L-band transmitter using Kahn EER technique

Abstract

This paper describes a 20-W peak-envelope power linear L-band transmitter based upon the Kahn envelope-elimination-and-restoration technique. A double envelope-feedback loop assures high linearity. The radiofrequency (RF) power amplifier employs a two-stage monolithic-microwave integrated-circuit driver amplifier and a 20-W power amplifier biased for class-AB operation. The class-S modulator includes a high-speed comparator and 1/2-m heterojunction field-effect transistors in its output stage. A double envelope-feedback loop assures both high linearity and time-delay equalization for RF bandwidths to 150 kHz. With a two-tone signal, the transmitter achieves an efficiency of 56% at full power (41 dBm), and 35% at 18 dB into back-off. The third-order intermodulation distortions for a two-tone signal vary from 030 to 040 dBc over a 20-dB range of back-off. For quaternary phase-shift keying, the first and second adjacent-channel powers are 048 and 057 dBc.

Comparison of bandwidth reduction schemes in dynamic load modulation power amplifier architectures

“…As shown in Fig. 6, the reduced-bandwidth baseband control signal is larger than the original baseband control signal for all the samples which satisfies (1).…”

“…Envelope elimination and restoration (EER) [1], envelope tracking (ET) [2] and dynamic load modulation (DLM) [3] are some of the most promising examples. The basic principle of these PA architectures is to keep the operating point of the PA close to saturation by manipulating the power supply (ET and EER) or load impedance (DLM), for a wide range of power levels.…”

High efficiency power amplifier for high frequency radio transmitters

“…Thanks to this technique, the efficiency of the transmitter is almost constant for wide load range and it does not depend heavily on the level of the transmitted signal, as in the case of linear amplifiers [4]. Average efficiency three to five times those of linear amplifiers have been demonstrated from HF to L band [5,6]. In [7] a prototype of Kahn's transmitter for HF Band is presented.…”

Envelope tracking of a radio frequency amplifier for Long Term Evolution using a three-level class-G modulator

“…For broadband signals such as LTE, this results in switching frequencies above 100 MHz, leading to high switching losses for large power transistors. Therefore, buck converters with output powers above 2 W are either used in narrow-band applications (Raab, 1998;Andersen, 2007, 2009) or implemented as integrated circuits in RF power technologies such as LDMOS (Pinon et al, 2008) or GaAs (Busking et al, 2012).…”