Engineering topics
Publications and source records attributed to Potter, P. D..
Geometry of reflector plate adjusted to compensate for undesired effects. Design change reduces depolarization and noise in thick microwave dichroic reflecting plate tilted 30 degrees from orientation broadside to incident beam.
The use of K sub A-band to alleviate the radio metric degradation caused by charged particles is discussed. Those aspects of radio metrics which are relevant to the possible future use of K sub A-band deep space to Earth and Earth to deep space links are reviewed. In particular the effects of the Earth ionosphere, troposphere, and solar plasma are examined. It is concluded that, from the standpoint of reducing the harmful effects of charged particles, the use of K sub A-band appears highly desirable. While stability will be a more serious design constraint at K sub A-band than it is at X-band (for example in the ground power amplifier and the spacecraft multiplier stages) this problem is amenable to a state of the art engineering solution.
The future potential of the 32 GHz K sub A band frequency region to planetary exploration, and the expected performance of the 64 m antenna network at 32 GHz is addressed. A modest level of noninterference upgrade work is assumed to achieve reasonable antenna aperture efficiency and alleviate antenna pointing difficulties. Electronic compensation of antenna aperture phasing errors is briefly considered as an alternative to the physical upgrade.
Single antenna using two feed horns (one for receiving and radiation X-band signals, and one for S-band signals), in conjunction with ellipsoid reflector and dichronic plate, can accommodate two different frequencies simultaneously.
The HYBRIDHORN computer program was developed to serve as an item of general purpose antenna feedhorn design and analysis software. The formulation contains a small flare angle approximation which is subject to question for designs such as the S- and X-band feedhorn. Additionally, the original formulation did not allow azimuthal variation indexes other than unity. The HYBRIDHORN program was upgraded to correct both of these deficiencies. A large flare angle formulation was found. In the upgrade, all of the major program elements were converted to Univac 1108 compatible structured FORTRAN (SFTRAN) for ease of software maintenance. The small and large angle formulations are described and sample numerical results are presented.
The closed-loop conical-scan (conscan) technique has proven to be a useful method for pointing the DSN antennas more accurately than is possible by open-loop methods. As presently implemented, the antenna beam is scanned about the received signal direction by physical movement of the antenna. While straightforward, this approach has at least two disadvantages. Firstly, because of structural distortions, finite angle encoder resolution, and drive servo response, the actual antenna beam direction only approximates the commanded beam direction. Secondly, because of the large mass moved during scan, the rate of scan is severely restricted. If there are significant gain or signal level variations during a scan period, the conscan system interprets these variations as antenna pointing error. Both of these disadvantages would be alleviated in an inertialess conscan system in which the beam scanning was performed electronically. Recently, standard JPL antenna feedhorn software was upgraded to calculate, among other things, asymmetric corrugated horn radiation patterns of the type that would be needed for electronic beam scan. The required horn excitation is discussed and the results were described.
A computer model of the JPL hydrogen maser frequency standard was developed. This model allows frequency stability data to be generated, as a function of various maser parameters, many orders of magnitude faster than these data can be obtained by experimental test. In particular, the maser performance as a function of the various automatic tuning servo parameters may be readily determined. Areas of discussion include noise sources, first-order autotuner loop, second-order autotuner loop, and a comparison of the loops.
To support the Mariner 1973 X-band experiment, it was necessary to implement a dual-frequency microwave feed system for the Cassegrainian-fed DSS 14 64-m antenna. This system must be capable of simultaneous low noise reception at S- and X-bands and high power transmission at S-band. The design and measured perfromance of the DSS 14 reflex feed system is described.
Segmented subreflector surface of Cassegrainian antenna is distorted and shaped by mechanical means to compensate for loss of figure in main reflector. Number of segments necessary is determined by gravity distortion pattern of main reflector at zenith and at horizon.
Weather-dependent data links for deep space applications, and five potential systems
Program designs the feed system geometry and the subreflector surface, with the main reflector configuration and frequency of operation as input data. Although the feedhorn is not designed, its required gain, beamwidth, and approximate radiation pattern are specified.
Spherical wave expansion technique for analyzing Cassegrain paraboloidal antenna feed systems and synthesizing subreflector
Multiple mode horn antenna with radiation pattern of equal beamwidths and suppressed sidelobes
Antenna systems for deep space communication emphasizing ground station, balancing of ground antenna aperture with spacecraft performance, arrays, etc
Very high power and low noise Cassegrain feed system for planetary radar in Deep Space Instrumentation Facility /DSIF/
Cassegrain feed for 85-ft-diam antenna of planetary radar system noting operative conditions, polarization capabilities and performance data
Effect of frequency on communications capability, single antennas and arrays, and economic balance between ground station and spacecraft development
Cassegrain antenna subreflector flange for suppressing ground noise and increasing antenna transmitting efficiency