the memory 13. FIG. 13 schematically shows an example in which amplitude level weighting is used as an example of the band limitation. As a result, better demodulation performance can be obtained as compared with the third embodiment.

[0065]

As described above, according to the present invention,
By spreading the spreading code on the frequency axis, it is possible to eliminate the need for a spreading code synchronization acquisition circuit, eliminate the time overhead at the time of initial information demodulation for spreading code synchronization,
The initial synchronization can be performed at high speed, and there is an effect that spread spectrum communication having a wide application range can be realized.

Further, according to the present invention, the code synchronization between the transmitting side and the receiving side is not lost during communication, so that it is not necessary to resynchronize, and highly reliable communication can be realized.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram showing a waveform of an analog signal based on data stored in a memory in the first embodiment.

FIG. 3 is a waveform chart showing a waveform of an analog signal based on data stored in a memory according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing an example of the related art.

FIG. 5 is a block diagram showing another example of the related art.

FIG. 6 is a schematic diagram showing contents of memory data in the first embodiment.

FIG. 7 is a schematic diagram showing contents of memory data in the first embodiment.

FIG. 8 shows the memory data in the third embodiment of the present invention .
FIG.

FIG. 9 shows the contents of memory data in the third embodiment .
FIG.

FIG. 10 is a list of arithmetic expressions used in the description of the first embodiment .
It is a schematic diagram which shows a table.

FIG. 11 is a schematic diagram showing a list of arithmetic expressions used in the description of the third embodiment.

FIG. 12 is a waveform chart showing a waveform of an analog signal based on data stored in a memory in the third embodiment.

FIG. 13 is a waveform chart showing a waveform of an analog signal based on data stored in a memory according to a fourth embodiment of the present invention.

Claims (6)

(57) [Claims] 1. A wave of a plurality of predetermined analog signals.
A memo that stores data obtained by sampling each of the shapes
And means for responding to transmission data of the plurality of analog signals.
The data obtained by sampling the waveform of the analog signal
Reading means for reading from the memory means ; transmitting and receiving according to the data read from the memory means
A transmission signal generating means for generating a No.; has, each of said plurality of analog signals, a plurality of frequency components
Each of the minutes represents the multiple values that make up the spreading code.
A spread-spectrum communication device, characterized in that the signal is modulated according to each of them . 2. A spread code according to claim 1, wherein the displacement of each frequency component from the center frequency forms a spread code.
Analog determined by each of the multiple values
The data obtained by sampling the signal waveform is stored in the memory means.
A spread-spectrum communication device characterized by storing . 3. The method according to claim 1, wherein the phase of each frequency component is a plurality of values constituting a spreading code.
The waveform of the analog signal determined by
A spread-spectrum communication device wherein the coupled data is stored in the memory means . 4. A sampler for converting a predetermined analog signal into a sample signal.
Memory means for storing the data read out ; reading the data stored in the memory means
Means for sampling said analog signal
A conversion that converts the received signal to an intermediate frequency signal using the data.
Conversion means; clock recovery for recovering a clock from the intermediate frequency signal
Means; an address signal to be supplied to the memory means,
Generated from the clock recovered by the clock recovery means.
Signal generating means; according to the clock generated by the clock generating means.
And a demodulated signal for demodulating the intermediate frequency signal . The analog signal has a plurality of frequency components,
Modulated according to each of the multiple values that make up the spreading code
A spread-spectrum communication device, characterized in that the signal is a modulated signal . 5. The method according to claim 4, The displacement of each frequency component from the center frequency forms a spreading code
Analog determined by each of the multiple values
The data obtained by sampling the signal waveform is stored in the memory means.
Spread spectrum communication apparatus characterized by storing
Place. 6. The method according to claim 4, The phase of each frequency component is the sum of a plurality of values that make up the spreading code.
The waveform of the analog signal determined by
That the memory means stores the pooled data.
Spread spectrum communication equipment.