Gardner, Projects

GARDNER RESEARCH COMPANY

Synchronization in a satellite communications system: frequency, phase, and timing acquisition; precision of tracking; cycle slips; block vs. feedback algorithms; Cramer-Rao bounds; phase noise; analog vs. digital implementation; interference; delay requirements; simulation models; frequency drift; frequency hopping.

Wireless data transmission system: modulation tradeoffs; polyphase synchronization codes; simulations; frequency measurement; frequency tolerances; timing recovery; interpolation.

Data transmission on TV cable and fiber (HFC): downstream and upstream characteristics; ingress interference from HF and impulses; modulation methods (TDMA, FDMA, DMT, CDMA); QAM vs. VSB; differential vs. coherent demodulation; frequency correction; frequency accuracy; access schemes; pulse shaping; frequency plans; demultiplexers; unique-word detection; receiver configurations; filter characteristics; timing recovery; interpolation; differential encoding; carrier recovery; ambiguity resolution; channel capacity; efficient digital implementations of transmitter and receiver; filter banks; multiplicative disturbances; dissemination of frequency reference; pilot tones; SSB transmission of multicarrier.

Autotuner for transmitter filter bank: phase-shift basis; reflection basis; phaselocked error detectors; homodyne (direct conversion) implementation; filter plan; intermodulation between transmitters; system equations; interference; I-Q imbalance; DC offsets; signal levels; automatic level control; signal bursts.

Digital demodulator for spread-spectrum data signal: quantization; sampling rates; chip timing; penalty due to timing irregularity; signal acquisition; filters; I-Q conversion; code correlators; frequency rotator; symbol timing recovery; word sizes; AGC; images; phase noise; timing-jitter loss; delay-lock loops.

Synchronization for demodulator of satellite data signal: filter issues; jumps in oscillator frequency; frequency quantization; sampling plan; signal acquisition; frequency search and estimation; Cramer-Rao bound; clock and carrier lock; s-curves.

Tracking system for missile range safety: signal design; processing; acquisition; accuracy; flame effects; coherent Doppler; diversity reception; PRN-code ranging; phase jitter; tape recording of signals.

Data recording on tape cassettes: signal formats; equalization; timing recovery; circuit designs.

Fiber optic telemetry system: noise sources; modulation options; modulation choice; FM modulator/demodulator.

FM/FDM transmission of TV signals: signal formats; demodulator elements; frequency plans; baseband operations; VSB remodulation; CNR; spectral occupancy; nonlinearities.

Frequency quantization in NCOs: phase jitter arising from frequency granularity.

Pulselet processing of data signals: decompose signal pulses into pulselets; simplified matched filters; processing methods; pitfalls.

Frequency detectors for digital demodulators: signal formats; maximum-likelihood approach; algorithms; s-curves; self noise; pitfalls; periodic data; search strategies.

Timing adjustment via interpolation: nonsynchronized sampling; sampling incommensurate with symbol rate; filter model of interpolator; interpolator control; requirements on interpolator; polynomial-based interpolation; interpolator structures; digital algorithms.

Digital implementation of synchronizers: categories of synchronizers; modem configurations; maximum-likelihood formulation; phase rotators; NCOs; timing correction; frequency error detection; carrier phase detection; timing detection; digital algorithms.

Satellite on-board processing for mobile communications: receiver architecture; FDMA demultiplexing; computationally efficient filter banks; digital demodulators.

Satellite-mobile communications link: multipath propagation; antennas; Doppler shift; diversity; ionspheric scintillation; receiver configurations; carrier tracking; phase noise; vehicle dynamics; modulation methods; digital algorithms.

Bandwidth-efficient aerospace telemetry: existing FM/PCM telemetry; MPSK alternative; modulation candidates; demodulation options; performance comparisons; differential encoding; differential detection; signal dynamics; clock recovery; QPSK demodulator; frequency/sampling plan; filters; digital algorithms.

Fast acquisition of TDMA carrier and clock: hangup in PLLs; feedback vs. feedforward synchronizers; transient response of filters; attainable speeds.

Self noise in synchronizers: origins of self noise; pulse shaping to suppress timing self noise; practical shaping filters.

HF communications system: propagation predictions; station siting; modulation tradeoffs; robust signals; test evaluations.

FM threshold of phaselocked discriminators: experimental study to measure click and threshold behavior; design guidelines.

Broadband indoor wireless: link budgets; supportable data rates; spectrum spreading; multipath characterization; broadband self interference; RAKE receiver; code acquisition; pilot aiding.

Pulse-Doppler radar, various studies: models of elements; pulse filtering; sampling/range gating; mistiming penalties; noise loading of A/D converter; I-Q imbalance; phase noise; signal processing; signal and noise relations; target detection; pulse statistics; IF vs. I-Q sampling; filter mismatch losses; I-Q rebalancing; sampling of chirp pulses; estimation of noise statistics; application of dither; sampling at a nonuniform rate; sampling jitter; beacon returns; Bessel vs. Butterworth filters; Hilbert transforms; digital algorithms.

Jitter accumulation in repeater chain: token-ring model; signal format; influence of repeater delay; jitter transfer function; measurement fixtures; interpretation of simulation and test results; jitter-reduction methods; delay in PLL; time-domain model of jitter accumulation.

Simulation program for communications links: math models; processing algorithms; communications operations; program architecture.

Dec. 2001