Low-noise amplifier supporting beam-forming function and receiver including the same
A low-noise amplifier in a receiver supporting a beam forming function may selectively change a phase shift for beam steering. The low-noise amplifier may include first and second transistors and a variable capacitance circuit connected to a gate of the second transistor. The variable capacitance circuit may selectively change capacitance thereof based on a capacitance control signal applied thereto according to beam-forming information, where the changed capacitance correspondingly causes a phase change in an output signal of the low-noise amplifier. A similar scheme may be employed for amplifiers in transmit signal paths to steer a transmit beam.
1. A receiver for receiving a beam-forming signal via a plurality of antennas, the receiver including:
a first amplifier circuit including a first transistor for amplifying an input signal to provide a first amplified signal, the input signal being derived from a portion of the beam-forming signal received by one of the antennas;
a second amplifier circuit including a second transistor for amplifying the first amplified signal to generate a corresponding output signal; and
a variable capacitance circuit for selectively changing capacitance thereof to cause a corresponding phase change in the output signal and form a beam pointing in a selectable direction according to the capacitance, for receiving the beam-forming signal,
wherein the variable capacitance circuit receives a capacitance control signal to change the capacitance.
2. The receiver of claim 1 , wherein the capacitance control signal is generated based on information about the beam-forming signal.
3. The receiver of claim 1 , wherein the first transistor and the second transistor operate as a cascade amplifier.
4. The receiver of claim 1 , wherein the input signal is a signal passed through a band-pass filter coupled between the first transistor and one of the plurality of antennas that provides the portion of the beam-forming signal from which the input signal is derived.
5. The receiver of claim 1 , wherein the output signal is applied to a mixer for down-conversion.
6. The receiver of claim 1 , wherein the capacitance control signal is received from a controller.
7. The receiver of claim 1 , wherein:
the second transistor includes a gate;
the variable capacitance circuit is connected to a node connected to the gate; and
the capacitance control signal is received at a circuit point other than the node connected to the gate.
8. The receiver of claim 1 , wherein the capacitance control signal includes a plurality of switches, and the capacitance control signal is applied to the switches and controls switching states of the switches.