Balanced Broadband Amplifier Design Using Lange Couplers

The design of a Balanced Broadband Amplifier which operates in an octave of 10 to 20 GHz has been illustrated in this project report. The term broadband means that the bandwidth of the amplifier in decibels, stretches over 6 db per octave and octave refers to the interval between any two frequencies having a ratio of 2:1. For example 2-4GHz is one octave. After doing an intensive search for a stable transistor, MGF4961B was chosen to be the best suitable transistor for this project because this low noise High Electron Mobility Transistor (HEMT) was stable for all the frequencies from 10 to 20 GHz. In the design, two MGA (Maximum Gain Amplifiers) were connected in parallel via lange coupler. This is known as balanced configuration. The maximum gain obtained by the transistor at a center frequency of 15 GHz came out to be 13.27dB. Various types of calculations from stability check to MGA design and from DC biasing to lange coupler design have been verified using MATLAB software, RF/MW EBook software and NI AWR Microwave office. All the calculations along with their verified proofs have been included in this report.