Verification of Differential Low Noise Amplifier Measurement

Abstract

Differential input to single ended output Low Noise Amplifiers (LNA) designs and fabrications are required for the front end of 2-PAD project in SKADS. The differential input for these LNAs are essential to match the differential output of the Bunny Ear Comb-line Antenna (BECA) connected before these LNAs. A low noise amplifier has been designed, fabricated and tested for 2-PAD project. Detailed explanation of this designed amplifier and its results will be described. A commercially available amplifier was used to devise a robust test plan to measure s-parameter responses and noise of various topologies of LNA designs for 2-PAD LNAs. This commercially available amplifier is ideal for this study as it allows us to use it in three different modes of operation including single ended input to differential output, differential input to differential output and differential input to single ended output. Therefore the later mode of operation is our interest. S-parameter response tests were carried out for the differential input to differential output and differential input to single ended output modes of this amplifier using a 4 port vector network analyzer. A noise measurement model for differential amplifiers was proposed by the author in more detail in Bhaumik et al. (2009). The commercially available amplifier and the designed LNAs operate in the same frequency range as well as having differential input and single ended output feature; therefore these tests and method of measurements are particularly useful for the reason that can be utilized in measuring the low noise amplifiers designed for 2-PAD project. As a result, the procedure used for measuring the differential input to single ended output operation mode of the commercially available amplifier would verify the precision and suitability of this method for the designed LNAs.