Phase lock loop acquisition of an angle modulated carrier
Angle modulated carrier acquisition and demodulation, developing baseband model for behavior of output signal from phase lock loop
Carden, F. F.↗
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Methods and apparatuses using filter banks for multi-carrier spread-spectrum signals
A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.
47 OTHER INSTRUMENTATION↗
Methods and apparatuses using filter banks for multi-carrier spread-spectrum signals
A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.
47 OTHER INSTRUMENTATION↗
Methods and apparatuses using filter banks for multi-carrier spread spectrum signals
A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.
42 ENGINEERING↗
Methods and apparatuses using filter banks for multi-carrier spread spectrum signals
A transmitter includes a synthesis filter bank to spread a data symbol to a plurality of frequencies by encoding the data symbol on each frequency, apply a common pulse-shaping filter, and apply gains to the frequencies such that a power level of each frequency is less than a noise level of other communication signals within the spectrum. Each frequency is modulated onto a different evenly spaced subcarrier. A demodulator in a receiver converts a radio frequency input to a spread-spectrum signal in a baseband. A matched filter filters the spread-spectrum signal with a common filter having characteristics matched to the synthesis filter bank in the transmitter by filtering each frequency to generate a sequence of narrow pulses. A carrier recovery unit generates control signals responsive to the sequence of narrow pulses suitable for generating a phase-locked loop between the demodulator, the matched filter, and the carrier recovery unit.
42 ENGINEERING↗
Improved phase locked loop receiver
Improved phase locked loop receiver tracks and demodulates a signal whose signal-to-noise ratio may be low and whose information sidebands are close in frequency. This receiver recovers the carrier from input signals and applies it to a demodulator which recovers the sidebands.
Daley, T. J.↗
Optimal space communications techniques
The design, development, and analysis are reported of a digital phase-locked loop (DPLL) for FM demodulation and threshold extension. One of the features of the developed DPLL is its synchronous, real time operation. The sampling frequency is constant and all the required arithmetic and logic operations are performed within one sampling period, generating an output sequence which is converted to analog form and filtered. An equation relating the sampling frequency to the carrier frequency must be satisfied to guarantee proper DPLL operation. The synchronous operation enables a time-shared operation of one DPLL to demodulate several FM signals simultaneously. In order to obtain information about the DPLL performance at low input signal-to-noise ratios, a model of an input noise spike was introduced, and the DPLL equation was solved using a digital computer. The spike model was successful in finding a second order DPLL which yielded a five db threshold extension beyond that of a first order DPLL.
Schilling, D. L.↗
Developments in fiber optics for distribution automation
An optical fiber based communications system of unusual design is described. The system consists of a network of optical fibers overlaid on the distribution system. It is configured as a large number of interconnected rings, with some spurs. Protocols for access to and control of the network are described. Because of the way they function, the protocols are collectively called AbNET, in commemoration of the microbiologists' abbreviation Ab for antibody. Optical data links that could be optically powered are described. There are two versions, each of which has a good frequency response and minimal filtering requirements. In one, a conventional FM pulse train is used at the transmitter, and a novel form of phase-locked loop is used as demodulator. In the other, the FM transmitter is replaced with a pulse generator arranged so that the period between pulses represents the modulating signal. Transmitter and receiver designs, including temperature compensation methods, are presented. Experimental results are given.
Kirkham, H.↗
Digital Demodulator For Advanced Receiver
Complexity and cost reduced by new design for half-band filters. Digital demodulator designed for use in reception of phase- and amplitude-modulated digital signals of bandwidths up to 15 MHz on microwave carriers. System performs coherent demodulation in phase and in quadrature with carrier locked in phase to intermediate frequency of 10 MHz. Design suitable for fabrication in very-large-scale integrated circuitry. Principal innovative feature of demodulator is design of half-band digital low-pass filters that remove sum-frequency components.
Sadr, Ramin↗
Acquisition of the QPSK demodulator in the presence of interference
The acquisition behavior of the tracking and data relay satellite system (TDRSS) receiver (a quadrative phase-shift keying (QPSK) demodulator using a dither lock detector) in the presence of interference from another user has been analyzed using a simulation model. The demodulator is composed of an automatic gain control, a QPSK Costas loop, a frequency sweep unit, lock test units, and a control unit. The simulation model has been tested for the following variables: signal and interference Doppler frequencies and phase offsets (with respect to initial voltage control oscillator setup), signal-to-interference ratio (SIR), and signal I/Q power ratio. The simulation results are discussed.
Ghazvinian, Farzad↗
Portable digital lock-in instrument to determine chemical constituents with single-color absorption measurements for Global Health Initiatives
Innovations in international health require the use of state-of-the-art technology to enable clinical chemistry for diagnostics of bodily fluids. We propose the implementation of a portable and affordable lock-in amplifier-based instrument that employs digital technology to perform biochemical diagnostics on blood, urine, and other fluids. The digital instrument is composed of light source and optoelectronic sensor, lock-in detection electronics, microcontroller unit, and user interface components working with either power supply or batteries. The instrument performs lock-in detection provided that three conditions are met. First, the optoelectronic signal of interest needs be encoded in the envelope of an amplitude-modulated waveform. Second, the reference signal required in the demodulation channel has to be frequency and phase locked with respect to the optoelectronic carrier signal. Third, the reference signal should be conditioned appropriately. We present three approaches to condition the signal appropriately: high-pass filtering the reference signal, precise offset tuning the reference level by low-pass filtering, and by using a voltage divider network. We assess the performance of the lock-in instrument by comparing it to a benchmark device and by determining protein concentration with single-color absorption measurements. We validate the concentration values obtained with the proposed instrument using chemical concentration measurements. Finally, we demonstrate that accurate retrieval of phase information can be achieved by using the same instrument.
60 APPLIED LIFE SCIENCES↗
Receiver design and performance characteristics
The basic design, principles of operation, and characteristics of deep space communications receivers are examined. In particular, the basic fundamentals of phase-locked loop and Costas loop receivers used for synchronization, tracking, and demodulation of phase-coherent signals in residual carrier and suppressed carrier systems are addressed.
Simon, M. K.↗
Costas loop demodulation of suppressed carrier BPSK signals in the DSN environment: Experimental results obtained at TDL
Suppressed carrier binary phase-shift keyed (BPSK) signalling is currently being considered as a design alternative for future DSN telemetry in the multimegabit range. Carrier tracking of such signals is usually achieved by a Costas loop, as opposed to the ordinary phase lock loop. A Costas loop capable of demodulating BPSK signals with data rates up to 1 Msps was designed and constructed and its Doppler tracking performance with respect to a Block 3 receiver was tested at the Telecommunications Development Laboratory (TDL). The compatibility of suppressed carrier signalling with the current radiometric system, specifically Doppler tracking and ranging, was investigated. The experimental results obtained to-date with respect to Doppler tracking are presented.
Reasoner, R.↗
Phase-locked loops and their application
A collection of papers is presented on the characteristics and capabilities of phase-locked loops (PLLs), along with some applications of interest. The discussion covers basic theory (linear and nonlinear); acquisition; threshold; stability; frequency demodulation and detection; tracking; cycle slipping and loss of lock; phase-locked oscillators; operation and performance in the presence of noise; AGC, AFC, and APC circuits and systems; digital PLL; and applications and miscellaneous. With the rapid development of IC technology, PLLs are expected to be used widely in consumer electronics.
Lindsey, W. C.↗
Design and performance evaluation of a wideband FM spread-spectrum multiple-access system
The system described performs the tracking and communications functions of a tracking and data relay satellite system (TDRS). The spread-spectrum signal format is achieved through wide deviation FM by a sinusoidal subcarrier unique to each multiple-access user. A compound phase-locked loop tracks carrier and subcarrier and demodulates data and ranging signals. Design parameters of user and ground terminals for TDRS are given. Acquisition procedures are described. Performance analyses are presented including the effects of noise, RFI, multipath and other users.
Wachsman, R. H.↗
The use of interleaving for reducing radio loss in trellis-coded modulation systems
It is demonstrated how the use of interleaving/deinterleaving in trellis-coded modulation (TCM) systems can reduce the signal-to-noise ratio loss due to imperfect carrier demodulation references. Both the discrete carrier (phase-locked loop) and suppressed carrier (Costas loop) cases are considered and the differences between the two are clearly demonstrated by numerical results. These results are of great importance for future communication links to the Deep Space Network (DSN), especially from high Earth orbiters, which may be bandwidth limited.
Divsalar, D.↗
Unbalanced quadriphase demodulator
A new and improved apparatus and method are described for demodulation of quaternary phase shift keyed (QPSK) data, particularly unbalanced QPSK. Phase adjustment of the output of a phase locked loop local oscillator is performed to reduce sensitivity to amplitude variations internal to the demodulator.
Koybayashi, H. S.↗
The use of interleaving for reducing noisy reference loss in trellis-coded modulation systems
The use of interleaving/deinterleaving in trellis-coded modulation systems to reduce the SNR loss due to imperfect carrier demodulation references is demonstrated. Both the discrete carrier (phase-locked loop) and the suppressed carrier (Costas loop) cases are considered, and the differences between the two are clearly demonstrated by numerical results. The special case of convolutional codes is also treated and illustrated with an example of practical interest.
Divsalar, Dariush↗