Abstract: A radio, and related methods of radio communication, consisting of a multi-modulation modem, wherein the multi-modulation modem that modulates and demodulates signals using a plurality of modulations. The radio also comprises a frequency converter coupled to the multi-modulation modem for converting the signals to a radio frequency and a transceiver unit including an antenna coupled to the frequency converter for transmitting the signals over a radio communications link. The multi-modulation modem includes a modulator that includes a modulation selector unit that selects respective ones of the plurality of modulations to modulate the signals. The multi-modulation modem also includes a demodulator for demodulating the signals having been modulated using the plurality of modulations.

Abstract: A method and apparatus to enable high-quality digital transmissions to a satellite terminal operating in proximity to a radar source combines interleaving a sequence of channel symbols at a land station before transmission of an RF signal to a satellite, increasing the satellite's EIRP to compensate for the effects of the radar's duty factor on received signal power and code distance, detecting the radar pulses at a satellite terminal, blanking the received RF signal to prevent reception of the signal by the modem at the satellite terminal during the radar's ON time, having the modem recognize and eliminate the effect of the gap in the channel signals on its metric calculation, and de-interleaving the sequence of channel symbols. As a result, satellite terminals operating in proximity to radar sources can provide the same quality of service as if there were no radars operating.

Abstract: An enhanced nonlinear processor for RFI suppression uses a biased inverting limiter circuit. There are two parallel paths in the device; the first one is used to estimate the intensity of the RFI signal, the second one is used to process the signal. The first signal path employs an envelope detector and filter (to estimate RFI intensity) followed by a comparator circuit to avoid use of the processing if the RFI is too small; the second path has a biased inverting limiter whose characteristic is controlled by the output of the first path. When the estimate of the RFI intensity is close to being correct, the biased inverting limiter traps the large RFI signal, converting it into a higher order harmonic which is filtered out. The wanted signal is not trapped, but instead sees an "effective" positive gain which allows it to pass through unaffected except for a gain factor. The net result is a reduction in the ratio of unwanted signal to wanted signal.

Abstract: An enhanced nonlinear signal processor for RFI suppression using either biased null zone amplifier or a biased inverting limiter. Two or more nonlinear interference processors are connected in cascade. As a result, a deliberate tracking error, selected to provide only a small amount of relative interference rejection, is introduced into each processor. The effect of each stage is cumulative until some limit to performance improvement, determined by the input/output characteristic of each stage, is reached. The benefits of this discovery are increased dynamic range capability (higher levels of interference-to-wanted signal ratio can be fully rejected), simplification of gain control, and increased flexibility in hardware implementation options resulting from reduced sensitivity to RFI tracking error.

Abstract: Improved automatic gain control for an amplifier is obtained by controlling the size of a null zone in a drive signal for the amplifier. The size of the null zone is controlled by estimating strength of an interference signal, and dynamically varying the size of the null zone based on the estimated strength of the interference signal. As a result, the amplifier rarely saturates, regardless of signal strength. The invention is useful to reduce the harmful effects of jamming or interference.