A DSP-based microwave landing system (MLS) post-IF processor

The authors describe the digital signal processor (DSP)-based implementation of the microwave landing system's (MLS's) post-IF processing functions. An MLS overview, the DSP-based post-IF processing module and MLS post-IF processing algorithms are discussed. All MLS post-IF processing functions, including carrier acquisition, differential phase shift keying (DPSK) demodulation and synchronization, data decoding and scanning beam processing are implemented in a single DSP, Analog Devices' ADSP2100A. An input signal sampling rate of 25 Ks/sec is accommodated by using decimating filters, a modified fast Fourier transform algorithm, and by setting up a direct memory access between the analog-to-digital (A/D) converter and memory.<
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