Author(s): B. E. Bjerde
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 23, Number 2
Pages: 119 - 127
Cite this article: Bjerde, B. E., "A UNIFIED SIGNAL PROCESSOR FOR TACAN NAVIGATION SETS", NAVIGATION, Journal of The Institute of Navigation, Vol. 23, No. 2, Summer 1976, pp. 119-127.
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Abstract: The Unified Signal Processor (USP) performs the functions of dedicated analog and digital hardware using a timeshared microprocessor which is controlled by a program stored in a read only memory (ROM). The basic advantages are high reliability, low cost and parts count, high flexibility, freedom from drift and adjustments, unlimited precision in signal processing and the USP lends itself ideally to micro-electronic implementation. It has been incorporated in the AN/ARN-119 TACAN navigation set, resulting in improved performance and a two-fold improvement in parts count and reliability as compared to conventional TACAN signal processors. The integrated system has success- fully completed flight, qualification and reliability tests. All functions have been verified and the performance equals or exceeds that of conventional microelectronic TACAN sets. The USP extracts and displays range and bearing, performs automatic gain control and self test, and switches antennas. It operates off the TACAN video signal and simultaneously, generates serial digital output signals and analog output signals compatible with synchro indicators. Algorithms for range and bearing acquisition, discrete phase-locked loops, digital filters, automatic gain control, synchro to digital conversion, and data formatting were developed and verified through computer simulations. The microprocessor was designed around the INTEL 8008-l central processing unit chip. The control program consists of 6000 8-bit instructions, which are stored in 3 read only memories. A common 8-bit tri-state data bus is used to communicate between the central processing unit, the memory and the interfaces. Interfaces necessary to convert between analog signals and digital signals compatible with the data bus form an integral part of the signal processing functions. Portions of these circuits are based on similar circuits used in conventional TACAN sets. Other circuits such as the digital-to-synchro converter, the synchro-to-digital converter, the range and bearing counters, the ID-tone detector, the pulse pair detector, the north burst detector, the encoder and the data rate limiter are new designs.