3.2.1 12GHz-band Broadcasting-satellite Channel Plan In expectation of the World Radiocommunication Conference in 2000 (WRC-2000), we worked on examining a revision draft of the satellite broadcasting Channel Plan, which designates satellite orbital positions and broadcasting channels for each country. Although the previous Plan was established in 1977 (and partially revised in 1997), replanning procedures were to take place at the WRC-2000 after a resolution requesting the distribution of more channels for each country and consideration of satellite broadcasting system technical advancement. Our laboratories, in cooperation with related NHK departments, drafted a new satellite orbital Channel Plan based on the current one, which would give each Region 3 (Asia/Oceania) country a 12 channel assignment. This Plan would maintain interference under the regulated amount based on interference calculation for each satellite system through computer simulation we performed. The new draft Plan was presented to an expert group meeting of the APT (Asia-Pacific Telecommunity), which finalizes discussion 11.7 GHz 12.0 GHz 12.2 GHz 1 Previously assigned channels Newly assigned channels 3 5 7 9 11 13 15 17 19 21 23 Digital broadcasting regarding Region 3, in which an APT draft Plan was compiled based on the draft proposed by the STRL. At the WRC-2000 meeting held in Istanbul, Turkey, in May 2000, this APT draft Plan was utilized as a basic Plan, resulting in many parts of the draft being reflected in the Plan. Some of the STRL engineers also participated in the conference as members of the Japanese delegates, and contributed to replanning procedures. It was decided to assign each Region 1 country (Europe including former Soviet Union/Arabia/Africa) 10 channels, and each Region 3 country 12 channels. With regard to Japan, an additional four channels (17,19,21,23) for digital broadcasting were allocated (inserted figure) to the present satellite location at 110 east longitude. The existing eight channels (1-15 odd numbered channels) can now be used as either analog or digital. Therefore, Japan is now internationally recognized as using 12 channels (1-23 odd numbered channels) for digital broadcasting services (34.5MHz-channel band-width), and can transmit in a consecutive range of approximately 1GHz (11.7 GHz to 12.75GHz) from a 110 east longitudinal orbit as 12.75 GHz CS broadcasting-band (N-SAT-110) Channel assignments (BS/CS at 110 east longitude) Analog broadcasting BS and CS broadcasting service in total. We also attended at a WP6S (satellite broadcasting services) meeting at the ITU-R held in September 2000, and continued discussions on interference regulations for satellites and preparation for regulatory or procedural matters after the replanning process. 40
3.2.2 Advanced Satellite Broadcasting System Satellite Broadcasting System with No Service Interruptions Caused by Rain Research has continued on an advanced satellite broadcasting system, which will make it possible to reduce the broadcast interruption due to rain attenuation (Figure 1). In order to better understand the characteristics of rain attenuation, we have studied an estimation technique for the probability of rain attenuation, using 10-minute-rainfall data from nationwide AMeDAS (Automated Meteorological Data Acquisition System) measuring points. Comparative analysis of the maximum 10-minute-rainfall and the maximum rain attenuation probabilities (April through December 2000) within one hour of rainfall of 5mm observed in, Okinawa, and Kagoshima, revealed the following: 1) the relative frequency of both precipitation and attenuation can be approximated as being log-normal distribution, 2) an appropriate scaling to relate ten-minute precipitation and max. attenuation can help to overlap the cumulative relative frequencies with no dependence on measuring points (Figure 2). These results showed the estimation potential for peak rain attenuation possibility distribution in a certain location by calculating 10-minuterainfall data in the area, along with the frequency distribution of maximum rain attenuation at a standard point (e.g. ) for a one-hour period. In researching the use of on-board phased-array antennas for satellites, we proceeded with basic radiation pattern forming studies focusing on an array antenna configuration that combined a primary feed-horn array with a reflector. During fiscal 2000, a computing method was being developed that separately calculated both the relation between a far-field pattern and the electrical field distribution at the antenna aperture, and the relation between the aperture electrical field distribution and the driving amplitude/phase distribution for elements of primary feed-horn array. This technique allows an aperture distribution with a far-field pattern, which does not generate unnecessary radiation outside the service area, yet corresponds to the service area's rain attenuation distribution to be computed independently of the antenna configuration (direct radiating, single reflector, dual reflector). We also constructed a prototype antenna consisting of a 1.3m reflector and a 19-primary-radiator array for problem extraction on a feed horn array with reflector and for pattern forming Cumulative relative frequency 99.99% 99.9% 99.0% 90.0% 50.0% 10.0% 1.0% 0.1% 0.01% 1-hour-rainfall: 5mm Kagoshima 0.0 0.5 1.0 1.5 Maximum 10-minute-rainfall (logarithmic value) Cumulative relative frequency 99.99% 99.9% 99.0% 90.0% 50.0% 10.0% 1.0% 0.1% 0.01% Fukuoka Large phased-array antenna Hiroshima Osaka Increase in transmission power for an arbitrary area Necessary power for broadcasting services Figure 1: Advanced broadcasting satellite system with no service interruption by rain technique verifications, and then conducted a comparative analysis of the actual measured values and the design. Research on the amplifier used for the on-board array antenna continued on a miniature TWT with potentially high efficiency in comparison with the SSPA (solid-state power amplifier). Application of TWTs as array elements will require a condensed configuration of multiple TWTs in an interval of approximately one wavelength. To accomplish this, further improvements were made on a small-diameter input/output connection and an electron gun to achieve a 20mm 20mm TWT, as well as collector efficiency. This resulted in an output of 10W or greater and an overall efficiency of more than 40%. In relation to a national research project, "Studies on 21GHz-band Advanced Broadcasting Satellite System," which was launched in fiscal 2000, we pursued studies involving rainfall and rain attenuation analysis, broadcasting satellite system and services, and component technology developments such as array antenna technology and miniature TWT. We contributed to the national project with the results of this research. Nagoya Advanced Satellite Transmission System Severe attenuation of received signals by rain is observed in high frequency(21ghz or higher) bands leading to service interruptions. As one effective technique to resolve this problem, research continued on the 1-hour-rainfall: 5mm Kagoshima -1.0-0.5 0.0 0.5 Peak rain attenuation (logarithmic value) Figure 2: Maximum 10-minute-rainfall and peak rain attenuation cumulative relative frequency (April - December 2000) Sendai Sapporo super long block-length interleave transmission scheme. We proceeded with a hierarchical interleave transmission scheme that enables the combined use of multiple interleave periods. A prototype interleave system with multiple hard disks was manufactured experimentally. Investigation of a coded modulation scheme, which combines error correction coding and multilevel modulation, has also continued with the aim of adopting a higher channel-use efficiency modulation scheme for satellite transmission. 41
Insertion loss (db) 3.2.3 Microwave and Millimeter-wave Technologies Millimeter-wave Broadcasting System Research is being promoted on future broadcasting systems using millimeter waves with broadband propagation characteristics. During fiscal 2000, we conducted computer simulations to calculate coverage on the road assuming mobile reception. We also measured delay profiles using propagation experiments. A computer simulation was done to calculate coverage on the road using a residential map and a ray tracing method. Three areas in, the Kinuta area of Setagaya-ku, the Ginza Chuo-dori area, and the Shibuya Station area, which vary in building and road distribution, were selected for the simulation. As an example, the Kinuta area, which consists of a 500m square with one transmitting base station, showed that many of the surveyed areas received reflected waves along with direct waves without dependence on the reception carrier to noise (CN) ratio (Figure 1). We further studied the relation between the number of transmitting base stations and coverage on the roads in the abovementioned three areas. As a result, we clarified that 90% of the roads can be covered in any of the three areas by installing a maximum of 10 transmitting base stations per 500m square. The delay profiles for millimeter-wave propagation were experimentally studied in the 21GHz band. Although reception on non-line-of-sight road areas tends to involve a number of reflected waves by surrounding buildings, it was confirmed that reception with nearly no multipath disturbance can be achieved by use of a directional antenna to receive the appropriate reflected wave. Reception characteristics were also measured on non-line-of-sight road areas near intersections where reflectors were installed. This revealed that coverage on the road could be significantly improved by such reflector use, even in the case where the transmitting base station antenna is positioned at a low elevation. Microwave Devices Noting that the permittivity of liquid crystal changes greatly with application of a control voltage, we have been developing a microwave device whose transmission characteristics can be controlled electronically by liquid crystal. In fiscal 2000, improvements were made on an 0 10 20 1.5 Improved device Conventional device Glass substrate Microwave Reduction Frequency (GHz) Liquid crystal Ground plane 21.5 Figure 2: Insertion loss in-band frequency characteristics 100 (%) 90 Coverage on the road 80 70 60 50 40 20 10 Diffracted wave Frequency Bandwidth Transmission output Transmitting antenna Receiving antenna Reflected wave Direct wave 0 0 10 15 20 25 Reception CN ratio 21GHz 100MHz 1W 0dBi (10m height) 20dBi (1.5m height) (db) Figure 1: Coverage on the road calculation example experimental microwave variable delay line using liquid crystal (Figure 2). The conventional liquid crystal variable delay line had a large insertion loss. Attempts to reduce this insertion loss resulted in decay time deterioration, due to the need for a thicker liquid crystal layer. One of the solutions was the employment of a new type of liquid crystal, which changed the molecular alignment of the liquid crystal according to the frequency of the control voltage. This liquid crystal has alignment characteristics that allow its molecules to be aligned horizontally to the control voltage at low frequencies near d.c., and switch to vertical alignment when frequencies of several khz are applied. Attempts were made to utilize these characteristics for insertion loss reduction without decay time deterioration. We succeeded experimentally in reducing the insertion loss to approximately 9dB at 10GHz, while maintaining a decay time equal to the conventional liquid crystal variable delay line (Figure 2). We obtained a delay time change of 60ps in a 193mm line length, and an output phase shift of 215 at 10GHz, which showed the same delay characteristic as the conventional model. Frequency Sharing Regarding frequency sharing among the broadcasting and other services, we investigated the electromagnetic radiation from ADSL (Asymmetric Digital Subscriber Line) communications using a telephone line that would interfere with medium frequency radio reception. Control voltage Alignment film 60GHz-band Applications for broadcasting in the 60GHzband are under examination. The 60GHz-band has propagation characteristics suitable for large capacity short-range transmissions. As a method for households, including communal residences, where the direct reception of satellite broadcasting is difficult, we conducted research on how to convert BS-IF signal frequencies to the 60GHzband for re-transmission. We obtained encouraging results for the system's practical use. We also initiated basic research on 60GHz-band wireless cameras during fiscal 2000. 42
3.2.4 Phased Array Antenna Technology Multi-beam Receiving Flat Antenna for Multiple Satellites Research continued on a multi-beam receiving flat antenna for multiple satellites capable of the simultaneous reception of signals transmitted from satellites in different orbital positions. A microstrip patch antenna makes it difficult to obtain good receiving characteristics covering all frequencies in the 12-GHz band for satellite broadcasting (approx. 1GHz at 11.7-12.75GHz), including the service bandwidths of both BS and CS satellites. For this reason, we recently constructed experimental antenna elements that allow us to receive radio waves coming from several directions simultaneously. With these, we were able to configure a parasitic patch near the patch antenna element. Evaluation tests revealed that this antenna could obtain good Integration Amplifying element Output line Metal base Slots Amplifier Slot-array plate Slots Input Electromagnetic coupling-type single element active slot antenna Structure of low-type active antenna Sectional view frequency characteristics and cross-polarization discrimination over the abovementioned bandwidths. We further arrayed this antenna element, and fabricated an active sub-array antenna with an integrated low-noise amplifier utilizing high electron mobility transistors (HEMTs). Portable SNG Antenna With the aim of realizing a portable SNG terminal, studies are being conducted on a low profile, lightweight antenna that integrates such active elements as a power amplifier. Using the active integrated antenna structure studied through electromagnetic field simulations during fiscal 1999, we constructed an experimental electromagnetic couplingfed active slot antenna, and evaluated its characteristics. As a result, it has been found that good Radiation Amplifying element radiation characteristics are obtained by applying the values obtained during the electromagnetic field simulation to the distance between the output line of the amplifier and the slot plate, as well as to the metal groove size. We also promoted studies of the array structure (inserted figure), which consists of a layered slot-array plate fastened onto the upper portion of the abovementioned electromagnetic coupling-fed active slot antenna. 43
3.2.5 Optical Transmissions Dense wavelength division multiplexing (DWDM) technology is the basic technology that is utilized for optical video routing networks for broadcasting stations, which enables the transmission of large quantities of video materials between studios. Research has continued on a narrow-bandwidth wavelength-tunable filter for realizing advanced functions, such as high-speed video signal selection and routing on optical networks using DWDM technology. In order to attain both narrow-bandwidth and high-speed response in an optical filter, we proceeded with the examination of an optical waveguide filter with a Fabry-Perot structure. Although this filter has the advantage of having a fast switching time of 50 nsec., it has the disadvantage of having unnecessary transmission peaks over the frequency span where the DWDM signals are allocated. To resolve this issue, we developed an optical filter using two Fabry-Perot filters with slightly different transmission peaks. These are cascaded to suppress unnecessary transmission peaks, thus realizing a single transmission peak in a wide range of wavelengths (inserted figure). Computer simulations clarified that wavelength multiplexing in 0.1nm intervals is feasible with this filter. We fabricated a prototype optical Greater Transmission waveguide filter and tested the cascaded filter operation. Based on the results obtained, we compiled a design guideline for cascaded filters used for DWDM. Optical filter I Optical filter II Cascade-type filter Wavelength Required suppression Transmission characteristics of cascade-type optical waveguide filter and corresponding component filters (optical filter I, II) 44