Abstract: A receiver signal is sampled at a sampling rate equivalent to a chip rate at which chips of a known signal are timed. The resulting receiver signal samples are segmented into receiver signal segments, which are filtered by respective matched filters that are matched to known signal segments segmented from the known signal. Indexes are assigned to elements of the resulting filter response sequences to define an array thereof. Frequency transforms are computed of elements of the filter response sequences in respective columns of the array. Indexes are assigned to elements of the resulting frequency response sequences to define another array thereof. Channel effects imparted on a radio signal are jointly estimated from characteristics of the other array at which at least one local maximum is located.

Abstract: A receiver signal is sampled at a sampling rate equivalent to a chip rate at which chips of a known signal are timed. The resulting receiver signal samples are segmented into receiver signal segments, which are filtered by respective matched filters that are matched to known signal segments segmented from the known signal. Indexes are assigned to elements of the resulting filter response sequences to define an array thereof. Frequency transforms are computed of elements of the filter response sequences in respective columns of the array. Indexes are assigned to elements of the resulting frequency response sequences to define another array thereof. Channel effects imparted on a radio signal are jointly estimated from characteristics of the other array at which at least one local maximum is located.

Abstract: A satellite communication system for airborne and reachback communications may include a formation orbiting in one or more slots of a geosynchronous orbit. The formation may include two or more communications satellites (COMSATs) encircling a ring. Each COMSAT of the two or more COMSATs may include a communication module configured to communicate with a plurality of communications assets in a benign or contested environment. The formation may be configured to allow a first communications asset having a dish antenna with a first configuration to communicate independently with each of the two or more COMSATs in a first scenario. The formation may also be configured to allow a second communications asset having a dish antenna with a second configuration to communicate simultaneously with the two or more COMSATs in a second scenario.

Abstract: An electrically small antenna includes a first plurality of helical arms extending in one direction from a central portion of the antenna and a second plurality of helical arms extending from the central portion in a direction opposite from the direction of the first plurality of helical arms. A plurality of switches are coupled to control signal transmission and reception on the helical arms, each of the plurality of switches is coupled between a corresponding one of the first plurality of helical arms and the second plurality of helical arms.