JP2001217681A - Surface acoustic wave convolver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide surface acoustic wave convolver as a wide-band variable delay line type correlator, which is widely adaptive to high-speed SS radio data transmission, a millimeter wave radar of an ITS, etc. SOLUTION: First and second surface acoustic wave transducers 111 and 112 and output electrodes 121 and 122 have multitrack structure, composed of plural groups each of one track, and the output electrodes 121 and 121 are each divided into plural output electrode pieces, which are equal in the number of pieces among the groups and all equal in the length and division ratio. Furthermore, cascade connecting circuits 123 and 124 and an external control circuit 125 are provided as a means which combines some or all of output electrode pieces by the groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface acoustic wave convolver used for a device for performing high-speed signal processing in real time in a spread spectrum (SS) communication system.

[0002]

2. Description of the Related Art An SS receiver using a surface acoustic wave convolver as a correlator of the SS wireless communication system has already been commercialized. FIG. 2 shows a schematic structure of a conventional surface acoustic wave (SAW) convolver. In FIG. 2, reference numeral 17 denotes a first surface acoustic wave converter having IDTs composed of positive and negative electrodes, which receives a received signal 11 and converts the electric signal into a surface acoustic wave. Reference numeral 18 denotes a second surface acoustic wave converter, which receives the reference signal 12 and converts an electric signal into a surface acoustic wave in the same manner as the first surface acoustic wave converter 17. An output electrode 13 extracts a convolution output 16 of the surface acoustic wave propagated from the surface acoustic wave converters 17 and 18 as an electric signal. These surface acoustic wave converters 1
The electrodes 7, 18 and the output electrodes 13 are provided on a piezoelectric substrate (including a piezoelectric thin film substrate) 14 or an electrostrictive substrate.

The surface acoustic wave convolver shown in FIG. 2 propagates two surface acoustic waves corresponding to a received signal and a reference signal from oppositely disposed surface acoustic wave converters 17 and 18 in opposite directions. They are superimposed on the output electrode 13 arranged between the two surface acoustic wave converters 17 and 18. As a result, the two surface acoustic waves are multiplied, and a voltage having a double frequency is generated at the output electrode 13. That is, a convolution output (convolution output 16) of two input signals (the reception signal 11 and the reference signal 12) is obtained. Since the surface acoustic wave convolver can externally set a reference signal arbitrarily in accordance with a received signal, it is suitably used as a programmable correlator in a despreading (SS demodulation) circuit of an SS receiver. In such a surface acoustic wave convolver, a wideband chirp type surface acoustic wave converter that strengthens a surface acoustic wave in one direction is employed to reduce insertion loss.

[0004] With the recent increase in the frequency of wireless communication, there has been an increasing demand for devices in the GHz band.
With respect to the surface acoustic wave convolver, the conventional SAW convolver operates at a frequency lower than the VHF band (for example, 200 MHz band). It was difficult to reduce the size. The problem is that, as a result of the shift of the operating frequency to ultra-high frequency, the length of the input / output electrodes is made thinner and shorter by ultra-fine processing to form a device in the 1 GHz band, and an IF such as spread spectrum communication in the millimeter wave band.
It can be solved by using it as an (intermediate frequency) correlator.

[0005]

On the other hand, an intelligent transport system (Intelligent Transport)
Systems: hereinafter referred to as “ITS”)
In the S-millimeter wave radar, the time required for a radio wave to reciprocate between an antenna and an object is measured. Therefore, if the delay line (output electrode) is short, it is not suitable for measuring a distance longer than a medium distance (for example, 100 m or more). . Therefore, in the conventional SAW convolver for data communication, the length of the output electrode is short,
A SAW convolver for the VHF band corresponding to the SS data communication has a problem that the spreading bandwidth is narrow and, as a result, the distance resolution is poor, so that it cannot be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a wideband variable delay line type surface acoustic wave convolver that can be widely used for high-speed wireless SS data transmission and high-resolution millimeter wave radar of ITS. The task is to

[0007]

In order to solve the above problems, a surface acoustic wave convolver according to the present invention comprises first and second surface acoustic wave convolvers.
Disposed between the first and second chirped surface acoustic wave converters by weighting for exciting respective surface acoustic waves, and between the first chirped surface acoustic wave converter and the second chirped surface acoustic wave converter A surface acoustic wave convolver comprising: a first set of output electrodes and a second set of chirped surface acoustic wave converters;
The track has a multi-track structure composed of a plurality of sets, each of the output electrodes is divided into a plurality of output electrode pieces, the number of the output electrode pieces is the same in all the sets, and the length of the output electrode pieces is the same. Are all equal.

In the present invention, the first chirp type surface acoustic wave converter is a unidirectional chirp type surface acoustic wave converter that strongly excites a surface acoustic wave in one direction, and the second chirp type surface acoustic wave converter is the second type.
Is preferably a unidirectional or bidirectional chirped surface acoustic wave converter.
Further, it is preferable that a means for combining a part or all of the plurality of output electrode pieces for each set is further provided.

[0009]

In the surface acoustic wave convolver according to the present invention, the length of the delay line can be selected by cascading a plurality of divided output electrode pieces for the output electrode (delay line). In other words, for the high-speed data communication, the waveguide of the divided central delay line (output electrode piece having a short length) is selected, and S
For S millimeter wave radar, a long delay line can be secured by cascading and combining the output electrode pieces.

A surface acoustic wave convolver according to the present invention comprises a first unidirectional chirped surface acoustic wave converter by weighting and a second unidirectional or bidirectional chirped surface acoustic wave converter by weighting and output. Because the electrodes are configured in a multi-track structure consisting of multiple sets,
S by parallel combination corresponding to high-speed SS data communication
It can also support S parallel data transmission.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a main part of a wideband variable delay line type elastic surface acoustic wave convolver having a multitrack structure according to an embodiment of the present invention. In the figure, reference numeral 111 denotes a unidirectional chirped surface acoustic wave converter based on a first weighting to which a received signal is input, and 112 denotes a unidirectional or bidirectional chirped surface acoustic wave converter according to a second weighting to which a reference signal is input. It is a surface wave converter. First
The surface acoustic wave converter 111 includes a first interdigital transducer having a positive electrode 113 and a negative electrode 117, and a third interdigital transducer having a positive electrode 114 and a negative electrode 117. That is, the first surface acoustic wave converter 111
Has a parallel structure of a first interdigital electrode and a third interdigital electrode. The second surface acoustic wave converter 112 also corresponds to the first surface acoustic wave converter 111 and has a positive electrode 115.
And a negative electrode 118 (second interdigital electrode), and a parallel structure of a positive electrode 116 and a negative electrode 118 (fourth interdigital electrode).

Reference numeral 121 denotes an output electrode (delay line) corresponding to the first and second interdigital electrodes, and is composed of a plurality of output electrode pieces 121a, 121b and 121c. The first and second interdigital electrodes and the output electrode 121 form a first track. Reference numeral 122 denotes an output electrode (delay line) corresponding to the third IDT and the fourth IDT, and a plurality of output electrode pieces 122a and 122a.
2b and 123c. The third and fourth interdigital electrodes and the output electrode 122 form a second track. That is, the SAW convolver of FIG. 1 has a multi-track structure including the first and second tracks.

Reference numeral 123 denotes a cascade connection circuit for cascade-connecting the output electrode pieces to combine a plurality of output electrode pieces of the output electrode 121 of the first track, and has output terminals outA and outB and an external SW 137. The cascade connection circuit 123 forms an output electrode of the first track by combining suitable lengths of the output electrode pieces,
Extract the convolution output signal from each output terminal. Reference numeral 124 denotes a cascade connection circuit for cascade-connecting the output electrode pieces in order to combine a plurality of output electrode pieces of the output electrode 124 of the second track, and an output terminal out.
A ′, outB ′ and an external SW 137 are provided.
The cascade connection circuit 123 forms an output electrode of the first track by combining suitable lengths of the output electrode pieces, and extracts a convolution output signal from each output terminal.

In FIG. 1, cascade connection circuit 123
Connects the output electrode piece 121a and the output electrode piece 121c,
The cascade connection circuit 124 connects the output electrode piece 122a and the output electrode piece 122c. The first track side outputs the delay line length 2L from the output terminal outB, and the second track side outputs the delay line length 2L from the output terminal outA '. select. Also,
The external SW control circuit 125 simultaneously turns ON / OFF the output electrodes 121 and 122 of the first track and the second track.
It is means for turning off. 119 is a first surface acoustic wave converter 111 (first and third interdigital transducers 113, 11).
4, 117 parallel structures), the second surface acoustic wave converter 11
2 (second and fourth IDTs 115, 116, 1
18 in parallel) and the shield electrodes between the output electrodes 121 and 122.

131 and 135 are band-pass filters (B
PF) and 132 are orthogonal PN (pseudo noise) oscillators (OS
C) 133 is a PLL frequency synthesizer, 134, 1
Numeral 36 denotes a double balanced modulator (DBM), which respectively constitutes an external circuit. The external circuit is a circuit for generating the SS reference signal.

The first surface acoustic wave converter 111 has two terminals for inputting a received signal (IN1 and IN1 in the figure).
3) Yes. Each terminal is arranged on the positive electrode side 113 and 114 of the unidirectional chirp type IDT by weighting, respectively, and the negative electrode 117 is common. Corresponding to the first surface acoustic wave converter 111, the second surface acoustic wave converter 112 is constituted by a unidirectional or bidirectional chirp type IDT by weighting, and has two input terminals for the reference signal.
It has terminals (IN2 and IN4). The first and second surface acoustic wave converters 111 and 112 each have a unidirectional or bidirectional chirp type IDT by weighting.
Are made in a parallel structure with a common negative electrode. These unidirectional or bidirectional broadband chirp type IDTs are disclosed in JP-A-7-212184 and JP-A-6-212184.
-260881 or the like can be used. In other words, the first and second surface acoustic wave converters 111 and 112
Are disclosed in JP-A-7-212184 and JP-A-6-260.
No. 881 and other chirp type IDTs are constructed in parallel. These chirp type IDTs are characterized by high convolution efficiency, wideband characteristics, low insertion loss, flat frequency characteristics, and low ripple.

In FIG. 1, the output electrodes 121 and 122 also correspond to the parallel structure of the first and second surface acoustic wave converters 111 and 112, and are provided on the first track side.
An output electrode 122 is arranged on the second track side, and a convolution output is extracted from the output electrodes 121 and 122 as an electric signal by correlating a received signal with a reference signal from an external circuit. Here, the output electrodes 121 and 12
In order to correspond to the data transmission speed signal to be received, the length 2 is composed of a plurality of divided output electrode pieces, and is compatible with various SS modulation / demodulation methods by the cascade connection circuits 123 and 124 and the external SW control circuit 125. By providing a multi-track configuration (combining the length of each output electrode piece to form an output electrode length) to provide a SAW convolver that becomes a wideband variable delay line correlator.

The length (gate electrode) of one output electrode piece of the output electrodes 121 and 122 is L in the first track in the drawing.
The second track also becomes L, and part or all of this output electrode piece is connected to the cascade connection circuits 123 and 124 and the external S.
DPSK combined by W control circuit 125
It also supports differential detection, which is a demodulation method of. For example, DP
The method of using the output electrode for the SK demodulation method (adopting the delay detection) is such that a portion corresponding to one bit of high-speed data (one cycle of PN) has an output electrode having a length L at the center of the output electrode 121 of the first track. Envelope detection is performed using the piece 121b and the remaining 2L of the output electrode pieces 121a and 121c except for the center of the output electrode 122 of the second track delayed by one bit of data. At that time, the output terminal out
A and outA 'to the external DBM Lo. The signal is input to each RF port (not shown), and an envelope detection waveform of a convolution signal having a phase difference of 180 ° corresponding to data H and L is output from the IF port. When 1 bit of low-speed data (1 cycle of PN), the first track is combined with a total of 3 L and the second track is combined with a total of 3 L, and envelope detection of a convolution signal is performed corresponding to data H and L as in the case of high-speed data. .

The reason for dividing the output electrodes 121 and 122 is to increase the output efficiency.
It is designed in consideration of an optimum division ratio that facilitates impedance matching of 1,122. Here, the output electrode 12
The number of divisions of 1,122 is the same in the first track and the second track. Although the number of divisions is three in the first and second tracks in FIG. 1, the number of divisions may be three or more. In that case, the external control circuit system also differs. Basically, it is preferable to configure with a small number of SWs. By cascading the division numbers, the present invention can be applied to a high-resolution distance measuring correlator or the like by the SS method using a long output electrode. Also, as shown in FIG. 1, the gate electrode has a first track and a second track.
This device is configured by setting all the tracks to the same length (ratio). Dotted lines shown at the right and left ends of the output electrodes 121 and 122 for each of the left and right IDTs and each track in the drawing indicate that there are a plurality of output electrode pieces.

Further, the multi-track structure of the SAW convolver of this embodiment can be used as a device such as an M-ary / DS-system and a parallel combination DS-system, and can use Wideband-CDMA (US standard communication system IS). (Established in 1995 as −665). First and second surface acoustic wave converters 11
Arrows shown below 1, 112 and the output terminal outA 'indicate that the present surface acoustic wave convolver is vertically arranged to correspond to various SS modulation / demodulation methods. Furthermore, the SAW convolver of the present embodiment is a correlator device for a wideband and ultra-high-speed synchronization that can cope with a wide range because the length of an output electrode (delay line) can be varied by a cascade connection circuit of each output electrode piece.

The above is the description of the present embodiment.
The main specifications of a wideband variable delay line type elastic SAW convolver device having a multi-track structure developed by the present inventors are shown below. (1) Center frequency (used in IF band): f ₀ = 1000M
Hz (2) Maximum spreading bandwidth (main lobe width): BW = 40
0 MHz MAX (3) Minimum delay time: T = 0.155 μs (31 chip length) (4) Efficiency (f ₀ = 2000 MHz): * Ft = −50
dBm * Ft = 10log (Pout / Pin1, Pin2
...) (when Pin1 and Pin2 = 1 mW) (5) BT product (B = 400 MHz, T = 5.115 μm)
s): BT = 2046 (T = 1023 chip length) (6) Output frequency: f _out = 2000 MHz (7) Maximum input power: Pin = + 25 dBm (8) Dynamic range: D = 70 dB or more (9) Input / output impedance : Zio = 50Ω (10) Longest chip: Cip = 1023

[0022]

The surface acoustic wave convolver according to the present invention comprises:
Being configured in a multi-track structure, having an output electrode divided into a plurality of output electrode pieces having the same length, and having means for combining some or all of the plurality of divided output electrode pieces; and By adopting a unidirectional or bidirectional chirp type IDT that supports wide bandwidth, it can be used as a correlator for parallel data transmission etc. for high speed SS data communication, and as a correlator for high resolution SS millimeter wave radar in ITS Can be used together. In particular,
By dividing the output electrode into a plurality of output electrode pieces having the same length, it is possible to provide a high-speed broadband device that can widely support high-speed data communication, high-resolution long-distance measurement, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part of a wideband variable delay line type elastic SAW convolver having a multi-track structure according to an embodiment of the present invention.

FIG. 2 is a schematic structural view of a conventional surface acoustic wave convolver.

[Explanation of symbols]

11: reception signal, 12: reference signal, 13: output electrode, 1
4: piezoelectric substrate, 15: ground electrode, 16: convolution output, 17: first surface acoustic wave converter, 1
8: second surface acoustic wave converter, 111: first surface acoustic wave converter, 112: second surface acoustic wave converter, 113,
115: Positive electrode of first track, 114, 116: Second electrode
Track positive electrode, 117: negative electrode of first track, 1
18: negative electrode of the second track, 119: shield electrode
121: output electrode (delay line) of the first track, 122:
Output electrode (delay line) of the second track, 123: cascade connection circuit of the first track, 124: cascade connection circuit of the second track, 125: external SW control circuit, 131, 135: band pass filter (BPF),
132 orthogonal PN (pseudo noise) oscillator (OSC), 13
3: PLL frequency synthesizer, 134, 136: double balanced modulator (DBM).

Continuation of the front page (72) Inventor Shunji Kato 1-28-22 Atago, Ageo-shi, Saitama Arai No. 2 Building 602 F-term (reference) 5J097 AA09 AA19 BB08 CC09 CC13 5K022 EE02 EE33

Claims (3)

[Claims] 1. A first and second chirped surface acoustic wave converter by weighting for exciting first and second surface acoustic waves, respectively, the first chirped surface acoustic wave converter and a second A surface acoustic wave convolver having an output electrode disposed between the chirp type surface acoustic wave converters, wherein the first and second chirp type surface acoustic wave converters and the output electrode form one set as one track. It has a multi-track structure consisting of a plurality of sets, the output electrodes are each divided into a plurality of output electrode pieces, the number of the output electrode pieces is the same in all sets, and the length of the output electrode pieces is A surface acoustic wave convolver characterized by all being equal. 2. The first chirp type surface acoustic wave converter is a one-way chirp type surface acoustic wave converter that strongly excites a surface acoustic wave in one direction, and the second chirp type surface acoustic wave converter. The surface acoustic wave convolver according to claim 1, wherein the device is a unidirectional or bidirectional chirped surface acoustic wave converter. 3. The surface acoustic wave convolver according to claim 1, further comprising means for combining a part or all of the plurality of output electrode pieces for each set.