Design of an L-band radiometer front end for medical radiometry

A low noise, linear phase and medium gain frontend board is presented for medical microwave radiometry in the L-band. The front-end consists of a bandpass filter and a low noise amplifier operating at 1.3 GHz with 200 MHz bandwidth (BW). A Kaiser hairpin filter is implemented with constant group delay and -0.4 dB insertion loss in passband and 20dB out-of-band rejection. The low noise amplifier (LNA) is designed for 16dB gain, 0.9dB noise figure and -10 dB S11 at 1.3 GHz. Noise power measured by the cascaded filter and LNA is presented for a 50 μ termination.