Terrestrial digital television broadcasting is going to put into operation in Europe and America. In Japan, discussion is actively performed to standardize the specification until 1999. OFDM, Orthogonal Frequency Division Multiplexing, is advantageous to multipath distortion and SFN(Single Frequency Network). NHK proposed terrestrial ISDB(Integrated Services Digital Broadcasting)system based on OFDM. This paper describes outline of terrestrial ISDB and its transmission performance.
We propose a new detection technique of the transmission mode for OFDM systems. A main advantage of the technique is that no demodulation is required for OFDM signals nor even special carriers. The effective symbol duration is detected by the autocorrelation of the received signal with a suitable delay, and the guard interval is detected by estimation of the period of the autocorrelated signals. Numerical results show that the detection error rate of 10^<-2>can be realized at lower CNRs of -5dB with the observation duration of 3 maximum symbols in case of 4 possible transmission modes (8k and 2k-FFT systems with the guard intervals of 1/4 and 1/8).
OFDM transmission system including nonlinear AMPM amplifier is simulated using one of communication system design support tool. Many parameters can be changed while simulation program is running. Thus simulation efficiency was remarkably improved. Simulated BER(Bit Error Rate)s due to C/N and IBO(Input Back Off) well coincide with actually measured data. Future issues are pointed out.
Multi-carrier transmission via one satellite transponder is simulated using one of communication system design support tool. Many parameters can be changed while simulation program is running. Thus simulation efficiency was remarkably improved. Using this simulation, 4 channel up-link into one satellite transponder system is analyzed. Effects of non-linear amplifier(TWT)on BER(Bit Error Rate)and inter-channel interference are discussed.
In recent years, the office, hospital and so on are equipped with various electric and electronic devices. Electromagnetic waves that are radiated from these devices, reflect on the wall of the building or penetrate to the wall from outside, then they interfere to the other device. It's necessary to decrease the reflection and penetration by the concrete wall. In this paper, we analyzed the reflection and transmission characteristics of the corrugated surface wall by the FD-TD method. Its surface has asperity form that newly proposed. As a result, we obtained that the corrugated surface wall consumed a power of electromagnetic wave in the wall more than a plain wall. Then the corrugated surface wall can oppress reflection and transmission.
Until now electric field intensity maps which are used to predict service areas of FM or television broadcasting stations have been made manually. In this method, a lot of skills and efforts are required. So we have developed an automatic computing program named as Ele-MAP k which uses the numerical topographical map "mesh-data". This paper introduces Ele-MAP and explain the theories on which Ele-MAP is based. And we analyze difference between calculated and measured values.
Almost all broadcasting systems and their equipment would be digitalized in the near future. Investigation of digital broadcasting has been going on for a long time, aiming at a realization of improvement of picture quality, new services, system flexibility, etc. Japanese digital broadcasting systems under development have a lot of technical merits, for example, a high transmission capacity and a hierarchical transmission scheme, compared to American and European systems. This paper discusses about the systems towards the realization of digital satellite broadcasting.