We developed an evolutional wideband (3M〜26MHz) short-wave transmitter with an output of 1kW using PSM (Pulse Step Modulation) that digital (DRM: Digital Radio Mondiale) and analog AM modulation are possible. This equipment employs digital processed PSM method that high sound quality can be easily achieved in the modulation section and class E amplification for obtaining higher efficiency in the PA section composed of eight 125W PA. In addition, new output circuit for phase compensation of the load impedance. As a result, in the 125W PA, a drain efficiency of 95% at 3.925MHz and 86% at 25.885MHz was obtained. As analog AM characteristics, S/N of 54dB and above, distortion factor of 4% and under were obtained ranging from 3M to 26MHz. In digital modulation (DRM), S/N of about 24.5dB that satisfies target performance sufficiently was obtained.
It is necessary to establish the evaluation technology for the effect of SFN-GF for the digital terrestrial television broadcasting. At first, the three-dimensional space numerical model corresponding to the propagation model of the metropolitan is constructed. And, it is tried to analyze a local poor reception by the computer simulation of the three-dimensional space propagation. This report shows comparative study of the electric field value by the theoretical model and field measurements.
A novel non-linear signal processing method is proposed in this paper. Enhancers are commonly used in real time signal processing machines to improve the resolution. It only improves the feeling of human visual systems. It is almost impossible to create the elements over the Nyquist frequency as long as we use the linear signal processing methods. SR (Super Resolution) is a very interesting research field and many ideas have been proposed. However, these ideas have not been discussed in the frequency domain and we do not know some of them create the element over the Nyquist frequency. We propose a novel signal processing method that creates the elements over the Nyquist frequency.
Digitization of broadcasting began in 1990s, and it was said to be superior to analog because of its clear vision, multi-channel service, and data broadcasting. On the other hand, digitization costs a lot of money, but its business model remains unclear in many fields. For example, Britain's DTT broadcaster ITV Digital went bankrupt in 2002, and DTT had to be changed to the model of 「Freeview」. After that, although some service remains unpopular because of losing money or disturbance by competitors, digitization in general gathered momentum. I report in this paper about the recent development of DTT, HDTV, IPTV and Mobile TV in the world.