A fully integrated power amplifier (PA) employing a transformer combiner with enhanced back-off efficiency includes a first PA to amplify a first radio frequency (RF) signal and a second PA to amplify a second RF signal. A first variable capacitor is coupled between differential output nodes of the first PA. A second variable capacitor is coupled between differential output nodes of the second PA. The differential outputs of the first PA and the second PA are coupled via respective first and second transformers to a load. Capacitance values associated with the first and second variable capacitors are dynamically adjustable based on an amplitude of the RF signal to achieve a desired power efficiency at an output power level.

A fully integrated power amplifier (PA) employing a transformer combiner with enhanced back-off efficiency includes a first PA to amplify a first radio frequency (RF) signal and a second PA to amplify a second RF signal. A first variable capacitor is coupled between differential output nodes of the first PA. A second variable capacitor is coupled between differential output nodes of the second PA. The differential outputs of the first PA and the second PA are coupled via respective first and second transformers to a load. Capacitance values associated with the first and second variable capacitors are dynamically adjustable based on an amplitude of the RF signal to achieve a desired power efficiency at an output power level.

In an aspect of the present invention, provided is a method for receiving an uplink signal by a base station (BS) in a wireless communication system where a reference signal is not used, including: obtaining information bits by demodulating and decoding a signal of a first user equipment (UE) that is modulated through a differential modulation scheme; estimating a channel between the first UE and the BS using the information bits; and performing successive interference cancellation (SIC) using the signal of the first UE restored through the channel estimation results and the information bits. In this case, the BS may estimate the channel between the first UE and the BS by assuming that an Nth modulation symbol among modulation symbols of the information bits modulated through the differential modulation scheme is fixed to a predetermined constellation point.

An audio amplifier system includes a delta-sigma modulator configured to receive an m-bit digital audio input signal and to generate a pulse density modulated signal based on the m-bit digital audio input signal. An analog power stage is coupled to the delta-sigma modulator to receive the pulse density modulated signal and amplify the pulse density modulated signal to generate an amplified pulse density modulated signal. A feedback circuit is coupled to the delta-sigma modulator and the analog power stage. The feedback circuit is configured to receive the amplified pulse density modulated signal and the pulse density modulated signal and to determine a digital error signal representative of a difference between the amplified pulse density modulated signal and the pulse density modulated signal. The feedback circuit is further configured to provide the digital error signal to the delta-sigma modulator for applying the digital error signal to a representation of the m-bit digital audio input signal.

According to a first example aspect there is provided a charge pump circuit that includes a first chopper circuit configured to switch first and second chopper circuit outputs between first and second chopper circuit inputs at a chopping frequency, wherein successive input signals at the first chopper circuit input are output alternatively at the first and second chopper circuit outputs in successive cycles of the chopping frequency and successive input signals at the second chopper circuit input are output alternatively at the second and first chopper circuit outputs in successive cycles of the chopping frequency. A differential charge pump is configured to receive the signals output from the first and second chopper circuit outputs and produce corresponding first and second charge pumped signals.

RF filtering circuitry includes a first transmit signal node, a second transmit signal node, a common node, first transmit signal filtering circuitry, second transmit signal filtering circuitry, and transmit signal cancellation circuitry. The first transmit signal filtering circuitry is coupled between the first transmit signal node and the common node and is configured to pass RF transmit signals within a first transmit signal frequency band while attenuating signals outside the first transmit signal frequency band. The second transmit signal filtering circuitry is coupled between the second transmit signal node and the common node and is configured to pass RF transmit signals within a second transmit signal frequency band while attenuating signals outside the second transmit signal frequency band. The transmit signal cancellation circuitry is coupled between the common node and the second transmit signal node and is configured to generate a transmit cancellation signal.

A cellular radio architecture that includes a programmable bandpass sampling radio frequency front-end and an optimized digital baseband. The architecture includes a receiver module having a plurality of signal channels for different frequency bands, where each signal channel in the receiver module includes a receiver delta-sigma modulator that converts analog receive signals to a representative digital signal. The architecture also includes a transmitter module having a transmitter delta-sigma modulator for converting digital data bits to analog transmit signals, where the transmitter module includes a power amplifier and a switch for directing the transmit signals to one of the signal paths. The architecture also includes a dual self-cancellation circuit providing digital and analog cancellation of the transmit signal in the receiver module.

A cellular radio architecture that includes a programmable bandpass sampling radio frequency front-end and an optimized digital baseband. The architecture includes a receiver module having a plurality of signal channels for different frequency bands, where each signal channel in the receiver module includes a receiver delta-sigma modulator that converts analog receive signals to a representative digital signal. The architecture also includes a transmitter module having a transmitter delta-sigma modulator for converting digital data bits to analog transmit signals, where the transmitter module includes a power amplifier and a switch for directing the transmit signals to one of the signal paths. The architecture also includes a dual self-cancellation circuit providing digital and analog cancellation of the transmit signal in the receiver module.

Transport of differential signals is provided. In one aspect, a telecommunications system includes a first unit and a second unit. The first unit can calculate a differential signal from an original signal. The differential signal can represent a change in signal levels between constant time intervals in the original signal. The second unit can estimate the original signal from the differential signal received from the first unit over a communication medium.

A feedback control system may include a feedback controller for controlling a plant using pulse density signals. The feedback controller may include a pulse density signal generator and a controller logic circuit. The pulse density signal generator may receive input command signals and generate signed or unsigned pulse density input signals. The controller logic may receive the pulse density input signals from the pulse density signal generator and feedback pulse density signals from the plant and may generate corresponding pulse density control signals for controlling the plant based on the input command signals. The controller logic may include a sign change logic, an addition circuit, and an optional amplifier circuit. The pulse density signal generator may also include rate transition circuits for ensuring that the pulse density input signals and the feedback pulse density signals are uncorrelated.