A communication unit (200) employs a method and apparatus for increasing an output impedance of a transmit amplifier during a receive mode of the communication unit. The communication unit includes a transmit amplifier, an antenna (209), and a signal receiver (211), and is operable in at least a transmit mode and a receive mode. During the transmit mode, the transmit amplifier, which includes an amplifying device (201), amplifies an input signal (221) and provides the amplified signal (233) to the antenna for transmission. During the receive mode, the antenna receives signals and provides the received signals to the signal receiver. To mitigate the transmit amplifier's effect on the received signals during the receive mode, the communication unit, during the receive mode, couples the transmit amplifier to the antenna and applies a bias (225) to the amplifying device to increase the output impedance (Z.sub.out) of the transmit amplifier, such that the transmit amplifier does not significantly load the received signals.
A variable phase shifter and a system for the variable phase shifter are provided. The phase shifter includes fixed phase shift elements, active devices for amplifying the outputs of the fixed phase shift elements, a combiner for combining the outputs of the active devices. For controlling the phase of the output signal, a bias controller is provided. The bias controller controls the bias of amplification in the fixed phase shift elements. The active devices may be FET or Bipolar Transistors, and are inductively connected to the ground. The phase shifter can be integrated into a system on chip with a smart antenna front-end system.
A wireless communications device uses an amplifier module to transmit signals. The amplifier module is configured to amplify a signal. The amplifier module includes an amplifier circuit and a control module. The control module is configured to vary the operating parameters of the amplifier circuit based on a desired output power level. The control module relies on stored data values to dynamically vary the operating parameters of the amplifier circuit so as to increase the efficiency of the amplifier circuit.
A radio transceiver circuit which includes an antenna, a transmitter, a receiver, an antenna switching circuit for selectively connecting the transmitter and the receiver to the antenna, and a power source for driving the transmitter and the receiver. The antenna switching circuit includes two semiconductor elements. The current (.vertline..sub.BRX, .vertline..sub.BTX) provided by the power source to the receiver and to the transmitter is directed through the respective semiconductor elements which are each set to its conductive electrical state by the respective current (.vertline..sub.BRX, .vertline..sub.BTX) and thereby selectively coupling the radio signal between the receiver and the transmitter to the antenna.
A wireless communications device uses an amplifier module to transmit signals. The amplifier module is configured to amplify a signal. The amplifier module includes an amplifier circuit and a control module. The control module is configured to vary the operating parameters of the amplifier circuit based on a desired output power level. The control module relies on stored data values to dynamically vary the operating parameters of the amplifier circuit so as to increase the efficiency of the amplifier circuit.
Open-Loop RF Transmitter Output Power Control for Increased Power Efficiency (NC#97507) system includes microprocessor, battery, bias control circuitry, supply control circuitry and power amplifier. Microprocessor receives desired RF output power and battery voltage value and transmits bias control voltage and supply control voltage. Bias control circuitry is operatively coupled to microprocessor and receives bias control voltage and transmits bias output voltage. Supply control circuitry is operatively coupled to battery and microprocessor, and receives battery voltage and supply control voltage, and transmits supply collector voltage. Power amplifier is operatively coupled to supply control circuitry and bias control circuitry via inductor, and receives supply collector voltage and bias output voltage, and transmits RF output signal in response to RF input signal, supply collector voltage and bias output voltage.
