Design and Analysis of Frequency-Tunable Amplifiers using Varactor Diode Topologies

Nesimoglu T.

CIRCUITS SYSTEMS AND SIGNAL PROCESSING, vol.30, no.4, pp.705-720, 2011 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 30 Issue: 4
  • Publication Date: 2011
  • Doi Number: 10.1007/s00034-011-9309-6
  • Page Numbers: pp.705-720


The design of frequency-tunable amplifiers is investigated and the trade-off between linearity, efficiency and tunability is revealed. Several tunable amplifiers using various varactor diode topologies as tunable devices are designed by using load-pull techniques and their performances are compared. The amplifier using anti-series distortion-free varactor stack topology achieves 38% power added efficiency and it may be tuned from 1.74 to 2.36 GHz (about 35% tunable range). The amplifier using anti-series/anti-parallel topology is tunable from 1.74 to 2.14 GHz (about 23% tunable range) and provides 42% power added efficiency. It is demonstrated that tunable amplifiers using distortion-free varactor stack topologies provide better power added efficiency than the tunable amplifiers using reverse biased varactor diodes and their linearity is similar to that of a conventional amplifier. These amplifiers may facilitate the realization of frequency agile radio frequency transceiver front-ends and may replace several parallel connected amplifiers used in conventional multimode radios.