Design and Implementation of a 1420 MHz Microstrip Bandpass FIlter for use in Radio Astronomy

The 1420 MHz radio frequency band is an important band in radio astronomy. This band contains the 21 cm wavelength radiation emitted from the spin flip of electrons in cold Hydrogen clouds in the Milky Way. The observation of this radiation has helped astronomers map the structure of the Milky Way. We have designed a low loss, low cost, microstrip structure band pass filter (BPF) for this frequency range to apply in Hydrogen line radio astronomy. Performance efficiency, bandwidth and material cost make it an excellent choice for the application of amateur software defined radio telescope. We have designed and simulated the device using Sonnet Lite EM simulator. The physical device is constructed using FR-4 dielectric based printed circuit board and conducting copper tape. The scattering parameter (S21) of the physical circuit is tested using a vector network analyzer to determine its efficiency which shows a low loss near the Hydrogen line spectrum with a peak in the power output at the target frequency.