Comtech SEU-100 Signal Excision Unit

Overview

Our SEU-100 Signal Excision Unit significantly enhances the performance of geolocation systems, improving location accuracy and enabling emitters to be successfully located in many situations where geolocation without signal excision is not possible. The SEU-100 is a signal suppression device that suppresses a strong signal from the satellite receive spectrum to enable the background signal(s) to have a higher effective signal-to-noise ratio (SNR). The strong signal can be any signal present on the satellite operating at conventional signal to noise levels such that commercial modems can be configured to demodulate the signal. Figure 1 below shows the data processing flow. The SEU-100 has two input channels and two output channels. Input Channel 1 contains a composite of the strong signal to be excised (S E ) and a copy of the signal to be located (SL ). Input Channel 2 contains the primary copy of SL .Conceptually the terminal to be geolocated is transmitting the signal S L to a primary satellite, and this received signal is input to the SEU on Channel 2. Due to antenna sidelobes, an attenuated copy of SL is also received by a secondary satellite. The secondary satellite has the signal S E occupying (or partially occupying) this frequency channel. The composite of S E and the attenuated copy of SL are input to the SEU on Channel 1.

Channel 1 Processing:

Signal S E is suppressed in Channel 1 by demodulating and making hard decisions on the input composite waveform, then remodulating these decisions to generate the “reference” signal for a carrier cancellation algorithm.

Channel 2 Processing:

Signal S L is delayed and frequency shifted such that the frequency and time offset between the input Channel 1 and Channel 2 signals are minimized. Any operation that affects frequency/phase/time delay on Channel 1 is matched by the same/similar operation on Channel 2 in order to maintain coherence between the two channels.