Abstract: An amplifier circuit includes a power amplifier biased for saturated mode operation, and a controllable current source to provide supply current to the power amplifier. The controllable current source effects desired amplitude modulation of the output signal from the power amplifier by modulating the supply current it provides responsive to an amplitude information signal. In one or more embodiments, the current source includes a circuit that is configured to adjust one or more transmitter operating parameters responsive to detecting changes in the effective DC resistance of the power amplifier. For example, the circuit may generate a compensation signal that reduces the effective DC resistance responsive to detecting that the effective DC resistance has undesirably increased. By way of non-limiting examples, such compensation may be effected by changing a current mirror, an amplifier-to-antenna impedance matching, an amplifier bias or device size, or imposing some form of transmit signal back-off.

Abstract: A method according to one embodiment includes using a quadrature set of local oscillator signals having duty cycles of substantially less than fifty percent to perform a mixing operation on a radio-frequency current signal. Other embodiments include using a quadrature set of local oscillator signals having duty cycles of less than twenty-five percent.

Abstract: A diversity receiver capable of receiving a CDMA system (e.g., a W-CDMA system) and a TDMA system (e.g., a GSM system), with receive diversity for at least one system, is described. W-CDMA is often referred to as UMTS. In one design, the diversity receiver includes a first receiver for GSM and a second receiver for UMTS. The first receiver may be implemented with one receiver design, may be spec-compliant for GSM, and may also support UMTS. The second receiver may be implemented with another receiver design, may be spec-compliant for UMTS, and may also support GSM. The first receiver may include a lowpass filter having a bandwidth that is adjustable for GSM and UMTS. The second receiver may include a bandpass filter used to attenuate a transmit frequency range for UMTS. Each receiver may include circuit blocks that are used for both GSM and UMTS.

Abstract: Polar modulators include a phase splitter, a controller, variable current sources, transistor circuits, and a combiner. The phase splitter splits a RF carrier signal into quadrature component signals that are 90 degrees out of phase with each other. The controller generates modulation control signals based on information that is to be transmitted. The variable current sources each generate a variable amplitude current signal based on a different one of the modulation control signals. Each of the transistor circuits amplify a different one of the quadrature component signals with a variable amplification based on the variable amplitude current signal from a different one of the variable current sources to generate an amplitude adjusted quadrature component signal. The combiner combines the amplitude adjusted quadrature component signals from each of the transistor circuits to generate a phase-modulated RF carrier output signal.

Abstract: Polar modulators include a phase splitter, a controller, variable current sources, transistor circuits, and a combiner. The phase splitter splits a RF carrier signal into quadrature component signals that are 90 degrees out of phase with each other. The controller generates modulation control signals based on information that is to be transmitted. The variable current sources each generate a variable amplitude current signal based on a different one of the modulation control signals. Each of the transistor circuits amplify a different one of the quadrature component signals with a variable amplification based on the variable amplitude current signal from a different one of the variable current sources to generate an amplitude adjusted quadrature component signal. The combiner combines the amplitude adjusted quadrature component signals from each of the transistor circuits to generate a phase-modulated RF carrier output signal.

Abstract: An amplifier circuit includes a power amplifier biased for saturated mode operation, and a controllable current source to provide supply current to the power amplifier. The controllable current source effects desired amplitude modulation of the output signal from the power amplifier by modulating the supply current it provides responsive to an amplitude information signal. In one or more embodiments, the current source includes a circuit that is configured to adjust one or more transmitter operating parameters responsive to detecting changes in the effective DC resistance of the power amplifier. For example, the circuit may generate a compensation signal that reduces the effective DC resistance responsive to detecting that the effective DC resistance has undesirably increased. By way of non-limiting examples, such compensation may be effected by changing a current mirror, an amplifier-to-antenna impedance matching, an amplifier bias or device size, or imposing some form of transmit signal back-off.

Abstract: An amplifier circuit includes a power amplifier biased for saturated mode operation, and a controllable current source to provide supply current to the power amplifier. The controllable current source effects desired amplitude modulation of the output signal from the power amplifier by modulating the supply current it provides responsive to an amplitude information signal.

Abstract: A branched power amplifier circuit includes two or more amplifier segments or branches, each with a corresponding lossy modulator. The branched power amplifier may be dynamically resized by enabling different ones of its branches, to deliver peak efficiency at a number of different amplifier output power levels. Each amplifier branch operates in a saturated mode and selectively amplifies an RF input signal. The lossy modulators provide either supply voltage or supply current modulation to corresponding amplifier branches, thus imparting highly linear amplitude modulation to the overall output signal generated by branched power amplifier, despite its saturated mode operation. The branched power amplifier circuit may be configured such that particular combinations of segments have peak efficiencies matched to the needs of one or more air interface standards used in wireless mobile communication systems.

Abstract: An amplitude modulation circuit (modulator) provides modulated supply current, possibly in combination with modulated supply voltage, to a radio frequency (RF) power amplifier (PA), and includes a detection circuit responsive to changes in the ratio of that voltage to the modulated supply current, described herein as its AM modulation impedance. Such impedance (resistance) changes commonly arise from changing coupling characteristics at the RF antenna assembly driven by the PA. A gain control circuit may be associated with the detection circuit, and made responsive thereto, thus allowing adjustment of modulation gain control responsive to changes in PA AM modulation impedance. In one embodiment, this arrangement permits the modulator to hold a fixed modulation gain over changing PA AM modulation impedance, while in other embodiments, modulation gain varies in response to PA impedance changes to avoid signal clipping.

Abstract: A branched power amplifier circuit includes two or more amplifier segments or branches, each with a corresponding lossy modulator. The branched power amplifier may be dynamically resized by enabling different ones of its branches, to deliver peak efficiency at a number of different amplifier output power levels. Each amplifier branch operates in a saturated mode and selectively amplifies an RF input signal. The lossy modulators provide either supply voltage or supply current modulation to corresponding amplifier branches, thus imparting highly linear amplitude modulation to the overall output signal generated by branched power amplifier, despite its saturated mode operation. The branched power amplifier circuit may be configured such that particular combinations of segments have peak efficiencies matched to the needs of one or more air interface standards used in wireless mobile communication systems.

Abstract: An amplifier circuit includes a power amplifier biased for saturated mode operation, and a controllable current source to provide supply current to the power amplifier. The controllable current source effects desired amplitude modulation of the output signal from the power amplifier by modulating the supply current it provides responsive to an amplitude information signal.

Abstract: A radio frequency power amplifier circuit provides linear amplitude modulation of a radio frequency output signal while operating in a saturated amplification mode. The power amplifier circuit incorporates a lossy modulator that functions as a variable resistance responsive to an amplitude modulation signal. A supply voltage is coupled to the voltage supply input of the power amplifier circuit through the lossy modulator, such that the supply voltage applied to the power amplifier varies with the amplitude modulation signal. The radio frequency power amplifier circuit modulates the envelope of an RF output signal generated by saturated mode amplification of a constant envelope radio frequency input signal.

Abstract: An input buffer circuit is operable to selectively present either low or high input impedance while maintaining uniform output impedance. The buffer is characterized by first and second amplifier circuits connected in parallel between an input to and an output from the buffer. The amplifiers are individually controlled between enabled and disabled states. When enabled, the first amplifier has low input impedance and predetermined output impedance and the second amplifier has high input impedance and the predetermined output impedance, and when disabled each amplifier has high input and output impedance. To operate the buffer to have low input impedance, the first amplifier is enabled while the second amplifier is disabled. To operate the buffer to have high input impedance, the second amplifier is enabled while the first amplifier is disabled.

Abstract: A wide range single stage variable gain amplifier is provided for receiving an input signal and outputting an amplitude varied version of the received input signal. In its most basic form, the wide range single stage variable gain amplifier includes an input circuit receiving an input signal and developing an input current, a first control circuit receiving the input current, the first control circuit being selectively controllable to output an attenuated version of the received input current, a second control circuit directly connected to the first control circuit for receiving the attenuated input current therefrom, the second control circuit being selectively controllable to output a further attenuated version of the attenuated input current, and an output circuit receiving the further attenuated input current and developing an amplitude varied version of the received input signal.