JP3293278B2 - Transceiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transceiver for wirelessly transmitting information data between OA equipment and the like.

[0002]

2. Description of the Related Art Conventionally, as a method of transmitting information data between OA devices in an office or the like, a method of connecting the devices with a cable has been adopted. However, wiring work is required to connect a large number of devices with cables, and it becomes difficult to move the devices due to a change in office layout, to introduce new devices, and the like. As a means for solving this, there is a method of using radio waves, but there are problems such as output power of radio waves, frequency limitation, interference with other devices, and the like, and it has not been widely spread.

On the other hand, as a communication system used for a special purpose, a system (a spread spectrum system) in which a signal is spread over a wide band and transmitted by a radio wave having a low power density is known. Since this system has low power density, it is difficult to interfere with other devices.
It is characterized by being less susceptible to interference from other devices. In spread spectrum communication, a spread code called a PN code is generally used to modulate an information signal into a spread signal of a wide band. In a transmitter and receiver using spread spectrum, this P
The correlation demodulation circuit that demodulates the signal spread by the N code into the original signal becomes the most complicated in terms of circuit, and several demodulation methods have been proposed. As a method of demodulating a signal with the simplest configuration and high reproducibility, Japanese Patent Laid-Open No. 4-34652 discloses a method.
As shown in FIG. 8, a method using a SAW matched filter for correlation demodulation has been proposed.

[0004]

In the SAW matched filter, a PN code is formed as an electrode pattern in advance at the time of manufacturing an SAW electrode pattern.
A generator circuit, a synchronization circuit, and the like become unnecessary, and there is a feature that the circuit can be simplified and the synchronization time can be shortened. However, since the PN code is fixed, only one code can be used for communication, and the PN code is selected. As a result, there is a problem that it is difficult to use the communication device for performing a plurality of communications at the same time.

[0005]

Therefore, the present invention proposes a system which can make use of the features of the SAW matched filter and can set a plurality of PN codes. As one means, a configuration is proposed in which counter electrodes are provided on both sides in the signal transmission direction of the electrodes constituting the PN code of the SAW matched filter.
Further, as a second means, a configuration in which electrodes having different PN codes are arranged so as not to interfere with each other is proposed.

[0006]

The basic operation principle of the SAW matched filter is P
A signal spread-modulated by the N code is input to the excitation electrode, converted into a surface acoustic wave, transmitted to the electrodes that have been previously patterned according to the PN code, and at the moment the received signal and the excitation direction of each electrode match. Each excitation power is added and a correlation output appears at the output. On the other hand, since the one-period PN code has no symmetry, the PN code is formed for a signal input from an electrode in the opposite direction to the input electrode and the electrode forming the PN code. Electrodes can be considered as another PN code in the reverse arrangement. Therefore, a counter electrode is provided in the signal transmission direction on both sides of the electrode constituting the PN code,
By selecting one, a correlation demodulation circuit that can handle two PN codes can be configured.

Further, since the surface acoustic wave transmits a signal in the direction of the counter electrode, interference can be reduced by arranging electrodes of different PN codes at intervals in parallel in the signal transmission direction. The combination with the electrodes provided on both sides in the signal transmission direction described above makes it possible to select from a large number of PN codes and perform reception demodulation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a transmitter, 2 is a receiver, 3 is an information modulator, 4 is a spread modulator, 5 is a PN generator, 6 is a selector, 7 is an information input unit, 8 is an antenna, and 9 is selected. Part 10,
Is a correlation demodulator, 11 is an information demodulator, 12 is an antenna, 1
3 is an information output unit. The information signal input to the transmission unit 1 from the information input unit 7 is input to the spread modulation unit 4 after being information-modulated by the information modulation unit 3. On the other hand, the PN generator 5 selects one spreading code (hereinafter referred to as a PN code) by the selector 6 and the information modulation signal input to the spreading modulator 4 is P
The signal is spread-modulated into a signal of a wide band by the PN code generated by the N generator 5 and then transmitted from the antenna 8.

The signal thus transmitted is received by the antenna 12 and input to the receiver 2. In the receiver 2, the selection unit 9 selects the terminal of the correlation demodulation unit 10, sets the PN code of the correlation demodulation unit 10, and sets the PN code of the received signal.
A demodulated signal is output when the signal coincides with the N code, and further demodulated by the information demodulation unit 11 into the original information signal.
3 is output.

[0010] By using the transceiver of the present invention, P
Information is demodulated for a signal having the same N code, and PN
Since demodulated signals do not appear for signals whose codes do not match, communication can be simultaneously performed between a plurality of sets of transceivers by selecting a PN code. Further, since the selection unit 9 for selecting the PN code of the correlation demodulation unit 10 can be realized with a simple configuration simply selecting the connection of the input or output terminal of the correlation demodulation unit 10, the PN signal generation circuit for the correlation demodulation is used. It is not necessary to prepare a code synchronization circuit or the like, and the configuration can be simplified.

FIG. 2 shows an embodiment of a specific circuit in the case where a SAW matched filter is used in the correlation demodulator 10. In FIG. 2, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. Reference numeral 10 denotes a correlation demodulation unit using a SAW matched filter, 14 denotes an input terminal of a signal received by the antenna 12, and 15 and 16 denote first and second signals of the signal selected by the selection unit 9 to the correlation demodulation unit 10. Input terminal, 17, 1
8 is a first and second input excitation electrode of the SAW matched filter 10, 19 is an output excitation electrode with a PN code set,
Reference numerals 20 and 21 denote electrodes 17 and electrodes 18 to 19, respectively.
The direction of the wave heading toward 22 is a correlation demodulation signal output terminal.

A signal received by the antenna 12 is input from the input terminal 14 to the selection unit 9, and is transmitted to one of the input terminals 15 and 16 of the correlation demodulation unit 10 by the selection unit 9. When the input terminal 15 is selected, the input signal is SAW
The electric signal is converted into a surface acoustic wave by the input excitation electrode 17 of the matched filter, transmitted in the direction indicated by 20, and
The N-code is transmitted to the set output electrode 19. The PN code is a pseudo-noise code in which almost the same number of 1/0 codes are randomly arranged. When the PN codes match, the excitation directions of all the electrodes are in phase, and the combined demodulated signal is output to the output terminal 22.
Output. On the other hand, when the PN codes do not match, the number of in-phase signals and the number of out-of-phase signals are stably the same, so that the signals cancel each other out and no demodulated signal appears at the output. Similarly, when the input terminal 16 is selected by the selection unit 9, the input signal is converted from an electric signal into a surface acoustic wave by the input excitation electrode 18 of the SAW matched filter and transmitted in the direction indicated by 21, and is transmitted to the output electrode 19. When the PN code is correlated, a correlation demodulated output is output from the output terminal 22. Here, the difference between the operation of the wave in the direction of 20 and the operation of the wave in the direction of 21 in the SAW matched filter will be described with reference to FIG. FIG.
FIG. 8 is a diagram showing the operation of the output electrode 19 of the W matched filter,
The same reference numerals as those in FIG. 2 are used. Now, a _1, a ₂ a code written to the output electrode 19 of the SAW matched filter from the side near the electrode 17, ..., when a _n-1, a _n, electrode 1
7 the wave 20 which is input from _{(a n, a n-1} , ..., a 2,
The signal is demodulated when an input signal modulated by the PN code in the order of a ₁ ) is input. On the other hand, the wave 21 input from the electrode 18 is demodulated when an input signal modulated with the PN code of (a ₁ , a ₂ ,..., _{An 1} , a _n ) is input. Therefore P
By selecting an asymmetric code for the N code, the input terminal 1
The PN code to be demodulated in 7 and 18 can be changed, and a plurality of codes can be selected and demodulated by one SAW matched filter only by selecting an input terminal.

In this embodiment, the electrodes 17 and 18 are used for signal input, and the electrode 19 is used for demodulation output. However, the relationship between input and output can be reversed. Although not particularly shown in the present embodiment, by performing a terminating process such as grounding / opening on the non-selected terminal in the selecting unit 9, the demodulation efficiency of the SAW matched filter can be improved.

FIG. 4 shows another embodiment of the present invention. In the figure, components having the same functions as those in FIG. Reference numerals 23 and 24 denote a part of the selection unit 9 for selecting the input and output of the demodulation unit 10, 25 and 26 denote output electrodes composed of different PN codes, and 27 and 28 denote electrodes 17 and 18 to the electrode 25, respectively. Transmitted waves 29, 3
0 is a wave transmitted from the electrodes 17 and 18 to the electrode 26, respectively, and 31 and 32 are demodulation output terminals from the electrodes 25 and 26, respectively.

As in the embodiment shown in FIG.
Signals 27 and 28 input from 5 and 16 are demodulated by electrodes 25 with different PN codes, respectively, and output from an output terminal 31. Similarly, signals 27 and 28 input from the input terminals 15 and 16 are respectively different PN
The signal is demodulated by the code and output from the output terminal 32. SAW
Since the surface acoustic wave signal is transmitted in the direction of the excitation electrode in the matched filter, the electrodes 25 and 26 are arranged with a distance such that they do not interfere with each other, the output electrode extraction direction is separated, and the output selection unit 24 is This arrangement reduces the interference between the electrodes 25 and 26 due to the sneak of the output signal. According to the present embodiment, it is possible to select four types of PN codes only by selecting the input / output connection by the input selector 23 and the output selector 24.

Although the input electrodes 17 and 18 are shared by the electrodes 25 and 26 in the present embodiment, interference can be further reduced by separating the input electrodes 17 and 18 from each other. FIG.
As described in the embodiment, the same effect can be obtained even if the signal input and output are reversed. In this embodiment, two output electrodes 25 and 26 are used. However, the number of switching electrodes can be increased by further increasing the number of output electrodes. Further, in this embodiment, the embodiment in which the electrodes having different PN codes are formed on the same SAW substrate is shown. However, it is needless to say that the same effect can be obtained by arranging a plurality of SAW matched filters of the embodiment of FIG.

[0017]

According to the present invention, by using a SAW matched filter for correlation demodulation, a transceiver capable of switching a plurality of PN codes with a simple configuration without using a complicated PN generation circuit, synchronization circuit, and switching circuit. Can be configured.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing one embodiment of a transmission unit and a reception unit of a transceiver using the present invention.

FIG. 2 is an embodiment of a correlation demodulation unit of a receiver using the present invention.

FIG. 3 is an explanatory diagram of an operation of the correlation demodulation unit in FIG. 2;

FIG. 4 is another embodiment of the correlation demodulation unit of the receiver using the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission part, 2 ... Reception part, 3 ... Information modulation part, 4 ... Spreading modulation part, 5 ... PN generation part, 6 ... Selection part, 7 ... Information input part,
8 antenna, 9 selector, 10 correlation demodulator, 11
Information demodulation unit, 12 antenna, 13 information output unit, 14
... Switching section signal input terminal, 15, 16 ... Demodulation section signal input terminal, 17, 18 ... Input excitation electrode, 19 ... Output excitation electrode,
20, 21 ... surface acoustic wave, 22 ... demodulation output terminal, 23 ...
Input selection unit, 24: Output selection unit, 25, 26: Output excitation electrode, 27, 28, 29, 30: Surface acoustic wave, 31, 3
2: Demodulation output terminal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Daihi Okajima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. AV Equipment Division, Hitachi, Ltd. JP-A 64-32735 (JP, A) JP-A-51-90511 (JP, A) JP-A-6-77759 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04J 13 / 00-13/06 H04B 1/069-1/713

Claims (2)

(57) [Claims] A first modulator for modulating an information signal, a second modulator for spreading and modulating a signal modulated by the first modulator in accordance with a spreading code, and a spreading code used for the spreading modulation. A plurality of sets of PN generators, a transmitter having a selector for selecting a spread code transmitted by the PN generator, a first demodulator for selecting a plurality of spread codes and performing correlation demodulation; The first demodulation unit includes a selection unit that selects a spread code, and a reception unit that includes a second demodulation unit that demodulates information of a signal demodulated by the first demodulation unit. Uses a SAW matched filter
And the SAW matched filter has a second
One electrode and the first electrode in the direction of wave transmission
The second and third electrodes formed on both sides;
By selecting one of the second and third electrodes, the spreading code
And a demodulator for selecting and demodulating . 2. The SAW matched filter comprises a plurality of electrodes having different spreading code information and not interfering with each other, and one or a plurality of electrodes facing in a wave transmission direction of the electrodes. The transmitter / receiver according to claim 1, wherein a spreading code is selected and demodulated by selecting one set from an electrode having information and a counter electrode.