Harris Corporation

Other

Guy M Pelchat

Robert A Frosch

Robert W Boyd

Robert C Hildebrand

Lock R Young

Raymond F Cobb

Charles A Baird

Luther L Crabtree

George G Rassweiler

Anthony J Gianatasio

Stephen G Powers

A satellite communications scheme for enhancing the communications system with existing satellites is disclosed. The existing satellites include a transponder having a phase locked loop phase demodulator at the front end thereof. The present invention discloses a technique wherein the phase demodulator is locked by transmitting a relatively high-power carrier from the ground to the satellite transponder. Once the demodulator has been locked, remote ground terminals operating at much lower power levels can access the satellite transponder by transmitting at carrier frequencies spaced apart from the primary high-power carrier. These are down-converted by the transponder phase demodulator and then typically amplitude and frequency limited before being remodulated and retransmitted.

Low-power access technique for certain satellite transponders

To enhance the detection of a desired signal in the presence of interference, the degree of modulation of a received input signal is amplified. In the preferred embodiments, this is accomplished by amplifying the degree of amplitude modulation. This works especially well in situations where constant or substantially constant envelope jamming is employed. However, the arrangement is also effective in some cases where the jamming signal has a rapidly fluctuating envelope. The success of the technique in cases of rapidly fluctuating envelopes depends upon the probability distribution of the envelope.

Receiver having a modulation amplifier for enhancing reception of a

A scheme for monitoring the performance of a multiple access satellite communication network, particularly an antijam pseudo-noise spread code division multiple access network, operational in the presence of one or more up-link jammers having arbitrary waveforms, wherein the probability of error (or some directly related quantity) in the output data is considered to be the measure of link quality. Measurements on signal quality received over a selected (strong) link are performed at a prescribed (control) terminal. Such measurements include deriving a statistical mean and variance of decision voltages on a symbol-by-symbol basis. The measured means and variances are processed to account for differences in the link parameters of any desired link and the link used for measurement. The means and variances for the desired link are further processed to give output error probability, accounting for any error correction decoding in use. The desired link may be one of the actual links in the network or another link whose parameters differ from the links of the network.

Performance monitoring of antijam satellite communication network

A broadband adaptively controlled polarization separation network. Two transmitted signals vertically and horizontally polarized are received as elleptically polarized signals. One of the two received elliptically polarized signals is automatically adjusted to make it linear and thereafter automatically adjusted to make it vertical. If the other signal does not have any vertical polarization on it then the two signals are easily separated and nothing else is needed. However, if there is any vertical polarization on the other signal this invention provides for separating the resulting crosstalk between the two signals. This is done automatically by the use of two sets of crosscouplers which couple a single line to the other line to complete the polarization decoupling operation.

Adaptive polarization separation

An automatic polarization decoupling circuit for decoupling first and second signals originally transmitted with orthogonal polarizations comprising a rotatable quarter-wave plate and a rotatable half-wave plate for linearizing the first signal and rotating its polarization direction to a reference polarization direction, an Orthomode (trademark) transducer for separating energy in the reference polarization direction from energy with a polarization in quadrature thereto and utilizing this quadrature energy as the decoupled second signal. The system further comprises a second Orthomode transducer for recombining the in-phase and quadrature energy separated by the first Orthomode transducer and applying this recombined energy to a second rotatable quarter-wave plate and a second rotatable half-wave plate for linearizing the second signal and rotating its polarization direction to a direction in quadrature with the reference polarization direction. A third Orthomode transducer is provided to separate the energy in this quadrature reference polarization direction from the energy polarized in the reference direction. The reference direction energy separated by this third Orthomode transducer comprises the first signal in decoupled form.This system further includes a correlator for generating control signals from the two decoupled output signals to thereby control the alignments of the first and second quarter-wave plates and the first and second half-wave plates. In respective embodiments of the invention, the correlator employs a phase comparison process, one using pilot signals, the other without pilot signals.

Automatic polarization decoupling network

An adaptive interference reduction system for removing cross talk from a dual polarization system comprising a first adjustable filter for varying the phase and the weight of a first input signal, a second adjustable filter for varying the phase and the weight of a second input signal, a first adder for adding this first input signal and the weighted and phase adjusted output from the second adjustable filter, a second adder for adding the second input signal and the weighted and phase adjusted output from the first adjustable filter, a first noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the first adder, a second noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the second adder, and a dither-type control logic for dithering in-phase and quadrature square-waves in accordance with the signals generated by the first and second noise-to-signal measuring devices to control the first and second adjustable filters. This system is further characterized in that the first and second noise-to-signal measuring devices comprise a slow response control circuit for maintaining the average value of the input signal from the adder at a reference value, and means for filtering this averaged value and detecting the power fluctuations remaining in the signal and generating a signal proportional to these fluctuations. Additionally, the first and second adjustable filters may be structured to have transfer functions across a predetermined bandwidth of W.sub.0 [1+W.sub.1 .omega.+W.sub.2 .omega..sup.2 ] or W.sub.0 [1+W.sub.1 .omega.+W.sub.2 .omega..sup.2 +W.sub.3 .omega..sup.3 ], where W.sub.0 , W.sub.1, W.sub.2 and W.sub.3 are signal weights and .omega. represents the frequency variation of the input signal from its carrier.

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Indialantic, FL, United States of America

Guy M Pelchat