Fundamental perspective of high power devices and amplifiers for use in wireless communication systems are described in this paper. First, high power devices and device modeling techniques are presented, focusing on the emerging device technologies such as wide bandgap devices (GaN, SiC) and SiGe devices. Then the commercially available device, circuit and system simulators for wireless communication applications are introduced. Recent active load-pull measurements have made a remarkable progress in fundamental, harmonic, and envelope frequencies for high efficiency and low distortion designs. In addition, pulsed DC/RF and on wafer load-pull measurements have also become popular, which are briefly reviewed. Finally the advances in high power amplifier design techniques for achieving high efficiency and low distortion are presented.

In the FDTD simulation of microwave circuits, a device in very small size compared with the wavelength is often handled as a lumped element, but it may still occupy more than one cell instead of a wire structure without volume routinely employed in classical extended FDTD algorithms. In this paper, two modified extended FDTD algorithms incorporating a lumped element occupying more than one cell are developed directly from the integral form of Maxwell's equations based on the assumption whether displacement current exists inside the region where a device is present. If the displacement current exists, the modified extended FDTD algorithm can be represented as a Norton equivalent current-source circuit, or otherwise as a Thevenin equivalent voltage-source circuit. These algorithms are applied in the microwave line loaded by a lumped resistor and an active antenna to illustrated the efficiency and difference of the two algorithms.

Directional couplers with flat coupling are designed by using an asymmetrical coupled-HNRD-guide consisting of two HNRD guides of different cross sections arranged closely. First, propagation characteristics of the asymmetrical coupled-HNRD-guide are analyzed by the transverse resonance technique. Next, the whole directional couplers including tapered sections are designed from the S-parameters of the coupled HNRD guides derived from a superposition of the even-like and odd-like modes. Finally, the validity of the design procedure is confirmed by an em-simulator (HFSS).

This paper presents a miniaturized reverse-phase hybrid ring by the use of shunt capacitors, and successfully designs a very miniature hybrid ring of a 0.28-wavelength circumference with a wide bandwidth comparable to the regular reverse-phase hybrid ring based on the equivalent admittance approach. Moreover, a method of broadening the bandwidth with adding a matching network consisting of a very short transmission line and two shunt capacitors at each port is also described. The validity of the proposed design is demonstrated by electromagnetic simulator (Sonnet em) for a uniplanar hybrid ring.

This paper describes a three-port power divider with compensation networks for non-ideal isolation resistor. The compensation networks consist of two pairs of transmission lines and cancel out the parasitic reactance of the non-ideal isolation resistor. The design equations to provide perfect return loss and isolation at a center frequency are presented. The availability of the proposed power divider has been verified by the comparison between calculated and experimental results in the Ku-band.

A high temperature superconductor (HTS) 5 GHz 10-pole bandpass filter (BPF) is designed by using coplanar waveguide (CPW) quarter-wavelength resonators. The 10-pole Chebyshev BPF has a center frequency 5.0 GHz and a fractional bandwidth 3.2%. Based on an equivalent circuit with J- and K-inverters, the filter is first designed by using an EM simulator. Next an optimization algorithm is employed to diagnose the discrepancy between the filter responses calculated by the EM simulator and the equivalent circuit. Adjustment of the dimensions of the filter is made thereby. The frequency response of the adjusted filter satisfies well the design specifications.

A design methodology of bandpass filters (BPFs) using λ/4 resonators for improving out-of-band characteristics is proposed. Firstly, the basic characteristics of various λ/4 resonators are examined. In this study, we focus on four types of λ/4 resonators, i.e., (1) direct-coupled λ/4 resonator, (2) loaded-element λ/4 resonator, (3) tapped λ/4 resonator and (4) loaded-element tapped λ/4 resonator. Secondly, the application examples of BPFs with improved out-of-band characteristics are provided. We examine the improvement of filter characteristics, i.e., sharp skirt characteristics and low spurious responses. The results of this study lead us to the conclusion that the methodology is very useful for improving the out-of-band characteristics of the BPFs using the λ/4 resonators.

Adaptive antenna is a promising to increase the spectral efficiency of mobile radio systems. We developed a compact, cost effective planar Butler Matrix as a beam forming network of a multi beam antenna. This circuit consists of a thin substrate that the conductor attaches to both sides, and two thick substrates that the ground conductor attaches to one side. In this circuit, coupling by crossover causes amplitude and phase error of the Butler Matrix. By narrowing the strip width of the crossover, crossover coupling can be suppressed 10 dB. The measurement results of the experimental 88 Butler Matrix were 0.75 dB amplitude deviation, 9.5 degree phase deviation and VSWR of less than 1.15 within the relative bandwidth of 10% at 900 MHz band.

Transmission characteristics of a high permittivity NRD guide were investigated. A preferable operating mode of the high permittivity NRD guide was newly identified and the wide bandwidth and low loss nature of the millimeter-wave region were observed. Moreover, a technique for construction of a millimeter-wave antenna was developed based on the high permittivity NRD guide. The novelty of the present technique lies in the use of a simple radiator, which consists of a tapered dielectric strip of simple structure which has good compatibility with millimeter wave integrated circuits. Since this radiator has a broad radiation pattern, a new type of antenna compatible with millimeter-wave integrated circuits for marine radar use was fabricated by locating the radiator at the focal point of a cylindrical parabolic reflector. Suitable beam patterns with half-power beam widths of 4in the azimuth plane and 38in the elevation plane can be obtained at 35 GHz.

A slot pair array using a post-wall waveguide is a promising candidate for a Fixed Wireless Access (FWA) sector antenna to be used in a base station. This array is formed by a traveling wave antenna, and therefore its main beam direction varies with frequency. To overcome this difficulty, we propose a new structure that comprises of a cosecant array and an additional Talor array. This structure can fix the main beam in a constant direction whilst maintaining a cosecant radiation pattern. We conducted an investigation based on an array factor, and the validity of the method was confirmed by experiment.

The radiation patterns are synthesized by properly disposing surface variations on dielectric rod waveguides. The genetic algorithm (GA) is applied for searching the optimum disposition of variation sections. A very fast calculation method used in the optimization is presented. The guided waves are related in the form of a 2-port circuit and the radiation field is expressed by superposition of the waves from variation sections. Various conical beams can be synthesized. Short variation sections and combination of several variation sections with different height are used to improve the synthesis performance. The ripple of the mainlobe and the sidelobe levels become small. Spherical sector patterns with a steep fall are synthesized and the agreement with the experimental values is confirmed.

A phased array behavior of a unilaterally coupled active antennas has been investigated. The active antenna is composed of a patch antenna and a parallel feedback type oscillator which can be coupled unilaterally to other oscillators without other nonreciprocal components. Numerical calculations of the reduced equations describing the behavior of the coupled oscillators array demonstrated that the phase differences between the oscillators can be varied up to about π/2 by giving the frequency changes from the injection locking frequency to the oscillators except of the first one. The oscillator mounted with the varactor diode for wide tuning range exhibited the property suitable for constructing the unilaterally coupled array. In the experiments at X-band, the electromagnetic wave radiated from the five element array was successfully scanned.

Two types of p-i-n diode devices, namely an amplitude shift keying switch and a phase shift keying switch, were developed by using an NRD guide at 77 GHz. In order to apply these devices to radar systems, an SPDT switch with a low insertion loss of less than 2.5 dB and a high isolation of more than 25 dB was fabricated by using the former switch. Moreover, a BPSK modulator, composed of the latter switch together with a circulator and a ceramic resonator loaded band-pass filter, was designed and evaluated for use in spread spectrum radar systems in this frequency range.

To measure temperature dependent complex permittivity of dielectric materials, a rectangular cavity resonator with a heating system has been developed. In the experiment, microwave power with the frequency of 2.45 GHz is applied to heat the dielectric material. In order to reduce the error of the complex permittivity of dielectric material obtained from the perturbation method, an electromagnetic (EM) field simulator is applied which uses the Transmission Line Modeling (TLM) method. The uniformity of the temperature is also discussed by the use of heat transfer equation which applies the results of TLM simulation. It is found from the results that the accurate temperature dependence of complex permittivity of the material can be obtained by the method presented here.

We newly propose an optical coherence domain reflectometry for optical subscriber networks with measurement range enhancement. This reflectometry is based on our own technique to synthesize an optical coherence function. An optical switch after a light source generates optical pulses, which select the measuring region, in which one coherence peak is scanned with high spatial resolution. An optical fiber loop delay line including a frequency shifter is placed in a reference-path of the interferometer. In this method, the measuring region could be easily changed by the hetelodyne intermediate frequency selected at the electronic band pass filter. In the basic experiments, the reflections at 5 km distance are measured with a spatial resolution of 8 cm, and the change of the measuring region is successfully demonstrated.

This paper describes a method for assessing the structural integrity of International America's Cup Class (IACC) yachts using a fiber optic distributed strain sensor. IACC yachts are made of advanced composite materials designed for high stiffness and lightness, however, a number of critical accidents have occurred during sailing. So we developed a health monitoring system and applied it to two Japanese IACC yachts to measure the distributed strain by using an optical fiber sensor installed in their hulls. We then estimated the three-dimensional distributed strain and compared the results with simulated data obtained by finite element analysis (FEA) to confirm the designed strength of these yachts.

A simple phase detector reducing the pattern dependent jitter in clock recovery circuit is developed in this paper. The developed phase detector automatically aligns the recovered to clock in the center of the data eye, while producing no ripple to the control voltage in locked condition of the PLL based clock recovery circuit. The UP and DOWN signals are separately generated to align them in locked condition. Thus, no explicit transient waveforms do not exist at the output of the phase detector. The elimination of high frequency ripple improves the jitter characteristics of the clock recovery circuit. The delay unit used in our phase detector requires no accurate control of the delay time. This feature eliminates the use of DLL to generate the precise delay time, which reduce the power consumption and area of the phase detector. The simulation shows that the RMS timing jitter is reduced by more than four times when compared with the conventional scheme. The rms jitter is 32 ps for the proposed phase detector and 133 ps for the phase detector in conventional scheme. In conventional scheme, even when the lock is achieved, the phase detector produces a triwave transient on the control voltage of the VCO, which depends on the data pattern. In the proposed phase detector, no such transient waveforms do not exist. The proposed phase detector can be incorporated in high performance clock recovery circuit for data communication systems.

A parallel current-mode multilevel identifying circuit for flash memories is proposed. The sensing scheme based on the CMOS cross-coupled structure modified from the clamped bit-line sense amplifier achieves high speed and low power dissipation. The offset of the proposed sense amplifier due to mismatch is also reduced significantly. The circuit has been fabricated using 0.6 µm CMOS technology. The simulation and measurement indicate the sensing speed reaches 1 ns at 3 V supply voltage with average power consumption about 2 mW at 50 MHz.

A four-pole quasi-elliptic function bandpass filter is designed and fabricated using a miniaturized microstrip square Stepped Impedance Resonator (SIR). The Nonuniform Finite Difference Time Domain (NUFDTD) method is used to design the resonator and to calculate the coupling coefficients of three basic structures. Theoretical and experimental results are presented. This filter is not only compact size but also has a wide upper stop band.

This paper presents a baseband filter for multi-mode applications with a new automatic tuning method. 5th-order Chebyshev low pass filter is designed for implementing the baseband channel-select filter. Capacitors and resistors were shared between modes to minimize the area. The new corner frequency tuning method is proposed to compensate the process variation. This method can reduce the noise level due to MOS switches.

This study investigates the anisotropy substrate and dielectric cover effects of the rectangular microstrip patch antenna on anisotropy substrates with air gap, based on rigorous full-wave analysis and Galerkin's moment method. Results show that the resonant frequencies in the variation of air gap, patch length, and permittivity of superstrate can be determined and analyzed with varying dielectric cover thickness.