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

Abstract

The design of frequency-tunable amplifiers is investigated and the tradeoff between linearity, efficiency and tunability is revealed. Several tunable amplifiers using various varactor diode topologies as tunable devices are designed by using loadpull 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.

Design and investigation of 12–50 Ohm tunable microstrip impedance transforming filter

“…4 (a) and (b) respectively. Also its element values are given in TABLE II which are computed by using (1) and (2). Furthermore, TPG simulation and measurement results are compared in Fig.…”

“…The design of broadband, programmable and tunable radio frequency (RF) front-end components carries extreme importance for the realization of a high frequency SDR terminal. Previous works, such as [2]- [5], have shown that tunable filters and amplifiers which are appropriate to SDR's can be designed by using different approaches.…”

“…The objective of SDR technology is to realize reconfigurable radios that may be used for various communications systems without the need of modifying or replacing any hardware components [2], thus it has the potential of facilitating the design of low cost, compact and future-proof commercial mobile equipment. The design of broadband, programmable and tunable radio frequency (RF) front-end components carries extreme importance for the realization of a high frequency SDR terminal.…”

Design of tunable matching networks over 800–5200 MHz using real frequency techniques

“…The objective of SDR technology is to realize reconfigurable radios that may be used for various communication systems without the need of modifying or replacing any hardware components [1]. The design of programmable and tunable radio frequency (RF) front-end components carries extreme importance for the realization of a high frequency SDR terminal.…”

Design of a multimode tunable low noise amplifier for software defined radios

“…Additionally, varactor diodes were explored to achieve continuous frequency tuning in LNAs. In [8,9] varactor diodes were implemented in the output stage of LNA to achieve reconfiguration. However, the frequency tuning range in both circuits was limited to 500 MHz.…”