JP3433987B2 - Data communication system and interrogation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits and receives data between a fixed station (interrogation device) and a mobile station (response device), and in particular, in the response device , a carrier wave from the interrogation device is reflected, The present invention relates to a data communication system and an interrogation device that modulate and respond to the reflector.

[0002]

2. Description of the Related Art Conventionally, there is a data communication system in which a transmitter / receiver of a mobile station is provided with a reflection type modulator, which reflects a carrier wave from a fixed station and modulates a reflected wave with data. .

FIG. 3 shows a data communication device using a conventional reflection type modulator. This data communication device includes an interrogation device 1 installed at a fixed point and a response device 2 attached to a moving object.

The interrogator 1 has an oscillator 11 for generating a carrier wave.
It has a circulator 12, a transmitting / receiving antenna 13, a detector 14, a controller 15, and an input / output terminal 16. The input / output terminal 16 is connected to the external device 3 for controlling the interrogation device 1. Then, data is exchanged with the external device 3 via the input / output terminal 16.

The response device 2 has a transmission / reception antenna 21, a reflection type modulator 22, a control circuit 25, and an input / output terminal 26. An external device 4 for controlling the transponder is connected to the input / output terminal 26. Then, data is exchanged with the external device 4 via the input / output terminal 26.

The operation of the data communication apparatus shown in FIG. 3 will be described. In order to call the response device 2 from the interrogation device 1, the carrier wave from the oscillator 11 is supplied to the transmission / reception antenna 13 via the circulator 12. A carrier wave is radiated from the transmitting / receiving antenna 13 as an interrogation signal.

The response device 2 receives this by the transmission / reception antenna 21 and guides it to the reflection type modulator 22. The control circuit 25 gives the data output from the external device 4 to the reflective modulator 22 in response to the reception of the inquiry signal. This reflection type modulator 22
Is a capacitor 22a, a diode 22b, and a coil 22c.
Including and The reflective modulator 22 reflects the unmodulated carrier (carrier wave) from the interrogation apparatus 1 and modulates the reflected carrier wave with the unique data. As this modulation method, there are an amplitude modulation method and a phase modulation method.

The reflected wave modulated as described above is radiated from the transmitting / receiving antenna 21 toward the interrogation apparatus 1.
The interrogator 1 receives the response signal at the transmitting / receiving antenna 13,
It is guided to the wave detector 14 via the circulator 12. As the detector 14, a homodyne detector is generally used. This is because the signal / noise ratio is better than in the case of direct detection using a diode. The detector 11 includes an oscillator 11
The local oscillation signal from is also supplied. The detector 14 multiplies the local oscillation signal and the response signal, and the result of the multiplication is passed through a low-pass filter (not shown) to extract a demodulation signal. This demodulated signal is input to the control unit 15, and the data is demodulated. The data thus read is transferred to the external device 3 via the input / output terminal 16.

However, when performing homodyne detection, when the relative distance between the interrogation device 1 and the response device 2 reaches a certain value, the local oscillation signal and the response signal input to the detector 14 of the interrogation device 1 Phase difference with ± 90 °, ± 27
It becomes 0 °. In this case, there is a disadvantage that the intermediate frequency signal disappears and the data cannot be demodulated.

This will be described in more detail using mathematical expressions. The local oscillator signal Vl and the response signal Vs from the oscillator 11 are input to the detector 14, and the signal Vd is extracted. Consider now that the reflective modulator 22 of the response device 2 is not operating. The frequency of the response signal Vs at this time is
Since the frequency is the same as that of the local oscillation signal Vl, the local oscillation signal Vl, the response signal, and the response signal Vs are expressed by the following equations (1) and (2).

Vl = | Vl | cos (wt) ... (1) Vs = | Vs | cos (wt−θ) ... (2) where θ = 2wl / C = (4π / λ) l (3) where C: speed of light w: angular frequency of carrier λ: wavelength of carrier │Vl│: amplitude of local oscillation signal │Vs│: amplitude of response signal θ: phase difference detector between Vl and Vs The detection result by 14 is expressed by the following equation (4).

Vl · Vs = (| Vl | · | Vs | / 2) · {cos (2wt−θ) + cosθ} (4) In the equation (4), the first term is a double component of the carrier. Therefore, it is removed by the low-pass filter. Therefore, from the homodyne detection output, only the DC voltage VDC of the second term is taken out. This VDC is shown in equation (5).

VDC = (│Vl│ · │Vs│ / 2) cosθ (5) In FIG. 4, the amplitude of the local oscillation signal Vl is constant and the amplitude of the response signal Vs is used as a parameter in the equation (5). This is the result of calculating VDC at the time with respect to the phase difference θ. This is a characteristic of a so-called phase detector. As can be seen from FIG. 4, VDC increases as the amplitude of the response signal Vs increases. Also, the phase difference θ is ± 90 °, ± 270 °,
.., VDC = 0. Phase difference ± 90 °, ± 2
According to the formula (3), 70 ° becomes 2 × 360 × l / λ = ± 90 °, ± 270 ° ... l = λ / 8, 3λ / 8, 5λ / 8, ... Since (2n−1) λ / 8 (n: positive integer), a point where VDC = 0 occurs at every quarter wavelength in the communication distance.

Next, consider a case where the reflection type modulator 22 of the response device 2 operates to perform amplitude modulation on the received interrogation signal. This corresponds to changing the magnitude of Vs in equation (5). The operation of this amplitude modulation will be described with reference to FIG.

FIG. 5 is a diagram for explaining the detection operation of the interrogation device 1 when the response device 2 is amplitude-modulated. The reflective modulator 22 changes the amplitude of the response signal Vs to the period T.
Then, it changes sinusoidally like Vs2 → Vs1 → Vs2 → Vs3 → Vs2. In this case, assuming that the phase difference between the response signal Vs and the local oscillation signal Vl is θ1, the homodyne detection output VDC changes as B2 → B1 → B2 → B3 → B2 ... As shown in FIG. 5 (b). To do.
However, since θ1 changes depending on the relative distance between the interrogation device 1 and the response device 2, cos θ1 sometimes becomes 0. For example, when θ1 = ± 90 °, ± 270 °, ... Like C1, C2, and C3 in FIG. 5A. In this case, the demodulated signal disappears although the magnitude of the response signal Vs changes.

Next, consider a case where the interrogation signal received by the reflective modulator 22 of the response device 2 is subjected to phase modulation.
This corresponds to changing θ in equation (5). This phase modulation operation will be described with reference to FIG. FIG. 6 shows the response device 2.
FIG. 6 is a diagram for explaining the detection operation of the interrogation device when is phase-modulated. The reflective modulator 22 has a constant Vs (Vs = V
s2), the phase angle θ is θ2 with a cycle T →
When sinusoidally changing as θ2L → θ2 → θ2U → θ2 ..., the output VDC of the detector 14 is B2 → of FIG. 6B.
A2 → B2 → D2 → B2 ... Change. However, the central value θ2 of the phase change is 0 °, ± 180 °, ± 36
When there is a relative distance relationship such that 0 ° ... (For example, A2 in FIG. 6A), the demodulated signal becomes only the component of the period T / 2 as shown in FIG. 6C. , The fundamental wave component (cycle T) disappears.

As described above, when the homodyne detector of one system is used as the detector 14 of the interrogation apparatus 1, a position where communication becomes impossible occurs. As a device for identifying an object that solves this problem, there is a query device shown in FIG. FIG. 7 is a block diagram showing a conventional inquiry device. Referring to the figure, the interrogator 1 ′ differs from the interrogator of FIG. 3 in that the distributor 17 connected between the oscillator 11 and the circulator 12 and the 90 ° connected to the distributor 17 are different. In-phase distributor 1 connected to distributor 18 and circulator 12.
9 and a detector 14 for multiplying the local oscillation signal by the response signal
a, a detector 14b that multiplies the local oscillation signal phase-shifted by 90 ° and the response signal, and a controller 15 'that decodes the multiplication result of the detectors 14a and 14b. However, the response device is the same as that shown in FIG.

The operation of the interrogation apparatus shown in FIG. 7 will be described. The received response signal Vs is Vs1, Vs1,
It is distributed to Vs2. On the other hand, the local oscillation signal Vl is 90 °
Two signals Vl whose phases differ by 90 ° due to the distributor 18
1, V12. When these signals are input to the homodyne detectors 14a and 14b, the demodulated signals V1 and V
2 is taken out. This will be described using mathematical expressions. If the phase difference between the local oscillation signal Vl and the response signal Vs is θ,
The phase difference between Vl1 and Vs1 becomes θ, and Vl2 and Vs2
And the phase difference is θ−90 °, the demodulated signal V1,
V2 is represented by the equations (6) and (7), respectively.

V1 = (│Vl│ ・ │Vs│ / 2) cosθ (6) V2 = (│Vl│ ・ │Vs│ / 2) sinθ = (│Vl│ ・ │Vs│ / 2) cos (Θ−90 °) (7) As can be seen from the equations (6) and (7), the detector 14
Since the outputs V1 and V2 of a and 14b are out of phase with each other by 90 °, the demodulated signals V1 and V2 do not become 0 at the same time, regardless of the relative distance relationship between the interrogator 1 ′ and the responder 2. That is, by processing the demodulated signals V1 and V2 by the control unit 15 ′, the demodulation of data is surely performed.

Next, a case will be described in which the amplitude-modulated local oscillation signal Vs is demodulated by the interrogator 1'of FIG. In the case of the amplitude modulation shown in FIG. 5, the detector 14a outputs θ = 90 °.
(State of points C1, C2, C3), the other detector 14b has θ = 0 ° (state of points A1, A2, A3).
Will be in. As a result, the output V1 of the detector 14a
Disappears, but the output V2 of the detector 14b becomes the maximum value. This relationship can be similarly explained in the case of the phase modulation shown in FIG.

[0021]

Since the interrogation device of FIG. 7 requires two systems of the homodyne detection circuit and the demodulation circuit, the interrogation device circuit becomes large in size and high in cost.
Even if the interrogation apparatus 1 ′ of FIG. 7 (same as the interrogation apparatus of FIG. 3) is used, when the interrogation signal and the response signal propagate through a plurality of routes (multipath) as shown in FIG. As can be seen from an example of the path characteristics (varies depending on the positions of the interrogation device and the response device), when the used frequency is point D, the received signal does not reach the required level and data communication cannot be performed.

The present invention has been made in view of the above problems, and enables reliable data communication regardless of the positional relationship between the interrogation device and the response device, and uses a compact and low-cost interrogation device. The purpose is to provide a device.

[0023]

SUMMARY OF THE INVENTION The present invention according to claim 1 for achieving the above object, responds to a carrier wave from an interrogator.
Answering device
Data communication system for transmitting and receiving data between a device and a response device
An interrogation device used for
Whichever of the multiple carrier waves of different frequencies
Order determined to generate a carrier of one frequency
Carrier wave output from the transmitting / receiving antenna by switching in sequence
The generating means and the response received by the transmitting / receiving antenna.
A signal from the device and an oscillation signal from the carrier wave generating means
Homodyne detection means for performing synchronous detection with
And means for demodulating the signal detected by the in-detection means.
Used in data communication systems characterized by
There is an interrogator. Further, the present invention according to claim 2 is
The carrier wave from the interrogator is reflected at the responder and the reflection
Data is transmitted and received between the interrogator and response device by modulating the wave
Is an interrogation device used in a data communication system that
The transmitting and receiving antennas and a plurality of different predetermined
Generates a carrier wave of any one of the wave number carrier waves
Carrier wave of different frequency when
Carrier wave output from the transmitting / receiving antenna by switching to
Live means and said response received by said transmitting and receiving antenna
A signal from a device and an oscillation signal from the carrier wave generating means
Homodyne detection means for performing synchronous detection of the
And means for demodulating the signal detected by the detection means.
Used in data communication systems characterized by
It is in the interrogator.

The interrogation device of the present invention according to claim 3 is
Modulating means for modulating the carrier wave from the carrier wave generating means
The said claim 1 or 2 characterized by the above-mentioned.
It is in the interrogator. Further, the quality of the present invention according to claim 4
The interrogator is a carrier for rewriting the data of the responding device.
The interrogation device according to claim 3, wherein the interrogation device generates a wave transmission.
It is in the table. Further, the carrier wave generation of the present invention according to claim 5 is
The live means is a single oscillator that oscillates at a frequency corresponding to the control signal.
Or equipped with a plurality of oscillating means
The inquiry apparatus according to any one of claims 1 to 4 is provided. Change
In the data communication system of the present invention according to claim 5,
The question according to any one of claims 1 to 5.
Carrier wave from device and interrogator
Response to send and receive data with the interrogator by modulating the
In a data communication system characterized by having a device
It

[0025]

In the interrogation device according to the present invention, the oscillating unit generates carrier waves having a plurality of frequencies. As a result, the demodulated signal does not disappear regardless of the relative distance between the fixed station and the mobile station. Further, even if the signal emitted from the interrogation device, reflected and modulated by the response device, and received by the interrogation device passes through a plurality of paths, it is received as a signal of a required level or higher. Therefore, data communication is performed regardless of the relative positions of the fixed station and the mobile station.

[0026]

FIG. 1 is a block diagram showing an embodiment of a communication device according to the present invention. The interrogator 1 has a plurality of oscillators (11a, 11b ...) Which oscillate different frequencies and a SW which selects an arbitrary oscillator by a control signal from the controller 15a.
Reference numeral 10 includes a circulator 12, a transmission / reception antenna 13, a detector 14, a controller 15 a, and an input / output terminal 16.

The oscillation frequencies (fa, fb ...) Of the plurality of oscillators (11a, 11b ...) Are the frequency F1 at which the phase difference θ has a value different from the point N in FIG. 5, and the point D in FIG. Unlike the above, the frequency F2 at the point E is set to be included. It is assumed that the reflective modulator 22 of the interrogator 2 is amplitude-modulated.

The operation of the inquiry device 1 of FIG. 1 will be described. The control unit sets SW10 to the oscillator 11a. Oscillator 11a
Is the oscillation frequency fa. The inquiry device 1 and the response device 2 are
Local oscillation signal V1 and response signal V at oscillation frequency fa
It is assumed that there is a positional relationship such that the phase difference θ of 2 becomes the N point in FIG. At this time, as can be seen from the conventional example, the demodulated signal disappears and data communication cannot be performed. The control unit sets SW10 to the oscillator 11b. Oscillation frequency fb of oscillator 11b
Then, the phase difference θ between the local oscillation signal Vl and the response signal Vs is usually different from the N point, and the demodulated signal is extracted and data communication is performed. This relationship is similarly explained when the reflective modulator 22 is performing phase modulation. Next, a case of propagating through a plurality of routes as shown in FIG. 8 will be described. The control unit is SW
10 is set to the oscillator 11a. The oscillation frequency fa is shown in FIG.
The frequency becomes the point D. At this time, as shown in the section "Problems to be solved by the invention", reflected signals cancel each other out, and data communication cannot be performed. The control unit sets SW10 to the oscillator 11b. The oscillation frequency fb of the oscillator 11b is usually different from the point D, and the data communication is performed without the reflected waves canceling each other. Even at the oscillation frequency fb,
Even if data communication is not possible like the oscillation frequency fa, the oscillation frequencies (fa, fa) of the plurality of oscillators (11a, 11b ...).
Since the frequencies f1 and F2 are always included in fb ...), data communication is always performed by sequentially switching the oscillators (11a, 11b ...).

In the above description, the control unit is described as a mode in which the SW10 is switched when data communication cannot be performed. However, regardless of the communication situation, the SW1 can be switched in a predetermined procedure.
You may switch 0.

Oscillators (11a, 11b ...) And SW
10 may use a synthesizer type oscillator, and may use a system of switching the frequency by giving data of the oscillation frequency from the control unit.

In the above embodiment, the oscillators (11a, 11b) are
..) is used as it is, but the same effect can be obtained by using a signal obtained by modulating the signal of the oscillator (11a, 11b ...) With a modulator.
In order to increase the communication range, an amplifier may be inserted in the path for receiving and re-radiating the carrier wave at the transponder. There are various ways to insert an amplifier,
FIG. 2 shows an example thereof.

In the above, the interrogation device reads data from the response device, but the response device may be provided with a demodulation function to write data.

[0033]

According to the present invention, by switching the oscillator (that is, switching the oscillating frequency), no matter what the relative distance between the fixed station and the mobile station is, the signals to be transmitted and received can be transmitted through a plurality of routes. Even if the data passes through, the data can be surely demodulated.

Further, the detecting means of the fixed station needs only one system, and it is possible to reduce the size and cost as compared with the conventional example (FIG. 7).

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a data communication device according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the response device in the data communication device according to the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional data communication device using a reflection type modulator.

FIG. 4 is a diagram showing a relationship between VDC and a phase difference θ.

FIG. 5 is a diagram illustrating the detection operation of the interrogation device when the response device performs amplitude modulation.

FIG. 6 is a diagram illustrating the detection operation of the interrogation device when the response device performs phase modulation.

FIG. 7 is a block diagram showing a configuration of a conventional inquiry device.

FIG. 8 is a diagram illustrating a case where an interrogation device and a response device have a multipath relationship.

FIG. 9 is a diagram showing multipath characteristics of an inquiry device and a response device.

[Explanation of symbols]

1 Interrogation device 2 response device External device 11a, 11b oscillator 10 switches 12 Circulator 13 Transmit / receive antenna 14 Detector 15 Control unit 21 transmitting and receiving antenna 22 Reflective modulator 25 Control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-323025 (JP, A) JP-A-3-85931 (JP, A) JP-A-4-140685 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H04B ^7/ 24-7/26 102 H04Q ^7/ 00-7/38

Claims (6)

(57) [Claims] 1. A response device receives a carrier wave from an inquiry device.
The interrogator and the response device are reflected by modulating the reflected wave.
Quality used in data communication systems that send and receive data over and over
The transmitting and receiving antenna and the carrier wave of a plurality of predetermined different frequencies.
Defined to generate a carrier of one frequency
Transport that switches in order and outputs from the transmitting / receiving antenna
From the response device received by the wave generating means and the transmitting / receiving antenna
Synchronous detection of signal and oscillating signal from the carrier generating means
Homodyne detection means for performing, and demodulating the signal detected by the homodyne detection means
And a data communication system
Interrogation device used for . 2. A carrier from an interrogator in a responder
The interrogator and the response device are reflected by modulating the reflected wave.
Quality used in data communication systems that send and receive data over and over
The transmitting and receiving antenna and the carrier wave of a plurality of predetermined different frequencies.
It generates a carrier wave of one frequency and cannot perform data communication.
When the carrier wave of different frequency is selected,
A carrier wave generating means for outputting from an antenna, and the response device received by the transmitting / receiving antenna.
Synchronous detection of signal and oscillating signal from the carrier generating means
Homodyne detection means for performing, and demodulating the signal detected by the homodyne detection means
And a data communication system
Interrogation device used for. 3. The interrogation device is provided from the carrier wave generating means.
A modulation means for modulating the carrier wave of
The inquiry device according to claim 1 or 2. 4. The interrogation device collects data from the response device.
A contract characterized by generating a carrier wave for rewriting
The inquiry device according to claim 3. 5. The carrier wave generating means corresponds to a control signal.
A single or multiple oscillating means
The method according to any one of claims 1 to 4, further comprising :
Inquiry device. 6. The method according to any one of claims 1 to 5.
Reflects the interrogator described and the carrier wave from the interrogator
Then, the reflected wave is modulated and data is transmitted with the interrogator.
Data communication characterized by having a response device for transmitting and receiving
Belief system.