No abstract

This paper presents design and linearization techniques for a highly efficient but nonlinear Class-E power amplifier (PA) applied to a dual-mode RF transmitter for W-CDMA/WiMAX systems. At first, a Class-E PA design is carried out for dual-band operation based on the proposed modified Class-E condition. Then, the envelope tracking and digital predistortion techniques are applied to linearize the Class-E PA by improving the PA AM/AM and AM/PM distortions. Consequently, the designed Class-E PA, although classified as a switching-mode PA, can act as a linear PA for diverse high peakto-average-power-ratio (PAPR) wireless systems. The experimental results show that a quadrature modulation transmitter incorporating the presented envelope-tracking dualband Class-E PA can simultaneously achieve high average efficiency and adjacent channel power rejection for 1.95 GHz W-CDMA and 2.6 GHz WiMAX applications.

Abstract-A novel cognitive polar receiver that utilizes two injection-locked oscillator stages to extract the modulation envelope and phase components of a received nonconstant envelope modulation signal without using phase-locked-loop-based carrier recovery circuitry is presented. The paper begins with a theoretical analysis of injection locking and pulling phenomena based on the discrete-time computation approach, and then develops the principles of the proposed receiver. The implemented prototype can cover a sensing bandwidth of 140 MHz at a central frequency of 2.43 GHz and perform 4 differential quadrature phase-shift keying and quadrature phase-shift keying demodulation with the best error vector magnitudes of 6.6% and 7.9%, respectively, both at a symbol rate of 2 Ms/s. Due to its simplicity, the proposed receiver has great potential as an energy-efficient architecture with low complexity for short-range wireless communications.

No abstract

No abstract