JP2966810B2 - Spread spectrum multiplexing 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 multiplex communication apparatus using a chirp signal for spread spectrum.

[0002]

2. Description of the Related Art Spread spectrum communication, which is a communication for modulating a signal in a band much wider than the minimum frequency bandwidth necessary for transmitting information, in other words, the frequency bandwidth of a modulated signal to be information-modulated has information. It has been proposed to use a chirp signal for spread spectrum communication, which is communication much wider than the bandwidth.

In spread spectrum communication, a plurality of users can communicate simultaneously in the same frequency band, and is different from frequency division multiplexing or time division multiplexing in which a frequency-division or time-division slot and a communication channel correspond one-to-one. In the vicinity of the limit of the communication channel, the S / N is gradually lowered, but has the advantage of not causing sudden saturation. In addition, since signals superimposed on the same frequency can be separated based on the spreading code, systems with different information rates can be operated independently in the same frequency band, enabling flexible support for communication systems. It also has the advantage of being.

Therefore, attention has been paid to the channel capacity and the flexibility to change the system, and the spread spectrum technology has already been put to practical use in a cellular system for mobile communication. Here, in a code division multiplexing system using spread spectrum communication in the same frequency bandwidth, code division multiplexing using an orthogonal sequence such as a Hadamard sequence is performed in order to secure the maximum channel capacity. In addition, when the channels are superimposed evenly at the time of reception, in order to equalize the reception signal level depending on the transmission / reception distance and the environment of the communication channel, take measures such as applying power control by feeding back to the transmission side. ing.

[0005] In such a system, when a base station is installed, the environment of the communication channel is sufficiently examined, the base station is installed according to the situation, and a plurality of base stations belonging to the area of the base station are operated during system operation. Unless the mobile terminal is sufficiently controlled, it is not possible to achieve the maximum performance of the system.

Furthermore, such a system cannot maintain its maximum performance without a technician having sufficient knowledge of wireless communication.

[0007] On the other hand, in addition to the conventional communication based on voice conversation, due to the spread of the current miniaturized computers, global communication on a global scale regardless of at home and abroad is always possible as needed. It is necessary to be.

However, at the same time as long-distance communication can be easily realized, higher-quality communication has been demanded in short-distance communication.

[0009] In order to satisfy the demands in the short-range communication, frequent and irregular communication in a small room, in a room, in a building, or in a factory, which does not require social communication equipment, is required. It is not appropriate to use a system that requires the development of a social infrastructure for such communications, and a system that is smaller, more flexible, and requires less initial investment is needed. Was.

In response to such a demand, a wireless LAN effective for local communication that does not require complicated components
(Local Area Netwaork)
A method of multiplexing using the same code by the difference in correlation time has been proposed [for example, Yasushi Maruta, Daisuke Takayama, Taketoshi Kamada, Tsuyoshi Yamazaki, Takuro Sueji, Kazuya Masu, Kazuo Tsubouchi, "2.4G
Card-size SS demodulator using a front-end SAW correlator in the Hz band ", IEICE Technical Report (also referred to as IEICE Technical Report), SST95-74 (1995)].

[0011]

This type of multiplexing method has an advantage that it can be easily realized by a quadrature modulator or the like that uses a modulated signal for general digital modulation on the transmitting side. In the case of multiplexing from another transmitter, there is a problem that a propagation condition periodically changes at a beat corresponding to the frequency difference due to a subtle difference in carrier frequency. Therefore, it is necessary to cope with a multi-carrier system requiring a plurality of carrier frequencies or to change the mutual positional relationship at the time of signal synthesis at random, and it is difficult to perform multiplexing with a simple communication device. was there.

On the other hand, for a chirp signal whose frequency changes continuously with time, a good S / N ratio and a high distance resolution can be obtained by using a matched filter at the time of reception. Widely used for distance. However, the chirp SS system that uses a chirp signal as a spread spectrum modulation signal (spread spectrum is also referred to as SS) is disclosed in RCDixon “Spread Spe
ctrum Systems ", John Wiley & Son. , New York (19
In 76), although it has already been classified as one genre of spread spectrum, there are few examples of use in communication.

As an example used in communication, J. Burnswei
g, J. Wooldridge, "Ranging and Data Transmissio
n using Digital Encoded FM− 《Chirp》 Surface Acou
sticWave Filters ", IEEE Ttrans. Microwave Theory
& Tech., MTT-21, No. 4, pp. 272-279 (1973). FIG. 9 shows the configuration of this digitally encoded chirp carrier device.

The digitally encoded chirp carrier apparatus shown in FIG. 9 generates a high-frequency (high-frequency is also referred to as RF) pulse for generating a surface acoustic wave (a high-frequency SAW is also referred to as SAW) based on a clock pulse. , And "0" of data constituting a digital message by the switch driver 32,
Single pole double throw (SPDT) switch 33 corresponding to "1"
To switch the RF pulse to two input electrodes 3 of a distributed delay line (hereinafter referred to as a DDL) 34.
4 _1, 34 ₂ of the type from either, are transmitted from the chirp electrode 34 ₃ the distance between the electrode fingers are gradually varied to obtain the chirp signal.

The chirp electrode is an electrode formed such that the pitch of the electrode fingers gradually changes depending on the location.

Here, the RF pulse is applied to the chirp electrode 34 _3.
When the electrode finger pitch is input from the wide side and the pitch gradually narrows, the up-chirp signal whose frequency increases with time is input when the electrode finger pitch is input from the narrow side and the pitch gradually increases. A down-chirp signal whose frequency gradually decreases is output.

Here, if the message data "1" and "0" are made to correspond to the up-chirp and the down-chirp, respectively, the matched filter 35 of the up-chirp and the down-chirp at the receiving side causes the matching of the message data. “0” and “1” can be identified.

The digital encoded chirp carrier apparatus shown in FIG. 9 has an advantage that the deterioration of the correlation characteristic is small even if the carrier frequency is changed due to the shift of the carrier frequency, that is, the Doppler effect or the like. Is used for communication. This device has a sufficient frequency bandwidth, a relatively low speed communication, and a large process gain [for a chirp signal, the BT product (B: frequency bandwidth,
T: chirp time)] is effective because the cross-correlation between up-chirp and down-chirp is good.

However, in the case of consumer use, the frequency bandwidth is limited. In addition, when high-speed data transmission is required as compared with the use frequency bandwidth, the cross-correlation between the up-chirp and the down-chirp is not sufficient. There is a problem that it is difficult to say that it is an effective communication means because it deteriorates.

As another example, Hitoshi Takai, Yoshio Urabe, Hidetoshi Yamazaki, and Akihiro Tatsuta, "Proposal of SR-chirp PSK System Maintaining Both Multipath and Antijamming at Low Spreading Ratio", IEICE Tech. There is a transceiver described in SST94-47 (1994). FIG. 10 shows the configuration of the transmission unit of the transceiver, and FIG. 11 shows the configuration of the reception unit. The transmitter shown in FIG. 10 is a transmitter that uses a chirp signal for a spread spectrum signal.

According to the transmitter shown in FIG. 10, the message data I and Q encoded by the differential / gray encoder 61 are differentially phase-modulated by the data modulator 62 and the differential phase-modulated message data The signal is spread-spectrum modulated by multiplying by a multiplier 64 using a chirp signal generated by a chirp signal generator 63 and transmitted.

The signal transmitted from the transmitter shown in FIG. 10 is received by the receiver configured as shown in FIG. In the receiver illustrated in FIG. 11, a part of the frequency band of the received signal that has been frequency-converted by the frequency converter 65 and subjected to spread spectrum modulation is cut out by the sub-band filter 66.
The output signal is subjected to delay detection by the delay detector 67 to perform data demodulation.

FIG. 12 is a waveform diagram for explaining the operation of the receiving section shown in FIG. 11, and FIG. 12 (a), (b),
(C) and (d) respectively show a received signal waveform that is a spread spectrum modulation signal using a chirp signal, a low band signal waveform of a subband signal, a middle band signal waveform of a subband signal, and a high band signal of a subband signal. The waveform is shown.

The receiver is configured as shown in FIG.
By changing the transmission frequency of the local oscillator constituting the frequency converter 65, the frequency band of the frequency-converted received signal can be changed, for example, if a part of the used frequency bandwidth has interference or the like. In addition, a frequency band avoiding the frequency band can be extracted by the sub-band filter 66, and the anti-jamming characteristic of the system can be improved by the frequency diversity effect.

However, when using such a transceiver, only a part of the transmitted power is used, so that there is a problem that the efficiency of using the transmitted power is poor.
Also, to transmit radio waves to unused frequency bands,
There was also a problem that it would unnecessarily interfere with other systems.

An object of the present invention is to provide a spread spectrum multiplexing communication device capable of multiplexing with a simple configuration.

[0027]

According to a first aspect of the present invention, there is provided a spread spectrum multiplex communication apparatus using a chirp signal for spreading a spectrum, wherein a time of an input high-frequency pulse is reduced. A channel multiplexed with the input high-frequency pulse is applied to an input electrode of a surface acoustic wave dispersion type delay line that performs N-valued differential phase modulation between chirp signals generated by changing the interval from a reference interval corresponding to one bit of data. When the number is K, a number (K-1) of high-frequency pulses are input between each of the input high-frequency pulses, and a multiplexed N-valued differential phase-modulated chirp signal is transmitted from an output electrode. A delay line as a modulator.

A spread spectrum multiplexing communication device according to a second aspect of the present invention is a spread spectrum multiplexing communication device using a chirp signal for spread spectrum, wherein a time interval between input high-frequency pulses is set to one bit of data. 2 based on the reference frequency for determining the amount of differential phase from the corresponding reference period
The number of multiplexed channels together with the input high-frequency pulse is set to the input electrode of a surface acoustic wave dispersion type delay line that performs N-valued differential phase modulation between chirp signals generated by changing the phase step by π / N radians. And the number (K
A surface acoustic wave dispersion type delay line for transmitting a multiplexed N-valued differential phase modulation chirp signal from an output electrode by inputting the high frequency pulse of -1) between the input high frequency pulses is provided as a modulator. It is characterized by the following.

According to the spread spectrum multiplexing communication apparatus of the first and second aspects of the present invention, a high-frequency pulse based on a number K of N-valued differential phase data multiplexed on a surface acoustic wave dispersion type delay line is temporally transmitted. , And a multiplexed modulated chirp signal modulated based on the multiplexed N-valued differential phase data is transmitted from the surface acoustic wave dispersion type delay line. In this case, the configuration of the modulator for multiplexing is simplified.

A spread spectrum multiplex communication apparatus according to a fifth aspect of the present invention is a spread spectrum multiplex communication apparatus using a chirp signal for spread spectrum, and
A multiplexed chirp-modulated signal obtained by multiplexing an N-valued differential phase-modulated chirp signal that changes in a phase step of 2π / N radians based on a reference frequency for determining a differential phase amount from a reference interval corresponding to a bit is An input electrode as an input, and two pairs of output electrodes corresponding to the input electrode and cascaded in a propagation path of the surface acoustic wave converted by the input electrode are provided in N systems, and the surface acoustic wave propagation of the reference frequency is provided. Wavelength λ
_{When set to 0} , the two output electrodes forming each system are provided with a position shifted by λ ₀ / N at a center-to-center position, and at least one of the input electrode and the output electrode pair is a resilient surface having a chirp electrode. The wave matched filter is provided as a demodulator.

According to the spread spectrum multiplexing communication apparatus of the present invention, the multiplexed modulated chirp signal modulated by the N-valued differential phase data input to the surface acoustic wave matched filter is elastically transmitted by the input electrode. In-phase addition and reverse-phase addition are performed over two continuous periods based on the phase shift of the differential phase data by the output electrode pair that has been converted to the surface acoustic wave and received the surface acoustic wave, and corresponds to the differential phase data. The demodulated electric signal is output, and data demodulation is performed. In this case, the configuration of the demodulator is simplified.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spread spectrum multiplex communication apparatus according to the present invention will be described below with reference to an embodiment.

FIG. 1 is a block diagram showing a configuration of a spread spectrum multiplex communication apparatus according to an embodiment of the present invention.

A spread spectrum multiplexing communication apparatus according to one embodiment of the present invention includes a transmission section TX and a reception section RX, and generates an RF pulse generated based on data obtained by differentially phase-shifting message data. Surface wave dispersion type delay line (the surface acoustic wave dispersion type delay line is also referred to as SAW-DDL)
To generate a chirp signal in the SAW-DDL and supply the SAW-DDL to the SAW-DDL.
A modulator that performs differential phase modulation based on message data between multiplexed chirp signals based on message data and performs multiplexing, and a SAW matched filter is configured as a data demodulator.

In the spread spectrum multiplexing communication apparatus according to one embodiment of the present invention, the differential phase modulation is the case of binary differential phase modulation and the case of multiplexing three pieces of information.
That is, a case where the number K of multiplexed channels is 3 will be described as an example.

First, a transmitting unit TX of a communication device using a chirp signal spread spectrum multiplexing modulator / demodulator according to an embodiment of the present invention will be described.

The digital message data supplied to the differential encoder 1 is differentiated by the differential encoder 1 and sent out to the pulse generator 3. Here, the differential encoder 1
Even if the message data is supplied in a time-division manner and the differentially-divided time-division message data is transmitted from the differential encoder 1 to the pulse generator 3, the number Alternatively, outputs from a plurality of differential encoders may be extracted in a time-division manner, and time-divisionalized differential message data may be sent to the pulse generator 3.

On the other hand, for example, the frequency 3
Upon receiving the oscillation output from the oscillator 2 oscillating at 00 MHz, the pulse generator 3 corresponds to the data rate, and at time intervals based on the codes “0” and “1” input to the differential encoder 1, A pulse generator 3 generates a plurality of (in this case, K = 3) superimposed RF pulse sequences that are multiplexing numbers. The RF pulse sequence generated by the pulse generator 3 is a SAW-D distributed delay line using SAW-D.
The multiplexed chirp signal is transmitted to the DL 4 and the frequency gradually changes with time to generate a multiplexed chirp signal.

It is preferable that the frequency of the RF pulse is set to the center frequency of the chirp signal. The frequency bandwidth of the RF pulse is determined based on the width of the RF pulse.
The frequency bandwidth generated by the RF pulse must be wider than the frequency bandwidth of the chirp signal. For this purpose, the pulse width of the RF pulse must be set narrow.

Here, the SAW-DDL 4 is a delay line having a different delay time depending on the frequency. When an RF pulse of a multiplex channel is added to the SAW-DDL 4, the delay time differs depending on the frequency component of the RF pulse.
A multiplexed modulated chirp signal in which the frequency of the output signal of W-DDL4 gradually changes with time is transmitted by SAW-DDL4. When the delay time of the SAW-DDL 4 increases with an increase in frequency, the output signal increases in frequency with time and becomes an up-chirp signal.
-If the delay time of DDL4 decreases with frequency,
The output signal is a down-chirp signal whose frequency decreases with time.

FIG. 2 shows the configuration of SAW-DDL4. S
The AW-DDL 4 is provided with an input electrode 42 made of a chirp electrode on a piezoelectric substrate 41,
An output electrode 43 made of a chirp electrode is arranged on the AW propagation path. Here, when the electrode finger pitch is different on one side or both of the input electrode 42 and the output electrode 43, that is, in the example of the SAW-DDL4 shown in FIG. Since the electrode finger pitch on the side closer to each other is formed long, transmission and reception of the SAW on the low frequency side are performed, and the electrode finger pitch on the side farther from the input / output electrodes is formed short, so that the SAW on the high frequency side is formed. Transmission and reception are performed. As a result, SAW-
In the DDL 4, the lower frequency signal of the frequency components of the input RF pulse is output earlier, and an up-chirp signal is generated.

Such a SAW-DDL has been put to practical use in radar systems. W. Arthur,
`` Modern SAW-Based Pulse Compression Systems For R
ader Applications ", Electronics & Communications
Engineering J. , Vol.7, No.6, pp. 236 −246 (19
95).

Here, the RF pulse sequence of the K channel generated by the pulse generator 3 at the time interval δT is nk
According to the differential data value D (nk) of the bit. When the time interval δTk (n) is set, the time interval δTk
(N) is represented by the following equation (1).

[0044]

(Equation 1)

Here, T ₀ is a reference interval (hereinafter also referred to as a reference time) corresponding to one bit of the differential data, and f ₀ is a reference frequency corresponding to the reference time T _0. This is a reference frequency for determining the amount of differential phase based on dynamic phase modulation, and has the relationship shown in the following equation (2).

[0046]

(Equation 2)

Here, Nb (Nb is a positive real number) means that one bit of the differential data is Nb times the period based on the reference frequency f ₀ .

Although the center frequency of the chirp signal generally generated is applied to the reference frequency f ₀ , even if the lower limit frequency (minimum frequency) or the upper limit frequency (maximum frequency) of the chirp signal is applied, the chirp signal is not affected. Other frequencies can be applied. Φ (nk) in the equation (1) is a differential phase amount at the reference frequency f ₀ corresponding to the n-bit value D (nk) of the k-th multiplexed data sequence.

From the equations (1) and (2), the time interval δT
k (n) is given by the following equation (3).

[0050]

(Equation 3)

Hereinafter, a case where the reference frequency f ₀ is set to the center frequency of the chirp signal will be described as an example.

The amount of differential phase φ (nk) is 2π / N radians. In the case of binary differential phase modulation, φ (nk) can be expressed by the following equation (4).

[0053]

(Equation 4)

Here, it is assumed that the compound ± takes a sign that the following equation (5) approaches nT ₀ .

[0055]

(Equation 5)

In the equation (1), the second term on the right side is a phase term, and the equation (4) is 0 or ± in the case of binary differential phase modulation.
0.5 / f ₀ , but the double sign ± nT ₀ as described above
Are taken.

In the multiplexing, the RF pulse time Tk (n) of the n-th bit of the k-th RF pulse train is expressed by the following equation (6).

[0058]

(Equation 6)

It is assumed that Here, Tl (ell) (n) is l
The RF pulse time of the n-th bit of the (L) -th RF pulse train, B is the frequency band of the window function, and γ is the spread rate of the pulse width depending on the window function during pulse compression. For example, in the case of a Hamming window function, γ = 2 (null point width). As an example, if B = 56 MHz and T ₀ = 1.5 μsec, it is theoretically possible to multiplex up to 42 with k = 42.

The above-mentioned plurality of superposed pulse trains are represented by S
By inputting to AW-DDL4, SAW-DDL
From 4 onward, each pulse train generates a chirp signal that spreads over a time width of T ₀ = 1.5 μsec without interruption, and the repetition of the chirp signal generated by each pulse train is superimposed and output. Therefore, at a specific time, frequency division multiplexing is performed, and when attention is paid to a specific frequency, a multiplexed modulated chirp signal subjected to time division multiplexing is transmitted. The multiplexed modulated chirp signal is amplified by the amplifier 5, and the amplified output is frequency-converted by the frequency converter including the local oscillator 6 and the mixer 7, amplified by the transmission power amplifier 8, and transmitted via the transmission / reception switch 9. Is supplied to the antenna 10 and transmitted from the antenna 10.

More specifically, pulse generator 3 and SA
The operation of W-DDL4 will be described with reference to FIGS. In FIG. 3, the pulse waveform is a waveform of a half cycle on the positive side of the RF pulse.

The RF pulse waveform for the first channel multiplexed in FIG. 3A (k = 1 in FIG. 3A) is multiplexed in FIG. 3B. In the case of the next channel (k =
2) is applied to the next channel multiplexed in FIG. 3C (FIG. 3).
(K = 3 in (c)) is shown as an example.

The case where the time interval δTk (n) is k = 1 on the basis of the differential code of the message data will be described as an example.

In the case of binary differential phase modulation, for example, the sign (phase) is not inverted from the first bit to the third bit, and the sign is inverted from the third bit at the fourth bit. It is assumed that the sign is inverted at the bit number.

The time interval δT ₁ (1) between the _first RF pulse and the second RF pulse is determined based on the data value of the first bit, and the time interval δT 1
₁ (1) is the same as the reference interval T ₀ . 2nd RF
Time interval δT ₁ between the pulse and the third RF pulse
(2) Sadamari based on the data values of the second bit is the same as the reference interval T _0.

The time interval δT ₁ (3) between the third RF pulse and the fourth RF pulse is determined based on the data value of the third bit, and the position of the broken line is the time interval δT
₁ Same as (1), but as shown by the solid line in the figure, 時間 of the reciprocal of the reference frequency f ₀ compared to the time interval δT ₁ (1).
Only being stretched.

[0067] fourth time interval? T ₁ (4) between the RF pulse and the fifth RF pulse Sadamari based on data values of the fourth bit, time from the dashed line position interval? T ₁
Same as (1), but is shortened from the generation time of the fourth RF pulse by １ ／ of the reciprocal of the reference frequency f ₀ .

As described above, these are based on the differential codes "0" and "1" of the message data. The same applies to FIGS. 3B and 3C, and a description thereof will be omitted.

The RF pulse shown in FIG. 3D on which the RF pulses shown in FIGS. 3A, 3B and 3C are superimposed is input to the SAW-DDL4. Here, assuming that one bit (also referred to as one symbol) of the differential data is spread by one chirp signal, the SAW-DDL4 to which the RF pulse sequence is input corresponds to the RF pulse of k = 1. A chirp signal having the waveform shown in FIG. The time interval δT indicated by a broken line in FIG.
₁ (3) The phase of the chirp signal based on the RF pulse after elapse is shifted by π at the reference frequency f ₀ ,
When the time interval δT ₁ (4) has elapsed, the phase of the chirp signal based on the RF pulse has returned to its original state.

The chirp signal waveforms shown in FIGS. 4B and 4C are chirp signal waveforms based on the RF pulses shown in FIGS. 3B and 3C.

Therefore, taking advantage of the fact that the SAW-DDL 4 is a time-invariant linear circuit, the SAW-DDL 4 is obtained by superimposing the chirp signals shown in FIGS. 4 (a), 4 (b) and 4 (c) on FIG. The chirp signal shown in (d) is transmitted. In this case, K = 3, and FIG.
A multiplexed modulated chirp signal, which is a spread spectrum modulated signal shown in FIG. 4D in which the chirp signals shown in FIGS. 4B and 4C are multiplexed, is output from the SAW-DDL 4 and transmitted.

Next, the receiving section RX of the spread spectrum multiplex communication apparatus according to one embodiment of the present invention will be described.

The transmitted spread spectrum modulated signal is received via antenna 10 and transmission / reception switch 9,
After being amplified by the amplifier 11, the frequency is converted by the frequency converter comprising the local oscillator 6 and the mixer 12, and the data demodulating SAW matched filter 13 provided with a plurality of input / output electrodes based on the phase shift of data is provided.
To be demodulated. The data demodulated outputs are respectively squared and rectified by squaring circuits 14 and 15, respectively. The squared outputs are supplied to a subtracting circuit 16 and an adding circuit 17 to perform subtraction and addition. Are demultiplexed by the demultiplexer 18 and transmitted.

SAW matched filter 13 for data demodulation
Is generally composed of an input electrode and an output electrode composed of a chirp electrode on the surface of a piezoelectric substrate.

FIG. 5 is a schematic diagram showing the configuration of the SAW matched filter 13 for data demodulation.

FIG. 5 shows an example of binary differential phase modulation in a spread spectrum multiplex communication apparatus according to an embodiment of the present invention. 2 shows a SAW matched filter 13 for two types of phase shift, namely, 0 radian phase shift and π
In response to the radian phase shift, a first system m1 of the input electrode 132, the output electrodes 133 and 134, and the input electrode 1
35, two systems of output electrodes 136 and 137 and a second system m2 are formed on the same piezoelectric substrate 131, and outputs are taken out from the output electrodes 134 and 137.

The input electrodes 132 and 135 are formed by chirp electrodes in which the electrode finger pitch gradually decreases from the input side.
In addition, a frequency-converted reception signal is supplied to each of the input electrodes 132 and 135. Output electrodes 133, 134,
136 and 137 are formed by chirp electrodes in which the electrode finger pitch gradually increases from the input side to the output side of the SAW, and the output electrode 133 and the output electrode 134 are separated by a distance (Nbλ ₀ ) described later at the center position. The output electrodes 133 and 1 are formed on the same piezoelectric substrate 131 and
34 is cascaded. Output electrodes 136 and 137
Means (Nbλ ₀ + λ ₀ /
Output electrodes 136 and 137 are formed on the same piezoelectric substrate 131 at a distance of 2), and the output electrodes 136 and 137 are connected in cascade so as to extract output from the output electrodes 134 and 137.

SAW matched filter 13 for data demodulation
The spread-spectrum modulated signal using the multiplexed and frequency-converted chirp signal input to the
2 and 135, and converted from an electric signal to SAW by the input electrodes 132 and 135. Input electrode 1
The SAW converted by 32 and 135 is the piezoelectric substrate 1
31.

Here, S propagating on the piezoelectric substrate 131
The AW has a phase difference corresponding to the data between two sweeps of the chirp signal (two bit periods) based on the message data. For example, when demodulating a signal that has been subjected to 0 radian or π radian phase modulation at the center frequency of the chirp signal between two sweeps, the differential phase-modulated chirp signal is applied to the input electrodes 132 and 135 at 0 radian or 135 radian. It is converted into a SAW having a phase difference of π radians and propagates on the piezoelectric substrate 131.

Conversion by input electrodes 132 and 135
The SAW for the two sweeps is divided into the two
The output electrodes 133 and 134 and the two
Output electrodes 136 and 137 respectively.
You. At this time, the waveform corresponds to two cycles of the chirp signal
And two cascaded output electrodes
In the first system m1 side, the output electrode 133 and
134 is the reference frequency f₀, Reference time T₀From (2)
Using Nb obtained by the equation, Nbλ
₀The output electrode 136 and the output electrode 136 are provided on the second system m2 side.
137 is Nbλ at the center position.₀To λ₀1/2 of
It is provided in isolation between additions. Where λ ₀Is the reference frequency
Number f₀Is the wavelength of the SAW.

Assuming that the speed of the SAW is v, the wavelength λ ₀ of the SAW is expressed as shown in the following equation (7).

[0082]

(Equation 7)

Accordingly, the interval Lp between the output electrodes of the first system m1 and the second system m2 is as shown in the following equation (8). Here, p is as shown in equation (9).

[0084]

(Equation 8)

[0085]

(Equation 9)

The difference between the value obtained by dividing the interval Lp between the output electrodes by the speed v of the SAW is the delay time difference Tp of the SAW between the output electrodes, and can be expressed by the following equation (10).

[0087]

(Equation 10)

Here, the time interval δTk of the RF pulse generation
Compared with (n), according to the equations (3) and (10), the output electrodes 133 and 134 on the first system m1 side or the output electrodes 136 and 137 on the second system m2 side have the same phase or the opposite phase. And the modulation phase difference φ (nk) can be detected.

In other words, with this arrangement, when the two-cycle chirp signal has a phase difference of 0 radian, that is, the SAW having a phase difference of 0 radian is applied to the piezoelectric substrate 1.
When propagating on the output line 31, the in-phase addition is performed by the output electrodes 133 and 134, and the anti-phase addition is performed by the output electrodes 136 and 137.
4 and an output based on the differentiated code is sent out,
When the two-period chirp signal has a phase difference of π radians, that is, the SAW having a phase difference of π radians
When the signal propagates over 1, the output electrodes 133 and 134 add the opposite phases, and the output electrodes 136 and 137 add the same phase. Therefore, the differential signal is output only from the output electrode 137 of the second system m2. An output based on the code is sent.

SAW matched filter 13 for data demodulation
The output from is, for example, as shown in FIG. FIG.
FIG. 6A shows a waveform of an output from the first system m1, and FIG.
(B) shows the waveform of the output from the second system m2.

The operation of the data demodulating SAW matched filter 13 is shown in Table 1 below.

[0092]

[Table 1]

As described above, the output from the output electrode 134 and the output from the output electrode 137 are output in conflict with each other in accordance with the differential data, and the data is demodulated. Here, this operation of the data demodulating SAW matched filter 13 is also referred to as performing a correlation operation over two consecutive periods based on the phase shift of data.

SAW matched filter 13 for data demodulation
Are squared by squaring circuits 14 and 15, and the output of squaring circuit 15 is subtracted from the output of squaring circuit 14 through a low-pass filter (not shown).
7 from the subtraction circuit 16 as shown in FIG.
The output shown in FIG. This output corresponds to an output based on the message data. For example, the positive side corresponds to “1” of the message data, and the negative side corresponds to “0” of the message data.

The output of the squaring circuit 14 and the output of the squaring circuit 15 that have passed through the low-pass filter (not shown) are added by an adding circuit 17, and an output such as that shown in FIG. . This output indicates the timing at which the message data is being output.

The output from the subtraction circuit 16 and the output from the addition circuit 17 are supplied to a demultiplexer 18, and the output from the subtraction circuit 16 is demultiplexed and transmitted at the timing of the output from the addition circuit 17.

In the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention, since the frequency of the chirp signal changes gradually, when the time-shifted addition is performed, the vector addition of the added signal is always 2π. The signals are rotated and added while continuously changing in radians, and if the signals are observed over time, a signal having a substantially averaged amplitude is synthesized. Therefore, the envelope of the phase-combined signal becomes zero when the spread spectrum signal is time-shift multiplexed with the same carrier frequency by the spread code, or the envelope of the added signal varies significantly in an extreme case. The problem that the problem does not occur is obtained.

Further, according to the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention, a data-modulated chirp signal can be easily generated and multiplexed at the same time. DPS multiplexed with a simple configuration to perform correlation detection using
An effect of generating a K-modulated chirp signal and performing spread spectrum demodulation is also obtained.

FIG. 8 shows an example of a bit error rate characteristic for a multiplexed chirp signal in the case of the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention. In FIG. 8, the solid line indicates the theoretical value, １ indicates the case of one-signal multiplexing, Δ indicates the case of two-signal multiplexing, □ indicates the case of three-signal multiplexing, Δ indicates the case of four-signal multiplexing, ◇ indicates the case of 7 signal multiplexing, X indicates the case of 8 signal multiplexing, and ● indicates the case of 9 signal multiplexing. As can be seen from FIG. 8, a characteristic with almost no deterioration due to multiplexing is obtained.

In the above-described spread spectrum multiplex communication apparatus according to the embodiment of the present invention, the SAW-D
In the DL4, the case where both the input and output electrodes are formed by chirp electrodes is illustrated, but one of the input electrode and the output electrode may be formed by chirp electrodes. In the data demodulating SAW matched filter 13, the case where both the input and output electrodes are formed by chirp electrodes is illustrated, but at least one of the input electrode and the output electrode may be formed by chirp electrodes.

In the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention described above, the case of binary differential phase modulation has been exemplified. You may. For example, in the case of ternary differential phase modulation, three matched filters are prepared as in the case shown in FIG. 5, and the positions of the two chirp electrodes constituting the output electrodes of each system are set to the center frequency of the chirp signal. In this case, it may be arranged so that they are different from each other by ３ wavelength.
Only one of the three output electrodes is added in-phase to a signal that has been subjected to differential phase modulation with a phase difference of π / 3 radian or 4π / 3 radian, and the ternary value Demodulation of differential phase modulation data is also possible. Similarly, it is possible to cope with the case of differential phase modulation of four or more values.

In the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention, the reference frequency f
_{Although the} case where differential phase modulation is performed using ₀ as the center frequency of the chirp signal is illustrated, it is not particularly necessary to perform multi-level modulation of two or more values at the center frequency of the chirp signal.
Differential phase modulation may be performed using ₀ as the maximum frequency of the chirp signal, or differential phase modulation may be performed using the reference frequency f ₀ as the minimum frequency of the chirp signal. When demodulating a signal that has been differentially phase-modulated by the maximum frequency of the chirp signal, the wavelength based on the maximum frequency of the chirp signal is placed between the two output electrodes constituting each system in the data demodulating SAW matched filter 13. What is necessary is just to give a difference of 1/2 of λ ₀ . When demodulating a signal that has been differentially phase-modulated by the minimum frequency of a chirp signal, the
In the W-matched filter 13, a difference of 波長 of the wavelength based on the minimum frequency of the chirp signal may be provided between the arrangements of the two output electrodes constituting each system. It is.

Furthermore, although the above-described data demodulating SAW matched filter 13 has been described for the case of an up-chirp signal, the same can be applied to the case of a down-chirp signal.

[0104]

As described above, according to the spread spectrum multiplex communication apparatus of the present invention, the modulator generates N by changing the time interval of the input RF pulse from the reference interval corresponding to one bit of data. A high-frequency pulse (the number of multiplexed channels minus one) is input between each of the input RF pulses to the input electrode of the SAW-DDL that performs the value differential phase modulation, and is multiplexed between each of the input high-frequency pulses. The present invention can be configured by a surface acoustic wave dispersion type delay line having an output electrode for transmitting a multiplexed chirp modulated signal modulated by the converted N-valued differential phase data, and the configuration is simplified.

As described above, according to the spread spectrum multiplex communication apparatus of the present invention, the demodulator uses the reference frequency for determining the amount of differential phase from the reference interval corresponding to one bit of data. An input electrode that receives a multiplexed modulated chirp signal obtained by multiplexing an N-valued differential phase modulation chirp signal that changes in a phase step of 2π / N radians and a surface acoustic wave corresponding to the input electrode and converted by the input electrode Two output electrode pairs connected in cascade in the propagation path are connected to N
A system comprising a surface acoustic wave matched filter having a center position of two output electrodes forming each system shifted by λ ₀ / N when a propagation wavelength of a surface acoustic wave having a reference frequency is λ _0. This has the effect of simplifying the configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a spread spectrum multiplex communication device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a configuration of a SAW-DDL in the spread spectrum multiplex communication apparatus according to one embodiment of the present invention.

FIG. 3 is a waveform chart for explaining an input to a SAW-DDL in the spread spectrum multiplex communication apparatus according to the embodiment of the present invention.

FIG. 4 is a waveform chart for explaining an output from a SAW-DDL in the spread spectrum multiplexing communication apparatus according to the embodiment of the present invention.

FIG. 5 is a schematic perspective view showing a configuration of a SAW matched filter in the spread spectrum multiplex communication device according to one embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of a SAW matched filter in the spread spectrum multiplex communication apparatus according to one embodiment of the present invention.

FIG. 7 is a waveform diagram of an input signal of a demultiplexer in the spread spectrum multiplex communication device according to one embodiment of the present invention.

FIG. 8 is a bit error rate characteristic diagram for a multiplexed chirp signal in a spread spectrum multiplexing communication apparatus according to one embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional digital encoded chirp carrier device.

FIG. 10 is a block diagram showing a configuration of a conventional transmitter using a chirp signal for spread spectrum.

FIG. 11 is a block diagram showing a configuration of a conventional receiver using a chirp signal for spread spectrum.

12 is a waveform chart for explaining the operation of the receiver shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Differential encoder 3 Pulse generator 4 SAW-DDL 9 Transmission / reception switch 13 SAW matched filter for data demodulation 14 and 15 Square circuit 16 Subtraction circuit 17 Addition circuit 18 Demultiplexer 41 and 131 Piezoelectric substrate 42, 132 and 135 Input electrode 43 , 133, 134, 136 and 137 Output electrodes m1 and m2 First and second systems

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-172338 (JP, A) JP-A-2-121424 (JP, A) JP-A-3-162146 (JP, A) JP-A-5-162146 276141 (JP, A) "Latest spread spectrum communication system", R.A. C. Dixon, translated by Tateno et al., November 1978, published by The Japan Techno-Economic Center, pp. 42-46 (58) Fields investigated (Int. Cl. ⁶ , DB name) H04J 13/02 H03H 9/44

Claims (5)

(57) [Claims] 1. A spread-spectrum multiplexing communication apparatus using a chirp signal for spread spectrum, wherein a time interval between input high-frequency pulses is changed from a reference interval corresponding to one bit of data. Is applied to the input electrode of the surface acoustic wave dispersion type delay line that performs N-valued differential phase modulation on the input high-frequency pulse with the input high-frequency pulse, where K is the number of multiplexed channels and K is the number of multiplexed channels. A spread-spectrum multiplexing communication device comprising, as a modulator, a surface-acoustic-wave dispersion-type delay line for transmitting an N-valued differential phase-modulated chirp signal inputted and multiplexed between respective pulses from an output electrode. . 2. A spread-spectrum multiplexing communication apparatus using a chirp signal for spread spectrum, wherein a time interval of an input high-frequency pulse is determined based on a reference period corresponding to one bit of data. 2π based on frequency
The number of multiplexed channels together with the input high-frequency pulse is represented by K, at the input electrode of a surface acoustic wave dispersion type delay line that performs N-valued differential phase modulation between chirp signals generated by changing the phase step by / N radians. When the number (K-
A) a surface acoustic wave dispersion type delay line for transmitting a multiplexed N-valued differential phase modulation chirp signal from an output electrode by inputting the high-frequency pulse between each of the input high-frequency pulses; A spread spectrum multiplexing communication device characterized by the above-mentioned. 3. A spread spectrum multiplex communication apparatus according to claim 1, wherein the input electrode and the output electrode are chirp electrodes. 4. A spread spectrum multiplex communication apparatus according to claim 1, wherein one of the input electrode and the output electrode is a chirp electrode. 5. A spread-spectrum multiplexing communication apparatus using a chirp signal for spread-spectrum, wherein 2π /／ is determined based on a reference frequency for determining a differential phase amount from a reference interval corresponding to one bit of data. An input electrode to which a multiplexed chirp-modulated signal obtained by multiplexing an N-valued differential phase-modulated chirp signal varying in a phase step of N radians is input, and a surface acoustic wave corresponding to the input electrode and converted by the input electrode Two output electrode pairs connected in cascade in the propagation path are connected to N
System, and the surface acoustic wave propagation wavelength of the reference frequency is λ ₀
In this case, the two output electrodes forming each system are provided with their positions shifted by λ ₀ / N at their center positions, and at least one of the input electrode and the output electrode pair is a surface acoustic wave having a chirp electrode. A spread spectrum multiplex communication device comprising a matched filter as a demodulator.