JP2006174255A - Surface acoustic wave device, radio transmitter, and radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve influence caused by a direct wave in a tapped SAW delay line, to improve dynamic range, and to enable circuit constitution of an ultra-wideband radio transmitter and receiver to be simple. <P>SOLUTION: Two tapped SAW delay lines each having the same constitution are to be disposed so as to be line symmetry, to be connected in parallel in an input side, and to be connected in serial in an output side, wherein at least one of taps from among taps which are held by the two tapped SAW delay lines has its tapped electrode finger of the tap to be disposed at a position different from the other all taps in propagation distance of the surface acoustic wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave (SAW) device, a radio transmitter, and a radio receiver suitable for use in a radio transceiver such as an ultra wide band (UWB) communication system.

  Conventionally, there is a technique for reducing the influence of a direct wave in a surface acoustic wave device. For example, Patent Document 1 discloses that a noise component that directly reaches an output bonding wire from an input bonding wire is reduced, and a correlation peak signal is stabilized. According to this conventional invention, in a surface acoustic wave matched filter having two “output IDTs (Inter Digital Transducers)” (output transducers) and two input IDTs (input transducers) to which the same signal is input, The first output IDT is arranged along the propagation direction of the surface acoustic wave excited by the first input IDT, and the second output IDT is arranged along the propagation direction of the surface acoustic wave excited by the second input IDT. The two output IDTs are arranged so that the phase relationship of the first output IDT with respect to the first input IDT and the phase relationship of the second output IDT with respect to the second input IDT are shifted by 180 °. Further, the output peak signal from the first output IDT and the output peak signal from the second output IDT are taken out as differential output signals.

  By the way, as a UWB communication system, a method is conceivable in which one data is divided into a plurality of pulse trains encoded by a PN code and transmitted. As a transceiver for realizing this, a method using a surface acoustic wave device as a correlator is conceivable. UWB communication is a system that communicates at a frequency of 3 to 10 GHz. However, if a correlator using a surface acoustic wave device is used, a digital circuit that generates an ultra-high speed clock of 3 to 10 GHz is not required. The circuit can be simplified.

The surface acoustic wave device is composed of a SAW delay line with tapped taps provided in a transducer. Such a tapped SAW delay line operates exactly the same as a transversal filter in an electric circuit and has a signal processing function. Since the SAW propagates while concentrating energy on the substrate surface, the signal can be sampled and extracted by arranging the transducer at an appropriate position in the propagation path.
That is, in UWB communication, by arranging a tap made of a transducer in accordance with a pulse train to be received, a strong correlation value is output from the output transducer when a necessary pulse train is input. FIG. 8 is a diagram showing a basic structure of a conventional tapped SAW delay line.

  A technique related to an ultra-wideband radio transmitter and an ultra-wideband radio receiver using a surface acoustic wave device as a matched filter is disclosed in Patent Document 2, for example. FIG. 9 is a block diagram illustrating a configuration of a transmission unit of a conventional two-dimensional pulse position modulation system. In FIG. 9, the pulse signal generated by the pulse generator 101 is input by the distributor 102 to the switch 103 and the surface acoustic wave delay line 104a. The surface acoustic wave delay line 104a outputs a reference signal obtained by giving a delay time t1 to the pulse signal to the synthesizer 106. The surface acoustic wave delay line 104a has a structure that defines a spreading code PN0, and the reference signal is a code spread by the spreading code PN0. The surface acoustic wave delay line 104 b outputs a signal given a delay time (t 1 + τ) to the pulse signal input through the switch 103 to the combiner 106 through the switch 105. This output signal is output with a delay time τ from the reference signal. The surface acoustic wave delay line 104 c outputs a signal obtained by giving a delay time (t 1 −τ) to the synthesizer 106 via the switch 105 with respect to the pulse signal input via the switch 103. This output signal is output earlier than the reference signal by a delay time τ. The surface acoustic wave delay lines 104b and 104c have a structure that defines the spreading code PN1, and the output signals from the surface acoustic wave delay lines 104b and 104c are codes spread by the spreading code PN1. The control circuit 109 synchronizes and switches the switches 103 and 105 to the surface acoustic wave delay line 104b side or 104c side according to the transmission data. The synthesizer 106 synthesizes the reference signal from the surface acoustic wave delay line 104 a and the output signal from the surface acoustic wave delay line 104 b or 104 c and outputs the synthesized signal to the amplifier 107. The synthesized signal is transmitted from the antenna 108 after being amplified by the amplifier 107.

FIG. 10 is a block diagram illustrating a configuration of a receiving unit of a conventional two-dimensional pulse position modulation system. In FIG. 10, a signal received by the antenna 201 is amplified by the amplifier 202 and then input to the surface acoustic wave delay lines 204 a and 204 b by the distributor 203. The surface acoustic wave delay line 204 a detects a spread code spread by a spread code PN 0 having a delay time t 2 from the input signal, and outputs an output signal to the delay time measuring unit 205. The surface acoustic wave delay line 204b detects a spread code spread by the spread code PN1 of the delay time t2 from the input signal, and outputs an output signal to the delay time measuring unit 205. The delay time measuring unit 205 detects which of these two output signals is input first. The data determiner 206 demodulates the received data based on the detection result of the delay time measurement unit 205.
Japanese Patent Application No. 2003-434822 is a prior application of an invention relating to a surface acoustic wave device that has not been disclosed at the time of filing of the present application.
JP-A-10-335975 JP 2004-173082 A

However, when the above-described SAW delay line with a tap is applied to a transceiver of a UWB communication system, the frequency must be operated at a high frequency of 3 to 10 GHz. At such a high frequency, the capacitive coupling between the input and output increases, and electromagnetic waves (direct waves) that propagate directly between the input and output terminals increase, resulting in a significant deterioration of the dynamic range.
As a method for solving this problem, it may be possible to cancel the electric capacity between the input and output by performing balanced driving. However, the tapped SAW delay line has a poor symmetry of the output transducer on the structure, so that even if balanced driving is performed as it is, the direct waves are not canceled and the dynamic range cannot be improved.

  Also, as shown in FIG. 9, the transmitter unit requires three surface acoustic wave delay lines, and the receiver unit requires two surface acoustic wave delay lines. In addition, the circuit configuration of the receiver becomes complicated. This can be a factor that hinders downsizing of the apparatus.

  The present invention has been made in view of such circumstances, and an object of the present invention is to improve the dynamic range by improving the influence of direct waves in a tapped SAW delay line, and further to an ultra-wideband. An object of the present invention is to provide a surface acoustic wave device capable of simplifying the circuit configuration of a radio transmitter and a receiver.

  Another object of the present invention is to provide a radio transmitter and receiver including the surface acoustic wave device of the present invention.

  In order to solve the above problems, a surface acoustic wave device according to the present invention includes an input transducer and an output transducer formed on a piezoelectric substrate, and the surface acoustic wave generated by the input transducer in response to an input signal is transmitted to the output transducer. The two tapped SAW delay lines having the same structure are arranged so as to be line-symmetric, the input side is connected in parallel, the output side is connected in series, and the two tapped SAWs are detected. At least one of the taps included in the delay line is characterized in that tap electrode fingers of the tap are arranged at positions where the propagation distance of the surface acoustic wave is different from all other taps.

  The surface acoustic wave device according to the present invention has one input transducer and two output transducers, and the two output transducers are arranged opposite to each other with the input transducer as a boundary. .

  The radio transmitter according to the present invention is characterized in that the surface acoustic wave device described above is used for a matched filter.

  The radio receiver according to the present invention is characterized in that the surface acoustic wave device described above is used as a matched filter.

  According to the present invention, in the tapped SAW delay line, it is possible to improve the influence of direct waves and improve the dynamic range, and to simplify the circuit configurations of the ultra-wideband radio transmitter and the receiver.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a configuration diagram of a surface acoustic wave device 11 according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining a configuration of the surface acoustic wave device 11 according to the first embodiment.
In FIG. 1, an input transducer 12 and an output transducer 13 are formed on a piezoelectric substrate. As shown in FIGS. 1 and 2, in this embodiment, the surface acoustic wave device 11 arranges two multipath tapped SAW delay lines having the same structure so as to be line-symmetric, Are connected in parallel, and the output side is connected in series. One multipath-type tapped SAW delay line has a tap array 14_1 facing the input transducer 12. The other multipath tapped SAW delay line has a tap array 14_2 facing the input transducer 12. Although the two multipath tapped SAW delay lines have the same structure, they may have substantially the same structure, and the effect is not changed. Specifically, the arrangement positions of the tap electrode fingers of the tap may be different for each tap.

  In the example of FIGS. 1 and 2, the two tap arrays 14_1 and 14_2 of the output transducer 13 each have five taps T11 to T15 and T21 to T25. The tap arrays 14_1 and 14_2 are arranged to be line symmetric. The number of taps can be changed as appropriate. The input transducer 12 generates a surface acoustic wave according to an input signal from the input circuit. The surface acoustic waves reach the taps T11 to T15 and T21 to T25 through different propagation paths.

  The drive system is single input and balanced output. The input transducer 12 has terminals 1 and 3 connected to the ground, and a signal is input to the terminal 2. The output transducer 13 has a terminal 5 connected to the ground, and outputs a balanced output from the terminals 4 and 6.

  By configuring as in the present embodiment, the symmetry to the output (+) terminal and the output (−) terminal is improved structurally when viewed from the input terminal (terminal 2). Therefore, the value of the input-output (+) capacitance C1 and the input-output (-) capacitance C2 are substantially equal, and the direct wave by C1 and C2 is cancelled.

  Furthermore, in this embodiment, the structure portion (Bonding Pad, wiring, and Busbar) excluding the tap electrode fingers of the multi-pass tapped SAW delay line is line symmetric as shown in FIG. The tap can be individually changed with respect to the arrangement position. The arrangement position of the tap electrode fingers is such that the propagation distance of the surface acoustic wave is different from that of all other taps for at least one tap. As a result, the taps having different propagation distances have different propagation times of the surface acoustic waves generated by the input transducer 12, and therefore the arrival times of the surface acoustic waves are different.

  In the example of FIG. 1, the arrangement positions of the tap electrode fingers are different for each tap. Specifically, in the example of FIG. 1, the tap electrode fingers of the tap arrays 14_1 and 14_2 are arranged at an interval of a distance d corresponding to a predetermined propagation time τ of the surface acoustic wave. Furthermore, the tap electrode fingers of the tap arrays 14_1 and 14_2 are arranged so as to keep the distance d alternately. In the case of the example of FIG. 1, the surface acoustic waves generated by the input transducer 12 reach the taps T11 to T15, T21 to T25 with different propagation times. The arrival times are all different.

FIG. 3 is a diagram for explaining the operation of the surface acoustic wave device 11 of FIG.
In FIG. 3, the surface acoustic wave generated at time t = 0 first reaches the tap electrode finger of the tap T11 of the tap array 14_1 at time t = t1. Next, after the time τ has elapsed from the time t = t1 (time t = t1 + τ), the tap electrode finger of the tap T21 of the tap array 14_2 is reached. Next, when the time τ has elapsed from the time t = t1 + τ (time t = t1 + 2τ), the tap electrode finger of the tap T12 of the tap array 14_1 is reached. Next, when the time τ has elapsed from the time t = t1 + 2τ (time t = t1 + 3τ), the tap electrode finger of the tap T22 of the tap array 14_1 is reached. Thereafter, the surface acoustic waves reach the tap electrode fingers alternately alternately in the tap arrays 14_1 and 14_2.

  As a result, the pulse train P1 shown in FIG. 3 is generated by the tap array 14_1. The pulse train P1 has five identical pulse signals at time 2τ intervals from time t = t1. The pulse train P2 is generated by the tap array 14_2. The pulse train P2 has five identical pulse signals at time 2τ intervals from time t = t1 + τ. These pulse trains P1 and P2 are combined and output from the output circuit as an output pulse train P3. The output pulse train P3 has ten identical pulse signals at time τ intervals from time t = t1. The direct wave has been cancelled.

  Note that, by setting the propagation time τ to one pulse width or more, it is possible to prevent overlapping of pulse signals included in the output pulse train.

  Further, the position of the tap electrode fingers described above may be changed as appropriate according to the number and position of pulse signals included in the output pulse train. A candidate for a surface acoustic wave propagation distance may be determined according to the number and position of pulse signals included in the output pulse train, and a tap electrode finger may be arranged at a corresponding position for each candidate.

  In the present embodiment, the left transducer is used as input and the right side as output, but the right side may be used as input and the left side as output, which has the same effect.

As described above, according to the first embodiment, the two multipath tapped SAW delay lines are arranged so as to be symmetrical with each other, so that the capacitance between the terminal on the input transducer 12 side and the terminal on the output transducer 13 side is increased. As well as being equal, each tap is placed on a separate transmission path.
Therefore, since each multipath type SAW delay line with a tap is single-balance driven, a direct wave can be canceled due to the subjectivity of the transducer, and multiple reflections between taps can be prevented. The effect that can be reduced is obtained.

  Furthermore, for at least one of the taps of the two multipath-type tapped SAW delay lines arranged so as to be line-symmetric, the propagation distance of the surface acoustic wave is different from all other taps. Since the tap electrode fingers of the tap are arranged, the number of pulse signals included in the output pulse train can be appropriately changed. As a result, as in the example shown in FIG. 3, it is possible to include, in the output pulse train, pulse signals corresponding to the total number of taps included in the two multipath-type tapped SAW delay lines. Furthermore, the position of the pulse signal included in the output pulse train can be appropriately changed by changing the arrangement of the tap electrode fingers to adjust the propagation distance of the surface acoustic wave.

  FIG. 4 is a block diagram illustrating a configuration of a transmission unit of the two-dimensional pulse position modulation system to which the surface acoustic wave device 11 according to the first embodiment is applied. FIG. 5 is a block diagram illustrating a configuration of a receiving unit of the two-dimensional pulse position modulation system to which the surface acoustic wave device 11 according to the first embodiment is applied. In FIGS. 4 and 5, parts corresponding to those in FIGS. 9 and 10 described above are denoted by the same reference numerals, and description thereof is omitted.

  In the configuration of the transmission unit in FIG. 4, the surface acoustic wave device (surface acoustic wave delay line) 11a has a reference signal that gives a delay time t1 to an input pulse signal and a signal that gives a delay time (t1 + τ). An output pulse signal can be generated. In addition, the surface acoustic wave device (surface acoustic wave delay line) 11b generates an output pulse signal having a reference signal given a delay time t1 and a signal given a delay time (t1-τ) to the input pulse signal. can do. As a result, the number of surface acoustic wave devices (surface acoustic wave delay lines), distributors, and combiners can be reduced as compared with the conventional configuration of FIG.

  In the configuration of the receiving unit in FIG. 5, the surface acoustic wave device (surface acoustic wave delay line) 11c spreads the input signal from the spread code spread with the spread code PN0 with the delay time t2 and the spread code PN1 with the delay time t2. The spread codes can be detected simultaneously, and the respective output signals can be output to the delay time measuring unit 205. As a result, one surface acoustic wave device (surface acoustic wave delay line) and a distributor are reduced as compared with the conventional configuration of FIG.

[Second Embodiment]
FIG. 6 is an explanatory diagram for explaining the configuration of the surface acoustic wave device 21 according to the second embodiment of the present invention.
As shown in FIG. 6, the present embodiment has one input transducer 12 and two output transducers 13a and 13b. The two output transducers 13a and 13b are arranged opposite to each other with the input transducer 12 as a boundary. Each output transducer 13a, 13b is connected to a corresponding output circuit.

  The input transducer 12 generates a surface acoustic wave according to an input signal from the input circuit. This surface acoustic wave propagates to both sides of the output transducers 13a and 13b. Then, the taps of the output transducers 13a and 13b are reached through different propagation paths.

  According to the configuration of the second embodiment, one surface acoustic wave device 21 can generate two systems of output pulse trains from one input pulse signal.

  FIG. 7 is a block diagram illustrating a configuration of a transmission unit of a two-dimensional pulse position modulation system to which the surface acoustic wave device 21 according to the second embodiment is applied. In FIG. 7, portions corresponding to the respective portions in FIG. 9 described above are denoted by the same reference numerals, and description thereof is omitted.

  In the configuration of the transmission unit in FIG. 7, an output having a reference signal giving a delay time t1 to an input pulse signal and a signal giving a delay time (t1 + τ) to an input pulse signal by a surface acoustic wave device (surface acoustic wave delay line) 21. It is possible to simultaneously generate a pulse signal and an output pulse signal having a reference signal given a delay time t1 and a signal given a delay time (t1-τ) to the same input pulse signal. Thereby, one surface acoustic wave delay line and one switch are further reduced from the configuration of the first embodiment shown in FIG.

  As described above, according to the embodiments of the present invention, in the tapped SAW delay line, the influence of direct waves is improved, the dynamic range is improved, and the circuit configurations of the ultra-wideband radio transmitter and receiver are increased. It can be simplified. As a result, in a wireless communication system such as a UWB communication system, it is possible to contribute to high performance, downsizing, low loss, and low cost.

  The surface acoustic wave device according to the present invention uses an ultra wide band (Ultra Wide Band) used for connection of a PDA, a mobile phone, a peripheral device, etc. in a wireless LAN (Local Area Network) or PAN (Personal Area Network). The present invention can be applied to the used ultra wideband radio transmitter and ultra wideband radio receiver. Specifically, it can be used as a matched filter.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

1 is a configuration diagram of a surface acoustic wave device 11 according to a first embodiment of the present invention. It is explanatory drawing for demonstrating the structure of the surface acoustic wave apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the operation | movement which concerns on the surface acoustic wave apparatus 11 of FIG. It is a block diagram which shows the structure of the transmission part of the two-dimensional pulse position modulation system which concerns on 1st Embodiment. It is a block diagram which shows the structure of the receiving part of the two-dimensional pulse position modulation system which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the structure of the surface acoustic wave apparatus 21 which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the transmission part of the two-dimensional pulse position modulation system which concerns on 2nd Embodiment. It is a figure which shows the basic structure of the conventional SAW delay line with a tap. It is a block diagram which shows the structure of the transmission part of the conventional two-dimensional pulse position modulation system. It is a block diagram which shows the structure of the receiving part of the conventional two-dimensional pulse position modulation system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 21 ... Surface acoustic wave apparatus, 12 ... Input transducer, 13 ... Output transducer, 14 ... Tap arrangement, T11-T15, T21-T25 ... Tap, 101 ... Pulse generator, 103, 105 ... Switch, 107, 202 ... Amplifiers 108, 201 ... antenna, 109 ... control circuit, 205 ... delay time measuring unit, 206 ... data determination unit.

Claims (4)

In the surface acoustic wave device in which the input transducer and the output transducer are formed on the piezoelectric substrate, and the surface acoustic wave generated by the input transducer according to the input signal is detected by the output transducer,
Two SAW delay lines with the same structure are arranged so as to be line-symmetric, the input side is connected in parallel, the output side is connected in series,
For at least one of the taps of the two tapped SAW delay lines, the tap electrode finger of the tap is arranged at a position where the propagation distance of the surface acoustic wave is different from all other taps. A surface acoustic wave device.   2. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device has one input transducer and two output transducers, and the two output transducers are arranged opposite to each other with the input transducer as a boundary.   A radio transmitter using the surface acoustic wave device according to claim 1 as a matched filter. A wireless receiver using the surface acoustic wave device according to claim 1 for a matched filter.

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