This paper introduces a state-of-art on an ultra-wideband (UWB) technology in intelligent transport systems (ITS). To examine the detection performance of a UWB short-range radar for vehicular applications, we developed a 26-GHz band short-range UWB radar system with an embedded compact MMIC-based RF module. In this paper, we briefly comment on the current regulatory environment for UWB radar systems by outlining the structure of an international organization involved in examining the regulatory status of these systems. We then describe the principles of detection and system design for impulse radar, the radar system that we developed, and a MMIC-based RF module as well as the performance of these devices. We measured their performance in a series of laboratory experiments and also measured UWB radar cross sections of an automobile. The results of our experiments suggest that our radar system is capable of detecting targets with a range resolution of around 9 cm.

This paper describes multi-branch Wilkinson power dividers using multilayer MMIC technology. Circuit configuration is simplified and the circuit area is effectively minimized using thin film microstrip lines. An impedance transformer between the input port and the divided point is introduced to complete impedance matching and reduce insertion loss in multi-branch power dividers. Size-reduced planar-type 2-, 4-, and 8-branch Wilkinson power dividers are produced and performed well.

Novel transmission line structures for multilayer MMICs, which are constructed with thin dielectric layers on a GaAs wafer surface, are theoretically and experimentally investigated. Five thin film transmission line structures are discussed in this paper: (1) Microstrip lines, (2) Inverted microstrip lines, (3) Triplate lines, (4) Trapezoidal microstrip lines and (5) Valley microstrip lines. These transmission line structures are fabricated using thin polyimide films and chemical etching.

This paper reviews an application of optical techniques to Microwave Signal Processing (MSP), such as frequency multiplexing using external optical modulators (EOMs), and microwave frequency add-drop multiplexing and mixing using semisconductor optical amplifiers (SOAs), as well as microwave phase control in the optical domain. The cascaded EOM links can be applied to microwave and millimeter-wave signal distribution networks. The add-drop links using SOAs can make it possible to realize a compact and cost-effective radio repeater for radio signal distribution. The several SOA mixing link configurations are also described.

This paper proposes fiber optic link configurations for use in microwave and millimeter-wave transmission Higher frequencies,such as millimeter-waves, are well suited to transmission of broadband signals. Photodiodes can operate simultaneously as optical detectors and microwave frequency mixers thanks to their inherent nonlinearities. This allows us to increase the output radio frequncy. But, this also generates undesired spurious frequencies, necessitating the use of microwave filters. We discuss here two fiber optic link configurations, i.e., balanced/image canceling photodiode mixing links utilizing the combination of microwave functional components and optical devices to suppress the local/image frequency without filters. These configurations are experimentally investigated at microwave frequencies and local/image frequency suppression is successfully demonstrated.

This paper describes the characteristics and application of lumped double crosstie slow-wave transmission lines (DCT-SLWs) which we previously proposed. Firstly, the relationship between the DCT-SLW's characteristics and their parameters, i. e. triplate stripline widths and inductor resistances, are numerically and experimentally investigated. Excellent slow-wave lines with both high slow-wave factors (1240) and a wide characteristic impedance range (35100Ω) are achieved in good agreement with calculated results. A 50-Ω DCT-SLW that reduces circuit area more than 80%, and has an insertion loss less than that of 22-µm-wide TFMS lines is achieved by adapting a low-loss inductor in the frequencies below 14.5 GHz. Secondly, the application of DCT-SLW to non-dispersive, dispersive delay lines and branch-line hybrids is discussed. Specifically, very small 4-GHz-band branch-line hybrids are fabricated in a chip area of 0.7 mm2. Fundamental microwave circuits utilizing slow-wave lines in MMICs are demonstrated for the first time.

An optoelectronic technique to control both the amplitude and phase of a radio frequency (RF) signal is presented that uses two electrically controllable birefringence mode nematic liquid-crystal spatial light modulators (ECB mode nematic LC-SLMs). An experimental circuit was built and its performance was examined. The intensity could be changed down to -25 dB, and a phase shift of up to 240 degrees was achieved, by changing LC-SLM supplied voltages. Carrier-to-noise ratio (CNR) and intermodulation characteristics of an RF signal were measured. It was, for the first time, found that CNR was not degraded by the amplitude control and phase shift performed by the LC-SLMs.

This paper reviews fiber optic link techniques from the microwave and millimeter-wave transmission point of view. Several architectures of fiber optic links are reviewed. The application of MMIC technologies to the optical receivers are discussed and 26-GHz subcarrier transmission experimental works are described. Novel fiber optic links which utilize both optical device nonlinearities and microwave functional circuits are also reviewed. A system concept of millimeter-wave cellular radio using fiber optic links is finally discussed.

A vertically connected wireless link (VCWL) using the 60-GHz band has been proposed for reliable and economical transmission of various satellite media to individual building units. This paper describes a prototype of such a VCWL that employs a self-heterodyne scheme. The CNR performance of the prototype was evaluated in a real environment. The results showed that signals transmissions of the required quality could be delivered to the units of a five-story apartment. For the placement of multiple transmitters in close proximity, the prototype required 12 dB of CIR.

The 70-GHz band propagation characteristics of two different hot-spot zones are measured and analyzed: (1) a transmitter fixed to a ceiling servicing the area beneath it (type A), and (2) a transmitter fixed to a wall servicing the area in front of it (type B). Measurements were made in two different settings, a lobby and a train. The results show that zone B produces a smaller delay spread in relation to distance. A comparison of the use of vertical and circular polarization shows that circular polarization produces a smaller delay spread in the type B zone. The results also indicated that the function of the delay spread value for the distance in a lobby and train in type B zone.

A circuit configuration suitable for MMIC's (Monolithic Microwave Integrated Circuit) has been proposed. It is Planar MMIC possessing slotlines, coplanar waveguides etc. on the upper side of the substrate. Novel Planar MMIC hybrid circuits have been fabricated and tested at 26 GHz band.

The fiber-optic sectorized remote antenna system by using the radio frequency (RF) optical transmission technique was promising for increasing the number of subscribers in the millimeter-wave broadband wireless access (MMW BWA) networks. To realize the cost-effectiveness of the fiber-optic sectorized remote antenna system covering four areas, we reached the conclusion that the best multiplexing schemes were the sub-carrier division multiplexing (SCM) of the intermediate frequency (IF) signals of 2 GHz for the down link, the coarse wavelength division multiplexing (CWDM) with the IF signals optical transmission for the up link and 1.3/1.55 µm-WDM for multiplexing the down link and the up link. In addition, the target specifications of this SCM-CWDM system were described, and the designs of the carrier to noise ratio (CNR) and the third order intermodulation distortion (IM3) were examined.

A simple millimeter-wave quasi-maximal-ratio-combin-ing antenna diversity system based on the millimeter-wave self-heterodyne transmission technique is described. The millimeter-wave self-heterodyne transmission technique is useful for developing millimeter-wave systems with enhanced characteristics in regard to system miniaturization, development and fabrication cost, and the frequency stability of the signal transmission. We also show that applying this technique with an antenna diversity receiver configuration can easily solve a problem peculiar to millimeter-wave systems--the fact that the transmission link always requires a line-of-sight path--without requiring hardware designed with millimeter-scale precision. In this paper, we theoretically analyze the operating principle of a combining antenna diversity system based on the millimeter-wave self-heterodyne transmission technique. We further prove that we can obtain a diversity gain in accordance with that of a maximal-ratio combining diversity system without resorting to any complicated control of the received signal envelope and phase. Our experiments using the simplest two-branch diversity structure have validated the operating principle derived in our theoretical analysis. Our results show that a received CNR improvement of 3 dB is obtained as a diversity gain. We also demonstrate that circuit precision corresponding to the wavelength of the intermediate frequency, rather than to the millimeter wavelength, is sufficient to obtain the diversity effect when we control the signal phase or delay in combining the received signals.

A new configuration is proposed for an optoelectronic network (OEN) using microwave frequency mixing and multiplexing. The mn OEN consists of m optical sources, m-parallel n-stage cascaded optical intensity modulators, and m-photodetectors. The mn OEN matrix is theoretically discussed, and 12, 22 and 33 OENs are analyzed in detail. The 22 OEN, which mixes and multiplexes microwaves, is further investigated and the theoretical prediction derived from OEN equations is experimentally confirmed.

An optoelectronic beam forming network (BFN) is presented for a single beam, 3-element phased array antenna that utilizes electrically controllable birefringence mode nematic liquid-crystal cells (ECB mode NLC cells) for phase shifting and amplitude control. In the circuit, a microwave signal is carried by a pair of orthogonal linearly polarized lightwaves (signal and reference lightwaves) using the optical heterodyning technique. Birefringence of liquid-crystals is utilized to selectively control the phase of the signal and reference lightwaves. Because an interferometer is formed on a single signal path, the complexity of the optical circuit is much reduced, compared to the BFNs based on arrays of Mach-Zender interferometers. A prototype circuit is built using laser sources of 1.3 µm, and its performance experimentally examined. With small deviations among the three cells, phase shifts of up to 240 degrees are achived for MW signals from 0.9 GHz to 20 GHz with good stability; attenuation of more than 18dB is achieved. An optoelectronic technique for parallel control of amplitude and phase of MW signals was developed.

This paper describes the outline of recent standardization activities for Radio on Fiber (RoF) transmitter by IEC TC103/WG5. RoF transmitter consists of optical fibers, electrical to optical (E/O) converter, and optical to electrical (O/E) converter. IEC TC103/WG5 is working on standardization on measurement method of E/O and O/E devices, and technical specification of RoF transmitter. This paper overviews those standardization activities which are being developed by TC103/WG5 as well as the National Committee of WG5.

This paper proposes a photonic integrated beam forming and steering network (BFN) that uses switched true-time-delay (TTD) silica-based waveguide circuits for phased array antennas. The TTD-BFN has thermooptic switches and variable time delay lines. This TTD-BFN controls four array elements, and can form and steer a beam. An RF test was carried out in the 2.5 GHz microwave frequency range. The experimental results show a peak-to-peak phase error of 6.0 degrees and peak-to-peak amplitude error of 2.0 dB. Array factors obtained from the measured results agree well with the designed ones. This silica-based beam former will be a key element in phased array antennas.

The performance of a traveling wave Mach-Zehnder external optical modulator (EOM) mixer is described and compared with a conventional diode mixer's performance. Additionally, by incorporating external circuitry, the EOM mixer can provide single sideband suppression in addition to the inherent local oscillator suppression. The basic frequency mixing function of the EOM mixer is first described theoretically and then extended to the sideband suppression case. The performance of both configurations is also presented. Achievable electrical isolation between LO (carrier) and RF (upconverted data signal at LOIF) frequencies is greater than 95 dB and total link conversion loss is 37 dB in this demonstration with a laser diode source. Sideband suppression of greater than 43 dB with respect to the desired sideband at the photodetector output is achieved.

This paper proposes an MMIC image rejection mixer and an MMIC balanced mixer employing multilayer microstrip lines and high-electron-mobility-field-effect-transistor (HEMT)s with a LUFET configuration (line-unified HEMT module). The advantage of the mixers is remarkable chip size reduction by the combination of the two technologies. The multilayer microstrip line, in which one microstrip line is placed upon another, is used for stacking passive circuits, e.g. a 90 hybrid and distributed lines, to reduce the chip-area occupied by transmission lines, and to allow flexible line allocation. The line-unified HEMT module provides all functions required for in-phase/out-of-phase power divider/combiners in HEMT electrode and unified coplanar lines configuration. A 29-32 GHz image rejection mixer and a 3-27 GHz balanced mixer are realized in only 1.6 mm 1.0 mm and 1.8 mm 1.2 mm MMIC chip size, respectively.

The design and performance of a millimeter-wave video transmission system using 60-GHz band for indoor broadcasting-satellite (BS) signals transmission is presented. This system can transmit multiple video signals such as broadcasting signals and user-oriented signals to a television set indoors. To minimize the local oscillator's frequency offset and phase-noise effects, the system uses a remote-heterodyne scheme. Based on the concept, the system is developed to meet required carrier-to-noise-power-ratio (CNR) and 3rd-order intermodulation (IM). The BS transmission was experimentally done by using the transmitter and receiver setup. The results are very promising and show the feasibility of the system.