Miniaturised Portable Dual-Channel Receiver for Radio Astronomical Observations

Abstract

For carrying out sky observation at multiple / remote sites without having to spend significant amount of time in setting up the experiment, it is essential that the radio receiver be portable and compact in size. It features an improvement in the performance and reliability due to i) the use of miniaturized electrical components in the circuit which have good performance characteristics over a wide range of frequencies and ii) significant reduction in the number of connectors required for establishing electrical connectivity in the RF circuit. This report describes a compact portable dual channel receiver built to have these features and operate in the nominal frequency range of 100 – 1000 MHz. It has an instantaneous bandwidth of 14 MHz selectable anywhere in the whole range of above the frequency band. The analog receiver is superheterodyne in nature, converting the RF input signal to an IF centred around 140 MHz using an appropriate local oscillator. The receiver has a noise temperature of approximately 430 K over the entire receiver band and a gain of 65 dB. It has an input 1 dB compression point at an input level of -60 dBm and third-order intercept point at the input level of -55 dBm. The digital back-end receiver Nyquist samples the IF band, employing 8- bit digitization for the pair of channels and records directly the raw voltage time-sequences corresponding to 16 MHz bandwidth. The dual channel capability allows full polarisation measurement when the inputs are from a dual-polarisation antenna, as well as interferometric measurements with a pair of antennas, usually with same polarisation.