148results about "Amplitude modulation details" patented technology

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.

The present invention is related to methods and apparatus that advantageously permit the more efficient use of an input range of an analog-to-digital converter used by an adaptive predistortion linearized RF transmitter. A main signal component of a down-converted output of an RF transmitter is removed prior to the analog-to-digital conversion of the down-converted output, thereby allowing more of the input range of the analog-to-digital converter to capture an error signal component of the down-converted output. Embodiments of the present invention can thus adaptively tune the predistortion stage to a higher degree of linearity or can use lower cost analog-to-digital converters with fewer quantization steps for the same performance.

Non-linearities of signal-generation circuits that typically include a series arrangement of a modulator and a power amplifier are reduced by connecting a measurement circuit to an output of the signal-generation circuit and at another point along a signal path of the signal-generation circuit. A predistorted input signal is applied to an input of the signal-generation circuit. The pre-distorted signal includes a constant component and a time-varying component, such that the predistorted input signal excites non-linear modes of the signal-generation circuit. The measurement circuit is balanced so that a portion of the predistorted input signal that passes through the measurement circuit does not include a time-varying component and therefore does not excite non-linearities of the measurement circuit. Adjustments are made to the predistorted input signal in order to reduce non-linearities of the signal-generation circuit.

An RF power amplifier system is presented herein. It includes a plurality of RF power amplifier modules. At least two encoders are provided. Each encoder is associated with and controls the operation of some of the plurality of power amplifier modules. Each encoder is associated with different ones of the plurality of amplifier modules. An exciter receives an amplitude varying input signal and periodically provides a command signal to each of the modulation encoders and instructs that modulation encoder as to how many of its associated power amplifier modules are to be turned on as a function of the value of the input signal. Each modulation encoder responds to a received command signal and selects which of its associated power amplifiers to turn on.

A circuit for amplitude modulating a carrier signal includes a carrier signal input, circuitry for splitting the carrier signal into first and second paths, circuitry for phase modulating the carrier signal on the first path, circuitry for phase modulating the carrier signal on the second path, and circuitry for combining the phase modulated carrier signal on the first path with the phase modulated carrier signal on the second path for generating an amplitude modulated output signal. Feedback loops virtually eliminate residual phase shift and make the amplitude modulated output signal linearly proportional to the baseband signal.

A single side band transmitter having reduced DC offset includes a current source modulation module, a current mirror module, a 1st mixing module, a 2nd mixing module, a summing module, and a power amplifier. The current source module is operably coupled to modulate, in accordance with a modulation protocol (e.g., FSK) data to produce an in-phase current component and a quadrature current component. The current mirror module is operably coupled to mirror the in-phase current component to produce a mirrored in-phase current component and is also operably coupled to mirror the quadrature current component to produce a mirrored quadrature current component. The 1st mixing module is operably coupled to mix the mirrored in-phase current component with an in-phase current component of a local oscillation to produce a 1st mixed current signal. The 2nd mixing module is operably coupled to mix the mirrored quadrature current component with a quadrature component of the local oscillation to produce a 2nd mixed current signal. The summing module is operably coupled to sum the 1st and 2nd mixed current signals to produce an up converted signal. The power amplifier amplifies the up converted signal prior to transmission as a radio frequency signal.

Apparatus and method are presented for adaptively compensating for carrier signal phase distortion caused by amplitude modulating an RF carrier signal. A modulator-amplifier network receives an RF carrier signal and modulates it by a received amplitude varying signal to obtain therefrom a modulated RF carrier signal which is phase shifted from the phase of the carrier signal applied to the network by an amount that varies with the value of the amplitude varying signal. A phase shifter receives the RF carrier signal and phase shifts it in accordance with the value of a received phase correction signal to provide a pre-phase shifted carrier signal that is applied to the modulator-amplifier network. A phase detector receives and compares the modulated RF carrier signal and the carrier signal and provides an error signal in accordance with the comparison. An adaptive controller provides the correction signal and receives the error signal and the amplitude varying signal and varies the value of the correction signal in accordance with the value of the error signal and the value of the amplitude varying signal.

Aspects of a method and system for a high-precision frequency generator using a direct digital frequency synthesizer for transmitters and receivers may include generating a second signal from a first signal by frequency translating an inphase component of the first signal utilizing a high-precision oscillating signal that may be generated using at least a direct digital frequency synthesizer (DDFS) and at least a Phase-Locked Loop (PLL). A corresponding quadrature component of the first signal may be frequency translated utilizing a phase-shifted version of the high-precision oscillating signal. The inphase component of the first signal may be multiplied with the high-precision oscillating signal and the quadrature component of the first signal may be multiplied with the phase-shifted version of the high-precision oscillating signal. The second signal may be generated from the first signal by adding the frequency translated inphase component to the frequency translated quadrature component.

Aspects of a method and system for direct and polar modulation using a two input PLL are presented. Aspects of the system may include generating digital signals Wn and Vn from an input data signal Un and a feedback signal Yn. The generated digital signals Wn and Vn combined may carry the information content of Un while they compensate the non-idealities of the two-input analog phase locked loop (PLL). The digital signal Wn, which may be scaled appropriately in frequency, and the digital signal Vn may be provided as inputs to the PLL. The feedback signal Yn may be a digital signal that may correspond to the analog feedback signal Pt that may be generated by the PLL. Accordingly, the PLL may be adaptively controlled via the digital signals Wn and Vn for properly transmitting the input data signal Un.