The Aerospace Corporation

Other

Jack K Holmes

Srinivasa H Raghavan

Tien M Nguyen

Kenneth A Tarlow

Paul A Berman

Gee L Lui

Kris P Maine

Allan Douglas

Chit-Sang Tsang

Kristine P Maine

Srini H Raghavan

A code division multiple access (CDMA) communication system using spread spectrum signaling over a communication bandwidth uses two different signal spectra generated using two different respective spreading code formats, such as NRZ code formatting and staggered Manchester code formatting, for respectively providing nonsplit spectra having a center peak and split spectra having a center null. The spectra are combined during transmission as a CDMA communication signal having a composite spectrum. The use of different code formats produces the composite spectrum of respective center peak and center null spectra that enables increased channel capacity.

Code division multiple access enhanced capacity system

A code division multiple access (CDMA) communication system using spread spectrum signaling over a communication bandwidth uses two different signal spectra generated using two different respective spreading code formats, such as NRZ code formatting and Manchester code formatting, for respectively providing nonsplit spectra having a center peak and split spectra having a center null. The spectra are combined during transmission as a CDMA communication signal having a composite spectrum. The use of different code formats produces the composite spectrum of respective center peak and center null spectra that enables increased channel capacity.

A command and telemetry communication system includes a downlink subsystem having a spacecraft downlink transmitter communicating a quadrature component carrying a pilot code for coarse acquisition and an inphase component carrying a Walsh-Hadamard code and a PN code for fine acquisition using spread spectrum signaling and amplitude modulation for code division multiplexing to downlink receivers respectively disposed in a plurality of mobile surface landers, and includes an uplink subsystem having a spacecraft uplink receiver and lander uplink transmitters communicating code division multiple access telemetry data using spread spectrum signaling and phase modulation. The communication system enables command and telemetry control of a plurality of mobile surface landers.

Mobile surface terminal communication system

Unambiguous carrier phase estimation for frequency hop signals of a frequency hopping Gaussian minimum shift keying (GMSK) communication system using coherent demodulation is enabled by channel zeroing bits and channel guard bits positioned between each pair a preceding data portion and a succeeding synch word, functioning as cumulative data phase zero forcing bits that force the accumulative data phase to zero at the end of the synch word for determining the carrier phase for subsequent data demodulation so that each synch word may be arbitrarily placed within a hop of the hopping signal having an unknown carrier phase for improved interference immunity.

Method of determining the carrier reference phase of coherent demodulation of frequency hopped continuous phase modulated signals with synch words arbitrarily located within the hop

A GMSK timing recovery loop in a receiver of a Gaussian Minimum Shift Keying (GMSK) link with a low channel Bit Signal-to-Noise Ratio (BSNR) and a small bandwidth-bit period BT product in a high bandwidth efficiency channel, includes a hard limiter for converting at baseband a GMSK demodulated received signal into a hard clocking signal clocking a conventional digital tracking transition loop generating the bit timing signal in closed loop control for stable time tracking performance for coherent demodulation of GMSK signals. The hard limiter provides the hard clocking signal at baseband having transitions at multiple bit periods adjusted by the bit timing error signal from the digital tracking transition loop for providing reduced jitter of the bit timing signal for accurate timing recovery and detection of communicated data.

Digital timing recovery loop for GMSK demodulators

An NRZ and biphase-L formatted, quadriphase modulated GPS signal transmission communication method provides for the simultaneous modulation of two CDMA spread spectrum codes such as the GPS C/A code and either the P(Y) code, or an arbitrary NEW code modulating a single carrier for GPS use in one or both L1 and L2 bands. The use of NRZ formatting and biphase-L formatting provides spectral separation even though both spread spectrum signals are modulated onto the same carrier.

NRZ and biphase-L formatted quadriphase modulated GPS transmission method

An NRZ and biphase-L formatted, three code hexaphase modulated GPS signal transmission communication method provides for the simultaneous modulation of the C/A code, the P(Y) code and a NEW code all modulating a single carrier for GPS use in one or both L1 and L2 bands. The use of the C/A code and the P(Y) code which are NRZ formatted with a NEW code biphase-L formatted and using hexaphase modulation on the three signals provides for spectral separation between the C/A code signal and the NEW code signal, all three modulated on a single carrier frequency.

NRZ and biphase-L formatted hexaphase modulated GPS transmission method

An exercise cycle is propelled by a stair-stepping action of the driver's legs, with the feet placed on a pair of front-hinged footboards located along opposite sides of the vehicle. A novel cable and chain drive system delivers driving torque to the rear wheel assembly to propel the vehicle forward in response to the driver's weight being applied via the legs and feet to depress the footboards alternately: the driving mechanism is located in a lower forward portion of the cycle so as to keep the mechanism below the rear wheel height and thus provide a low profile.

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Agoura Hills, CA, United States of America

Jack K Holmes