This paper presents a new and simple approach for the Ka-band vernier pointing of a 34 m beam-waveguide (BWG) antenna (also applicable to a 70 m antenna). In this study, rotation of a BWG flat mirror, located at the elevation axis, is used to scan the beam instead of using the very large tipping structure of the antenna. The rotation of a BWG flat minor at another location is also investigated. The advantages of scanning the drastically smaller mirror with a less precise mechanism will be discussed. RF performance predictions will be presented.<>

An overview of a NASA/JPL antenna project, with specific focus on the methodology used to predict the microwave performance of a 34-m-diameter beam-waveguide (BWG) reflector antenna, designated DSS 13, is given. Microwave performance predictions are given, as well as a summary of test results for the antenna, which has Cassegrain and centerline BWG operating models at X-band (8.450-GHz) and Ka-band (32-GHz) frequencies. Predictions were used to identify critical and poorly understood areas needing further study and diagnostic testing, and assisted in planning, scheduling, and evaluating the final results of a detailed test program. Predictions were assembled for all known losses that contribute to antenna performance degradation. It was found that predictions and experimental results agreed reasonably well for beam-peak gain and corresponding efficiency, and for several (but not all) noise temperatures.< >

A novel approach is demonstrated which involves iterating Gaussian beam and beam waveguide (BWG) parameters to obtain a wideband BWG feed. The result is further improved by making a comparison with the physical-optics result and repeating the iteration. The basic goal was to design a BWG feed system with good performance from 2 to 32 GHz, utilizing mirror sizes of 20 lambda at the low frequency. The BWG antenna performance (e.g. gain, efficiency, noise temperature) at S, X, and Ka-bands is presented. It is noted that higher-gain horns are needed for higher frequencies.<>

The Gaussian beam technique has become increasingly popular for wideband beam waveguide (BWG) design. However, it is observed that the Gaussian solution is less accurate for smaller mirrors (approximately less than 30 lambda in diameter). Therefore, a high-performance wideband BWG design cannot be achieved by using the Gaussian beam technique alone. This article demonstrates a new design approach by iterating Gaussian beam and BWG parameters simultaneously at various frequencies to obtain a wideband BWG. The result is further improved by comparing it with physical optics results and repeating the iteration.

The measured Deep Space Network (DSN) 70-meter antenna performance at S- and X-bands is compared with the design expectations. A discussion of natural radio-source calibration standards is given. New estimates of DSN 64-meter antenna performance are given, based on improved values of calibration source flux and size correction. A comparison of the 64- and 70-meter performances shows that average S-band peak gain improvement is 1.94 dB, compared with a design expectation of 1.77 dB. At X-band, the average peak gain improvement is 2.12 dB, compared with the (coincidentally similar) design expectation of 1.77 dB. The average measured 70-meter S-band peak gain exceeds the nominal design-expected gain by 0.02 dB; the average measured 70-meter X-band peak gain is 0.14 dB below the nominal design-expected gain.

The design optimizations associated with the microwave and structural upgrade of the DSN 64-m antennas are discussed. Expected area efficiency/gain performances at S- and X-band are given for both the original 64-m systems and the upgraded 70-m systems, and error estimates are developed. The DSN 70-m Upgrade Project specifications, based on predesign estimates, were 1.4-dB gain at S-band and 1.9-dB at X-band, with no degradation to critical receiving system noise temperatures. The measurements show an S-band gain increase of 1.9 dB and an average increase of 2.1 dB at X-band. The Project also delivered small receiving system noise decreases at both frequency bands. The three DSN 70-m antennas, in the initial state of mechanical adjustment as of the end of calendar year 1988, are performing with very high peak microwave area efficiencies at very nearly the engineering design expectations of 76 percent at S-band and 71 percent at X-band.

A generalized solution is found for retrofitting a large dual-shaped reflector antenna for a beamwaveguide. The design is termed as a bypass beamwaveguide. Both highpass design feed imaging and bandpass design feed imaging are considered. Each design was studied using geometrical optics, Gaussian wave analysis, and both low-frequency and high-frequency diffraction analysis. An important extension of the Mizusawa-Kitsuregawa criteria was discovered (M.M. Zusama and T. Kitsuregawa, ibid., vol.AP-21, pp.844-8, Nov. 1973). The principle revealed shows how a two-reflector cell, although in itself distorting, may be combined with a second cell which compensates for the first and delivers an output beam which is a good image of the input beam.

The gain, phase, and pointing performance of the Deep Space Network (DSN) 70 m antennas are investigated using theoretical antenna analysis computer programs that consider the gravity induced deformation of the antenna surface and quadripod structure. The microwave effects are calculated for normal subreflector focusing motion and for special fixed-subreflector conditions that may be used during the Voyager 2 Neptune encounter. The frequency stability effects of stepwise lateral and axial subreflector motions are also described. Comparisons with recently measured antenna efficiency and subreflector motion tests are presented. A modification to the existing 70 m antenna pointing squint correction constant is proposed.