Abstract: An apparatus and method for transmitting and receiving a communication signal includes selecting a pulse shape for a continuous phase modulated waveform, encoding specific information into the waveform to form a communication signal and transmitting the communication signal. The system receives the transmitted communication signal and samples the received signal at a specified rate, the sample rate being less than the symbol rate, enabling reconstructing the waveform and extracting encoded information at sub sample per symbol rates, thereby reducing the reliance on high speed wideband analog to digital converters (ADC) for high speed applications.

Abstract: Blind source separation (BSS) of statistically independent signals with low signal-to-noise plus interference ratios under a narrowband assumption utilizes cumulants in conjunction with spectral estimation of the signal subspace to perform the blind separation. The BSS technique utilizes a higher-order statistical method, specifically fourth-order cumulants, with the generalized eigen analysis of a matrix-pencil to blindly separate a linear mixture of unknown, statistically independent, stationary narrowband signals at a low signal-to-noise plus interference ratio having the capability to separate signals in spatially and/or temporally correlated Gaussian noise. This BSS provides the ability to blindly separate signals in situations where no second-order technique has been found to perform the blind separation satisfactorily, for example, at a low signal-to-noise ratio when the number of sources equals the number of sensors or when the noise is spatially and temporally colored.

Abstract: Blind source separation (BSS) of statistically independent signals with low signal-to-noise plus interference ratios under a narrowband assumption utilizes cumulants in conjunction with spectral estimation of the signal subspace to perform the blind separation. The BSS technique utilizes a higher-order statistical method, specifically fourth-order cumulants, with the generalized eigen analysis of a matrix-pencil to blindly separate a linear mixture of unknown, statistically independent, stationary narrowband signals at a low signal-to-noise plus interference ratio having the capability to separate signals in spatially and/or temporally correlated Gaussian noise. This BSS provides the ability to blindly separate signals in situations where no second-order technique has been found to perform the blind separation satisfactorily, for example, at a low signal-to-noise ratio when the number of sources equals the number of sensors or when the noise is spatially and temporally colored.

Abstract: An output port centric digital data management architecture for a high speed packet switch employs a dual key-based content addressable memory (CAM)-based buffer access control mechanism for efficient storage and read out of relatively long data packets to one or more output ports of the switch. The CAM stores respectively different address pointer words, each containing a respectively different key field to identify a data packet to be delivered to a switch output port, and an address field that identifies the address of one of the storage locations of the packet buffer in which the data packet is stored. During a first portion of a dual key CAM search, a packet request key is coupled to the key fields of all address pointer words stored in the CAM. The location of the matching key is used to access the key field's companion address field in its address pointer word during a second portion of the dual search of the CAM.

Abstract: A signal to noise ratio estimator and method for a received signal which includes a communication component and a noise component is disclosed. One embodiment is an in-service, blind, decision-directed estimator for a CPFSK communication signal. A preferred embodiment determines the power of a communication signal component by combining the received signal with a signal that is a delayed complex conjugate of the received signal and then removing the real component of the combined signal.

Abstract: A method and system of communicating in free space comprises a first communication terminal having a multiplexer circuit for multiplexing a plurality of analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier signal, and an electro-optic modulator produces a phase modulated optical communications signal. A pointing and tracking beacon is also generated and transmitted with the optical communications signal to a receiver unit positioned at a second communications terminal, such as a second satellite. The receiver unit receives the phase modulated optical communications signal and pointing and tracking beacon and includes a cascaded Bragg cell and liquid crystal. A communications detector detects the optical communications signal and a pointing and tracking detector detects the pointing and tracking beacon.

Abstract: A method and system of communicating in free space using an optical communication system, such as for intersatellite and satellite-to-ground communications, is disclosed. Digital communication signals are multiplexed with a plurality of other analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier and an electro-optic modulator modulates the optical carrier signal with the frequency division multiplexed signal to produce a phase modulated optical communications signal. A receiver is positioned, such as in a satellite, to receive the phase modulated optical communications signal. The receiver includes a demodulator for demodulating the phase modulated optical communication system back into the broad band frequency division multiplexed signal and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of communication signals.

Abstract: A method and system of communicating in free space using an optical communication system, such as for intersatellite and satellite-to-ground communications, is disclosed. Digital communication signals are multiplexed with a plurality of other analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier and an electro-optic modulator modulates the optical carrier signal with the frequency division multiplexed signal to produce a phase modulated optical communications signal. A receiver is positioned, such as in a satellite, to receive the phase modulated optical communications signal. The receiver includes a demodulator for demodulating the phase modulated optical communication system back into the broad band frequency division multiplexed signal and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of communication signals.

Abstract: A method and apparatus for a free space optical non-processing satellite transponder includes the step of receiving a phase modulated optical communication signal in a satellite. This phase modulated optical communication signal has been formed by phase modulating an optical carrier signal with a broad band frequency division multiplexed communication signal. The signal is passed through an optical heterodyne receiver to produce a broad band frequency division multiplexed communication signal. Part of the signal is split off for on-board satellite processing. The balance of the signal is combined within a power combiner with a radio frequency signal from an on-board source of the satellite to form a combined broad band frequency division multiplexed communication signal.

Abstract: The need to employ three separate cycles for write, read and compare operations for operation of a content addressable memory cell is obviated by a memory cell architecture that allows simultaneous read and compare operations, thereby reducing memory cycle time by one-third of that of a conventional CAM. To enable the data bit stored in the memory cell to be compared with a reference bit, the memory cell is coupled with a comparator, that receives inputs from the data nodes of the memory cell and a set of comparison bit input lines. Rather than supplying reference data by way of the data lines through which data is written into and read from the memory cell, as in a conventional CAM, the compare bit and its complement are coupled to the match logic exclusively of the memory cell. Since application of the comparison bit does not involve the use of the normal data read and write lines, accessing data read and write paths for the memory cell is not required.

Abstract: A method and system of communicating in free space using an optical communication system, such as for intersatellite and satellite-to-ground communications, is disclosed. Digital communication signals are multiplexed with a plurality of other analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier and an electro-optic modulator modulates the optical carrier signal with the frequency division multiplexed signal to produce a phase modulated optical communications signal. A receiver is positioned, such as in a satellite, to receive the phase modulated optical communications signal. The receiver includes a demodulator for demodulating the phase modulated optical communication system back into the broad band frequency division multiplexed signal and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of communication signals.