Abstract: A PLL-type frequency synthesizer (10) in which a loop filter (24) state is recorded during an earlier hop to a given frequency then assigned back to the loop filter (24) during a subsequent hop to the same frequency is disclosed. The state is recorded through an A/D converter (48) and assigned through a D/A converter (60). Offset and linearity error is compensated in a compensation circuit (54) so that the state subsequently assigned to the loop filter (24) accurately matches the state that was previously measured for recording. Reference frequency and output signal dividers (16, 40) are both immediately initialized at a hop boundary (82) so that the signals compared by a phase comparator (20) are forced into a phase-matched condition.

Abstract: A flow of data (26) is regulated in a communication system (20). A data rate is established in each of a data source (24) and a data sink (28). The data (26) is transmitted by the data source (24) and written into a buffer (32) at the source data rate, then read from the buffer (32) and received by the data sink (28) at the sink data rate. The level (62) of data (26) in the buffer (32) is monitored, and a rate-control signal (74) is dispatched to either the data source (24) or sink (28) when it is determined the buffer data level (62) is decreasing or increasing while at a lower or upper data-level threshold (66, 68), respectively. One of the data rates is adjusted in response to a rate-control signal (74).

Abstract: A transmitter (400) offsets the transmission time and frequency of a burst transmission such that uncertainties in reception time and reception frequency are reduced. The transmitter includes an ephemeris store (454) that includes ephemeris data for one or more possible intended receivers (130). Orbits of possible intended receivers are propagated, and an intended receiver is selected. Transmission time offsets are generated as a function of transmitter location and intended receiver location. Transmission frequency offsets are substantially equal to a Doppler frequency derived from the transmitter velocity and the intended receiver velocity. Guard times and guard bands are reduced in size, resulting in greater available communications bandwidth and simpler receiver designs.

Abstract: A post-HPA filter rejection equalizer system and method locally equalizes post-HPA filtering. A predistorter (20) uses a phase error to control the predistortion, and an equalizer (46) uses a magnitude error to control the equalization. The equalizer samples the HPA output multiple occurrences in a burst fashion. The equalized signal is then used to determine phase and magnitude errors. The phase errors (54) are used to update the predistorter (20), and the magnitude errors (52) are used to update the analytic equalizer.

Abstract: Software execution control in which a series of two-way rule checks is performed between software-defined communications system component records to ensure and maintain system security and integrity. A system platform (20) performs a series of two-way rule checks between records of a system platform (20) and an application (22) called by the platform (20), between records of the called application (22) and a module (24) that defines the called application (22), and between the records of the module (24) that defines the called application (22) and the platform (20). Both the called application (22) and the module (24) that defines the called application (22) are then instantiated if the two-way rule checks are successful. Because the rule checks are performed in a two-way manner, restrictions such as licensing and source restrictions may be placed not only on system modules (24-30), but also on the applications (22) using the modules (24-30), thereby enabling higher levels of system security to be achieved.

Abstract: A transmitter (400) offsets the transmission time and frequency of a burst transmission such that uncertainties in reception time and reception frequency are reduced. The transmitter includes an ephemeris store (454) that includes ephemeris data for one or more possible intended receivers (130). Orbits of possible intended receivers are propagated, and an intended receiver is selected. Transmission time offsets are generated as a function of transmitter location and intended receiver location. Transmission frequency offsets are substantially equal to a Doppler frequency derived from the transmitter velocity and the intended receiver velocity. Guard times and guard bands are reduced in size, resulting in greater available communications bandwidth and simpler receiver designs.

Abstract: Apparatus and methods are provided for encoding an input frame of a video sequence for transmission over a channel. The method and apparatus decompose the input frame into multiple subbands and divide the multiple subbands into multiple blocks corresponding to a region of the input frame. The blocks in the highest frequency subbands of the multiple blocks are selected based upon a luminance component of the input frame and the multiple blocks in the highest frequency subbands are classified into a multiple classes to provide a multiple class labels. The multiple class labels are collected to form a subband class map for each of the multiple blocks in the highest frequency subbands and a global class map is constructed from a majority evaluation of the subband map for each of the multiple blocks. The multiple blocks within the multiple subbands are grouped which have one of the class labels to form multiple subband class sequences.

Abstract: A voice decoder detects channel errors and loss of cryptographic synchronization using the change in spectral energy between sequential frames. The change in energy between frames is determined between corresponding LSP's of said successive frames and summed together. A running average of the change in energy for a predetermined number of frames is maintained. Current voice frames are eliminated based on the difference between the change in energy associated with the current frame and the running average. Accordingly, offensive audio associated with such channel errors or cryptographic synchronization loss is eliminated.

Abstract: A high speed data transfer system includes a WAU (201) which is utilized to provide high speed data access to satellite transferred data. The system is configured such that a plurality of data utilization devices (205) may access the high speed data via wireless links to the WAU (201). Advantageously, high speed data services may be provided to users without the users requiring individual satellite antennas.

Abstract: A new modulation/demodulation method and apparatus are described for use with RF communication. A transmitter (1001T) modulates information onto a plurality of carrier signals transmitted simultaneously over a corresponding plurality of frequencies using cepstral modulation. A receiver (1003R) receives the plurality of carrier signals and demodulates the signals utilizing cepstral demodulation. Receiver (1003R) monitors the carrier signals and in response to predetermined conditions selects a cepstral constellation to be utilized. Receiver (1003R) provides the cepstral constellation information to a transmitter (1003T) that, in turn, transmits the cepstral constellation information to a receiver (1001R), in turn, provides the cepstral constellation information to transmitter (100T). Transmitter (1001T) utilizes the selected cepstral constellation information to modulate the next transmission of the plurality of carrier signals.

Abstract: A satellite vehicle compensation system (100) predicts the motion of two satellite vehicles and enhances the predictions with real-time updates of one or both of the vehicles. Using feedback loops (132, 134), the differences between the prediction and the actual motions are looped back to improve the accuracy of the motion predictor.

Abstract: A hyperspectral image encoder (10) for compressing hyperspectral imagery includes a differential pulse code modulation (DPCM) loop (26) to perform data decorrelation in the spectral domain and a discrete wavelet transform (DWT) processing means (28) to perform decorrelation in the spatial domain. The DPCM loop (26) determines an error image between a present image at the input of the encoder (10) and a predicted image. The DWT processing means (28) then divides the error image into a plurality of frequency subbands and quantizes information within the subbands in accordance with a plurality of predetermined quantization states to provide a coded output signal. In one embodiment, an interband predictor (24) is provided to predict an image, for use in calculating the error image, using the coded output signal.

Abstract: A method of determining the position of a satellite in a near geosynchronous orbit includes receiving at least one main lobe signal from an antenna on a first GPS satellite. A GPS signal, including GPS time and Doppler, is received from a pseudolite positioned on the Earth and an approximate position of each of a plurality of second GPS satellites is determined from an onboard almanac. Side lobe signals and accompanying noise are received from antennas on the plurality of second GPS satellites. The GPS signal and known sequential data bits are used for sorting or integrating the side lobe signals from the accompanying noise and the position of the satellite in a near geosynchronous orbit is determined using the one or more main lobe signals and the sorted side lobe signals.

Abstract: A system is presented for compression of hyperspectral imagery. Specifically, DPCM is used for spectral decorrelation, while an adaptive 2-D discrete cosine transform (DCT) (22) coding scheme is used for spatial decorrelation. Trellis coded quantization (23) is used to encode the transform coefficients. Side information and rate allocation strategies (36) are discussed.

Abstract: An interworking unit (14) for providing an interface between a digital communication network (12) and a public switched telephone network (PSTN) (16) includes a de-vocoder (30), a protocol termination unit (32), and a signal combiner (34) for processing signals being transferred from the digital network (12) to the PSTN (16). A digital communication signal received by the interworking unit (14) from the digital network (12) is processed by both the de-vocoder (30) and the protocol termination unit (32). The outputs of the de-vocoder (30) and the protocol termination unit (32) are then combined into a uniquely formatted signal that is then delivered into the PSTN (12). Similar functionality is also provided for processing signals in the reverse direction. The interworking unit 14 is capable of processing signals traversing the interface between the networks (12, 16) without a priori knowledge of the signal type being processed.

Abstract: A tracking radar receiver as described herein is relatively invulnerable to image frequency jamming. Partial image-rejection down-converters down-convert RF signals to IF signals in each of various sum and difference receiver channels. Image frequency components of the IF signals exhibit a predetermined amplitude and phase relationship relative to corresponding real frequency components for each of the channels. Thus, phase and amplitude tracking between the various channels is achieved even when image frequency signals are received.

Abstract: A projectile fuze detects transitions between target layers by an electronic antenna radiating laterally into the target material and coupled to a pullable oscillator whose frequency shifts as the target material changes while the projectile penetrates. A frequency shift threshold detector relates the observed frequency shifts to a stored target profile to detonate the projectile after the desired layer penetration.

Abstract: A projectile fuze detects transitions between target layers by an electronic antenna radiating laterally into the target material and coupled to a pullable oscillator whose frequency shifts as the target material changes while the projectile penetrates. A frequency shift threshold detector relates the observed frequency shifts to a stored target profile to detonate the projectile after the desired layer penetration.

Abstract: Key escrow is achieved without a key escrow facility. An escrow key pair is generated and stored in the terminal. A key escrow field that includes a traffic key encrypted with the escrow key is provided before encrypted traffic is communicated. When access to the traffic key is authorized, the escrow key is extracted from the terminal and used to decrypt the traffic key. The private portion of the escrow key is covered in the terminal with an escrow key access number. The escrow key access number is preferably generated by the terminal manufacturer with a secret algorithm using the terminal serial number. Alternatively, the escrow key is stored within a user token, rather than the terminal.

Abstract: An apparatus is disclosed for continuous load optimization of wireless communication networks by making use of statistical data about both the communication medium characteristics and the characteristics of messages that users desire to send over the network. The network comprises a network control base station (20) and a plurality of slave stations (22). One or more applications (72, 104) are associated with each station which are used to generate the messages in digital format. Each application is coupled to a protocol stack (88) that defines the required characteristics of the data and changes to the data that occur during the communication process. An interface (90) is coupled to the layers of each protocol stack (88) to allow tuning of the message characteristics to maximize successful transmission with minimum message latency.