JPH0456526A - Control circuit for antenna resonance circuit of radio transmitter-receiver - Google Patents

Abstract

PURPOSE: To enable a radio transmitter-receiver to transmit HF pulses and to use a single antenna for receiving HF signals by providing a switching device which connects a damping member to an antenna resonance circuit upon receiving a switching voltage. CONSTITUTION: When a start switch 16 is actuated, an AC voltage is induced in a winding W2 and applied to a damping circuit 24 and, as a result, a positive voltage and a negative voltage are respectively generated in capacitors C1 and C2 and the capacitor C2 starts an HF interrogating pulse. When the interrogating pulse ends, the negative charged voltage of the capacitor C2 starts to drop and a transistor T1 is conducted by a positive voltage jump at the emitter of a transistor T3 through a capacitor C3. When the voltage of the emitter rises and becomes higher than the threshold electric fields of transistors T4 and T5, a damping member composed of resistors R4-R6 is connected in parallel with the capacitor CA1 of an antenna resonance circuit 28. Thus the circuit 28 is actuated in a fully automated state when the HF interrogating pulse is generated and an answer is immediately returned by means of a transponder 26 when the interrogating pulse ends.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for transmitting a time-limited, high-energy HF interrogation pulse in a transmitting phase, and in response to transmitting a high frequency resonant signal in response to reception of the interrogating pulse in a receiving phase following the transmitting phase. the resonant signal coming from the device;
The present invention relates to a braking circuit for an antenna resonant circuit of a radio transmitter/receiver.

GB-A-2,077,555 discloses a transponder device in which a radio transceiver acting as an interrogator cooperates with one or more transponders. The co-operation is carried out by a radio transceiver transmitting an energetic HF interrogation pulse that is received by a transponder placed within the range of a transmitting antenna, whereby said transponder This is because it is activated to send back a signal containing a code that positively identifies it. In this case, the details of how the code is formed are not important. A feature of the transponder is that it does not contain its own energy source, but instead derives its energy from the received HF interrogation pulses by modification and storage. In order for the radio transmitter to transmit HF interrogation pulses containing as much energy as possible, the antenna resonant circuit must then be located as far as possible from a high-quality resonant circuit with a correspondingly narrow band. Since, as mentioned above, the transponder does not contain its own energy source but derives its energy from the received HF interrogation pulse, the return of the response signal must occur as quickly as possible because in this response operation the available energy is This is because there are few targets. In order for the code to be able to identify a large number of different transponders, the code requires a certain number of bits, which must be sent back to the radio transmitter.

The greater 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 the widest possible band width at the receiver side of the radio transmitter. In known transponder devices, these contradictory requirements for antenna resonant circuits are resolved by using separate antennas for transmitting and receiving, each with a corresponding antenna resonant circuit. However, to simplify the wireless transceiver, it is desirable to use one and the same antenna with a single antenna resonant circuit for transmitting and receiving.

The present invention transmits high-energy HF pulses and
It is based on the problem of providing a damping circuit for the antenna resonant circuit of a radio transmitter, which allows the use of a single antenna for the reception of F signals. The present invention solves this problem by providing a damping member that is connected to and disconnected from the antenna resonant circuit;
a switching device receiving a switching voltage to connect the damping member to the antenna resonant circuit; a first energy storage element chargeable by an HF interrogation pulse to provide the switching voltage; The switching voltage present in the first energy storage element is applied to the switching device by the temporal variation of the second energy storage element.

The damping circuit according to the invention makes it possible to switch the quality of the antenna resonant circuit, said switching occurring automatically due to changes in the HF interrogation pulse, which means that the antenna resonant circuit maintains the required high quality during the HF interrogation pulse. This means that the high-energy HF interrogation pulse can therefore be transmitted, while automatically occurring by connecting a damping member to the antenna resonant circuit at the end of said pulse switching to a lower quality. A wide band of antenna resonant circuits required for reception is achieved. This switching is done because the connection of the damping member causes a rapid attenuation of the oscillation of the antenna resonant circuit, so that reception of the HF signal expected to be transmitted by the transponder is possible immediately after the end of the HF interrogation pulse. A further advantageous effect is that the radio transceiver enters the ready state very quickly after the end of the interrogation pulse. This is a particularly great advantage when the transponder does not contain its own energy source but must operate with energy extracted from the HF interrogation pulse and stored in the capacitor. This energy storage is of course limited, so the transponder must send back its HF signal as soon as possible after the end of the HF interrogation pulse in order to optimally utilize 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 with a rod antenna 12 placed on the front side. The wireless transceiver 10 includes a grip 14 upon which an activation switch 16 is placed. Each actuation of the activation switch 16 activates the transmitter section so that a high energy HF interrogation pulse is transmitted by the antenna 12. As shown schematically, a ferrite rod 20 is incorporated within the tip 18 of the antenna 12, which is surrounded by an antenna winding 22. Additionally, a damping circuit 24, shown schematically in FIG. 1, is housed within the antenna 12.

The radio transceiver 10 shown in FIG. 1 cooperates with a transponder 26, which is shown only schematically. The transponder can be attached to or incorporated into the object to be identified. For example, the transponder 26 can also be attached to a cow's ear tag, so that the cow can be identified by the interrogation of the transponder attached thereto. If necessary, the transponder can also be inserted into the animal's skin.

Although only one transponder 26 is shown in FIG. There will be a number of transponders, each capable of receiving the interrogation as sent by the actuation.

In FIG. 2, an electrical circuit diagram of the antenna resonant circuit 28 and the damping circuit 24 connected thereto is shown. The antenna resonant circuit 28 is coupled to a winding (not shown) in the transceiver 1o by a winding W1. The winding 3 of the antenna resonant circuit 28 is wound around the ferrite rod 20. Winding W1, winding W2, and two capacitors CA1 and CA2 are connected in series in antenna resonant circuit 28.

The braking circuit 24 is connected to a winding W2, which is coupled to a winding within the radio transceiver 10 as well as a winding W1.
including individual manpower E1 and R2. The anode of diode D1 is connected to input E1, and its cathode is connected to the collector of transistor T1. There is a resistor R1 between the collector of transistor T1 and its base. The cathode of diode D1 is also connected to capacitor C1, which is connected to input E2. The potential of the human power E2 becomes the ground potential of the braking circuit 24. The line 30 connected to input E2 is therefore called a ground line.

The base of transistor T1 is connected to the collector of transistor T3, which has its base connected to ground line 30 via resistor R2. Furthermore, 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.

The emitter of transistor T1 is connected to another diode D
The diode D3 is connected to the anode of D3.
The cathode of is connected to the emitter of a transistor T2 whose collector is connected to the ground line 10. The base of transistor T2 is connected to the base of transistor T2 and the collector of transistor T3.

Furthermore, the cathode of the diode D3 is connected to the gate electrodes of two transistors T4 and T5, which are enhancement type MO8 field effect transistors, and the drain electrode of the field effect transistor T4 is connected to the winding W1 of the antenna resonant circuit 28 and the capacitor CAI. The source electrode is connected to the ground line 30. The drain electrode of field effect transistor T5 is connected to the connection point of two capacitors CA1 and CA2 through a series circuit of three resistors R4, R5 and R6, and its source electrode is connected to ground line 30. ing. The cathode of the diode D2 is also connected to the input E1, and the anode of the diode is connected to the capacitor C.
2 to ground line 30 and to the emitter of transistor T3 via a parallel circuit of capacitor C3 and resistor R3. The series circuit of three resistors can of course be replaced by just one resistor.

The operation of the brake circuit of the described construction is as follows.

If all capacitors in the braking circuit 24 are discharged and the transmitter section of the radio transceiver 10 is not working,
Braking circuit 24 is not activated. In this state, the series circuit of resistors R4, R5 and R6, acting as a damping member, is not connected in parallel to the capacitor CAI, and therefore the antenna resonant circuit is not damped by said damping member. Therefore, the antenna resonant circuit has a high circuit quality, so that when the winding W3 supplies the corresponding energy to the winding W1, it can generate a strong magnetic field with low harmonic components.

When actuation switch 16 is actuated, the AC voltage is applied to winding W
2 is induced in the braking circuit 2 via inputs E1 and R2.
Added to 4. Due to the effect of diode D1, input E
1 generates a positive voltage on capacitor C1, while
Diode D2 generates a negative voltage on capacitor C2. When the HF interrogation pulse is initiated on capacitor C2, the voltage jump stops and as a result a negative voltage is applied to the emitter of transistor T3 via capacitor C3, so that
The collector of transistor T3 takes the current flowing through resistor R1. At the same time, a voltage close to ground potential is thereby applied to the base of transistor T2, so that the emitter of transistor T2 keeps the gate electrodes of the two field effect transistors T4 and T5 with low resistance almost at ground potential. This low resistance state of field effect transistors T4 and T5 prevents said enhancement field effect transistors from self-conducting due to high AC' voltages at their respective drain terminals through their respective drain gate capacitances, thus connecting capacitors CA1 and Damping of the antenna resonant circuit is obtained by connecting resistors R4, R5, R6 in parallel.

When an HF interrogation pulse is received, Zener diode DZ conducts in the forward direction and together with resistor R2 prevents excessive saturation of transistor T3. The transistor T
Oversaturation of 3 must be avoided because the transistor must react as quickly as possible after the end of the HF interrogation pulse, which prevents oversaturation. Furthermore, the Zener diode DZ prevents the voltage from exceeding or falling below the maximum permissible gate voltage of the 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 a braking action, since transistor T1 remains non-conducting.

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

As soon as the HF interrogation pulse ends, the voltage in the antenna resonant circuit rises for a slightly longer time, but the current in the resonant circuit then drops due to the inherent damping action of the antenna resonant circuit, so that the negative charging voltage on capacitor C2 also drops. start. This appears as a positive voltage jump at the emitter of transistor T3 via capacitor C3.

Capacitors C1 and 02 and resistors R1 and R3 are set to values such that time constant C1/R1 is greater than time constant c2/R3. As a result, the voltage on capacitor C1, in contrast to the voltage on capacitor C2, remains virtually constant over the considered time. The aforementioned positive voltage jump at the emitter of transistor T3 causes transistor T1 to become conductive.

The voltage at its emitter therefore rises and passes through diode D3 to the gate electrodes of field effect transistors T4 and T5. These field effect transistors T4.
As soon as the threshold electric field of T5 is exceeded, resistors R4 and R
The damping member, consisting of a series circuit of 5 and R6, is itself connected in parallel with a capacitor CAI, which is a partial capacitance of the antenna resonant circuit 28.

The damping member is also connected to the antenna resonant circuit via an inductive tap, but a connection to the complete antenna resonant circuit is also possible. Connecting the braking member via an inductive or capacitive tap is a field-effect transistor T, no matter how large.
4. This is because the maximum resonant circuit voltage resulting in the maximum allowable drain/gate voltage of T5 must not be exceeded. moreover,
Connecting the braking member to such a tap limits the braking resistance to near or below the operating frequency of the entire device, together with the parasitic capacitance, especially taking into account the not insignificant capacitance of the non-conducting field effect transistors T4 and T5. It is a good idea to form an RC member with a frequency.

Charging or recharging the capacitance of field effect transistors T4 and T5 draws most of its energy from capacitance C1, which acts as an energy storage device. The part with the largest energy is the field effect transistor T4. During the switch-on phase of T5, it is used by the drain l-gate capacitance and the high AC voltage. After that, only the leakage current of the circuit needs to be considered, so for components with low leakage current, resistor R4,
The braking phase in which the braking member including R5 and R6 is activated will be several times the required receiving time.

Specific to the design, the field effect transistors T4 and T5 have an "inversive" between the drain and source electrodes.
diodes", so that operation with AC voltage requires the two field effect transistors to be decoupled, but which, depending on the polarity of one of the voltages, are always conducting via their internal diodes. Regarding winding W2, this means that it is connected to circuit points 32 and 3 of the resonant circuit.
1 of said "inverse diodes" alternately for 4
This means that AC' can be applied synchronously with the pressure through the two. Therefore, winding W2 must be properly insulated with respect to winding W1 to avoid dielectric breakdown occurring at peak values 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 comprising resistors R4, R5 and R6 is again separated from the antenna resonant circuit 28, so that the antenna resonant circuit 28 is dependent on the response of the transponder 26. The required high circuit quality allows the magnetic field to be released again.

The antenna damping circuit thus described operates completely automatically upon generation of an HF interrogation pulse; it does not require a self-current source and derives the energy required for its operation from the HF interrogation pulse. Antenna resonant circuit 2 obtained after completion of the HF interrogation pulse by using a damping circuit 24
The damping of 8 not only affects the switching of the quality of the antenna resonant circuit 28, but also makes said circuit so that the radio transceiver 10 is ready to receive the signal returned by the transponder 26 immediately after the termination of the HF interrogation pulse. Arrange.

[Brief explanation of the drawing]

1 is a basic diagram of a radio transceiver cooperating with a transponder and using a damping or damping circuit according to the invention, and FIG. 2 is a circuit diagram of an antenna resonant circuit with a damping circuit according to the invention. Explanation of symbols: 10... Radio transceiver; 12... Antenna; 14.
... Grip; 16... Operation switch; 18... Chip; 20... Ferrite rod; 22... Antenna winding; 24... Braking circuit; 26... Responder; 2
8...Antenna resonance circuit. FIG.2

Claims (4)

[Claims] (1) In the transmission stage, time-limited energy-rich H
Control for an antenna resonant circuit of a radio transceiver which transmits an F-interrogation pulse and which, in a reception phase following the transmission phase, attempts to receive said resonance signal coming from a transponder which transmits a high frequency resonance signal in response to reception of the interrogation pulse. a circuit comprising a damping member (R4, R5, R6) adapted to be connected to and disconnected from the antenna resonant circuit and receiving a switching voltage to connect the damping member (R4, R5, R6) to the antenna resonant circuit; Switching device (T4, T5)
a first energy storage element chargeable by the HF interrogation pulse to provide a switching voltage; A braking circuit characterized in that it has a second energy storage element (C2) applied to the switching device (T4, T5). (2) as a capacitance, characterized in that the damping member (R4, R5, R6) is connected in parallel with one of the capacitors (CA1, CA2) of the antenna resonant circuit (20) by means of a switching device (T4, T5); 2. A damping circuit according to claim 1 for an antenna resonant circuit comprising a series circuit of two capacitors. 3. A damping circuit according to claim 1, characterized in that the damping members (R4, R5, R6) are coupled to the antenna resonant circuit (20) via inductive taps. (4) The switching device consists of two field effect transistors (T4, T5) whose gate electrodes are connected together and whose drain-source path is connected to a braking member (R4,
Braking circuit according to claim 1, 2 or 3, characterized in that it is connected in series with R5, R6).