Aiichiro Tsuzuku

A Study of BER Degradation Caused by Phase Noise in OFDM Transmission

Digital terrestrial television broadcasting began in Japan in December 2003. The phase noise of the local oscillator degrades the bit error rate of the Orthogonal Frequency Division Multiplexing (OFDM) transmission. We have conducted indoor experiments to find the relationship between the phase noise level and the bit error rate. We found that the degradation of the bit error rate could be altered by the offset frequency of the phase noise, and the OFDM receiver could suppress the phase noise in the low offset frequency of-20dB/dec. In this paper, we also propose new methods of regulating the phase noise level in the local oscillator.

Digital Transmission Techniques that support Digital Broadcasting. OFDM Signal Degradation by Amplifiers and Measuring Method of the Nonlinearity.

An OFDM signal is easily degraded by amplifier nonlinearity. A method for measuring such nonlinearity has been developed and tested in two ways : vector measurement using the two-tone method and comparison between a sinc-shaped input signal and the output signal. Four amplifier characteristics were measured with the methods and represented as AM-AM/AM-PM conversion characteristics. Using these results, computer simulation was run to determine the effect of nonlinearity. OFDM signals were generated and the CN ratios were measured. The results agreed with those of the experiments. Testing of the predistortion in the amplifier with the most remarkable AM-PM characteristic confirmed the simulated predistortion.

Digital Broadcasting. Development of OFDM Modem Providing the Function of Graceful Degradation.

Terrestrial television broadcasting stations have been asked to use frequency bands more efficiently because of the shortage of frequencies. Digital transmission systems are therefore being extensively studied, particularly those using OFDM. We have developed an OFDM modem for use in digital terrestrial television broadcasting. Its characteristics are described in this paper. The modem has a function called graceful degradation to compensate for the cliff effect which is commonly seen in digital radio transmission systems. Of several graceful degradation technologies, we chose a method that uses multiple constellations. Computer simulations confirmed that the graceful degradation system made up of different constellations can compensate effectively for an insufficient D/U ratio and an extremely long excess delay time.

Advanced satellite broadcasting experiment using Japan's R&D satellite COMETS

The Communications Research Laboratory (CRL) and the National Space Development Agency of Japan (NASDA) have been studying an advanced satellite broadcasting system that uses the K-band such as 21 GHz band. This study has evolved into an experimental satellite project called COMETS (Communications and Broadcasting Engineering Test Satellite), which will be launched in 1997. The performance of the components, such as the high-power TWTA and multi-beam antenna, and planned experiments are described.

Satellite borne multibeam antenna for 21 GHz band regional satellite broadcasting

The Communications Research Laboratory (CRL) and the National Space Development Agency of Japan (NASDA) have been studying an advanced satellite broadcasting system that uses 21GHz band which was allocated in WARC-92 as the band for studio quality HDTV satellite broadcasting. Regarding this study, CRL and Toshiba corp. have developed a breadboard model (BBM) of the satellite borne 27/21 GHz band multibeam antenna as a key satellite component for future regional satellite broadcasting system. This paper describes the antenna configuration and the results of designing and measurements.

Broadcasting Technologies for Effective Utilization of the Radio Spectrum.

近年, 通信・放送分野のみならず, 電波測位・航法, リモートセンシング, 産業等, 多くの分野での電波利用が進み, 周波数の有効利用がますます重要となっている.放送分野では, その技術の歴史が, 周波数有効利用技術の歴史ともいえる.ここでは放送分野での周波数有効利用の例を紹介するとともに, 新周波数帯の開拓に関する話題を紹介する.

Study of the Efficient Usage of the TV Frequency Band.

This paper describes a method of estimating the service area of a TV broadcast, using the height of the land and the database of the TV broadcasting station. As an example we use it to optimize the position and strength of a new TV station. Design requirements for allocating digital audio broadcasting (DAB) using the TV band are also given. Examples of the calculated coverage are presented.