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This paper presents a 4th order continuous-time bandpass delta-sigma modulator (CT-BPDSM) with a programmable center frequency ranging from 1.55 GHz to 2.45 GHz. The modulator is suited to be applied in multistandard class-S power amplifiers. The circuit features a multifeedback architecture with return-to-zero (RZ) and half-return-to-zero (HRZ) pulses. The loop filters consist of LC-resonators with...
This paper investigates the supply modulation concept to improve the efficiency of power amplifiers in back off. The modulator is a class AD modulator which has a high efficiency while keeping a large signal bandwidth. In an experimental setup the efficiency of a 5 W GaAs power amplifier can be improved from 28% to 40% at 7dB back off.
This paper describes the losses and efficiency deteriorations due to several non-idealities of a current-mode class-D amplifier driven by a Delta-Sigma pulse sequence. The computation of the total efficiency of the amplifier is presented. Finally the results are verified by designing and measuring an amplifier driven by a pulse sequence with 50% duty cycle and a frequency of 30 MHz. The measured efficiency...
A continuous-time bandpass delta-sigma modulator (CT BPDSM) for class-S power amplifier applications with a center frequency of 2.2 GHz is presented. Class-S amplifiers are considered to provide a very power efficient way to amplify signals with high dynamic range. The modulator has a multi-feedback architecture. It features a low noise transconductor with series emitter degeneration, tunable LC resonators...
This paper investigates the adaptive bias control of a microwave Doherty amplifier using a programmable logic device. The gate bias of the peaking amplifier is controlled by the magnitude of the envelope of the RF input signal, which is digitized by a logarithmic detector. Compared with a class C peaking amplifier the peak output power at the 1 dB compression point is increased from 56 W to 85 W at...
Using ST 0.13-mum CMOS technology, a class A power amplifier has been developed for the global system for mobile communication in Europe. To solve the problem of low breakdown voltage in deep-submicrometer CMOS technology, the high-voltage/high-power (HiVP) device configuration is used. With the HiVP configuration, a large voltage can be divided by several devices so that the voltage drop on each...
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