Path Emulator for RF Systems

Gregory W. Heckler, Rishi Kurichh, J. Boegner

Abstract:	NASA Goddard Space Flight Center (GSFC) has created the Path Emulator for Radio Frequency Systems (PERFS) for hardware-in-the-loop testing of RF communication systems. PERFS simulates the effects of relative range, velocity, and acceleration between spacecrafts’ communications systems. PERFS takes in a radio frequency (RF) signal and down mixes it to an intermediate frequency (IF) signal. The IF signal is sampled by an analog-to-digital converter (A/D) and fed into a circular IF sample buffer. Samples are read from the buffer by a digital-to-analog converter (D/A), filtered, attenuated, and mixed back to the original RF frequency. Writing to and reading from the circular buffer is driven by two individual direct digital synthesizers (DDS). A DDS generates a low jitter clock that can be precisely adjusted in frequency and phase. Relative range, range rate, and range acceleration are simulated by controlling the delay, frequency offset, and frequency rate of the D/A DDS relative to the fixed frequency of the A/D DDS. Path loss is simulated by digital step attenuation (DSA) in the output RF section. PERFS is designed to simulate relative ranges between 250 m and 3500 km with a resolution of 5 cm. A range velocity requirement of ±730 m/s is supported with a resolution of 1 mm/s. Testing of PERFS is performed by synchronously recording a source signal at both the input and output of PERFS. Various analyses allow the performance of PERFS to be quantified, and compared to the requirements laid out above.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	231 - 239
Cite this article:	Heckler, Gregory W., Kurichh, Rishi, Boegner, J., "Path Emulator for RF Systems," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 231-239.
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