In this study, we present experimental results of bit error rate (BER) characteristics of 6Mbps QPSK signal, in the condition of various CTBs induced under fifty one VSB-AM channels optical hybrid transmission. We clarified the following items. (1)BER dependency of CTB cannot be specified by average CTB values. (2)In the case that maximum CTB values are considerd, amplitude probability distribution of CTB should be taken into account-(8)Amplitude probability distribution of CTB changes depending on modulation depth of DFB-LD.
This paper describes the development of an adaptive weighted code division multiplexing (AW-CDM) transmission system that employs a powerful coherent detection using pseudo-noise sequence as a pilot. In order to provide "graceful degradation" (variable picture quality with local reception conditions) of TV reception, hierarchical information is divided into 3 groups of spread-spectrum subchannels. Each group has a different priority and, thus, a different threshold. Hardware simulation for the AW-CDM reveals sound performance under strong propagation. This hierarchical transmission system can be used to detect problems that occur when a digital transmission is in its threshold, thus preventing the abrupt breakdown of digital TV systems.
Recently, high gain converter is applied widely to the BS receiving antenna and the Japanese BS broadcasthig channels will increase to eight in 1997. In such a situation, it is required to inspect the conventional measuring method of the intermodulation interference characteristics of the BS converter. We studied the problem of the conventional measuring method and proposed the new measuring method using the radiated seven signals of 12GHz band.
The described is the triple wave feeding circuit of radio antenna : its matching circuit design and the construction result. The circuit applying the conventional method for feeding of multiple medium waves is not suitable, for it deteriorates intra-band standing wave ratio (SWR), apparently when the antenna length is shorter than λ/4. We could realize triple feeding, however, since we made the SWR improved by way of employing the multi step impedance change at the base of radio antenna.
Four VHF television transmitting stations had ever been located seperately in Fukuoka city. These stations concentrated into new Fukuoka Tower and started to transmit their television programs all at once on June 14th in 1993. In this report we describe a background of this large-scale removal of television transmitting function, an outline of NHK's transmitting facilities and its construction. We also give a account of technical problem that we had studied to achieve all our aims.
Diffracted field from a strip is generally calculated as a sum of many components of diffracted fields, that is, single diffracted fields from two edges and multiple diffracted fields between two edges. This paper reports that these components were confirmed through measuring monostatic back scattered fields from a strip.
Mobile stations are widely spreading in recent information societies. However some difficulties occur when they are used in an underground building. Electromagnetic wave decays more rapidly in a tunnel than in the free space. In this paper, we perform an experiment based on the microwave simulation and compare the experimental results with an approximate solution in oder to investigate how electromagnetic waves propagate in rectangular cross-type and multi-cross-type tunnels. Present results give some important knowledges for mobile communications in the complicated underground buildings.
Microstrip antenna usually needs a cover to protect antenna element. It has to be designed effectively as it has higher gain. In this paper, we present a numerical analysis of circular patch microstrip antenna with dielectric element using the approach based on Hankel transform domain analysis. Several numerical results are compared with experimental data.
For the base station antenna of cellular mobile telephone systems, a beam tilting antenna, which achieves down beam tilt in the horizontal plane to control the zone shape, is desired. In this paper, the beam tilting of the antenna with sleeves is described. As the sleeve can control the phase of the current distribution effectively, the antenna with sleeves is effective for the beam tilting.
The input impedance of tubular dipole antennas are determined by the method of moments. The method of moments formulation used is based on a multifilament current approximation and solves for the surface currents of the antenna. And the network formulation was used to calculate the input impedance of the tubular antenna. The results of the analysis are compared with King's results.