Abstract: A communications system and methods for covert communications are provided. A first transmitter that transmits an information carrying signal to a target receiver, a second transmitter and a third transmitter transmit jamming signals to the target receiver, such that the information carrying signals and the jamming signals are interleaved when received by the target receiver The information carrying signals and the jamming signals can be at least partially overlapping by an eavesdropper.

Abstract: A communications system and methods for covert communications are provided. A first transmitter that transmits an information carrying signal to a target receiver, a second transmitter and a third transmitter transmit jamming signals to the target receiver, such that the information carrying signals and the jamming signals are interleaved when received by the target receiver The information carrying signals and the jamming signals can be at least partially overlapping by an eavesdropper.

Abstract: A communications system and methods for covert communications are provided. A first transmitter that transmits an information carrying signal to a target receiver, a second transmitter and a third transmitter transmit jamming signals to the target receiver, such that the information carrying signals and the jamming signals are interleaved when received by the target receiver The information carrying signals and the jamming signals can be at least partially overlapping by an eavesdropper.

Abstract: A communications system and methods for covert communications are provided. A first transmitter that transmits an information carrying signal to a target receiver, a second transmitter and a third transmitter transmit jamming signals to the target receiver, such that the information carrying signals and the jamming signals are interleaved when received by the target receiver The information carrying signals and the jamming signals can be at least partially overlapping by an eavesdropper.

Abstract: A position location system includes multiple base stations spaced over a region. A remote unit within the region transmits a locating signal which is received by the base stations. The base stations report amplitude, phase and time data related to the locating signal to a control station. The control station includes a processor and memory that combine the data from all of the participating base stations to directly compute an optimal estimate of the location of the portable unit. The control station generates a locator function based upon the probability that the portable unit is located at a particular position. By optimizing the locator function, the error in the computation is minimized to produce an accurate position estimate.

Abstract: A position location system includes multiple base stations spaced over a region. A portable unit within the region transmits a locating signal which is received by the base stations. The base stations report amplitude, phase and time data related to the locating signal to a control station. The control station includes a processor and memory that combine the data from all of the participating base stations to directly compute an optimal estimate of the location of the portable unit. The control station generates an ambiguity function based upon the probability that the portable unit is located at a particular position. By optimizing the ambiguity function, the error in the computation is minimized to produce an accurate position estimate.

Abstract: A meteor scatter communications system for communicating between a master station and one or more remote stations. In one exemplary embodiment, a broad beam transmitter probe signal is reflected from a meteor ionization trail to a remote station which then transmits a return data signal to the master station. The master station receiver has a plurality of antennas and a receiver beam forming network which forms a plurality of narrow beam receive signals, one of which has a high gain and corresponds to the narrow beam signal which illuminates the meteor trail and contains the reflected return data signal from the remote station. The master station processor selects such one narrow beam signal for processing the data therein.

Abstract: Sidelobe jamming in dual diversity troposcatter link receivers is effectively suppressed by providing an auxilliary low power antenna, the output of which is differenced from the high power main antenna signals prior to processing in the receivers's dual diversity demodulator. The auxilliary antenna power is substantially equal to the sidelobe power of the main antennas. The auxilliary antenna receives jamming power that is comparable to the jamming power received by the main antennas. However, it receives much lower desired signal power. Differencing of the signals therefore, cancels jamming power with minimal effect on the desired signals.

Abstract: A channel propagation simulator simulates a multi-diversity branch signal channel, which simulator uses in a preferred embodiment appropriate filter means, such as a plurality of tapped delay lines 11, 14, each capable of representing the impulse response of a diversity branch by means of correlated tap multipliers 12, 12A, 15, 15A . . . 15N, i.e., multipliers using correlated weighting signals 12', 12'A, 15', 15'A . . . 15'N as supplied from a matrix weighting correlator 19. The correlated weighted signals are combined for each diversity branch by suitable summation circuits 13, 16 to provide the diversity branch simulated outputs. By using correlated weighting signals, the simulator can more accurately reproduces the statistical behavior of a given communications link and verify that a given modem will satisfy the communication link specifications.

Abstract: An adaptive power equalizer circuit for use in a spread spectrum receiver system which includes an antenna system 12, 13 and a receiver 11, the circuit comprising adaptive power inversion circuitry 15 for producing a first signal having a minimized power level and a second signal having a substantially higher power level than that of the first signal. Such signals are supplied to a power equalizer circuitry 16 which equalizes the power levels thereof, such equalized power level signals then being combined in a suitable combiner circuit 30 for producing an output receiver output signal for the receiver 11.

Abstract: An apparatus for simulating the characteristics of a signal channel which uses two or more cascaded delay lines each of which in one embodiment has a single input and a plurality of tapped outputs. The tapped output signals from each delay line are each multiplied by randomly characterized signals and the multiplied signals are combined to supply an input signal to the next succeeding delay line. The input signal to the first of the cascaded delay lines is the channel input signal and the output of the last of the cascaded delay lines is the simulated channel output signal. The randomly characterized signals associated with all but one of the delay lines may be signals having random polarities or having random phases while the randomly characterized signals associated with the remaining one of the delay lines has Gaussian characteristics.