Abstract
Functional and thermal performance characteristics of a very high frequency/ultra high frequency (VHF/UHF) transceiver based on Gaussian minimum shift keying (GMSK) modulation are presented. The transceiver has been designed for CubeSats telemetry and commanding needs or low rate data download. The design is validated at 27 dBm, 30 dBm and 33 dBm transmitting powers over −20 $$^\circ \hbox {C}$$ to +51 $$^\circ \hbox {C}$$ . Under these thermal conditions, the transmitter spurious dynamic response shows little if any change and the average sensitivity of receiver at the 12 dB signal noise and distortion (SINAD) is −116.7 dBm at 140 MHz and −116.78 dBm at 149.98 MHz. The transmitter and receiver frequencies are stable and the current consumption as well the output RF levels are steady. The design has been verified against a simulation model which allows system tradeoff analysis. The measurements demonstrate the transceiver made with commercial grade parts has dependable performance at the low earth altitudes and orbital heating conditions.
Highlights
The Very High Frequency/Ultra High Frequency (VHF/UHF) is widely recognized as a model of authority for excellence in performance in space communications
We examine, through functional and temperature measurements, the several performance metrics of a Gaussian Minimum Shift Keying (GMSK) based VHF/UHF communications subsystem that has been successfully flying the ZA-CUBE-1 mission in full duplex mode and its simplex variant will be flying the ZA-CUBE-2
In GMSK modulation, the Non-Return-to-Zero (NRZ) binary pulse is shaped by a pre-modulation, Gaussian, lowpass filter which has an impulse response with no zero-crossings
Summary
The Very High Frequency/Ultra High Frequency (VHF/UHF) is widely recognized as a model of authority for excellence in performance in space communications. The technology rules as the standard communications fundament in the missions flying the CubeSat class of satellites [3] [4]. We examine, through functional and temperature measurements, the several performance metrics of a GMSK based VHF/UHF communications subsystem that has been successfully flying the ZA-CUBE-1 mission in full duplex mode and its simplex variant will be flying the ZA-CUBE-2. VHF/UHF transceiver (Fig. 1) is compatible with the CubeSat nanosatellite standard and CubeSat Kit PC/104 form factor. The frequency of RX/TX operation is software selectable within the band and is adjustable in channel bandwidth steps. A variant of the transceiver operates at the receiver.
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