SUMMARYA novel supply modulation scheme for envelope tracking for a power amplifier in a transmitter is proposed, which follows a control principle that is fundamentally different from the existing ones. Instead of regulating the supply modulator's output in accordance with a given reference signal, the system utilizes a look-ahead window and synthesizes pulses for the supply modulator such that its output tracks the envelope of the radio frequency signal amplified by the power amplifier, while minimizing its switching rate. Simulation results for a 5 MHz Long Term Evolution signal with 16 quadrature amplitude modulation indicates that the proposed technique provides very high average efficiency (84%) while maintaining a very low ratio between the switching frequency and the envelope bandwidth.
In digitally intensive direct conversion transmitters, the baseband data is up-sampled to the RF rate. As the bandwidth of the baseband data increases, carefully designed cascaded digital filters are required in order to attenuate the wide replicas generated during the digital up-sampling process. Though design methodologies for single stage digital filters are very well established, near-optimum design of such multistage filters typically requires selection of several parameters by trialand-error. This approach is time-consuming and does not assure the optimum solution (i.e. lowest area/power) under various performance constraints. In this paper, a genetic algorithm (GA) based generic automated search methodology for design of such cascaded filters is proposed. The proposed technique is demonstrated for digital WiMAX and WCDMA transmitters, for which near-optimal solutions appear to have been achieved in a relatively short time compared to the traditional manual design techniques.
Supply modulation for RF power amplifiers according to the modulated signal's envelope (i.e. envelope tracking and polar modulation) is an effective approach for achieving high efficiency in transmitters. Various current and emerging wireless standards produce signal envelopes with wide bandwidths and high peak-to-average ratio (PAR), which makes efficient supply modulation very challenging. In this paper, a reduced bandwidth class H supply modulation scheme is proposed, which provides efficient supply modulation with high PAR and wide bandwidth. It leverages a novel bandwidth reduction DSP algorithm to effectively exploit an efficient narrowband switching modulator without increasing its switching losses. Analyses and simulation results for LTE and WiMAX signals indicate significant modulator efficiency improvements (up to 15%) over similar existing techniques.
As the use of Artificial Neural Network(ANN) in mobile embedded devices gets more pervasive, power consumption of ANN hardware is becoming a major limiting factor. Although considerable research efforts are now directed towards low-power implementations of ANN, the issue of dynamic power scalability of the implemented design has been largely overlooked. In this paper, we discuss the motivation and basic principles for implementing power scaling in ANN Hardware. With the help of a simple example, we demonstrate how power scaling can be achieved with dynamic pruning techniques.
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