A single-chip narrowband frequency domain excisor for a Global Positioning System (GPS) receiver

In recent years we have witnessed the rapid adoption of the DoD's Global Positioning System (GPS) for navigation in a number of military and civilian applications. Unfortunately the low-power GPS signal is susceptible to interference. This paper presents a novel VLSI architecture that removes narrowband signals from the wide bandwidth CPS spectrum. The interference suppression technique employed is frequency domain excision. The single-chip frequency domain excisor transforms the received signal (GPS signal + noise + interference) to the frequency domain, computes signal statistics to determine an excision threshold, removes all spectral energy exceeding that threshold, and restores the remaining signal (GPS signal + noise) to the temporal domain; The heart of this VLSI implementation is an on-chip 256-point FFT processor that operates at 40 million complex samples per second (MCSPS). It processes 12-bit (for each I and Q) sampled complex data. The 1.5 million-transistor chip was fabricated in 0.5 mu CMOS triple metal technology and is fully functional.