Multimode transceiver circuit
View Patent ↗A multimode transceiver circuit comprises a four port coupler of a type which splits a signal applied to one port between two of the other ports. The split signals are phase shifted by a known amount. A first port of the coupler is for receiving a signal and for outputting a signal therefrom. A controllable oscillator is connected to a second port of the coupler and switchable impedances (Schottky diodes) are connected to the remaining ports. A controller is provided for controlling the operation of the oscillator and the impedances to determine the mode of operation of the circuit. In one mode of operation, the oscillator is inoperative and at least one of the impedances is switched to operate as a non-linear impedance such that the circuit detects amplitude-modulation of the signal applied to the first port. In a further mode of operation, the oscillator is operable and both impedances are switched to operate as non-linear impedance elements such that they operate as a mixer to produce an intermediate frequency signal in dependence on the signal applied to the first port. In yet a further mode of operation, the oscillator is operable, and the impedances are switched such that the oscillator frequency appears at the first port for transmission therefrom.
1. A multimode transceiver circuit, comprising:
a) a four port coupler for splitting an input signal into split signals which are phase shifted by a known amount, the coupler having a first port for receiving the input signal and for outputting an output signal therefrom;
b) a controllable oscillator connected to a second port of the coupler;
c) switchable impedances connected to the remaining ports of the coupler; and
d) control means for controlling operation of the oscillator and the impedances such that:
i) in one mode of operation, the oscillator is inoperative, and at least one of the impedances is switched to operate as a non-linear impedance to detect amplitude modulation of the input signal applied to the first port,
ii) in a further mode of operation, the oscillator is operable, and the impedances are switched to operate as non-linear impedance elements to operate as a mixer to produce an intermediate frequency signal in dependence on the input signal applied to the first port, and
iii) in yet a further mode of operation, the oscillator is operable, and the impedances are switched such that an oscillator frequency appears at the first port for transmission therefrom.
2. The transceiver circuit according to claim 1 , in which the control means controls the switchable impedances by controlling a bias voltage applied thereto.
3. The transceiver circuit according to claim 1 , in which at least one of the switchable impedances comprises a diode.
4. The transceiver circuit according to claim 1 , in which at least one of the switchable impedances comprises a transistor.
5. The transceiver circuit according to claim 1 , in which the split signals are phase shifted by zero and ninety degrees.
6. The transceiver circuit according to claim 1 , in which the split signals are phase shifted by zero and one hundred and eighty degrees.
7. The transceiver circuit according to claim 1 , in which the coupler comprises a branch arm coupler.
8. The transceiver circuit according to claim 1 , in which the coupler comprises a rat race coupler.
9. The transceiver circuit according to claim 1 , in which each mode of operation of the circuit is determined by an impedance match or mismatch of the switchable impedance to its respective port.
10. The transceiver circuit according to claim 1 , in which in the yet further mode of operation, each impedance is switched such as to present an impedance mismatch to its respective port thereby reflecting a signal from the oscillator to the first port.
11. The transceiver circuit according to claim 10 , and further comprising a fixed impedance element between the port and its respective switchable impedance, wherein the impedance of the fixed clement is selected such that the switchable impedance is substantially matched to its respective port when it is operated as a non-linear impedance.
12. A tag incorporating a transceiver circuit comprising:
a) a four port coupler for splitting an input signal into split signals which are phase shifted by a known amount, the coupler having a first port for receiving the input signal and for outputting an output signal therefrom;
b) a controllable oscillator connected to a second port of the coupler;
c) switchable impedances connected to the remaining ports of the coupler; and
d) control means for controlling operation of the oscillator and the impedances such that:
i) in one mode of operation, the oscillator is inoperative, and at least one of the impedances is switched to operate as a non-linear impedance to detect amplitude modulation of the input signal applied to the first port,
ii) in a further mode of operation, the oscillator is operable, and the impedances are switched to operate as non-linear impedance elements to operate as a mixer to produce an intermediate frequency signal in dependence on the input signal applied to the first port, and
iii) in yet a further mode of operation, the oscillator is operable, and the impedances are switched such that an oscillator frequency appears at the first port for transmission therefrom.