# Amplifiers

## Spatial Power Combining in Rectangular Waveguides using Dense Finline Arrays:

Spatial power combiners using dense finline arrays (tapered slot antennas) arranged in tray configuration and enclosed in a standard Ku band waveguide (WR-62) have been designed in this work. The design of the finline taper is the most challenging aspect in this work. Before the tapers can be synthesized, a relationship between phase constant of the finline array and its geometrical parameters must be established which can only be achieved through full wave EM analysis. Matlab codes were developed using Spectral Domain Method (SDM) to extract this relationship for single-tray finline, two-tray finline and four-tray finline configuration. Results of SDM codes were also compared with Ansoft HFSS and were found to be in good aggrement. Two tray finline and Four tray finline tapers along with dielectric matching, connected back to back were fabricated and tested using Time Domain Gating feature of Network Analyzer. Results indicate measured return loss of 26.3 dB as compared to simulated return loss of 23.5 dB for single tray finline, 19 dB as compared to simulated return loss of 18.6 dB for two tray finline and 16 dB as compared to simulated return loss of 15.5 dB for four tray finline at 16 GHz.

#### Publications:

• M. Anis Chaudhary, “Spatial Power Combining in Rectangular Waveguides using Dense Finline Arrays,” MS Thesis, College of E&ME, NUST, 2010.

## High Performance GaN based Switch Mode Class F and Inverse Class F Power Amplifier:

This work is based on design and development of Class AB, Class F and Class $\ F^{-1}$ power amplifiers using GaN based transistors. A comparison has been done between these amplifiers based on output power and efficiency. Effect of input harmonic termination on efficiency and output power in Class F and Class $\ F^{-1}$ power amplifiers has also been investigated.

#### Publications:

• Ali Ahmed, “High Performance GaN based Switch Mode Class F and Inverse Class F Power Amplifier,” MS Thesis, College of E&ME, NUST, 2012.