The approximate transient performance of a phase-locked loop on board a tumbling satellite
Transient performance of phase locked loop onboard tumbling satellite, noting relation to time, SNR and fade modulation
Yao, K.↗
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Diffraction coupled phase-locked semiconductor laser array
A new monolithic, diffraction coupled phase-locked semiconductor laser array has been fabricated. Stable narrow far-field patterns (approximately 3 deg) and peak power levels of 1 W have been obtained for 100-micron-wide devices with threshold currents as low as 250 mA. Such devices may be useful in applications where high power levels and stable radiation patterns are needed.
Katz, J.↗
Separate-contact phase-locked semiconductor laser arrays
The novel optoelectronic devices discussed, phase-locked semiconductor laser arrays with separate contacts can perform a variety of near field and far field pattern tailoring functions and control mutual coherence among array elements, as well as lasing wavelength selectivity and tunability. Attention is presently given to experimental results from such arrays, which indicate that the threshold currents of the 4-micron wide lasers employed are typically 60 mA. The separate contacts to each one of them are provided by means of two-level metallization.
Katz, J.↗
Phase-locked injection laser arrays with variable stripe spacing
A phase-locked injection laser array is described which utilizes variations in spacing of identical lasing elements to vary the coupling between them. A coupled-mode analysis indicates that excellent matching of fundamental array mode to a uniform gain distribution can be obtained. Observation of the array emission patterns confirms the results of the coupled-mode analysis.
Ackley, Donald E.↗
Flexible Loop Filter Design for Spacecraft Phase-Locked Receivers
A flexible loop filter design for spacecraft phase-locked receivers is proposed.
deep↗
Phase-lock demodulation of a PM signal contaminated with incidental AM
Signals from phase-modulated satellite transmitters usually exhibit some degree of incidental amplitude modulation. The effects of incidental AM are analyzed when this type of signal is demodulated by a phase-lock receiver which does not employ a limiter preceding the loop phase detector. The presence of incidental AM causes a reduction in the receiver output signal-to-noise ratio. The tolerable level of AM decreases in proportion to the phase modulation index Beta. For a square-wave modulating signal, a 1 db reduction results at the receiver PM channel output when Beta = 1 radian and the percentage of AM = 23, Beta = 1.2 radians and the percentage of AM = 16, or Beta = 1.5 radians and the percentage of AM = 4. Although only the PM channel of the receiver is used ordinarily, utilizing both the AM and PM channel by summing offers an improvement in S/N relative to the S/N ratio of the PM channel if the percentage of incidental AM is greater than fifteen.
Robinson, G. B.↗
Quasi-instantaneous (less than 20 ps) phase locking in single-lobe Y-coupled laser diode arrays
The time evolution of the far-field radiation pattern of an in-phase locked Y-coupled diode laser array has been observed with a streak camera. A strong central lobe 2.3 deg wide with faint secondary sidelobes separated by 15 deg forms in a time less than 20 ps. This indicates that the elements of the array are instantaneously locked in-phase.
Defreez, R. K.↗
Continuous-Wave Single-Frequency Operation of Fabry-Perot Laser Diodes by Self-Injection Phase Locking Using Feedback from a Fiber Bragg Grating
Single-frequency operation of uncoated Fabry-Perot laser diodes is demonstrated by phase- locking the laser oscillations through self-injection seeding with feedback from a fiber Bragg grating. By precisely tuning the laser temperature so that an axial-mode coincides with the short-wavelength band edge of the grating, the phase of the feedback is made conjugate to that of the axial mode, locking the phase of the laser oscillations to that mode.
Duerksen, Gary L.↗
Investigation of Fiber Optics Based Phased Locked Diode Lasers
Optical power beaming requires a high intensity source and a system to address beam phase and location. A synthetic aperture array of phased locked sources can provide the necessary power levels as well as a means to correct for phase errors. A fiber optic phase modulator with a master oscillator and power amplifier (MOPA) using an injection-locking semiconductor optical amplifier has proven to be effective in correcting phase errors as large as 4pi in an interferometer system. Phase corrections with the piezoelectric fiber stretcher were made from 0 - 10 kHz, with most application oriented corrections requiring only 1 kHz. The amplifier did not lose locked power output while the phase was changed, however its performance was below expectation. Results of this investigation indicate fiber stretchers and amplifiers can be incorporated into a MOPA system to achieve successful earth based power beaming.
Burke, Paul D.↗
Improved performance of a digital phase-locked loop combined with a frequency/frequency-rate estimator
When a digital phase-locked loop with a long loop update time tracks a signal with high Doppler, the demodualtion losses due to frequency mismatch can become very significant. One way of reducing these Doppler-related losses is to compensate for the Doppler effect using some kind of frequency-rate estimator. The performance of the fixed-window least-squares estimator and the Kalman filter is investigated; several Doppler compensating techniques are proposed. It is shown that the variance of the frequency estimator can be made as small as desired, and with this, the Doppler effect can be effectively compensated. The remaining demodulation losses due to phase jitter in the loop can be less than 0.1 dB.
Mileant, A.↗
The non-linear transient behavior of second, third and fourth order phase-locked loops.
Nonlinear transient behavior of second, third and fourth order phase locked loops from state space projections on hyperplanes
Carden, F. F.↗
Phase lock loop acquisition of a carrier modulated by a single sinusoid
Phase lock loop acquisition and tracking of carrier frequency modulated by single sinusoid, obtaining parameter values through mathematical model and digital simulation
Gilbert, A. L.↗
A Computer Model of a Phase Lock Loop
A computer model is reported of a PLL (phase-lock loop), preceded by a bandpass filter, which is valid when the bandwidth of the bandpass filter is of the same order of magnitude as the natural frequency of the PLL. New results for the PLL natural frequency equal to the bandpass filter bandwidth are presented for a second order PLL operating with carrier plus noise as the input. However, it is shown that extensions to higher order loops, and to the case of a modulated carrier are straightforward. The new results presented give the cycle skipping rate of the PLL as a function of the input carrier to noise ratio when the PLL natural frequency is equal to the bandpass filter bandwidth. Preliminary results showing the variation of the output noise power and cycle skipping rates of the PLL as a function of the loop damping ratio for the PLL natural frequency equal to the bandpass filter bandwidth are also included.
Shelton, Ralph Paul↗
Phase-locked arrays of semiconductor injection lasers - A review
Arrays of phase-locked semiconductor injection lasers integrated monolithically on the same substrate are one potential method for obtaining higher power levels (in controlled mode operation) than those available from a single laser. This paper describes basic methods for analyzing the electrical and optical characteristics of these devices, and discusses problems associated with maintaining a stable operation in a single array mode ('supermode'). Various experimental results are presented and compared with theory.
Katz, Joseph↗
Automatic carrier acquisition system for phase-lock-loop receivers
Programmable oscillator and zero-beat detector acquires phase-lock of carrier by frequency scanning. Generation of high-level dc pulse at instant of zero crossing provides positive trigger for decision gate to stop search and close loop for phase-coherent tracking.
Bunce, R. C.↗
Analysis of a first order phase locked loop in the presence of Gaussian noise
A first-order digital phase locked loop is analyzed by application of a Markov chain model. Steady state loop error probabilities, phase standard deviation, and mean loop transient times are determined for various input signal to noise ratios. Results for direct loop simulation are presented for comparison.
Blasche, P. R.↗
Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs
The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.
Chen, C.-C.↗
Experimental signal/noise-ratio comparison of the second-order phase-locked loop and the second-order frequency-locked loop.
Signal/noise performance of frequency locked loop FM threshold extension demodulator compared to phase locked loop demodulator and conventional FM discriminator
Schulman, R. J.↗