Abstract: A system and method for narrowing the range of frequency uncertainty of a Doppler shifted pilot signal in a satellite or other communications system with relative signal source and receiver motion. The satellite communications system includes a user terminal (for example, a mobile wireless telephone), a gateway (terrestrial base station), and at least one satellite with unknown position and unknown relative velocity. The method includes the steps of shifting the pilot signal over a plurality of frequency hypotheses, coherently accumulating samples of the pilot signal over a plurality of chips, measuring the energy of the accumulated pilot signal samples, accumulating the energy measurements over a plurality of chips to produce an energy accumulation value, and determining which of the plurality of frequency hypotheses results in the highest energy accumulation value.

Abstract: A system and method for narrowing the range of frequency uncertainty of a Doppler shifted pilot signal in a satellite or other communications system with relative signal source and receiver motion. The satellite communications system includes a user terminal (for example, a mobile wireless telephone), a gateway (terrestrial base station), and at least one satellite with unknown position and unknown relative velocity. The method includes the steps of shifting the pilot signal over a plurality of frequency hypotheses, coherently accumulating samples of the pilot signal over a plurality of chips, measuring the energy of the accumulated pilot signal samples, accumulating the energy measurements over a plurality of chips to produce an energy accumulation value, and determining which of the plurality of frequency hypotheses results in the highest energy accumulation value.

Abstract: A transceiver system for interfacing digital modems with radio frequency signals including an antenna, an antenna interface system and a modem interface system separated by a cable. The antenna is placed in a location having optimal reception and in close proximity to the antenna interface system. The cable couples the antenna interface system to the modem interface system. The modem interface system includes a two state variable attenuator and an attenuation register that are configured to either reduce the strength of the receive (Rx) signal when the modems are located near a base station, or to transmit the Rx signal without attenuation when the concentrated subscriber unit is at a more distant location. The outgoing, or transmit (Tx), signal is also attenuated in a similar manner to the incoming signal. A signal loss detection system includes a detector located in the modem interface system that receives an oscillating signal transmitted from the antenna interface system through the coaxial cable.

Abstract: A pulse density modulation circuit has a counter which produces a most significant bit through a least significant bit output based on a clock input. The circuit also has a comparator with two sets of most significant bit through least significant bit inputs that produces an output based on a comparison of the two sets of inputs. The first set of comparator most significant bit through least significant bit inputs receives respectively a most significant bit through a least significant bit of an input reference signal. The second set of comparator most significant bit through least significant bit inputs receives the counter most significant bit through least significant bit output in a non-sequential bit order. The non-sequential bit order can be a bit reversed order wherein the counter most significant bit through least significant bit output are respectively connected to the comparator least significant bit through most significant bit input.