JP2000251032A - Transmission/reception circuit and transmission/reception circuit system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission/reception circuit and a transmission/reception circuit system that an output is increased by utilizing a reception coil as the resonance coil of a transmission coil at the time of transmission and a reception sensitivity is improved by decreasing a signal to turn to the reception coil by canceling transmission coil matching at the time of reception. SOLUTION: This system performs the transmission of power and signals and the reception of signals with electromagnetic waves and is provided with a transmission coil 3, a reception coil 4 having an electromagnetic coupling relation with this transmission coil, a resonance capacitor 32 for transmission connected to the reception coil, a reception coil matching circuit 7 connected to the reception coil and switching means 30 and 31 for connecting the resonance capacitor for transmission between both the terminals of the reception coil at the time of transmission, disconnecting the reception coil from the reception coil matching circuit, disconnecting the resonance capacitor for transmission from the reception coil at the time of reception and connecting the reception coil to the reception coil matching circuit, and the resonance capacitor for transmission has capacitance so that the resonance frequency of the transmission coil can be a frequency for transmission when the reception coil is to be functioned as a resonance coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reader / writer, an IC card, an FA (Factory Automation) tag, and the like, which transmit power and a signal from one side to a non-powered side and receive only a response signal from the other side. And a transmission / reception circuit used in a batteryless non-contact data carrier system and the like, and a transmission / reception circuit system.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional transmission / reception circuit system of this kind, which comprises a reader / writer and a tag. The frequency of the reader / writer transmission power / data signal 52 transmitted from the reader / writer 1 to the tag 2 is f ₁ , and the frequency of the reader / writer received data signal 58 transmitted from the tag 2 to the reader / writer 1 is f ₂ .

[0003] The reader / writer 1 comprises a radio control device 20 and
The transmission circuit 9, the transmission coil matching circuit 6, and the transmission coil 3
(L ₁ ), receiving coil 4 (L ₃ ), and receiving coil matching circuit 7
And a receiving circuit 10. The transmitting circuit 9 includes a modulator 13 and an oscillator 23, and the receiving circuit 10 includes a filter 14 and a filter 15.

The tag 2 includes a transmitting / receiving coil 5 (L ₂ ), a tag resonance capacitor 8 (C _d ), and a load circuit 25. The load circuit 25 includes a tag transmitting circuit 11, a tag receiving circuit 12, a clock holding circuit 16, a rectifying circuit 17,
It comprises a smoothing circuit 24, a control unit 21 and a memory 22. The smoothing circuit 24 includes a capacitor 18 (C _c ) and a resistor 1
9 (R _c ).

FIG. 9 shows a transmitting circuit 9, a transmitting coil matching circuit 6, a transmitting coil 3, a transmitting / receiving coil 5, a tag resonance capacitor 8, a synthesizing circuit 25, a receiving coil 4,
This is an equivalent circuit of a transmission system including the reception coil matching circuit 7 and the reception circuit 10. In this example, the transmission coil matching circuit 6 includes a capacitor 70 (C _s1 ), a capacitor 71 (C _p1 ),
The receiving coil matching circuit 7 includes a capacitor 72 (C _s3 ) and a capacitor 73 (C _p3 ).

Referring to FIG. 9, a transmission coil matching circuit 6
A method of adjusting the transmission circuit 9 and the reception coil matching circuit 7 will be described. Since the adjustment is performed separately for the reader / writer 1 and the tag 2, the mutual inductance M ₂₁ 77 between the transmitting coil 3 and the transmitting / receiving coil 5 and the mutual inductance M ₃₂ 78 between the transmitting / receiving coil 5 and the receiving coil 4 are considered to be 0.

On the other hand, since it is desirable that the directivity of the reader / writer 1 at the time of transmission and reception is the same, the transmission coil 3 and the reception coil 4 are generally arranged on the same plane on the same concentric circle. Therefore, a mutual inductance M ₃₁ 79 between the transmission coil 3 and the reception coil 4 exists. Therefore, the input impedance Z ₁ 101 as viewed from the terminal of the transmitting coil matching circuit 6 is the output impedance Z _c3 7 of the receiving circuit 10.
6, and can be expressed as in equation (1). However, if the angular frequency is ω and the frequency is f, ω = 2πf.

[0008]

(Equation 1)

The reason is that the transmitting coil 3 and the receiving coil 4
Can be converted into an equivalent circuit as shown in FIG.
Similarly, the input impedance Z ₃ 102 as viewed from the terminal of the receiving coil matching circuit 7 can be expressed by the following equation (2) using the input impedance Z _c1 74 of the transmitting circuit 9.

[0010]

(Equation 2)

To match the transmission coil 3 with the transmission circuit 9 at the frequency f ₁ of the reader / writer transmission power / data signal 52, the following conditions must be satisfied.

[0012]

(Equation 3)

In order to match the receiving coil 4 with the receiving circuit 10 at the frequency f ₂ of the reader / writer received data signal 58, the following conditions must be satisfied.

[0014]

(Equation 4)

In order to satisfy the equations (3) and (4), the capacitors C _s1 70, C _p1 71, C _s3 72,
By adjusting the capacitor C _p3 73, the power supplied from the transmission circuit 9 to the transmission coil 3 and the power supplied from the reception coil 4 to the reception circuit 10 become maximum.

Next, a method of adjusting the tag resonance capacitor 8 will be described. When the input impedance Z ₂ 103 viewed from the terminal of the transmission / reception coil 5 matches the combined impedance Z _c2 75 of the load circuit 25, the tag reception power 54 becomes maximum. But,
In general, the combined impedance Z _c2 75 is high and difficult to adjust, so that the voltage V ₂ 1003 applied to the combined impedance Z _c2 75 is maximized by adjustment by the tag resonance capacitor 8. The input impedance Z ₂ 103 can be expressed as in equation (5).

[0017]

(Equation 5)

The voltage V ₂ 1003 can be expressed by the following equation (6) using the current I ₂ 104 flowing in the opposite direction to the current flowing through the combined impedance Z _c2 75 and the current I ₂ '84 flowing through the transmitting / receiving coil 5.

[0019]

(Equation 6)

Therefore, the relationship between the current I ₂ '84 and the current I ₂ 104 is

[0021]

(Equation 7)

The current I ₂ '84 is determined by the level of the reader / writer transmission power / data signal 52 of the reader / writer 1. From equation (7), the current I ₂ 104 is also determined by the level of the reader / writer transmission power / data signal 52. When the level of the reader / writer transmission power / data signal 52 is constant, the current I ₂ 104 is constant, and the voltage V ₂ 1003 becomes the maximum at the frequency f ₁ when Expression (8) is satisfied.

[0023]

(Equation 8)

In order to maximize the voltage V ₂ 1003,
The capacitance of the tag resonance capacitor 8 is determined as in Expression (9).

[0025]

(Equation 9)

When adjusting the transmission / reception coil 5 only by the tag resonance capacitor 8, the voltage V ₂ 10
When 03 is the maximum, the tag reception power 54 ( _Pt ) becomes the maximum.

[0027]

(Equation 10)

Next, the operation will be described. Always, in the oscillator 23, the carrier 51 of frequency f ₁ is generated.
A reader / writer transmission data signal 50 is transmitted from the wireless control device 20 to the transmission circuit 9. The reader / writer transmission power / data signal 52 obtained by modulating the carrier wave 51 with the reader / writer transmission data signal 50 by the modulator 13 is transmitted from the transmission coil 3 to the tag 2. The transmission coil 3 is impedance-matched with the transmission circuit 9 at the frequency f ₁ by the transmission coil matching circuit 6.

The tag 2 receives the reader / writer transmission power / data signal 52 by the transmission / reception coil 5 and sends it to the rectifier circuit 1.
7. The tag reception power 54 of the tag 2 through the smoothing circuit 24
Get. The resonance frequency of the transmitting / receiving coil 5 is adjusted to the frequency f ₁ by the tag resonance capacitor 8. A part of the reader / writer transmission power / data signal 52
Is transmitted to the control unit 21 via the clock holding circuit 16. Also, the reader / writer transmission power / data signal 52
Is transmitted to the tag receiving circuit 12 as a tag reception data signal 55, further demodulated, becomes a reader / writer transmission data signal (demodulation) 56, and transmitted to the control unit 21.
The information of the tag 2 stored in the memory 22 is extracted or rewritten as necessary.

Further, the tag transmission data signal
No. 57 is transmitted to the tag transmission circuit 11. Frequency f₁of
A frequency obtained by modulating a tag transmission data signal 57 on a carrier wave 51
Number f_TwoOf the reader / writer received data signal 58 (actually
Changes the frequency of the clock, which is the carrier from reader / writer 1.
To generate a carrier (subcarrier) from tag 2
Is modulated by the tag transmission data signal 57), the transmission / reception coil
5 to the reader / writer 1. Reader / writer
1 is a receiving coil 4 for receiving a reader / writer received data signal.
58 is received. The receiving coil 4 is a receiving coil matching circuit 7
The frequency f _TwoAnd the receiving circuit 10
Matching. Reader / writer received data signal 5
8 is demodulated by the receiving circuit 10 and the tag transmission data signal (decoding
Key) 59, which is transmitted to the wireless control device 20.

[0031]

In such a conventional transmission / reception circuit as described above, since the transmission coil 3 and the reception coil 4 are disposed close to each other, the coupling between the transmission coil 3 and the reception coil 4 is large. The binding amount S ₃₁ 96 of the transmission coil 3 and the receiver coil 4 (see FIG. 11) can be expressed as follows.

In the equivalent circuit of FIG. 9, when the tag 2 is sufficiently separated from the reader / writer 1, the mutual inductance M ₂₁ 77 and the mutual inductance M ₃₂ 78 are considered to be zero. At this time, the terminal 90 of the transmitting coil 3
(See FIG. 11) In order to obtain the scattering parameter between the terminals 92 of the receiving coil 4, the equivalent circuit of FIG. 9 is considered as shown in FIG. Voltage V ₁ '80, current I ₁ '83, voltage V ₃ '8
2. The current I ₃ '85 has a relationship as shown in Expression (11).

[0033]

[Equation 11]

The standard impedance parameters between the terminal 1 'and the terminal 3' are the combined impedance Z _c1 '93 of the input impedance Z _c1 74 of the transmission coil matching circuit 6 and the transmission circuit 9, and the reception coil matching circuit 7 and the reception circuit 1
When the combined impedance Z _c3 '95 of the output impedance Z _c3 76 is 0, the equation (12) is obtained.

[0035]

(Equation 12)

The scattering matrix between the transmitting coil 3 and the receiving coil 4 can be expressed by the following equation (13).

[0037]

(Equation 13)

The coupling amount S ₃₁ between the transmitting coil 3 and the receiving coil 4
96 is equal to the component of the second row and the first column of the equation (13).
It can be expressed as 4).

[0039]

[Equation 14]

In other words, when the tag 2 is at a position where the tag 2 does not affect the reader / writer 1, the reader / writer transmission power / data signal 52 has sneak into the receiving coil 4.
That is, it could be expressed as in equation (15).

[0041]

(Equation 15)

When the tag 2 approaches the reader / writer 1,
A part of the reader / writer transmission power / data signal 52 radiated from the transmission coil 3 was received by the tag 2. for that reason,
Reader / writer received data signal 5 received by receiving coil 4
8, the ratio of the term in equation (14) is large, so that S / N
The ratio was small. Therefore, there is a problem that the receiving sensitivity is deteriorated and the communication distance is shortened. Conventionally, the receiving circuit 1
0, a filter 14, a filter 15, etc. are provided,
Loss were many because it was cut component interrogator transmit power and data signals 52 for the frequency f _1.

The present invention solves the above problems,
This is made to effectively utilize the reader / writer transmission power / data signal. When the reader / writer transmission power / data signal is transmitted, the reception coil is used as the resonance coil of the transmission coil, so that the reader / writer transmission power / data signal is used. And increase the communication distance by reducing the reader / writer transmission power and data signal sneaking into the receiver coil by increasing the output of the receiver and removing the matching of the transmitter coil when receiving the reader / writer received data signal, and improving the reception sensitivity. It is another object of the present invention to provide a transmission / reception circuit and a transmission / reception circuit system capable of reducing the number of transmission coil matching circuits and the number of filters in the reception circuit.

[0044]

SUMMARY OF THE INVENTION In view of the above-mentioned object, the present invention relates to a transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave, wherein a transmitting coil and an electromagnetic coupling relationship with the transmitting coil are provided. A receiving coil, a transmitting resonance capacitor connected between both ends of the receiving coil, a receiving coil matching circuit connected to the receiving coil, and connecting the transmitting resonance capacitor between both ends of the receiving coil during transmission. Switching means for disconnecting the reception coil from the reception coil matching circuit, disconnecting the connection between the transmission resonance capacitor and the reception coil during reception, and connecting the reception coil to the reception coil matching circuit at the time of reception. The resonance frequency of the transmission coil is transmitted when the capacitor functions as a resonance coil when the reception coil transmits. In transceiver circuit characterized by having a capacity such that the frequency.

The present invention also relates to a transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave, wherein the transmitting coil, a receiving coil having an electromagnetic coupling relationship with the transmitting coil, and the receiving coil are connected to the transmitting coil. The connection between the receiving coil matching circuit and the both ends of the receiving coil at the time of transmission, the receiving coil is separated from the receiving coil matching circuit, the both ends of the receiving coil are separated at the time of receiving, and these are connected to the receiving coil matching circuit. Means having a position and a shape such that the resonance frequency of the transmission coil becomes a frequency for transmission when the reception coil functions as a resonance coil during transmission.

Also, the present invention is characterized in that the switching means connects the transmission resonance capacitor between both ends of the reception coil during transmission and disconnects the transmission coil during reception, and a transmission coil matching circuit which connects the reception coil during transmission. And a receiving switch for connecting them at the time of reception, and performing modulation for signal transmission by opening and closing the transmission switch or the receiving switch at the time of transmission. .

Further, according to the present invention, the transmission / reception means connects the transmission resonance capacitor between both ends of the reception coil during transmission, disconnects the transmission resonance capacitor during reception, and connects the reception coil to a reception coil matching circuit during transmission. And a receiving switch for disconnecting the receiving coil from the receiving coil matching circuit at the time of transmission and connecting them at the time of receiving, and one end of the transmitting resonance capacitor is connected to one end of the receiving coil. In addition, the reception coil matching circuit has two input terminals, and the reception changeover switch connects a connection point between the reception coil and the transmission resonance capacitor to one input terminal of the reception coil matching circuit during reception. A switch that connects and releases it at the time of transmission. A switch that connects the other end of the receiving coil to the other input terminal of the receiving coil matching circuit, and switches the other end of the receiving coil to the other end of the transmitting resonance capacitor for transmission during transmission. The transmission / reception circuit according to claim 1 or 2, wherein

The present invention also relates to a transmission / reception circuit for receiving power and a signal and transmitting a signal by using an electromagnetic wave, comprising: a reception coil; a transmission coil having an electromagnetic coupling relationship with the reception coil; , A receiving coil connected to the transmitting coil, a transmitting coil matching circuit connected to the transmitting coil, and the receiving resonant capacitor connected between both ends of the transmitting coil during reception, and the transmitting coil separated from the transmitting coil matching circuit. Switching means for disconnecting the reception resonance capacitor and the transmission coil at the time of transmission and connecting the transmission coil to the transmission coil matching circuit, wherein the reception resonance capacitor is used as the resonance coil at the time of reception by the transmission coil. When it functions, it has a capacity so that the resonance frequency of the reception coil becomes the reception frequency. In transceiver circuit according to claim Rukoto.

The present invention also resides in a transmission / reception circuit system comprising any one of the first to fourth transmission / reception circuits and the fifth transmission / reception circuit.

Further, according to the present invention, the switching means is FE
A transmission / reception circuit characterized by including a semiconductor analog switch using T.

According to the present invention, there is provided a transmission / reception circuit, wherein the switching means includes a relay switch.

[0052]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the embodiments of the present invention described below, the same or corresponding parts as those of the above-described conventional example are denoted by the same reference numerals.

Embodiment 1 FIG. 1 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to an embodiment of the present invention. In the figure, a transmission switch 30 is shown.
(SW ₁ ) and the receiving switch 31 (SW ₂ ) serve to switch the receiving coil 4 to the resonance coil of the transmitting coil 3. The transmission switch 30 is a two-terminal switch, and the reception switch 31 is a four-terminal switch. Transmitting resonance capacitor 32 (C _o) when the receiver coil 4 functions as a resonant coil, the resonant frequency of the transmitter coil 3 is adjusted to the frequency f _1. Receiving coil matching circuit 7 when the receiving coil 4 functions as a receiving coil, impedance matching and receiving coil 4 of the receiving circuit 10 at the frequency f _2.

Next, the operation will be described. Always, in the oscillator 23, the carrier 51 of frequency f ₁ is generated.
When transmitting the reader / writer transmission power / data signal 52,
The switch for transmission 30 is turned on and the switch for reception 31 is turned off by the switch signal 60 from the wireless control device 20. At this time, the receiving coil 4 is completely disconnected from the receiving circuit 10. Furthermore, the transmission coil 3 is impedance-matched with the transmission circuit 9 at the transmission frequency f ₁ by adjusting the transmission resonance capacitor 32. Hereinafter, a method of adjusting the transmission resonance capacitor 32 will be described.

FIG. 12 is an equivalent circuit of the transmission system of the reader / writer 1 when the transmission switch 30 is turned on and the reception switch 31 is turned off.
However, it is assumed that tag 2 is sufficiently far away. At this time, the input impedance Z ₁ 11 viewed from the terminal of the transmission coil 3
5 can be expressed as in equation (16).

[0056]

(Equation 16)

In order to match the impedance of the transmission coil 3 to the transmission circuit 9 at the frequency f ₁ of the reader / writer transmission power / data signal 52, it suffices to satisfy Expression (3). ).

[0058]

[Equation 17]

In this state, the reader / writer transmission power / data signal 52 is transmitted from the transmission coil 3 to the tag 2 in the same manner as in the conventional example.
Send to

Since the receiving coil 4 is completely separated from the receiving circuit 10, the coupling amount S _s1 '97 between the transmitting coil 3 and the receiving coil 4 becomes zero. Since the transmission coil 3 is impedance-matched to the transmission circuit 9, the amount of reflection S ₁₁ '98 at the terminal of the transmission coil 3 is also zero. In FIG. 12, since there is no transmission coil matching circuit 6, all input power to the transmission coil 3 is theoretically radiated to the air. Therefore, the transmission output increases as compared with the conventional example.

The reader / writer transmission power of tag 2
The reception of the data signal 52 and the transmission of the reader / writer received data signal 58 are the same as in the conventional example.

When the reader / writer received data signal 58 is received, the switch 31 for reception is turned on and the switch 30 for transmission is turned off by the switch signal 60 from the radio controller 20. Further, the receiving coil 4
Is adjusted by adjusting the receiving coil matching circuit 7 so that the receiving frequency f ₂
And impedance matching with the receiving circuit 7. Resonant frequency of the transmission coil 3 deviates from the frequency f _1. Hereinafter, a method of adjusting the reception coil matching circuit 7 will be described.

FIG. 13 shows an equivalent circuit of the transmission system of the reader / writer 1 when the receiving switch 31 is turned on and the transmitting switch 30 is turned off. However, it is assumed that tag 2 is sufficiently far away. At this time, the input impedance Z ₃ viewed from the terminal of the receiving coil matching circuit 7
116 can be expressed as in equation (18).

[0064]

(Equation 18)

In order to match the impedance of the receiving coil 4 to the receiving circuit 10 at the frequency f ₂ of the reader / writer received data signal 58, the expression (18) should satisfy the expression (4). By adjusting the capacitors C _s3 72 and C _p3 73 in this manner, the power supplied from the receiving coil 4 to the receiving circuit 10 is maximized, and the receiving sensitivity is improved.

At this time, the input impedance Z ₁ 115 as viewed from the terminal of the transmitting coil 3 is as shown in equation (19). As shown in the equation (20), the impedance of the transmission coil 3 cannot be matched with the transmission circuit 9 at the frequency f ₁ , and the reflection amount S ₁₁ '98 occurs.

[0067]

[Equation 19]

The coupling amount S ₃₁ ″ 100 between the transmission coil 3 and the reception coil 4 can be expressed as in the equation (21), as described above.

[0069]

(Equation 20)

As shown in equation (22), the coupling amount S ₃₁ ″ 100 between the transmitting coil 3 and the receiving coil 4 is smaller than the coupling amount S ₃₁ ′97 between the transmitting coil 3 and the receiving coil 4.

[0071]

(Equation 21)

As described above, the ratio of the reader / writer transmission power / data signal 52 to the reader / writer reception data signal 58 received by the receiving coil 4 is smaller than that of the conventional technique. Therefore, the S / N ratio is larger than that of the conventional technique, and the receiving sensitivity is improved. Further, compared with the conventional configuration, the number of filters 15 and the like in the receiving circuit can be reduced.

[0073] At this time, the resonant frequency of the transmission coil 3 is so out of the frequency f _1, the clock 53 and the tag received power 54, with the tag 2 decreases. To make up for this,
The tag 2 has a clock holding circuit 16 and a capacitor C _c 18 having a large capacity.

As described above, the transmission output is increased when the reader / writer transmission power / data signal 52 is transmitted, and the reception sensitivity is improved when the reader / writer reception data signal 58 is received, so that the communication distance can be extended. Becomes At the same time, the number of transmission coil matching circuits 6 and the number of filters in the reception circuit 10 can be reduced.

For the same input power, the transmission output of the reader / writer and the reception sensitivity of the prior art and the first embodiment, and the relationship between the tag reception power 54 and the time are as follows:
Each is shown in FIG. When transmitting the reader / writer transmission power / data signal 52, the transmission output and the tag reception power 5
4 is higher in the first embodiment. Also, when receiving the reader / writer received data signal 58, the receiving sensitivity is set to the value in the first embodiment.
Is higher.

Embodiment 2 In the first embodiment, the resonance frequency of the transmission coil 3 is adjusted to the frequency f ₁ by using the reception coil 4 and the transmission resonance capacitor 32. Next, the resonance frequency of the transmission coil 3 is adjusted by using only the reception coil 4. Embodiment 2 in which is adjusted to the frequency f ₁ is shown. FIG.
FIG. 3 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to the present invention in such a case. Compared with the first embodiment, the transmission resonance capacitor 32 does not exist. Alternatively, the position of the receiver coil 4, or shape by adjusting the resonant frequency of the transmitter coil 3 is adjusted to the frequency f _1. The adjustment method is described below.

FIG. 14 shows an equivalent circuit of the transmission system of the reader / writer 1 when the transmission switch 30 is turned on and the reception switch 31 is turned off.
However, it is assumed that the tag 2 is sufficiently far away. As described above, the input impedance Z ₁ '117 viewed from the terminal of the transmission coil 3 can be expressed as in Expression (23).

[0078]

(Equation 22)

In order to match the impedance of the transmission coil 3 to the transmission circuit 9 at the frequency f ₁ of the reader / writer transmission power / data signal 52, it is sufficient to satisfy Expression (3). Therefore, the mutual inductance M ₃₁ 79 is calculated by Expression (24) ).

[0080]

(Equation 23)

The position of the receiving coil 4 is adjusted on the same plane or on the concentric axis, or the position of the receiving coil 4 is adjusted so that the mutual inductance between the transmitting coil 3 and the receiving coil 4 becomes the amount as shown in the equation (24). Adjust the shape of coil diameter, number of turns, winding interval, coil wire diameter, etc.

In this state, the reader / writer transmission power / data signal 52 is transmitted from the transmission coil 3 to the tag 2 as in the conventional example.
Send to The operation is the same as in the first embodiment. In addition to the first embodiment, there is an advantage that the number of transmission resonance capacitors 32 is reduced.

Embodiment 3 In the first embodiment,
Modulation is performed by the modulator 13 in the transmission circuit 9 at the time of transmission. Next, a transmission and reception circuit that performs modulation by the transmission switch 30 or the reception switch 31 is described below. FIG. 3 is a configuration diagram of a transmission / reception circuit system including the transmission / reception circuit according to the present invention in such a case.

Next, the operation will be described. Always, in the oscillator 23, the carrier 51 of frequency f ₁ is generated.
Reader / writer transmission data signal 5 from wireless control device 20
When 0 is on, the transmission switch 30 is turned on. When the reader / writer transmission data signal 50 from the wireless control device 20 is off, the transmission switch 30 is turned off. The carrier wave 51 is subjected to amplitude modulation by utilizing the fact that the transmission output is increased or decreased by switching the transmission switch 30.

The principle of amplitude modulation will be described. When the transmission changeover switch 30 is on, the transmission coil 3 is impedance-matched to the transmission circuit 9 at the frequency f ₁ as shown in Expression (3). Therefore, theoretically, all input power to the transmission coil 3 goes into the air. Since it is radiated, the transmission power increases.
When the transmission selector switch 30 is off, the transmitter coil 3 at a frequency f ₁ will not take a transmitting circuit 9 and the impedance matching as in equation (20), the reflection amount S ₁₁ '98 occurs. The amount of input power to the transmission coil 3 radiated into the air decreases, and the transmission output decreases. The operation at the time of receiving the reader / writer received data signal 58 is the same as in the first embodiment.

The third embodiment has an advantage that the modulator 13 becomes unnecessary.

Embodiment 4 In the first embodiment, a coil circuit with a switch is realized by using a four-terminal switch as the receiving switch 31. Next, an embodiment in which a two-terminal switch is used as the receiving switch will be described. FIG. 4 is a configuration diagram of a transmission / reception circuit system including the transmission / reception circuit according to the present invention in such a case. In the figure, a transmission / reception switch 33 and a reception switch 34 serve to switch the receiving coil 4 to the resonance coil of the transmitting coil 3. Transmitting resonance capacitor 32 when the receiver coil 4 functions as a resonant coil, the resonant frequency of the transmitter coil 3 is adjusted to the frequency f _1. When the receiving coil 4 functions as a receiving coil, the receiving coil matching circuit 7
At the frequency f ₂ .

Next, the operation will be described. When the reader / writer transmission power / data signal 52 is transmitted, the transmission / reception switch 33 is connected to the terminal a and the reception switch 34 is turned off by the switch signal 60 from the wireless control device 20. Hereinafter, similarly to the operation method of the first embodiment, the reader / writer transmission power / data signal 52 is transmitted from the transmission coil 3 to the tag 2, and the tag 2 receives this signal.
A reader / writer reception data signal 58 is transmitted. At the time of receiving the reader / writer received data signal 58, the receiving switch 34 is turned on by the switch signal 60 from the wireless control device 20, and the transmitting / receiving switch 3
3 is connected to terminal b. Receiver coil 4 by the receiving coil matching circuit 7 is impedance matched at the receiving frequency f _2. Resonant frequency of the transmission coil 3 deviates from the frequency f _1.

The receiving switch is the same as that of the first embodiment.
In contrast to the four-terminal switch, the two-terminal switch is used, so there is an advantage that the number of terminals is reduced and the cost is reduced.

Embodiment 5 In the above embodiment, the transmission / reception circuit is applied to the reader / writer 1, but next, the case where the transmission / reception circuit is applied to the tag 2 will be described below. FIG. 5 is a configuration diagram of a transmission / reception circuit system including the transmission / reception circuit according to the present invention in such a case.

The tag 2 includes a tag receiving coil 40 (L ₂ )
The tag transmission coil 41 (L ₄ ) has two coils. The tag receiving coil 40 and the tag transmitting coil 41 are connected by a mutual inductance M ₄₂ 107 (see FIG. 15).
The tag receiving switch 42 (SW ₄ ) and the tag transmitting switch 43 (SW ₃ )
To the resonance coil of the tag reception coil 40 and the normal transmission coil. The tag reception resonance capacitor 44 (C _o ′) is adjusted so that the resonance frequency of the tag reception coil 40 becomes the frequency f ₁ when the tag transmission coil 41 functions as a resonance coil. Tag transmitting coil matching circuit 45 when the tag transmitting coil 41 functions as a transmit coil, tag transmit coil 41 at frequency f ₂
Impedance matching.

Next, the operation will be described. The operations of transmitting the reader / writer transmission power / data signal 52 and receiving the reader / writer received data signal 58 in the reader / writer 1 are the same as those in the related art.

When the tag 2 receives the reader / writer transmission power / data signal 52, the tag receiving signal switch 61 from the control unit 21 sends the tag receiving switch 42.
Is turned on, and the tag transmission changeover switch 43 is turned off. At this time, the tag transmission coil 41 is connected to the tag transmission circuit 11.
Completely separated from Further, the tag receiving coil 40
Is the adjustment of the tag receiving resonance capacitor 44, the frequency f ₁ of the reader writer transmission power data signal 52, a tag receiving circuit 12, a clock hold circuit 16, a rectifier circuit 17, a smoothing circuit 24, the control unit 21 and the combined impedance Z _c2 '105 of the memory 22 are matched. Hereinafter, a method of adjusting the tag reception resonance capacitor 44 and the tag transmission coil matching circuit 45 will be described.

FIG. 15 shows the tag receiving switch 4.
2 is an equivalent circuit of the transmission system of the tag 2 when the tag transmission switch 43 is turned off and the tag transmission switch 43 is turned off. The tag transmission coil matching circuit 45 includes a capacitor _Cs4 109 and a capacitor _Cp4 110. However, it is assumed that the reader / writer 1 is sufficiently far away. In this case, the input impedance Z ₂ 1 as viewed from the terminal of the tag information receiving coil 40
11 can be expressed as in equation (25).

[0095]

(Equation 24)

To match the impedance of the tag receiving coil 40 to the combined impedance Z _c2 '105 at the frequency f ₁ of the reader / writer transmission power / data signal 52, the following equation is used.
Since (25) satisfies Expression (26), the tag receiving resonance capacitor 44 is determined as in Expression (27).

[0097]

(Equation 25)

In this state, the reader / writer transmission power / data signal 52 is received by the tag receiving coil 40 as in the conventional example.

Since the tag transmission coil 41 is completely separated from the tag transmission circuit 11, the coupling amount S ₄₂ '108 between the tag reception coil 40 and the tag transmission coil 41 becomes zero. Since the tag receiving coil 40 is impedance-matched with the combined impedance Z _c2 '105, the amount of reflection S ₂₂ ' 1100 at the terminal of the tag receiving coil 40 is also zero, and the receiving sensitivity is improved as compared with the conventional example.

At the time of transmission from the tag 2 to the reader / writer 1, the tag receiving switch 42 is turned off and the tag transmitting switch 43 is turned on by the tag switch signal 61 from the control unit 21. Tag transmission coil 41
It is a tag transmission coil matching circuit 45 is the tag transmitting circuit 11 and the impedance matching at the frequency f _2. Resonant frequency of the tag receiver coil 40 deviates from the frequency f _1. Hereinafter, an adjustment method of the tag transmission coil matching circuit 45 will be described.

FIG. 16 shows the tag receiving switch 4.
2 is an equivalent circuit of the transmission system of the tag 2 when the tag transmission switch 43 is turned on and the tag transmission switch 43 is turned on. However, it is assumed that the reader / writer 1 is sufficiently far away. At this time, the input impedance Z ₄ 113 viewed from the terminal of the tag transmission coil matching circuit 45 can be expressed as Expression (28).

[0102]

(Equation 26)

In order to match the impedance of the tag transmission coil 41 to the tag transmission circuit 11 at the frequency f ₂ of the reader / writer received data signal 58, the expression (28) should satisfy the expression (29).

[0104]

[Equation 27]

As described above, by adjusting the capacitors C _s4 109 and C _p4 110, the tag transmission circuit 11
Power is maximized supplied to the tag transmitter coil 41, as compared with the conventional method, the transmission output at the frequency f ₂ is increased.

At this time, the input impedance Z ₂ 111 as viewed from the terminal of the tag receiving coil 40 is expressed by the following equation (30). As shown in Expression (25), at the frequency f ₁ , the tag receiving coil 40 cannot match the impedance with the combined impedance Z _c2 '105, and the reflection amount S ₂₂ ' 1100 occurs.

[0107]

[Equation 28]

Tag receiving coil 40 and tag transmitting coil 41
Binding amount S ₄₂ "114, like the above, expressed as equation (32).

[0109]

(Equation 29)

As shown in the equation (33), the coupling amount S ₄₂ '114
Is smaller than the binding amount S ₄₂ 108 described above.

[0111]

[Equation 30]

As described above, the ratio of the reader / writer reception data signal 58 to the reader / writer transmission power / data signal 52 received by the tag receiving coil 40 is smaller than that of the conventional technique. Therefore, the S / N ratio is larger than that of the conventional technique, and the receiving sensitivity is improved.

As described above, when the tag receives the reader / writer transmission power / data signal 52, the tag receiving coil 40 resonates with the tag transmitting coil 41, so that the receiving sensitivity is improved. During transmission of the reader-writer receives the data signal 58 in the tag 2, the resonant frequency of the tag receiver coil 40 deviates from the frequency f _1, the reader writer transmission power data signal 52 sneaking from the tag transmitting coil L ₄ 41 to the tag receiver coil 40 The transmission power of the tag 2 increases. Since the transmission output to the reader / writer 1 increases and the reception sensitivity of the tag 2 improves, the communication distance can be extended.

Embodiment 6 FIG. In the above embodiment, the switch-equipped coil circuit is connected to the reader / writer 1 or the tag 2.
However, the transmission / reception circuit is changed to the reader / writer 1
The case where the present invention is applied to both the tag and the tag 2 is shown below. FIG.
1 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to the present invention in such a case. The configuration and role of the transmission / reception circuit are the same as those in the first embodiment in the case of the reader / writer 1 and in the fifth embodiment in the case of the tag 2.

Next, the operation will be described. The operation of the reader / writer 1 up to the transmission of the reader / writer transmission power / data signal 52 is the same as in the first embodiment. Tag 2
The operation from reception of the reader / writer transmission power / data signal 52 to transmission of the reader / writer reception data signal 58 is the same as in the fifth embodiment. The operation of the reader / writer 1 after receiving the reader / writer reception data signal 58 is the same as that of the first embodiment.

As described above, in the reader / writer 1,
When transmitting the reader / writer transmission power / data signal 52,
Since the transmitting coil 3 resonates with the receiving coil 4, the magnetic field generated near the transmitting coil 3 increases, and the transmission output from the reader / writer 1 can be increased. When the tag 2 receives the reader / writer transmission power / data signal 52, the tag receiving coil 40
Resonates with the tag transmission coil 41, so that the reception sensitivity of the tag 2 is improved.

[0117] in the tag 2, when transmission of the reader-writer received data signal 58, the resonant frequency of the tag receiver coil 40 deviates from the frequency f _1, the reader-writer receives the data signal 58 sneaking from the tag transmitter coil 41 to the tag receiver coil 40 As a result, the transmission output from the tag 2 can be increased. In the reader writer 1, at the time of reception of the reader writer received data signal 58, the resonant frequency of the transmission coil 3 is deviated from the frequency f _1, the receiving coil 4 from the transmitter coil 3
Since the reader / writer transmission power / data signal 52 wrapping around is reduced, the receiving sensitivity is improved. Further, as compared with the conventional configuration of FIG. 7, since the transmission coil matching circuit 6 and the tag resonance capacitor 8 are not provided, losses in the transmission circuit 9 and the tag reception circuit 12 are small.

The communication output can be extended by increasing the transmission output of the reader / writer 1 and the tag 2 and improving the receiving sensitivity. At the same time, a synergistic combination of the first embodiment with respect to the reader / writer 1 and the fifth embodiment with respect to the tag 2 such that the transmission coil matching circuit 6, the filter 15 in the reception circuit 10, and the tag resonance capacitor 8 can be reduced. There is an advantage that a special effect can be obtained.

In the above embodiment, the reader / writer 1 according to the first embodiment is employed. However, the present invention is not limited to this, and any of the configurations according to the second to fourth embodiments may be applied. Is also possible, and a considerable effect can be obtained.

Embodiment 7 FIG. In this embodiment, the transmission changeover switches 30 and 43 of the above embodiments, and the reception changeover switches 31 and 42, for example, a semiconductor analog switch using an FET as shown in FIG. 17 are used. Since the transition time of the semiconductor analog switch is short, there is an advantage that high-speed communication is possible.

Embodiment 8 FIG. In this embodiment, for example, a relay switch using a coil as shown in FIG. 18 is used as the reception switch 31 and the transmission switch 43 in each of the above embodiments. Since the relay switch has a high withstand voltage, there is an advantage that high output transmission is possible.

[0122]

As described above, according to the present invention, there is provided a transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave, the transmitting coil, the receiving coil having an electromagnetic coupling relationship with the transmitting coil, and A transmission resonance capacitor connected between both ends of the reception coil, a reception coil matching circuit connected to the reception coil, and a transmission resonance capacitor connected between both ends of the reception coil during transmission and reception of the reception coil. Switching means for disconnecting from the coil matching circuit, disconnecting the transmission resonance capacitor and the reception coil during reception and connecting the reception coil to the reception coil matching circuit at the time of reception, wherein the transmission resonance capacitor is connected to the reception coil. When functioning as a resonance coil during transmission, the resonance frequency of the transmission coil becomes the frequency for transmission. Since the transmitting and receiving circuit, characterized in that it comprises a a capacity, the transmission output is increased at the time of transmission,
In addition, since the reception sensitivity is improved during reception, the communication distance can be extended, and the filters in the transmission coil matching circuit and the reception circuit can be reduced.

A transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave includes a transmitting coil, a receiving coil having an electromagnetic coupling relationship with the transmitting coil, and a receiving coil connected to the receiving coil. A matching circuit, connecting both ends of the receiving coil at the time of transmission and disconnecting the receiving coil from the receiving coil matching circuit,
Switching means for disconnecting both ends of the receiving coil at the time of reception and connecting them to a receiving coil matching circuit,
When the receiving coil functions as a resonance coil at the time of transmission, the transmitting and receiving circuit has a position and a shape such that the resonance frequency of the transmitting coil becomes a frequency for transmission. Can be reduced.

Further, the switching means connects the transmission resonance capacitor between both ends of the reception coil during transmission and disconnects the transmission coil during reception, and disconnects the reception coil from the reception coil matching circuit during transmission. A transmission / reception switch for connecting these at the time of reception, and a transmission / reception circuit characterized by performing modulation for signal transmission by opening / closing the transmission / reception switch during transmission. Modulators can be reduced.

The switching means connects the transmission resonance capacitor between both ends of the reception coil during transmission, disconnects the transmission resonance capacitor during reception, and connects the reception coil to the reception coil matching circuit during transmission. And a receiving switch for disconnecting the receiving coil from the receiving coil matching circuit at the time of transmission, and connecting these at the time of reception. One end of the transmitting resonance capacitor is connected to one end of the receiving coil, and The receiving coil matching circuit has two input terminals, the receiving switch connects a connection point between the receiving coil and the transmitting resonance capacitor to one input terminal of the receiving coil matching circuit during reception, It is a switch that releases this at the time of transmission, and the transmission / reception switch is
A switch that connects the other end of the receiving coil to the other input terminal of the receiving coil matching circuit during reception, and switches and connects the other end of the receiving coil to the other end of the transmitting resonance capacitor during transmission. Since the transmission / reception circuit is a characteristic, there is an advantage that the number of terminals of the reception switch is reduced and the cost is reduced.

A transmitting / receiving circuit for receiving power and signals and transmitting signals by electromagnetic waves, comprising: a receiving coil; a transmitting coil having an electromagnetic coupling relationship with the receiving coil; and a transmitting coil connected between both ends of the transmitting coil. A reception resonance capacitor, a transmission coil matching circuit connected to the transmission coil, and a reception resonance capacitor connected between both ends of the transmission coil at the time of reception, and the transmission coil is disconnected from the transmission coil matching circuit during reception. Switching means for disconnecting the connection between the reception resonance capacitor and the transmission coil and connecting the transmission coil to the transmission coil matching circuit, wherein the reception resonance capacitor functions as a resonance coil when the transmission coil receives. Having a capacity such that the resonance frequency of the reception coil becomes a reception frequency. The receiving coil resonates with the transmitting coil at the time of receiving, so that the receiving sensitivity is improved. At the time of transmitting, the resonant frequency of the receiving coil deviates from the frequency at the time of receiving. The power and data signals are reduced, the transmission output is increased, the transmission output is increased, and the receiving sensitivity is improved, so that the communication distance can be extended.

Further, according to the present invention, the transmission / reception circuit system is characterized by comprising any one of the first to fourth transmission / reception circuits and the fifth transmission / reception circuit. As a result, the communication distance can be extended, and at the same time, the transmission coil matching circuit, the filter in the receiving circuit, and the resonance capacitor for the tag can be reduced.

Since the switching means includes a semiconductor analog switch using a FET, the semiconductor analog switch has a short transition time, and thus has an advantage that high-speed communication is possible.

Further, since the transmission / reception circuit is characterized in that the switching means includes a relay switch, since the relay switch has a high withstand voltage, there is an advantage that high-output transmission is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a transmission / reception circuit system including a transmission / reception circuit according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a transmission / reception circuit system including a conventional transmission / reception circuit of this type.

FIG. 8 is a timing chart of a transmission / reception circuit system including the transmission / reception circuit of the related art and the present invention.

FIG. 9 is an equivalent circuit diagram of a transmission system of a transmission / reception circuit system including a conventional transmission / reception circuit.

FIG. 10 is a diagram showing an equivalent circuit of a transmission coil and a reception coil.

FIG. 11 is an equivalent circuit diagram when a tag is excluded in a transmission system of a transmission / reception circuit system including a conventional transmission / reception circuit.

FIG. 12 is an equivalent circuit diagram of the transmission system of the transmission / reception circuit system including the transmission / reception circuit according to Embodiment 1 of the present invention at the time of transmission.

FIG. 13 is an equivalent circuit diagram at the time of reception of a transmission system including a coil, a matching circuit, and a switch in the transmission / reception circuit system including the transmission / reception circuit according to the first embodiment of the present invention.

FIG. 14 is an equivalent circuit diagram at the time of transmission of a transmission system including a coil, a matching circuit, and a switch in a transmission / reception circuit system including the transmission / reception circuit according to the second embodiment of the present invention.

FIG. 15 is an equivalent circuit diagram at the time of reception of a transmission system including a coil, a matching circuit, and a switch in a transmission / reception circuit system including a transmission / reception circuit according to Embodiment 5 of the present invention.

FIG. 16 is an equivalent circuit diagram at the time of transmission of a transmission system including a coil, a matching circuit, and a switch in a transmission / reception circuit system including a transmission / reception circuit according to Embodiment 5 of the present invention.

FIG. 17 is an equivalent circuit diagram of a semiconductor analog switch using an FET related to a transmission / reception circuit system including a transmission / reception circuit according to a seventh embodiment of the present invention.

FIG. 18 is an equivalent circuit diagram of a relay switch using a coil related to a transmission / reception circuit system including a transmission / reception circuit according to an eighth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reader / writer, 2 tags, 3 transmitting coils, 4 receiving coils, 5 transmitting / receiving coils, 7 receiving coil matching circuits, 8 tag resonance capacitors, 9 transmitting circuits, 10
Receiving circuit, 11 tag transmitting circuit, 12 tag receiving circuit,
13 modulator, 14 filter, 16 clock holding circuit, 17 rectifier circuit, 18 capacitor, 19 resistor,
Reference Signs List 20 wireless control device, 21 control unit, 22 memory, 2
3 oscillator, 24 smoothing circuit, 25 load circuit, 30
Switch for transmission, 31 Switch for reception, 32 Resonance capacitor for transmission, 50 Reader / writer transmission data signal, 51 Carrier wave, 52 Reader / writer transmission power / data signal, 53 clock (carrier), 54 Tag reception power, 55 Tag reception Data signal, 56 Reader / writer transmission data signal, 57 Tag transmission data signal, 5
8 Reader / writer reception data signal, 59 Tag transmission data signal, 60 Switch signal.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B035 BB09 CA12 CA23 5B058 CA17 KA24 5K012 AA01 AB05 AC06 AC08 AC10 AD05 AE13 BA03

Claims (8)

[Claims] 1. A transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave, comprising: a transmitting coil; a receiving coil having an electromagnetic coupling relationship with the transmitting coil; and a terminal connected between both ends of the receiving coil. A transmission resonance capacitor, a reception coil matching circuit connected to the reception coil, and a transmission resonance capacitor connected between both ends of the reception coil during transmission, and the reception coil disconnected from the reception coil matching circuit during transmission. Switching means for disconnecting the transmission resonance capacitor and the reception coil and connecting the reception coil to a reception coil matching circuit, wherein the transmission resonance capacitor functions as a resonance coil when the reception coil transmits. In particular, the transmission coil has a capacitance such that the resonance frequency of the transmission coil becomes a transmission frequency. Transmission and reception circuit. 2. A transmitting / receiving circuit for transmitting power and a signal and receiving a signal by using an electromagnetic wave, comprising: a transmitting coil; a receiving coil having an electromagnetic coupling relationship with the transmitting coil; and a receiving coil connected to the receiving coil. A matching circuit, switching means for connecting both ends of the receiving coil during transmission and disconnecting the receiving coil from the receiving coil matching circuit, disconnecting both ends of the receiving coil during reception and connecting them to the receiving coil matching circuit, A transmission / reception circuit having a position and a shape such that a resonance frequency of the transmission coil becomes a transmission frequency when the reception coil functions as a resonance coil during transmission. 3. The transmission means includes a transmission changeover switch for connecting the transmission resonance capacitor between both ends of a reception coil during transmission and disconnecting the reception coil during reception, and disconnecting the reception coil from the reception coil matching circuit during transmission. 2. The transmission / reception apparatus according to claim 1, further comprising a reception switch for connecting these at the time of reception, and further performing modulation for signal transmission by opening and closing the transmission switch or the reception switch at the time of transmission. circuit. 4. The switching means connects the resonance capacitor for transmission between both ends of the reception coil during transmission,
It consists of a transmission / reception switch that disconnects the reception coil during reception and connects the reception coil to the reception coil matching circuit during transmission, and a reception switch that disconnects the reception coil from the reception coil matching circuit during transmission and connects them during reception. One end of the transmission resonance capacitor is connected to one end of the reception coil, the reception coil matching circuit has two input terminals, and the reception switch is connected to the reception coil and the transmission when receiving. A switch for connecting a connection point with the credit resonance capacitor to one input terminal of the reception coil matching circuit and releasing the connection at the time of transmission, wherein the transmission / reception switch is connected to the other end of the reception coil at the time of reception. Connect to the other input terminal of the coil matching circuit and connect the other end of the receiving coil to the A switch for connecting by switching to the other end of the vibration capacitors, transmission and reception circuit according to claim 1 or 2, characterized in that. 5. A transmission / reception circuit for receiving power and a signal and transmitting a signal by using an electromagnetic wave, comprising: a reception coil; a transmission coil having an electromagnetic coupling relationship with the reception coil; and a connection between both ends of the transmission coil. A reception resonance capacitor, a transmission coil matching circuit connected to the transmission coil, and a reception resonance capacitor connected between both ends of the transmission coil at the time of reception and the transmission coil disconnected from the transmission coil matching circuit during reception. Switching means for disconnecting the connection between the reception resonance capacitor and the transmission coil and connecting the transmission coil to a transmission coil matching circuit, wherein the reception resonance capacitor functions as a resonance coil when the transmission coil receives. In particular, it has a capacity so that the resonance frequency of the reception coil becomes a reception frequency. Transmission and reception circuit. 6. A transmission / reception circuit system comprising: the transmission / reception circuit according to claim 1; and the transmission / reception circuit according to claim 5. 7. The apparatus according to claim 1, wherein said switching means includes a semiconductor analog switch using an FET.
7. The transmission / reception circuit according to any one of claims 1 to 6. 8. The transmission / reception circuit according to claim 1, wherein said switching means includes a relay switch.