Kazuyoshi Shogen

Single shaped reflector antennas for broadcasting satellites

For future direct broadcasting satellites in Japan, precisely contoured beam antennas will be required for onboard antennas. Single shaped-reflector antennas are suitable for that purpose, since they do not need complex feed networks. However, in a previous study, discontinuities in the reflector surface were observed. The problem of the discontinuity was circumvented in this work and the shaped reflectors were successfully designed to produce contoured beams for covering the Japanese islands for the downlink and feederlink antennas. The downlink antenna was fabricated, and the radiation pattern was verified by measurement. The radiation pattern meets the radio regulations imposed on the onboard antenna, such as sidelobe and cross-polarization characteristics. >

A Method to Transform Rainfall Rate to Rain Attenuation and Its Application to 21 GHz Band Satellite Broadcasting

Satellite broadcasting in the 21-GHz band is expected to transmit large-capacity signals such as ultrahigh-definition TV. However, this band suffers from large amounts of rain attenuation. In this regard, we have been studying rain fading mitigation techniques, in which the radiation power is increased locally in the area of heavy rainfall. To design such a satellite broadcasting system, it is necessary to evaluate service availability when using the locally increased beam technique. The rain attenuation data should be derived from the rainfall rate data. We developed a method to transform rainfall rate into rain attenuation in the 21GHz band. Then, we performed a simulation that applied the method to the analysis of the service availability for an example phased array antenna configuration. The results confirmed the service availability increased with the locally increased beam technique.

21 GHz band Direct Broadcasting Satellite System

Satellite broadcasting in the 21-GHz band is expected to broadcast wide-band programs such as Super Hi-Vision, which is ultra-high-definition with more than 4000 scanning lines. The 21-GHz band, however, suffers from about three times heavier rain attenuation in terms of decibels than the 12-GHz band. This paper describes a mitigation technique using onboard array-fed reflector antennas that can boost the radiation power only in the areas with heavy rainfall, while maintaining a constant level of radiation power in the rest of the service area. Examples of antenna gain for such radiation patterns are shown. The transmission power and the power consumption for the two types of onboard phased array antenna are compared.

Experimental Model of Array-fed Imaging Reflector Antenna for 21GHz-band Satellite Broadcasting System

Satellite broadcasting in the 21GHz-band is expected to transmit large-capacity signals such as ultra high definition TV, called Super Hi-Vision in Japan with more than 4000 scanning lines. However, the 21GHz-band suffers from severe fading due to rain. In order to overcome the large rain attenuation, a reconfigurable antenna with an array-fed reflector is effective for the 21GHz-band satellite system. Therefore, we designed and manufactured an experimental model of an array-fed imaging reflector antenna for the 21GHz-band broadcasting satellite system. We verified the characteristics by measurement. We describe the configuration of the manufactured antenna and the radiation pattern of the imaging reflector calculated by using the measured radiation pattern of the feed array. A 7dB boosted beam has been successfully obtained.

Onboard array-fed reflector antenna for 21-GHZ-band direct broadcasting satellite

Satellite broadcasting in the 21-GHz band is expected to broadcast wide-band programs such as Super Hi-Vision, which is ultra-high-definition with more than 4000 scanning lines. The 21-GHz band, however, suffers from heavy rain attenuation about three times more than that of the 12-GHz band in terms of decibels. This paper describes a mitigation technique using onboard array-fed reflector antennas that can boost the radiation power only in the areas with heavy rainfall, while keeping a constant level of radiation power in the rest of the service area. The electrical performance of miniature TWTs is also described. Furthermore, we evaluated the power efficiency of the array feed and this is also discussed.

Radiation Characteristics of Multi-horn Antenna for 21 GHz Band Variable EIRP Broadcasting Satellite

This paper describes an onboard antenna for the 21 GHz band variable EIRP (equivalent isotropically radiated power) broadcasting satellite. This frequency band provides a large rain/vapor attenuation. For example, the atmospheric attenuation is about 10 dB for 1% of the time during the worst month in Tokyo. In order to overcome the large attenuation, a multi-beam system is studied, in which each of the beams covers a small area and the radiation power of the beam is controlled according to the atmospheric attenuation of that area. The onboard antenna is one of the key components in this system. We have developed a scale model of the multi-beam antenna. The characteristics of the antenna agree with the designed characteristics.

Folded Type Rectangular Loop Antenna in UHF Band

In this paper, we proposed a Folded type Rectangular Loop Antenna (FRLA) for one-seg. The measurement and simulation results indicated that the characteristics of the radiation patterns are similar to a rectangular loop antenna with full wavelength wire and resonates in the lower UHF band. The measured gain of the FRLA is -2.8dBi and the simulated gain is -2.2dBi. In the future, we will study configurations to achieve more wideband characteristics, and improvement of its radiation efficiency.

Broadcasting Satellite System Using Onboard Phased Array Antenna in 21-GHz Band

Satellite broadcasting in the 21-GHz band is expected to be used for advanced broadcasting services, such as ultrahigh-definition television, which requires extremely high information transmission rates. However, RF signal attenuation due to rainfall is very large in this band. A promising approach to solving this problem is to use an onboard phased array antenna to compensate for the attenuation in rain areas. We have been studying on a miniature traveling wave tube (mini-TWT) for an onboard active phased array antenna. It is necessary that we arrange radiation elements densely so as to achieve high gain of service area, and to suppress sidelobes. We developed a mini-TWT for its amplifier; the length of cross-sectional directions corresponded to the 1.5 wavelengths. This paper describes a concept of the satellite broadcasting in the 21-GHz band and the performance of the mini-TWT in the partial model of a mini-TWT array.

Hardware performance and experimental results of portable digital SNG equipment using a flat antenna

We have developed a Ku-band portable digital satellite news gathering (SNG) RF terminal and evaluated the hardware performance through experiments. This SNG RF terminal employs a 16-planar microstrip subarray antenna and an electronic antenna beam tracking circuit. The dimensions for the flat antenna are 60 cm by 60 cm. The terminal can promptly capture the satellite and transmit the video at 15-Mbps, 11-Mbps, and 7-Mbps coding rates. After satellite transmission experiments, we confirmed the stable transmission of a QPSK signal. This paper first describes the system configuration. It then shows the experimental results of the hardware performance such as antenna beam tracking performance and the radiation patterns. Finally, it shows the results of satellite transmission experiments of TV pictures. From these experimental results it is verified that (1) within the tilt angle of /spl plusmn/3 degrees, the off axis e.i.r.p. density level of the terminal is less than the technical standard specified in the ITU-R Recommendation 524; and (2) the SNG stably transmits TV programs and has a sufficient C/N margin of about 3 dB, 5 dB or 7 dB for the respective video coding rates of 15 Mbps, 11 Mbps, and 7 Mbps.

A Study of Adaptive Equalizer for APSK in the Satellite Broadcasting System

By making use of LDPC codes and a smaller roll-off factor, the advanced satellite broadcasting system proposed by us has a 30% higher transmission channel capacity in comparison with the current ISDB-S system. In addition, the transmission channel capacity can be more increased by using multi-level amplitude phase shift keying (M-APSK) modulation. However, the APSK signal is more sensitive to the non-linear distortion. Hence, a careful consideration for APSK should be paid for transmission over a satellite channel. In this paper, we report on adaptive equalizers that are designed for APSK transmission over a satellite channel. We also report on computer simulation results of equalized 16/32APSK performances under a satellite channel model and discuss the equalization effect for the advanced ISDB-S system transmission format.