JPH0748691B2 - Reflective microwave communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a wireless microwave as an information transmission means for an object for registering and holding specific information, to read or rewrite the information. The present invention relates to a communication device adapted to perform.

[Conventional technology]

As an application of such a microwave communication device, for example, registration data is registered and held in a mobile body, a carrier radio wave is transmitted from a management device at a fixed position, and the mobile body receives the carrier radio wave and is modulated by the registration data, It is well known that the management device receives the reflected radio waves and rereads the registered data by re-radiating the reflected waves.

[Problems to be Solved by the Invention]

As a conventional device, the device described in Japanese Examined Patent Publication No. 60-27077 converts the frequency by a reflection type phase modulator at the time of reflection, generates sidebands of a carrier signal,
The transmitter selects the sideband and receives it.

In the present invention, the management device is referred to as a main device, and the device provided to the object is referred to as a data carrier unit. Further, even when simply referred to as a reflected wave, a wave that is modulated and re-radiated by the data carrier portion as described above is referred to as a reflected wave.

By the way, in such an application, in order to reduce the cost and downsize the data carrier part, it is necessary to transmit / receive as an antenna.
I want to use the one for reception, but the interference of the transmitted and received waves is likely to occur, and the influence of the metal object in the vicinity of the data carrier makes it impossible to expect accurate data transmission. Further, since the selectivity of the frequency selection filter is insufficient, it has been proposed to try to obtain a special selectivity by polarization. This is 2 waves of horizontal polarization and vertical polarization as transmission waves.
By transmitting waves from one antenna and receiving reflected waves from the two antennas, circularly polarized carrier waves having opposite rotation directions are obtained. This method
There is a drawback that the antenna system becomes complicated.

As a measure against the above, the size of the data carrier part is reduced by using the antenna for both transmission and reception by making the polarization plane different from that of the reflected wave by 90 °, and at the time of the reflection of the microwave in the data carrier part, the antenna transmission port, A method has been proposed by the applicant of the present invention in which the reflection coefficient at the 2-output node of the branch line (hybrid coupler) connected to the receiving port is changed into a 4-valued vector based on the registered data (Japanese Patent Application No. 63-148165). This method is 4
As the reflection coefficient of the value, it is a modulation that rotates four reflection coefficients having a phase difference of 90 ° in a vector in one direction, and by making the planes of polarization of the transmitted wave and the reflected wave different from each other by 90 °, It is designed so as not to be affected by the reflected wave of the metal object near the part. However, it is inevitable to some extent not to reflected waves but to radio waves directly from other signal sources. For example, the most severe situation may be shown in FIG. 1 is a main unit, 2 is a data carrier part, and there are L columns and M columns in which a plurality of main devices 1 are arranged. The object (data carrier part) moves in two columns, and the L columns facing each other, This is the case where microwave communication is performed with the M column. This is appropriate when there are several series for managing articles moving on a belt conveyor and the space between the series cannot be sufficiently secured due to space restrictions. The antenna mounting surfaces 1A and 2A of the main unit 1 and the data carrier unit 2 are represented by thick solid lines, and their reception areas (directivity) are 1 respectively.
It becomes B, 2B. Since the microwave of GHz is used, the beam width is narrowed, but the reflected wave generally has weak energy. Therefore, when data is being read on the L example (M column) side, strong carrier waves from the M column (L column) side directly enter the antenna on the reading side as shown by the arrow. . Interference can be avoided if you can change the frequency drastically by using several carrier frequencies, but from the radio regulations,
There is a radio wave limitation, which makes it difficult to use the same radio wave or near radio waves.

In view of the above circumstances, an object of the present invention is to provide a microwave communication device which improves the reflected wave modulation method of the data carrier unit and enables stable operation even in the above severe environment. Especially.

[Means for Solving the Problems]

The reflection type microwave communication device of the present invention comprises a data carrier unit for holding registration data, and a main unit for reading the registration data held in the data carrier unit by transmitting and receiving radio waves to and from the data carrier unit. ing.

The data carrier unit is a reflection modulation unit that generates a reflected wave to be transmitted to the main device by performing phase modulation on the unmodulated carrier wave received from the main device according to the registered data being held and a subcarrier. Is equipped with.

The main unit, a transmission unit that transmits an unmodulated carrier that is a target for superimposing the phase modulation and the subcarrier to the data carrier unit,
The reflected wave transmitted by the data carrier section is received, mixed with the unmodulated carrier wave, and then passed through a band pass filter to extract the subcarrier phase-modulated according to the registered data of the data carrier section. The reception unit demodulates the registration data held by the data carrier unit from the received signal.

[Action]

The reflected wave of the microwave is subjected to phase modulation corresponding to the registered data. Now, for ease of understanding, a case of 4-value phase modulation will be described. In quaternary phase modulation, the reflection coefficient at two nodes at the output end of the branch line (hybrid coupler) connected to the receiving node and the transmitting node of the antenna is changed in a vector manner. The four-valued reflection coefficient is shown in FIG. 2 (a), but it is changed so as to rotate in one direction. The rotation speed is different depending on the registered data “1” and “0”.

The four-valued reflection coefficient above is 90 as shown in ().
° Determined according to the phase of two clock signals with a phase difference. Therefore, as shown in the figure, there is a point-symmetrical relationship with respect to the center as a vector, and the corresponding reflection coefficient is an inversion of two clock signals. In the present invention, when the reflection coefficient changes vectorally to 1, 2, 3, 4 due to the clock signal having a different frequency depending on the registered data, the subcarrier of a higher frequency is superposed, so that the dotted line in FIG. As shown in Fig. 3, while at each point, the corresponding reflection coefficients 3, 4, 1, 2 and the frequency of the subcarrier alternate.
In this way, the subcarrier is modulated by the registration data, and the phase of the reflected wave is modulated by this modulated signal.

Therefore, the reflected wave has a double sideband wave separated from the transmitted carrier frequency by the subcarrier frequency, and the double sideband wave also has a modulated wave on both sides in the vicinity due to the registered data frequency. FIG. 3 shows a case where the reflection coefficient of the four-valued phase is simply changed rotationally (a) and a case where the reflection coefficient is alternately changed by the subcarrier as in the present invention (b). , A frequency spectrum is shown. f _c is a carrier wave, f _O is a subcarrier, and f ′ ₁ and f ′ ₂ are both sidebands generated by the subcarrier. f ′ ₁ and f ′ ₂ are respectively f ₁ and f
₂ has modulated waves f ′ _m and f _m on both sides, and the distance between f ₁ , f ₂ and f _c is equal to the subcarrier f _O , and f ₁ and f ₂ and modulated waves f ′ _m and f _m
The distance from _m is Δf corresponding to the registration data.

The main device receives the reflected wave and obtains the Δf component including the information of the registration data from the frequency components P and Q in FIG. 2 (b).

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, when a plurality of objects move past the front surface of the fixed main device, the main device reads the data of the object when it comes to the front surface of the main device, An example is the case where data is rewritten in some cases, such as when counting and managing vehicles traveling on a road. On the contrary, the main device is installed, and multiple objects are placed along the road.
It can also be applied to the case of reading data from the object as the vehicle progresses.

The main device 100 includes a transmission unit 100A and a reception unit 100B, and is controlled by the control unit 111 and the information processing unit 112. Transmitter 1
From 00A, a carrier wave A that is not modulated and a modulated carrier wave C that is modulated are radiated. This modulated carrier radio wave is for controlling the operation of the data carrier unit 200 by the information carried on this radio wave. On the other hand, the receiver 100B
Receives the reflected radio wave B in which the carrier radio wave A is transmitted from the data carrier section 200 with the plane of polarization shifted by 90 °, and thereby the data from the data carrier section 200 is read.

The data carrier unit (hereinafter abbreviated as DC unit) 200 has a reflection modulation unit 200A and a reception unit 200B, and includes a controller 20.
Operation is controlled by 9. For such radio wave transmission, the antennas 101 and 105 of the main device 100 have different polarization planes, the antenna 101 transmits vertical polarization, and the antenna 105 receives horizontal polarization. In the DC unit 200, the antennas 201 and 206 receive vertically polarized waves, and the antenna 202 has different planes of polarization so that horizontally polarized waves are transmitted.

The operation when main device 100 reads data from DC unit 200 will be described below. The information processing unit 112 outputs a read command signal as a digital signal, and sends it to the modulation circuit 104 via the control unit 111. The modulation circuit 104 controls ON / OFF of the 2.45 GHz self-excited oscillator 103 in response to the signal “1” of 50 KHz and “0” of 30 KHz, for example. The output of this self-excited oscillator 103 is passed through the hybrid coupler 102 to the antenna 101.
to go into. The radio wave C radiated from this antenna 101 is DC
In the section 200, it is received by the antenna 206 and detected by the detection circuit 207. The detection circuit 207 is diode detection of a microstrip circuit, and is further converted into a digital signal by the demodulation circuit 208, and its output 208a transmits data to the controller 209. The controller 209 recognizes from this that the command from the main device 100 is a data read. On the other hand, the main device 100 stops the modulation and emits the carrier wave A after emitting the command wave.

Then, the DC unit 200 receives the carrier radio wave A at the antenna 201, modulates the received signal with the registration data held in the controller 209 at the reflection modulation unit 200A, and re-radiates the reflected wave B from the antenna 202.

Next, details of the operation of the reflection modulator 200A will be described. The hybrid coupler 203 and the modulation circuit 204 are constituted by a microwave distributed constant circuit as shown in FIG.
The hybrid coupler 203 is formed in a well-known branch line, and its input nodes P ₁ and P ₂ are connected to the nodes P _R and P _T of the antenna 201 (reception) and the antenna 202 (transmission),
The output nodes P ₃ and P ₄ are connected to the modulation circuit 204. The modulation circuit 204 is composed of a distribution circuit, and changes the reflection coefficients of P ₃ and P ₄ by turning on and off the diodes D1 and D2. This distributed circuit consists of the circuit connected to node P ₃ and node P ₄
The circuit connected to is identical except for the 1/8 length l ₄
It has a phase difference of °. Therefore, now simply
If the clock signals for turning on and off the diodes D1 and D2 are square pulse trains with a duty of 1/2 and φ ₀₁ and φ ₀₂ have a phase difference of 90 °, the reflection coefficients "3" and "4 are vectorial amplitudes". Have the same four values, and the phase is rotated as shown in Fig. 2 (a) .The rotation direction can be two directions, but it is determined by the design of this microwave antenna system.

In the case of the present embodiment, the clock signal for turning on / off the diodes D1 and D2 in the modulation circuit 204 is a simple square pulse train φ ₀₁ ,
Instead of φ ₀₂ , it is signals φ ′ ₁ and φ ′ _{2 obtained} by modulating a subcarrier of frequency f _o (10.738 MHz in the embodiment) with φ ₀₁ and φ ₀₂ . As shown in FIG. ₁ , from the controller 209, φ ₁ , φ
₂ is input to the oscillation / signal conversion circuit 205, and at the frequency f _o of the subcarrier oscillator incorporated in this circuit, φ ₁ → ₁ → φ ₁ →
, Φ ₂ → ₂ → φ ₂ → ... and signals φ ′ ₁ and φ ′ ₂ that repeat the phase inversion are created. Note that φ ₁ and φ ₂ are assigned, for example, 50 KHz if the registration data is “1” and 30 KHz if the registration data is “0”. The registration data is held in the memory of the controller 209, and in response to a command from the main device 100, the controller 209 outputs φ ₁ and φ ₂ based on its own registration data.

Next, the operation of the main device 100 that receives the reflected wave B will be described. The reflected wave B radiated from the antenna 202 has the spectrum shown in FIG.

Here _{f '1 = f c + f} o ± △ f, f' 2 = f c -f o ± △ f a,, f _'1 of the modulated wave _{f' m1 = f c + f} o + △ f, f _m1 = f _c + f _o −Δf, f ′ ₂ modulated wave f ′ _m2 = f _c −f _o + Δf, f _m2 = f _c −f _o −Δf. f _c is the carrier frequency, and Δf is the frequency corresponding to the registration data. The reflected wave B is transmitted to the antenna 105.
At the output of the hybrid coupler 102, combined with the output 102a of the hybrid coupler 102, frequency-converted by the mixer 106, and the both sidebands f ′ ₁ ,
The components (indicated by P and Q) corresponding to the one-side modulated waves f _m1 and f ′ _m2 are extracted from f ′ ₂ by the bandpass filter 107. The band pass filter 107 has a center at approximately 10.7 MHz and passes the modulated waves on both sides. The output 107a of the bandpass filter 107 is mixed by the mixer 108 with the same oscillation frequency as the subcarrier 10.738MHz, and the bandpass filter 109 outputs the frequency 30KHz or 50KHz.
The modulated signal of is extracted as a beat signal of the difference frequency. The output 109a of the bandpass filter 109 is converted into a digital signal by the demodulation circuit 110 composed of a digital PLL circuit, and is input to the information processing unit 112 via the control unit 111. This allows the information processing unit 112 to read the registration data of the DC unit 200.

〔The invention's effect〕

The present invention is a data carrier unit for holding registration data,
The data carrier section receives the microwave carrier from the main apparatus, and sends the reflected wave modulated by the registered data to the main apparatus section, thereby transmitting information by microwave. The reflected wave changes the reflection coefficient in vector according to the registered data. This change in the reflection coefficient is caused by a low frequency modulation frequency signal (eg 50KHz, 30KHz) corresponding to the registered data “1” or “0” and a subcarrier frequency signal (eg 10MHz) much higher than the modulation frequency signal. Therefore, the reflected wave has not only the carrier frequency but also the both sidebands which are spaced apart from the carrier frequency by the subcarrier frequency. And
The carrier and both sidebands each have a modulated wave component that slops only to the modulation frequency.

When the above-mentioned reflected wave is received by the main device, the carrier frequency is locally added to perform frequency conversion, and the one-side modulation frequency components of the both-side band wave signals are extracted by the band filter.

A modulated wave frequency signal is extracted from one side frequency component of the both sidebands through a bandpass filter and demodulated to obtain digital data (registered data).

The advantages of this method are as follows: (1) When a large number of main devices are installed and their oscillation frequencies are set to be the same or close to each other, the sidebands for which the main device acquires information are separated from the carrier frequency. (10MHz, for example), it is not affected by other main devices.

(2) When there is a metal plate larger than the device on the back surface of the data carrier part, the microwave radio wave from the main device is re-radiated by the metal plate. Therefore, when the main device receives the signal from the data carrier unit, the problem that the received signal is suppressed and cannot be received does not occur in the present invention because the information is not obtained from the carrier wave.

(3) When the subcarrier is not used, the modulation frequency component extremely close to the carrier frequency of the microwave must be selectively detected in the spectrum diagram of FIG. 3 (a), which complicates the receiving circuit, In addition, there are severe requirements for carrier oscillation frequency accuracy. In the present invention, since the information is read from the sidebands separated by the subcarrier frequency, the accuracy requirement of the oscillation frequency is not strict, and the bandpass filter is also a filter in the subcarrier frequency band, and the design requirement is not strict.

Incidentally, extraction of the modulation frequency component by band pass filter 109 of the main apparatus is not limited to the embodiments, may receive the f _'2 of f _m and f' ₁ of f _'m. Further, in the embodiment of the present invention, in order to reduce the size of the device and reduce the influence of disturbance in the external world, the reflected wave is re-radiated by shifting the polarization plane by 90 °, but the present invention is not always required. It is not limited to this.

As the phase modulation corresponding to the registration data, 90 ° in the example
Although the four-valued phase modulation in which the phase is changed each time has been described, it goes without saying that the modulation circuit becomes complicated, but it is also possible to perform high-order phase modulation of 8 values and 16 values.

Furthermore, even if the registration data in the present invention is an NRZ code, considering the clock recovery when the main device receives a reflected wave, and converting the NRZ code into a biphase code for modulation of the reflected wave, The reliability of the data is high.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a vector diagram of four-valued reflection coefficient, FIG. 3 is a conventional example, the spectrum of reflected waves of this embodiment, and FIG. 4 is reflection modulation. FIG. 5 is a diagram showing a portion of a hybrid coupler and a modulation circuit, which are microwave distribution circuits of the section 200A, and FIG. 5 is a diagram showing an example when the present embodiment is used. 100 …… Main unit, 100A …… Sending unit, 100B …… Reception unit, 10
1,105 …… antenna, 102 …… hybrid coupler,
103 ... Oscillator, 104 ... Modulation circuit, 106,108 ... Mixer, 107,109 ... Bandpass filter, 110 ... Demodulation circuit,
111: control unit, 112: information processing unit, 200: data carrier unit, 200A: reflection modulation unit, 200B: receiving unit, 201,
202,206 …… antenna, 203 …… hybrid coupler (branch line), 204 …… modulation circuit, 205 …… oscillation
Signal conversion circuit, 209 ... Controller.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References Japanese Patent Publication 6-5829 (JP, B2)

Claims (3)

[Claims] 1. A reflection type microwave communication device comprising: a data carrier unit for holding registration data; and a main unit for reading the registration data held in the data carrier unit by transmitting and receiving radio waves to and from the data carrier unit. The data carrier unit generates a reflected wave to be transmitted to the main device by performing phase modulation on the unmodulated carrier wave received from the main device according to the registered data being held and superimposition of a subcarrier. A reflection modulation section, wherein the main device transmits a non-modulated carrier, which is a target for superimposing the phase modulation and the subcarrier, to the data carrier section; and receives the reflected wave transmitted by the data carrier section. Then, after being mixed with the unmodulated carrier wave and passed through a band pass filter, the phase is modulated according to the registered data of the data carrier section. A reflection-type microwave communication device, comprising: a subcarrier, and a receiver that demodulates the registered data held by the data carrier from the extracted signal. 2. The receiving unit of the main device mixes the extracted signal and the subcarrier to create a beat signal,
The reflection type microwave communication device according to claim 1, further comprising means for demodulating the registration data held by the data carrier unit from the beat signal. 3. A reflection modulation section of the data carrier section rotates four complex reflection coefficients point-symmetrically arranged around an origin in a complex space at a speed according to the registered data being held. The reflection type microwave communication device according to claim 1 or 2, wherein the phase modulation is performed by the following method.