JP3038230B2 - Control circuit for antenna resonance circuit of wireless transceiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a response that transmits a time-limited HF interrogation pulse with a large amount of energy in a transmission stage, and transmits a high-frequency resonance signal in response to reception of an interrogation pulse in a reception stage following the transmission stage. Trying to receive the resonance signal coming from the vessel,
The present invention relates to a braking circuit for an antenna resonance circuit of a wireless transceiver.

GB-A-2,077,555 discloses a transponder device in which a radio transceiver acting as an interrogator cooperates with one or more transponders. This coordination is performed when the radio transceiver transmits an energetic HF interrogation pulse received by a transponder located within the range of the transmitting antenna, which causes the transponder to This is because it is actuated to send back a signal containing a clearly identifying code. In this case, the detailed formation of the code is not important. The feature of the transponder is that it does not contain a source of self-energy, but instead derives its energy from HF interrogation pulses received by modification and accumulation. In order for the radio transmitter to transmit HF interrogation pulses containing as much energy as possible, the antenna resonance circuit must then be as far as possible from high quality resonance circuits with correspondingly narrow bands. As mentioned above, the transponder does not include a self-energy source but derives its energy from the received HF interrogation pulse, so the response signal must return as quickly as possible because the available energy is compared in this response operation. This is because there is very little. The code requires a certain number of bits so that its own code can identify a number of different transponders, which must be returned to the radio transmitter. The higher the number of data bits, the higher the repetition frequency of each individual data bit. However, this high repetition frequency requires an antenna resonant circuit with a band as wide as possible on the receiver side of the radio transmitter. In known transponder devices, these conflicting requirements of the antenna resonance circuit are solved using separate transmitting and receiving antennas each having a corresponding antenna resonance circuit. However, in order to simplify the radio transceiver, it is desirable to use one and the same antenna with a single antenna resonant circuit for transmission and reception.

The present invention transmits high energy HF pulses and
It is based on the problem of providing a damping circuit for an antenna resonance circuit of a radio transmitter that can use a single antenna for signal reception.
In accordance with the present invention, this problem is addressed by providing a braking member connected to and disconnected from the antenna resonant circuit, a switching device for receiving the switching voltage and connecting the braking member to the antenna resonant circuit, and providing a switching voltage. A first energy storage element that can be charged by an HF interrogation pulse and a rechargeable element by an HF interrogation pulse
The problem is solved by a second energy storage element which causes a switching voltage at the first energy storage element to be applied to the switching device by a temporal change of the HF interrogation pulse.

Although the braking circuit according to the invention allows the quality of the antenna resonance circuit to be switched, said switching is automatically caused by a change in the HF interrogation pulse, which means that the antenna resonance circuit has the required high quality during the HF interrogation pulse. Means that the high-energy HF interrogation pulse can also be transmitted, while automatically occurring by connecting a damping member to the antenna resonance circuit at the end of said pulse switch to low quality, A wide hand of the antenna resonance circuit required for reception is achieved. This switching is performed because the connection of the braking member causes the oscillation of the antenna resonance circuit to attenuate at a high speed, so that the HF signal, which is considered to be transmitted by the transponder, can be received immediately after the end of the HF interrogation pulse.
An even more advantageous effect is achieved by the very quick transition of the radio transceiver to the reception ready state after the end of the interrogation pulse. This is a particular advantage when the transponder does not contain a source of self-energy but must be activated by energy derived from the HF interrogation pulse and stored in a capacitor. Since this energy storage is of course limited, the transponder must send back the HF signal as soon as possible after the end of the HF interrogation pulse in order to make optimal use of the stored energy.

Further advantages of the invention are characterized in the appended claims.

The transponder device shown in FIG. 1 includes a radio transceiver 10 in which a rod antenna 12 is located on the front side. The radio transceiver 10 has a grip 14 with an activation switch 16 on top.
including. Each actuation of the activation switch 16 activates the transmitter portion so that a high energy HF interrogation pulse is transmitted by the antenna 12. As schematically shown, a ferrite rod 20 is incorporated within the tip 18 of the antenna 12 and is surrounded by an antenna winding 22. In addition, the braking circuit 24 shown schematically in FIG.
Stored in 12.

The radio transceiver 10 shown in FIG. 1 cooperates with a transponder 26, shown only schematically. The transponder can be attached to the object to be identified or incorporated into the object to be identified. For example, the transponder 26 can also be attached to a cow's earstick, and the interrogator of the transponder attached thereto can identify the cow. If necessary, the transponder can be inserted into the animal's skin. First
Although only one transponder 26 is shown in the figure, in practical applications, the antenna 12 of the radio transceiver 10 is moved close to each transponder 26 and the interrogation pulse is activated.
There will be a number of transponders, each of which can be interrogated, as sent by the act of 16.

FIG. 2 shows an electric circuit diagram of the antenna resonance circuit 28 and the braking circuit 24 connected thereto. The antenna resonance circuit 28 is coupled to a winding (not shown) in the transceiver 10 by a winding W1. The winding 3 of the antenna resonance circuit 28 is wound around the ferrite rod 20. The winding W1, the winding W2 and the two capacitors CA1 and CA2 are connected in series in the antenna resonance circuit 28.

The braking circuit 24 includes two inputs E1 and E2 to which a winding W2 is connected which is coupled to a winding in the radio transceiver 10 as well as the winding W1. The anode of diode D1 is input E1
, And its cathode is connected to the collector of the transistor T1. There is a resistor R1 between the collector of the transistor T1 and its base. The cathode of the diode D1 is also connected to the capacitor C1 connected to the input E2. The potential at the input E2 becomes the ground potential of the braking circuit 24. Therefore, the line 30 connected to the input E2 is called a ground line.

The base of transistor T1 is connected to ground via resistor R2
Connected to the collector of transistor T3, which has a base connected to 30. Further, the cathode of a Zener diode DZ having an anode connected to the ground line 30 is connected to the base of the transistor T1. Transistor
The emitter of T1 is connected to the anode of another diode D3, whose cathode is grounded.
Connected to the emitter of transistor T2, which has a collector connected to 10. The base of the transistor T2 is connected to the base of the transistor T2 and the collector of the transistor T3. Further, the cathode of the diode D3 is connected to the gate electrodes of two transistors T4 and T5, which are enhancement type MOS field effect transistors. The drain electrode of the field effect transistor T4 is connected to the winding W1 of the antenna resonance circuit 28 and the capacitor CA1. The source electrode is connected to the ground line 30. The drain electrode of the field effect transistor T5 is connected to the connection point of the two capacitors CA1 and CA2 via a series circuit of three resistors R4, R5 and R6,
The source electrode is connected to the ground line 30. The input E1 is also connected to the cathode of a diode D2 whose anode is connected to the ground line 30 via a capacitor C2 and to the emitter of a transistor T3 via a parallel circuit of a capacitor C3 and a resistor R3. I have. A series circuit of three resistors can of course be replaced by only one resistor.

 The operation of the braking circuit of the described structure is as follows.

If all capacitors in the braking circuit 24 have been discharged and the transmitter portion of the radio transceiver 10 is not working, the braking circuit 24 will not operate. In this state, the series circuit of the resistors R4, R5 and R6 acting as a braking member is not connected in parallel with the capacitor CA1, and therefore the antenna resonance circuit is not braked by said braking member. Therefore, the antenna resonance circuit has a high circuit quality, so that when the energy corresponding to the winding W1 is supplied by the winding W3, it can generate a strong magnetic field with less harmonic components.

When actuation switch 16 is actuated, an AC voltage is induced in winding W2 and applied to braking circuit 24 via inputs E1 and E2. Due to the effect of diode D1, the voltage at input E1 produces a positive voltage on capacitor C1, while diode D2 produces a negative voltage on capacitor C2. When the HF interrogation pulse is initiated on capacitor C2, a voltage jump occurs, resulting in a negative voltage being applied to the emitter of transistor T3 via capacitor C3, so that the collector of transistor T3 takes current through resistor R1. At the same time, the emitter of transistor T2 has two field effect transistors T4 and T4, which have a low resistance at almost ground potential, since a voltage close to ground is thereby applied to the base of transistor T2.
Keep the gate electrode of T5. Field effect transistor T4 and
This low resistance state of T5 prevents the enhancement field effect transistor from self-conducting through the respective drain / gate capacitance due to the high AC voltage at the respective drain terminals, thus the resistors R4, R5 in parallel with the capacitor CA1. , R6, braking of the antenna resonance circuit is obtained.

When an HF interrogation pulse is received, a Zener diode
DZ conducts in the forward direction and, together with resistor R2, transistor T3
Is prevented from being excessively saturated. Oversaturation of the transistor T3 must be avoided because the transistor must react as quickly as possible after the end of the HF interrogation pulse, which prevents oversaturation. In addition, zener diode DZ prevents the voltage from dropping below or below the maximum allowable gate voltage of field effect transistors T4 and T5.

Diode D3 ensures that transistor T1 does not conduct during reception of the HF interrogation pulse.

After capacitor C3 has been charged to its final voltage, resistor R3 supplies enough current to the emitter of transistor T3 to prevent the occurrence of braking action,
This is because T1 remains non-conductive.

As soon as the capacitor C1 is charged to its final voltage, a quick braking of the antenna resonance circuit and a switching from a high quality value to a low quality value after the end of the interrogation pulse is required.

At the same time as the end of the HF interrogation pulse, the voltage of the antenna resonance circuit rises for a little longer time, but the current of the resonance circuit then drops due to the inherent braking action of the antenna resonance circuit, so that the negative charging voltage on the capacitor C2 also drops. start. This appears as a positive voltage jump through the capacitor C3 to the emitter of the transistor T3.

Capacitors C1 and C2 and resistors R1 and R3 have a time constant C1 / R
The value is set so that 1 becomes larger than the time constant C2 / R3.
As a result, in contrast to the voltage of capacitor C2, the voltage of capacitor C1 remains virtually constant over the time considered. Due to the aforementioned positive voltage jump at the emitter of transistor T3, transistor T1 becomes conductive.
Therefore, its emitter voltage rises and the diode
Proceed through D3 to the gate electrodes of field effect transistors T4 and T5. At the same time that the threshold electric field of these field effect transistors T4 and T5 is exceeded, the braking member composed of a series circuit of resistors R4, R5 and R6 is itself a capacitor CA.
1, the capacitor CA1 is a partial capacitance of the antenna resonance circuit 28.

The braking member is also connected to the antenna resonance circuit via an induction tap, but connection to a complete antenna resonance circuit is also possible. Connecting the damping member via an inductive or capacitive tap is no matter how large a field effect transistor
This is because the maximum resonant circuit voltage that results in the maximum allowable drain / gate voltage of T4 and T5 must not be exceeded. Furthermore, connecting a damping member to such a tap ensures that the damping resistance together with the parasitic capacitance is near or below the operating frequency of the entire device, especially considering the non-trivial capacitance of the non-conducting field effect transistors T4 and T5. It is advisable to form an RC member with a braking frequency of

Charging or recharging the capacitance of field effect transistors T4 and T5 derives most of its energy from capacitance C1, which acts as an energy storage device. The largest part of the energy is used by the drain / gate capacitance and the high AC electric field during the switch-on phase of the field effect transistors T4, T5.
Thereafter, only the leakage current of the circuit needs to be considered, so for components with low leakage current, the braking phase in which the braking member including the resistors R4, R5 and R6 is activated will be several times the required reception time.

The field-effect transistors T4 and T5, which are specific to the design,
Includes an "inverse diode" between the drain and source electrodes, such that for operation with AC voltage,
The field effect transistors are required to be disconnected, which is always conductive via its internal diode, depending on the polarity of one voltage. Regarding winding W2,
This means that it alternates with respect to the circuit points 32 and 34 of the resonant circuit via one of said "inverse diodes".
It means that it is applied in synchronization with the AC voltage. Therefore, winding W2 must be properly insulated with respect to winding W1 so as to avoid breakdown occurring at the peak value of the resonant circuit voltage.

At the same time that a new HF interrogation pulse is transmitted according to the functional cycle described above, the damping member including resistors R4, R5 and R6 is again separated from the antenna resonance circuit 28, so that the antenna resonance circuit 28 responds to the response of the transponder 26. Due to the required high circuit quality, the magnetic field can be re-established.

The antenna resonant circuit described in this way operates completely automatically with the generation of the HF interrogation pulse, which does not require a self-current source and derives the energy required for its operation from the HF interrogation pulse. The damping of the antenna resonance circuit 28 obtained after the completion of the HF interrogation pulse by using the braking circuit 24 not only affects the switching of the quality of the antenna resonance circuit 28, but also creates said circuit, and thus the radio transceiver 10
Ready to receive the signal returned by transponder 26 immediately after the end of the interrogation pulse.

[Brief description of the drawings]

FIG. 1 is a basic diagram of a radio transceiver which cooperates with a transponder and uses a braking or damping circuit according to the present invention, and FIG. 2 is a circuit diagram of an antenna resonance circuit having a braking circuit according to the present invention. Explanation of symbols: 10 …… Wireless transceiver; 12 …… Antenna; 14 …… Grip; 1
6 …… Operation switch; 18 …… Chip; 20 …… Ferrite
Rod; 22 antenna winding; 24 braking circuit; 26 transponder; 28 antenna resonance circuit.

Claims (4)

(57) [Claims] In the transmitting step, a time-limited HF interrogation pulse with high energy is transmitted, and in the receiving step following the transmitting step, the resonance signal coming from a transponder transmitting a high-frequency resonance signal in response to reception of the interrogation pulse. Trying to receive the
A control circuit for an antenna resonance circuit of a wireless transceiver,
A braking member (R4, R5, R6) connected to and disconnected from the antenna resonance circuit, and a switching device (T4) receiving the switching voltage and connecting the braking member (R4, R5, R6) to the antenna resonance circuit. , T5), a first energy storage element chargeable by an HF interrogation pulse to supply a switching voltage, and a first energy storage element chargeable by an HF interrogation pulse and being temporally varying in the HF interrogation pulse. A braking circuit, comprising: a second energy storage element (C2) for applying a switching voltage to a switching device (T4, T5). 2. The method according to claim 1, wherein the braking member (R4, R5, R6) is connected in parallel with one of the capacitors (CA1, CA2) of the antenna resonance circuit (20) by a switching device (T4, T5). 2. A braking circuit according to claim 1, for an antenna resonance circuit comprising a series circuit of two capacitors as capacitance. 3. The braking circuit according to claim 1, wherein the braking member is coupled to the antenna resonance circuit via an inductive tap. 4. The switching device comprises two field-effect transistors (T4, T5), the gate electrodes of which are connected together and the drain-source path of which is connected to the damping member (R4, R5).
4. The braking circuit according to claim 1, wherein the braking circuit is connected in series with (5, R6).