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At least 667 records · Page 37

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NASA NTRS1989

Effective amplifier noise for an optical receiver based on linear mode avalanche photodiodes

The rms noise charge induced by the amplifier for an optical receiver based on the linear-mode avalanche photodiode (APD) was analyzed. It is shown that for an amplifier with a 1-pF capacitor and a noise temperature of 100 K, the rms noise charge due to the amplifier is about 300. Since the noise charge must be small compared to the signal gain, APD gains on the order of 1000 will be required to operate the receiver in the linear mode.

Chen, C.-C.↗

NASA NTRS1988

A broad-band low-noise SIS receiver for submillimeter astronomy

A quasi-optical heterodyne receiver using a Pb-alloy superconductor-insulator-superconductor (SIS) tunnel junction as the detector and a planar logarithmic spiral antenna for the RF coupling is described, and its performance is compared with a the predicted performance of a theoretical model. Noise measurements were made in the laboratory at frequencies between 115 GHz and 761 GHz, yielding double-sideband noise temperatures ranging from 33 K to 1100 K. The receiver has also been used for astronomical spectroscopy on the Caltech Submillimeter Observatory (Mauna Kea, Hawaii) at 115, 230, 345, and 492 GHz.

Buttgenbach, Thomas H.↗

NASA NTRS1990

Simplified Calculation Of Solar Fluxes In Solar Receivers

Simplified Calculation of Solar Flux Distribution on Side Wall of Cylindrical Cavity Solar Receivers computer program employs simple solar-flux-calculation algorithm for cylindrical-cavity-type solar receiver. Results compare favorably with those of more complicated programs. Applications include study of solar energy and transfer of heat, and space power/solar-dynamics engineering. Written in FORTRAN 77.

Bhandari, Pradeep↗

NASA NTRS1988

Far-infrared heterodyne receivers

The development of open resonator mixer structures and laser local oscillators has made heterodyne spectroscopy at far infrared (FIR) wavelengths between 150 and 400 microns a reality. Several laser based receivers are now part of the instrument complement flown aboard the Kuiper Airborne Observatory. Lasers are eminently practical as FIR local oscillators whenever there is close frequency coincidence between a strong laser transition and the Doppler-shifted astronomical line. While it is desirable to have continuous frequency coverage in a spectrometer, it should be recognized that most astronomers will focus their interest on the few spectral lines deemed optimum for probing the cosmos. Ultimately, the development of a reliable thin film technology for the new high temperature oxide superconductors may favor SIS-type devices for all wavelengths in future space based FIR receivers.

Betz, Albert↗

NASA NTRS1990

A functional description of the advanced receiver

The breadboard Advanced Receiver 2 (ARX 2) that is currently being built for future use in NASA's Deep Space Network (DSN) is described. The hybrid analog/digital receiver performs multiple functions including carrier, subcarrier, and symbol synchronization. Tracking can be achieved for residual, suppressed, or hybrid carriers and for both sinusoidal and square-wave subcarriers. Other functions such as time-tagged Doppler extraction and monitor/control are also discussed, including acquisition algorithms and lock-detection schemes. System requirements are specified and a functional description of the ARX 2 is presented. The various digital signal-processing algorithms used are also discussed and illustrated with block diagrams.

Hinedi, S.↗

NASA NTRS1990

A two-telescope receiver design for deep space optical communications

A two-telescope system for a deep space optical communication receiver is proposed. To substantially improve the overall receiver efficiency, the design reserves the large telescope for signal-detection purposes only. A small diffraction-limited telescope is introduced to accomplish the task of navigational tracking.

Shaik, K.↗

NASA NTRS1990

Design of a hybrid receiver for the OLYMPUS spacecraft beacons

The theory and design of a hybrid analogue/digital receiver which acquires and monitors the OLYMPUS satellite beacons is presented. The analogue portion of this receiver uses a frequency locked loop for signal tracking. A digital sampling detector operating at IF is used to obtain the I and Q outputs.

Sweeney, D. G.↗

NASA NTRS1991

Optical Receiver Based On Luminescent Light Trapping

Experiment demonstrates feasibility of optical-communication receiver based on luminescent light trapping. Light-gathering element plate of transparent material impregnated with laser dye. Light from distant laser transmitter falls on plate and absorbed by dye molecules, which become excited and reradiate. Reradiated light confined within plate by total internal reflection as it propagates toward edge of plate. Light arriving at edge escapes from plate and detected by small, high-speed, high-gain photomultiplier tubes or other photosensitive devices. Simple, inexpensive, and accepts light from almost any angle. Receiver of this configuration supports reception of data at rate of 13 MHz and higher.

Perry, Joseph W.↗

NASA NTRS1990

Advanced Stirling receiver development program, phase 1

Critical technology experiments were designed and developed to evaluate the Stirling cavity heat pipe receiver for a space solar power system. Theoretical criteria were applied to the design of a module for containing energy storage phase change material while avoiding thermal ratcheting. Zero-g drop tower tests, without phase change, were conducted to affirm that the bubble location required to avoid ratcheting could be achieved without the use of container materials that are wetted by the phase change material. A full scale module was fabricated, but not tested. A fabrication method was successfully developed for the sodium evaporator dome, with a sintered screen wick, to be used as the focal point for the receiver. Crushing of the screen during hydroforming was substantially reduced over the results of other researchers by using wax impregnation. Superheating of the sodium in the wick under average flux conditions is expected to be under 10K. A 2000K furnace which will simulate solar flux conditions for testing the evaporator dome was successfully built and tested.

Lurio, Charles A.↗

NASA NTRS1990

Using a modified Hewlett Packard 8410 network analyzer as an automated farfield antenna range receiver

A Hewlett Packard 8410 Network Analyzer was modified to be used as an automated far-field antenna range receiver. By using external mixers, analog to digital signal conversion, and an external computer/controller, the HP8410 is capable of measuring signals as low as -110 dBm. The modified receiver is an integral part of an automated far-field range which features computer controlled test antenna positioning, system measurement parameters, and data acquisition, as well as customized measurement file management. The system described was assembled and made operational, taking advantage of off-the-shelf hardware available at minimal cost.

Terry, John D.↗

NASA NTRS1991

Phase-lock-loop application for fiber optic receiver

Phase-locked loop circuits are frequently employed in communication systems. In recent years, digital phase-locked loop circuits were utilized in optical communications systems. In an optical transceiver system, the digital phase-locked loop circuit is connected to the output of the receiver to extract a clock signal from the received coded data (NRZ, Bi-Phase, or Manchester). The clock signal is then used to reconstruct or recover the original data from the coded data. A theoretical approach to the design of a digital phase-locked loop circuit operation at 1 and 50 MHz is described. Hardware implementation of a breadboard design to function at 1 MHz and a printed-circuit board designed to function at 50 MHz were assembled using emitter coupled logic (ECL) to verify experimentally the theoretical design.

Ruggles, Stephen L.↗

NASA NTRS1991

The Advanced Receiver II telemetry test results at Goldstone

The telemetry performance of the Advanced Receiver II (ARX-II) in tracking and demodulating signals from various deep space missions is described. The tests were performed at Goldstone, and the spacecrafts tracked were Pioneer 10, Pioneer 11, Voyager 2, Magellan, and the International Cometary Explorer (ICE). These missions present a broad range of operating conditions to test the ARX-II in terms of signal-to-noise ratio (SNR) and the symbol rate of the received signal.

Sadr, R.↗

NASA NTRS1991

Carrier-to-noise power estimation for the Block 5 Receiver

Two possible algorithms for the carrier to noise power (P sub c/N sub 0) estimation in the Block V Receiver are analyzed and their performances compared. The expected value and the variance of each estimator algorithm are derived. The two algorithms examined are known as the I arm estimator, which relies on samples from only the in-phase arm of the digital phase lock loop, and the IQ arm estimator, which uses both in-phase and quadrature-phase arm signals. The IQ arm algorithm is currently implemented in the Advanced Receiver II (ARX II). Both estimators are biased. The performance degradation due to phase jitter in the carrier tracking loop is taken into account. Curves of the expected value and the signal to noise ratio of the P sub c/N sub 0 estimators vs. actual P sub c/N sub 0 are shown. From this, it is clear that the I arm estimator performs better than the IQ arm estimator when the data to noise power ratio (P sub d/N sub 0) is high, i.e., at high P sub c/N sub 0 values and a significant modulation index. When P sub d/N sub 0 is low, the two estimators have essentially the same performance.

Monk, A. M.↗

NASA NTRS1990

Receiving efficiency of monostatic pulsed coherent lidars. I - Theory. II - Applications

Pulsed coherent radars' receiving efficiency, eta, is presently investigated as a function of range z on the basis of a theory which relates eta(z) to both the transmitted laser intensity and the point-source receiving efficiency; this efficiency is calculated by a backward method employing the back-propagated local oscillator (BPLO) approach. The theory is applied to the ideal case, in order to study system optimization when both the transmitted and the BPLO fields at the antenna are Gaussian. In the second part of this work, eta(z) is calculated for various conditions of the NOAA/ERL Wave Propagation Laboratory CO2 Doppler lidar; the sensitivity of eta(z) to transmitted laser beam quality, telescope focal setting, telescope power, scanner astigmatism, and system misalignment.

Zhao, Yanzeng↗

NASA NTRS1990

Application of a novel multi-stage signal parameter estimator to high dynamic GPS receivers

The performance of a novel multistage estimator when applied to the estimation of the position, velocity, and acceleration of high dynamic Global Positioning System (GPS) receivers is discussed. For the present application, a two-stage specialization of the more general estimation scheme is considered, wherein the first-stage algorithm is selected to be a modified least-squares algorithm operating upon the differential signal model and referred to as differential least-squares (DLS) and the second stage is simply an extended Kalman filter (EKF). In terms of the threshold on received carrier power-to-noise power spectral density ratio (CNR), when compared to the single-stage EKF algorithm, the DLS-EKF algorithm is about 1.5-2.0 dB better in terms of threshold and outperforms the crossproduct AFC (automatic frequency control) loop by 2-5 dB. For the case when data modulation is present, the proposed scheme provides an improvement of about 6 dB in terms of CNR compared to an earlier approximate MLE (maximum likelihood estimation) scheme. There are also very significant improvements in terms of other performance measures.

Kumar, R.↗

NASA NTRS1992

Advanced Receiver For Phase-Shift-Keyed Signals

ARX II is second "breadboard" version of advanced receiver, a hybrid digital/analog receiving subsystem, extracting symbols and Doppler shifts from weak phase-shift-keyed signals. Useful in terrestrial digital communication systems.

Hinedi, Sami M.↗

NASA NTRS1992

Digital Extraction Of Doppler Shift In An Advanced Receiver

Report describes demonstration of ability of Advanced Receiver II (ARX II) to extract Doppler shifts in radio telemetry signals from spacecraft by digital processing. Frequency of sampling clock fixed and derived from frequency-and-timing subsystem. Although this can result in noninteger number of samples per symbol, it enables digital extraction of Doppler shift. ARX II operates with older receiver called "Block IV". ARX II performed at least as well as, and in most cases better than, Block IV.

Hinedi, Sami M.↗

NASA NTRS1990

Streak camera receiver definition study

Detailed streak camera definition studies were made as a first step toward full flight qualification of a dual channel picosecond resolution streak camera receiver for the Geoscience Laser Altimeter and Ranging System (GLRS). The streak camera receiver requirements are discussed as they pertain specifically to the GLRS system, and estimates of the characteristics of the streak camera are given, based upon existing and near-term technological capabilities. Important problem areas are highlighted, and possible corresponding solutions are discussed.

Johnson, C. B.↗