A large-signal simulation program for multi-stage power amplifier modules by using a novel interpolation is presented. This simulation program has the function to make the Load-Pull and Source-Pull (LP/SP) data required for the simulation. By using the interpolation, a lot of LP/SP data can be made from a small number of measured LP/SP data. The interpolation is based on the calculation method using a two-dimensional function. By using the simulation program, we can calculate the large-signal characteristics depended on frequency and temperature of the multi-stage amplifier module. We apply the simulation program to the design of the amplifier. The calculated and measured results agree well. The accuracy of the presented interpolation is confirmed. It is considered that the presented program is useful to calculate large-signal characteristics of the amplifier module.

The microwave coagulation therapy has been used mainly for the treatment of hepatocellular carcinoma (small size tumor in the liver). In the treatment, a thin microwave antenna is inserted into the tumor, and the microwave energy heats up the tumor to produce the coagulated region including the cancer cells. At present, a problem occurs: the size of the coagulated region is insufficient, especially in the perpendicular direction of the antenna axis. In order to overcome this problem without increasing the physical load of the patient, the authors introduced a new type of array applicator composed of two coaxial-slot antennas. However, we cannot estimate heating characteristics of this array applicator precisely by using the FDTD calculation, because the use of staircasing approximation, which employs rectangular parallelepiped cells, is unsuitable for the analysis. Therefore, in this paper, we introduce the finite element method (FEM), which employs tetrahedral cells, to estimate the heating characteristics of the array applicator.

Signal path loss and propagation delay spread were measured at microwave frequencies of 3.35, 8.45, and 15.75 GHz along a straight quasi line-of-sight (LOS) street in an urban environment under different traffic conditions: daytime and nighttime. Comparison between daytime and nighttime measurements reveals that the break points shift toward the base station because of the increase in the effective heights of the road and sidewalk; break points were not seen during the daytime at a mobile antenna height (hm) of 1.6 m. According to the cumulative probabilities of the delay spreads during the nighttime, frequency dependence is not clearly observed and the delay spreads for hm = 1.6 m were clearly larger than those for hm = 2.7 m. This is because a lower hm results in stronger blocking of the LOS wave, as was also observed during the daytime. The plot of path losses versus delay spreads is confirmed to be represented by an exponential curve. The exponential coefficients during the daytime were observed to be greater than those during the nighttime. This indicates that a LOS wave is more likely to be blocked during the daytime.

C-axis junction-arrays, with a-b plane sizes of sub-microns to 10 microns, were patterned on Bi2Sr2CaCu2O8+x single crystals with either a mesa or an overlap structure. We measured the current-voltage (I-V) characteristics with microwave irradiation at a few to 100 gigahertz. At a few gigahertz, often observed were chaotic properties. Under irradiation at 100 GHz, we successfully performed harmonic mixings between the 100 GHz signal and up to the 100th harmonic of a local oscillator at about 1 GHz. Given in this paper are discussions on the observation of individual Shapiro steps, and descriptions of the relevant results. Our experimental results show that intrinsic Josephson junctions in layered superconductors can be good candidates for high frequency applications.

This paper deals with a quantitative inversion algorithm for reconstructing the permittivity and conductivity profiles of bounded inhomogeneous buried objects from measured multifrequency and multiincidence backscattered field data. An Edge-Preserving regularization scheme is applied leading to a significant enhancement in the profiles reconstructions. The applications concern civil engineering and geophysics as well as mine detection and localization. The performance of the reconstructions are illustrated with different synthetic data.

A novel method for image reconstruction of a microwave hologram synthesized from one-dimensional data is proposed. In the data acquisition, an emitting antenna is shifted along a line. At every position of the emitting antenna, the amplitude and phase of diffraction fields are measured with a detecting antenna along a line perpendicular to the shifted direction. An equivalent two-dimensional diffraction field is synthesized from the one-dimensional data sets. The conventional reconstruction method applied to the one-dimensional configuration was the Fresnel approximation method. In this paper, an equivalent diffraction is introduced in order to obtain better images than the Fresnel approximation. An experiment made at 10 GHz shows the usefulness of the proposed method.

This paper proposes higher-order spread spectrum direct optical switching CDMA system and an aliasing canceler to remove the aliasing distortion caused by higher-order bandpass sampling. Theoretical analysis of the signal quality shows that the 3rd order bandpass sampling scheme can improve the carrier-to-interference-power ratio compared with the conventional 1st order bandpass sampling scheme, by 5 dB.

Leaky waves have been known for many years in the context of leaky-wave antennas, but it is only within the past dozen years or so that it was realized that the dominant mode on printed-circuit transmission lines used in microwave and millimeter-wave integrated circuits can also leak. Such leakage is extremely important because it may cause power loss, cross talk between neighboring parts of the circuit, and various undesired package effects. These effects can ruin the performance of the circuit, so we must know when leakage can occur and how to avoid it. In most cases, these transmission lines leak only at high frequencies, but some lines leak at all frequencies. However, those lines can be modified to avoid the leakage. This paper explains why and when leakage occurs, and shows how the dominant mode behaves on different lines. The paper also examines certain less well known but important features involving unexpected new physical effects. These include an additional dominant mode on microstrip line that is leaky at higher frequencies, and a simultaneous propagation effect, which is rather general and which occurs when the line's relative cross-sectional dimensions are changed. The final section of the paper is concerned with three important recent developments: (a) the new effects that arise when the frequency is raised still higher and leakage occurs into an additional surface wave, (b) a basic and unexpected discovery relating to improper real modes, which are nonphysical but which can strongly influence the total physical field under the right circumstances, and (c) the important practical issue of how leakage behavior is modified when the circuit is placed into a package.

Measurements of delay spread were performed at microwave frequencies of 3.35, 8.45 and 15.75 GHz along quasi line-of-sight streets in metropolitan Tokyo. It is found that the delay spreads increase with the measurement distance and reach around 600 ns up to 1 km. It is also confirmed that a cumulative probability of the delay spreads follows a log-normal distribution. The gradients of delay spreads against the distance are greater for a lower mobile antenna height hm = 1.6 m than for hm = 2.7 m in these measurements because of blocking effect by the traffic of vehicles and pedestrians on the road. When the mobile antenna height is 2.7 m, the delay spreads within the range before the break points are observed relatively small: 90 ns (3.35 GHz), 140 ns (8.45 GHz) and 150 ns (15.75 GHz) at the cumulative probability of 90%. The gradients of delay spreads against the distance are greater for wider streets in our measurements.

Silicon-based monolithic microwave integrated circuits (MMICs) present an interesting option for low-cost consumer wireless systems. SiGe/Si heterojunction bipolar transistors (HBTs) are a major driving force behind Si-based MMICs, because they offer excellent microwave performance without aggressive lateral scaling. This article reviews opportunities for receiver frontend components (low-noise amplifiers and mixers) using SiGe HBTs.

Heterojunction bipolar transistors (HBTs) are key devices for a variety of applications including L-band power amplifiers, high speed A/D converters, broadband amplifiers, laser drivers, and low phase noise oscillators. AlGaAs emitter HBTs have demonstrated sufficient reliability for L-band mobile phone applications. For applications which require extended reliability performance at high junction temperatures (>250) and large current densities (>50 kA/cm2), InGaP emitter HBTs are the preferred devices. The excellent reliability of InGaP/GaAs HBTs has been confirmed at various laboratories. At a moderate current density and junction temperature, Jc = 25 kA/cm2 and Tj = 264, no device failures were reported out to 10,000 hours in a sample of 10 devices. Reliability testing performed up to a junction temperature of 360 and at a higher current density (Jc = 60 kA/cm2) showed an extrapolated MTTF of 5 105 hours at Tj = 150. The activation energy for AlGaAs/GaAs HBTs was 0.57 eV, while the activation energy for InGaP/GaAs HBTs was 0.68 eV, which indicated a similar failure mechanism for both devices.

A GSM900/DCS1800 dual-band AlGaAs/GaAs HBT (heterojunction bipolar transistor) MMIC (monolithic microwave integrated circuit) power amplifier has been developed. It includes power amplifiers for GSM900 and DCS1800, constant voltage bias circuits and a d. c. switch. In order to achieve high efficiency, the outside-base/center-via-hole layout is applied to the final-stage HBT of the MMIC amplifier. The layout can realize uniform output load impedance and thermal distribution of each HBT finger. The developed MMIC amplifier could provided output power of 34.5 dBm and power-added efficiency of 53.4% for GSM900, and output power of 32.0 dBm and power-added efficiency of 41.8% for DCS1800.

A 100 W, low distortion AlGaAs/GaAs heterostructure FET has been developed for CDMA cellular base stations. This FET employs the longest gate finger ever reported of 800 µm to shrink the chip size. The size of the chip and the package are miniaturized to 1.242.6 mm2 and 17.4 24.0 mm2, respectively. The developed FET exhibits 100 W (50 dBm) saturation output power, and 11.5 dB power gain at 1 dB gain compression at 2.1 GHz. The third-order intermodulation distortion and the power-added efficiency under the two-tone test condition (Δf=1 MHz) are -35 dBc and 24%, respectively at 42 dBm output power, that is 8 dB back off from the saturation power.

Wide-band CDMA (W-CDMA) distortion characteristics of a fabricated double-doped heterojunction FET (HJFET) are presented. Measured results demonstrate that the first and second adjacent channel W-CDMA adjacent channel leakage power ratios (ACPRs) of the HJFET are correlated to the third- and fifth-order intermodulation (IM3 and IM5) distortions respectively under various quiescent drain current operation (Iq). A first channel ACPR dip phenomenon is observed under a low Iq condition, resulting in improved power added efficiency. Due to its close correlation to the IM3 distortion, the ACPR dip phenomenon is explained in terms of the similar IM3 characteristic. Simulated results reveal that the dip is a consequence of the cancellation of distortions generated by the third- and fifth-order nonlinearities at the IM3 frequency. The conditions for the cancellation are detailed.

Miniaturized opto and microwave receiver module using DCCPWs (Double Conductor Coplanar Waveguides) have been developed for active phased array antennas. The module comprised by a microstrip-to-slot transition, two chips of low-noise MMIC amplifiers, and a laser diode module is fabricated on an ultra-thin package with 10301.5 mm3 in size and 2 g in weight to achieve an ultra-thin structure of active phased array antenna panels. The ultra-thin structure is attributed to the design of low-noise MMIC amplifiers using DCCPWs and laser diode modules using silicon V-groove technology and fiber alignment method.

A new harmonic termination that controls the waveform of the drain current to be rectangular is developed for high-efficiency power amplifier modules. Its harmonic termination is a short circuit at the third harmonic and a non-short circuit at the second harmonic. It is found experimentally and confirmed by simulation that the load-matching condition at the third-order harmonic improves the efficiency of a transistor by more than 13%. By using this tuning, 57.7% power-added efficiency of the module is achieved at the output power of 29.9 dBm with ACP of -50 dBc, NACP of -65 dBc at 925 MHz and Vdd of 3.5 V.

We review advances in GaN-based microwave power field-effect-transistors (FETs). Evolution in device technology included metal-semiconductor-field-effect-transistors (MESFETs), heterostructure-field-effect-transistors (HFETs), modulation-doped-field-effect-transistors (MODFETs) or high-mobility-transistors (HEMT), HEMTs with high Al contents, HEMTs with gate recess and GaN-channel HEMTs grown on SiC substrates. The power density was first reported as 1.1 W/mm at 2 GHz using an AlGaN/GaN HEMT structure grown on sapphire substrate, and was subsequently improved to 1.5-1.7 W/mm at 4-10 GHz by refinement in device structure and processing techniques. This was advanced to 2.6-3.3 W/mm at 8-18 GHz by adopting a high-Al-content AlGaN barrier layer. Success in gate recess helped to further increase the power density of these GaN HEMTs on sapphire substrates to 4.6 W/mm at 6 GHz. Substrate replacement of sapphire by SiC, for excellent thermal dissipation, has boosted performance to 6.9 W/mm at 10 GHz, which is higher than GaAs-based FETs by a factor of 6. Device periphery was scaled up to obtain high total output power. On one hand, GaN HEMTs on sapphire, using a flip-chip bonding technology for thermal management, have generated 7.6 W at 4 GHz. On another hand, GaN HEMTs on SiC, taking advantage of the high substrate thermal conductivity, have achieved 9.1 W at 7.4 GHz. Two types of initial GaN-based power amplifiers were also demonstrated using a flip-chip IC scheme. The transistors used were 0.7 to 0.8-µm-long-gate GaN HEMTs. Bandwidths of 1-8 GHz and 3-9 GHz were achieved with gains up to 11.5 dB. The output power levels ranged from 3.2 to 4.6 W using devices with 2 and 3-mm gate peripheries, which were higher than that achievable with GaAs-based HEMTs of the same size by a factor of 2. Traps in the device structure currently limit performance of most GaN FETs. These traps cause dispersion in the I-V characteristics, which increases knee voltage and reduces channel current under RF gate drive. However, they are believed to be not inherent in the GaN semiconductor system and can be minimized as the technology matures.

This paper presents two types of two-variable analog filters with maximally flat magnitude-squared attenuation response in the two-dimensional pass region. These are applied in order to obtain five types for the distribution of two-dimensional pass regions with respect to the design of microwave band pass filters consisting of a cascade of commensurate-line filter and lumped LC filter or a cascade of two commensurate-line filters in different propagation times.

This paper discusses microwave path-loss characteristics as a function of mobile antenna height in an urban line-of-sight environment. Measurements were made in metropolitan Tokyo with high-density buildings, using base station antenna heights of 4 and 8 m. We describe the path-loss characteristics of vehicle-mounted mode (mobile antenna height is 2.7 m) and portable mode (mobile antenna heights are 1.6 and 0.5 m). Dependence of path loss on the distance between base and mobile stations was analyzed. This reveals that the break points shift to the near side in the vehicle-mounted mode. This phenomenon can be interpreted by the existence of an effective height h of the road. The typical value of h was found approximately 1.4 m. In the portable mode, on the other hand, break points were not observed. The mobile antenna heights (1.6 and 0.5 m) in this mode are close to or less than the average height (1-2 m) of pedestrians on the sidewalk; and the received waves at the mobile station are often disturbed by pedestrians. This explains the nonexistence of break points in portable mode. The average attenuation coefficients is observed 3.2 in this mode. The attenuation coefficients tend to be larger at lower base station antenna heights and narrower road widths.

This paper presents a technique for miniaturization of microstrip line and coplanar waveguide for microwave integrated circuits by using airbridge technology. A theoretical analysis is given by a combination of the conformal mapping technique and the variational principle. Numerical results demonstrate significant effects on size reduction as well as wide range of the characteristic impedance variation due to the airbridge.