System for transmitting and receiving
A system for transmitting and receiving. In some embodiments, the system includes a radio-frequency current source power amplifier, a buffer amplifier, and a transmit-receive switch. The transmit-receive switch may have a transmit port connected to an output of the radio-frequency current source power amplifier, a receive port connected to an input of the buffer amplifier, and a common port. The transmit-receive switch may be configured: in a first state, to connect the radio-frequency current source power amplifier to the common port; and in a second state, to connect the buffer amplifier to the common port.
1 . A system, comprising:
a radio-frequency current source power amplifier;
a buffer amplifier;
a transmit-receive switch,
the transmit-receive switch having a transmit port connected to an output of the radio-frequency current source power amplifier, a receive port connected to an input of the buffer amplifier, and a common port,
the transmit-receive switch being configured:
in a first state, to connect the radio-frequency current source power amplifier to the common port; and
in a second state, to connect the buffer amplifier to the common port;
an antenna operatively coupled to the common port of the transmit-receive switch; and
a resonating inductor directly connected in series with the antenna,
wherein the buffer amplifier has an input impedance greater than a resonated antenna impedance.
2 . The system of claim 1 , wherein the input impedance of the buffer amplifier is greater than 100 ohms.
3 . The system of claim 1 , wherein the transmit-receive switch is a single-pole double-throw switch.
4 . The system of claim 1 , wherein the antenna is a monopole antenna.
5 . The system of claim 1 , wherein the resonating inductor is a variable inductor.
6 . The system of claim 1 , wherein the buffer amplifier comprises a common-source amplifier.
7 . The system of claim 6 , wherein the buffer amplifier comprises shunt feedback.
8 . A method for transmitting and receiving with a system,
the system comprising:
a radio-frequency current source power amplifier;
a buffer amplifier;
a transmit-receive switch,
the transmit-receive switch having a transmit port connected to an output of the radio-frequency current source power amplifier, a receive port connected to an input of the buffer amplifier, and a common port;
an antenna operatively coupled to the common port of the transmit-receive switch; and
a resonating inductor directly connected in series with the antenna,
the method comprising:
operating the transmit-receive switch in a transmit mode, the transmit port being connected to the common port in the transmit mode;
amplifying, by the radio-frequency current source power amplifier, a first signal; and
transmitting the first signal, from the common port, to the antenna, an electrical path from the radio-frequency current source power amplifier to the antenna having a length less than one fifth of a wavelength corresponding to a center frequency of the first signal,
wherein the buffer amplifier has an input impedance greater than a resonated antenna impedance.
9 . The method of claim 8 , wherein the antenna is a monopole antenna.
10 . The method of claim 8 , wherein the antenna has a first resonance frequency within 30% of the center frequency of the first signal.
11 . The method of claim 8 , wherein the inductor is connected between the common port of the transmit-receive switch and the antenna.
12 . The method of claim 8 , wherein the antenna has a resonance frequency within 30% of the center frequency of the first signal.
13 . The method of claim 12 , wherein:
the input impedance of the buffer amplifier is greater than 0.1 times an impedance of the antenna over a range of frequencies extending from (1−1/Q) f0 to (1+1/Q) f0;
f0 is the resonance frequency; and
Q is the quality factor of the resonance.
14 . The method of claim 8 , wherein the inductor is a variable inductor.
15 . The method of claim 8 , wherein the buffer amplifier comprises a common-source amplifier.
16 . A system, comprising:
a radio-frequency current source power amplifier;
a buffer amplifier;
a transmit-receive switch;
the transmit-receive switch having a transmit port connected to an output of the radio-frequency current source power amplifier, a receive port connected to an input of the buffer amplifier, and a common port;
an antenna operatively coupled to the common port of the transmit-receive switch; and
a resonating inductor directly connected in series with the antenna,
the transmit-receive switch being configured:
in a first state, to connect the radio-frequency current source power amplifier to the common port; and
in a second state, to connect the buffer amplifier to the common port,
an input impedance of the buffer amplifier having a magnitude greater than 0.1 times a magnitude of a resonant impedance of the antenna,
wherein the buffer amplifier has an input impedance greater than a resonated antenna impedance.
17 . The system of claim 16 , wherein the antenna comprises a self-resonant antenna.