In December 2018, satellite broadcasting for 4K/8K ultra-high-definition television (UHDTV) will begin in Japan. It will be provided in the 12-GHz (11.7 to 12.75GHz) band with right- and left-hand circular polarizations. BSAT-4a, a satellite used for broadcasting UHDTV, was successfully launched in September 2017. This satellite has not only 12-GHz-band right- and left-hand circular polarization transponders but also a 21-GHz-band experimental transponder. The 21-GHz (21.4 to 22.0GHz) band has been allocated as the downlink for broadcasting satellite service in ITU-R Regions 1 (Europe, Africa) and 3 (Asia Pacific). To receive services provided over these two frequency bands and with dual-polarization, we implement and evaluated a dual-band and dual-circularly polarized parabolic reflector antenna fed by 12- and 21-GHz-band microstrip antenna arrays with a multilayer structure. The antenna is used to receive 12- and 21-GHz-band signals from in-orbit satellites. The measured and experimental results prove that the proposed antenna performs as a dual-polarized antenna in those two frequency bands and has sufficient performance to receive satellite broadcasts.

Predicting the receiving sensitivity of an offset Gregorian reflector system antenna requires an accurate prediction of the antenna noise temperature. Calculating the antenna noise temperature is computationally intensive especially for the electrically larger reflector systems. Using the main reflector masking technique, which removes the main reflector from the calculation domain, considerably reduces the computation cost. For an electrically smaller reflector system, diffraction effects affect the accuracy of this technique. Recently an improvement to the technique was proposed that introduces diffraction compensation correction factors. In this paper we introduce new compensation factor and interpolation techniques that improve the accuracy of the approximated antenna noise temperature calculation. The techniques are applied to several offset Gregorian reflector systems similar to those considered for the Square Kilometre Array, with various feeds and the accuracy in terms of receiving sensitivity is evaluated. The techniques can reduce the prediction error of the receiving sensitivity for frequency-invariant feeds to fractions of a percent, while maintaining a significant speed-up over direct calculations.

Designing shaped offset Gregorian reflector systems to operate with several interchangeable feed horns, over frequency bandwidths of more than a decade, with multiple, often conflicting, performance figures of merit such as aperture efficiency, receiving sensitivity, sidelobe levels, and cross polarization isolation is a difficult optimization problem. An additional complication may be that the radiation patterns of all the feeds to be used in the system are not known at the time of the dish designs, as upgrades to the feeds may happen throughout the lifetime of large reflector systems. This paper presents a systematic parametric study to quantify the effects of the main causes of performance degradation in such a system, i.e. reflector diffraction and feed pattern variations. First, ideal Gaussian feed patterns are used in order to isolate the diffraction effects, and then the ideal patterns are varied to model the effect of using wideband feeds exhibiting radiation pattern variations over frequency. It is shown that the peak position in the shaping parameter space of the receiving sensitivity is not strongly influenced by diffraction - although the peak value is, as expected, reduced at lower frequencies. This allows similar feed patterns to be used in different frequency bands to still produce systems operating near the maximum sensitivity. When using non-ideal feed patterns it is shown that, for most performance metrics, diffraction effects dominate the feed variation performance degradation in smaller dishes. This allows possibly relaxed requirements on the radiation patterns of feeds used to illuminate electrically small reflector systems.

Japan Broadcasting Corporation (NHK) started test satellite broadcasting of ultra-high-definition television (UHDTV) on August 1st, 2016. The test broadcasting is being provided in the 12-GHz (11.7 to 12.75GHz) band with right-hand circular polarization. In 2018, left-hand circular polarization in the same frequency band will be used for satellite broadcasting of UHDTV. Because UHDTV satellite broadcasting uses the 16APSK modulation scheme, which requires a higher carrier-to-noise ratio than that used for HDTV in Japan, it is important to mitigate the cross-polarization interference. Therefore, we fabricated and tested a dual-circularly polarized offset parabolic reflector antenna that has a feed antenna composed of a 2×2 microstrip antenna array, which is sequentially rotated to enhance the polarization purity. Measured results showed that the fabricated antenna complied with our requirements, a voltage standing wave ratio of less than 1.4, antenna gain of 34.5dBi (i.e., the aperture efficiency was 69%), and cross-polarization discrimination of 28.7dB.

Shaped beam reflector antennas are widely used because they can achieve a shaped beam even with a single primary feed. Because coverage shapes depend on service areas, optimum primary radiators and reflector shapes are determined by the service areas. In this paper, we propose a simultaneous optimal design method of the primary radiator and reflector for the shaped beam antenna. Particle swarm optimization and the conjugate gradient method are adopted to optimize the primary radiator and reflector. The design method is applied to Japan coverage to verify its effectiveness.

We investigate a phased array-fed dual reflector antenna applying one-dimensional beam-scanning of the center-fed type, using an elliptical aperture to provide wide area observation. The distinguishing feature of this antenna is its elliptical aperture shape, in which the aperture diameter differs between the forward satellite direction and the cross-section orthogonal to it. The shape in the plane of the forward satellite direction, which does not have a beam-scanning function, is a ring-focus Cassegrain antenna, and the shape in the plane orthogonal to that, which does have a beam-scanning function, is an imaging reflector antenna. This paper describes issues which arose during design of the elliptical aperture shape and how they were solved, and presents design results using elliptical aperture dimensions of 1600 mm × 600 mm, in which the beam width differs by more than two times in the orthogonal cross-section. The effectiveness of the antenna was verified by fabricating a prototype antenna based on the design results. Measurement results confirmed that an aperture efficiency of 50% or more could be achieved, and that a different beam width was obtained in the orthogonal plane in accordance with design values.

We propose a novel phased array-fed dual-reflector antenna that reduces performance degradation caused by multiple reflection. The marked feature of the proposed configuration is that different reflector profiles are employed for the two orthogonal directions. The reflector profile in the beam-scanning section (vertical section) is set to an imaging reflector configuration, while the profile in the orthogonal non-beam-scanning section (horizontal section) is set to a ring-focus Cassegrain antenna configuration. In order to compare the proposed antenna with the conventional antenna in which multiple reflection was problematic, we designed a prototype antenna of the same size, and verified the validity of the proposed antenna. The results of the verification were that the gain in the designed central frequency increased by 0.4 dB, and the ripple of the gain frequency properties that was produced by multiple reflection was decreased by 1.1,dB. These results demonstrated the validity of the proposed antenna.

We propose a new, compact, center-fed reflector antenna that is capable of one-dimensional electronic beam scanning. The reflector profile in the vertical section (beam-scanning) is set to an imaging reflector configuration, while the profile in the orthogonal horizontal section (non-beam-scanning) is set to a Cassegrain antenna configuration. The primary radiator is a one-dimensional phased array antenna. We choose a center-fed configuration in order to reduce the antenna size as much as possible, despite the fact that the increased blocking area from the primary radiator causes degradation in efficiency compared to the typical offset-type configuration. In the proposed configuration, beam scanning is limited to one dimension, but utilize a compact, center-fed configuration that maintains the features of an imaging reflector antenna. We present the antenna configuration and design method and show that results obtained from the prototype antenna verify the predicted performance.

A design method is proposed for a low-profile dual-shaped reflector antenna for the mobile satellite communications. The antenna is required to be low-profile because of mount restrictions. However, reduction of its height generally causes degradation of antenna performance. Firstly, an initial low-profile reflector antenna with an elliptical aperture is designed by using Geometrical Optics (GO) shaping. Then a Physical Optics (PO) shaping technique is applied to optimize the gain and sidelobes including mitigation of undesired scattering. The developed design method provides highly accurate design procedure for electrically small reflector antennas. Fabrication and measurement of a prototype antenna support the theory.

The paper overviews and surveys Japan's reflector antennas for earth stations and radio telescopes since the 1960's. Some interferometers for radio astronomy are included. Japanese original technologies regarding reflector antenna design and measurement are also described. There are 35 figures and 3 tables.

Antennas for Japanese terrestrial microwave relay links have been developed since the1950's and put into commercial use up to now in Japan. In particular, the path-length lens antennas developed in 1953 represents a monumental achievement for terrestrial microwave relay links, and the offset antenna for 256 QAM radio relay links developed in 1989 has the best electrical performance in the world. This paper reviews the antennas for Japanese terrestrial microwave relay links that have historical significance and describes the antenna design technologies developed in Japan.

This paper describes a historical review of satellite onboard reflector antenna systems in Japan.

Electric beam scanning reflector antennas provide beam scanning and pattern control, and can create narrow beams efficiently. However, they are not popular because the beam control circuit is large and difficult to realize. This paper proposes a new BFN configuration for cluster feeding of highly functional scanning antenna. The Enhanced PAttern Control nonswiTch (EPACT) BFN simplifies the beam control circuit and its control algorithm by using a fast Fourier transform (FFT) circuit, phase shifters, and a power divider. Furthermore, this paper proposes a design technique that uses modules to implement the FFT circuit and a method that optimizes amplifier placement to improve antenna efficiency. The design technique facilitates the manufacture of large-scale FFT circuits. The optimized amplifier location improves the antenna efficiency by eliminating the partial concentration of signal power.

Beam reconfiguration by structural reconfigurable antenna, such as the small multi-panel reconfigurable reflector antenna, has an aspect of great concern, that is the effects due to the use of a number of small panels to form the reflecting surface. It is thus a matter of great interest to numerically investigate all possible factors affecting the performance of this type of antenna such as: neighboring panels blocking, diffraction. The "null-field hypothesis" and PTD are employed to account for the effects of both phenomena on the main beam steering ability and the cross-polar level. In addition, the transformation of the polygonal flat domains into the square domains is applied in calculating the PO radiation field due to the various irregular polygonal flat sections of the arbitrary initial approximate reflector e.g., the flat circular reflector and the paraboloidal reflector. It is found that the main contribution to the total cross polarization is depolarization due to the finite size of the panels. The maximum cross-polar gain predicted using PTD is around -30 dB. The blocking effect has minor influence on cross-polarization. Both effects cause distortion on the co-polar pattern for the observer far from boresight but blocking has more influence than edge diffraction. Both effects have minor influence on the co-polar gain. The co-polar gain has variation of less than or equal to 0.07 dB in the flat case and 0.16 dB in the paraboloid case.