Linearized bipolar junction transistor distributed amplifier
Student thesis: Doctoral Thesis
Related Research Unit(s)
Distributed amplifiers are able to operate over a broad bandwidth, which fits the primary need of today’s commercial market. If the distributed amplifier can be linearized, then this linearized distributed amplifier can amplify the high bandwidth efficient modulation format signal needed to fulfill low distortion/error high data rate transmission. Past works on distributed amplifiers have not considered the possibility of linearization and operation was based on how much to back-off the amplifier for a given amount of intermodulation distortion. The work presented here uses a parallel diode to linearize a distributed amplifier allowing it to operate with a lower back-off for the same intermodulation distortion of a non-linearized distributed amplifier. Here the optimum number of diodes and its placement for the best linearization is presented theoretically as well as experimentally. The main contribution of research presented in this thesis is to show the feasibility and present the results of applying linearization to a distributed amplifier. The resultant linearized amplifier can give a 13dB gain from 800MHz to 2200MHz with a low linearization loss of less than 1dB and a 5-12dB reduction in spectral re-growth for the first side-lobe. Comparisons of spectrum with high bandwidth-efficiency modulation format at chosen frequencies are also presented in this thesis. The linearization of the distributed amplifier will give the RF engineers more choices on the amplifier topologies for use in wideband communication system.
- Distributed amplifiers, Junction transistors, Bipolar transistors