A three-mode switched-LNA has been developed using a 0.25 µm SiGe BiCMOS technology. The LNA features low noise figure (NF) performance, while achieving both low dissipation power and low distortion characteristics. The proposed MOSFET switch incorporating a newly developed switch circuit with a triple-well structure, which changes the LNA's mode, provides a parasitic capacitance of just 0.52 times that of a conventional MOSFET switch. This results in a significant NF improvement, by 0.16-0.33 dB, for the three-mode switched-LNA compared to a conventional LNA. Extensive studies of the MOSFET switch with regard to the structural parameters and the doping profiles are reported. Experimental results and the overall performance of a trial IC incorporating the three-mode switched-LNA are also given.

A new method of cancellation of IM3 using current feedback has been proposed for a multi-stage RFIC amplifier. In order to cancel the IM3 present in an output signal of the amplifier, the IIP3 level and IM3 phase of the amplifier are adjusted by means of feedback circuit techniques, so that the target specification is satisfied. By estimating the IIP3 level and IM3 phase variations for two states in situations with and without feedback possessing linear factors, the parameters of a feedback circuit can be calculated. To confirm the validity of the method, we have investigated two approaches; one including an analytical approach to designing a two-stage feedback amplifier, achieving an IIP3 level improvement of 14.8 dB. The other method involves the fabrication of single-stage amplifiers with and without feedback, operating at 850 MHz, both of which were designed as an integrated circuit using a 0.18 µm SiGe BiCMOS process. The fabricated IC's were tested using a load-pull measurement system, and a good agreement between the estimated and measured IIP3 level and IM3 phase variations has been achieved. Further studies show that the error in these variations, as estimated by the method, has been found to be less than 1.5 dB and 15 degrees, respectively, when the load admittance at 1701 MHz was greater than 1/50 S.

A new Waffle-iron Ridge Guide (WRG) structure that has the ability to control both wavelength and impedance is proposed. With the proposed structure, not only can the wavelength be controlled over a wide range for both fast- and slow-waves in free space but the impedance can also be controlled. These features can improve the performance of array antennas in terms of reducing grating lobes and side lobes. In this paper, we discuss and evaluate a design scheme using equivalent circuits and EM-simulation. This paper also discusses how the conductivity and dielectric loss in the WRG affect the total gain of the array antenna.

A low distortion and low noise differential amplifier using the difference between the even- and odd-mode impedances is proposed. In order to realize an amplifier with high OIP3 and low NF characteristics, the impedance of the bias circuit should be low (<300 Ω) at the difference frequency and high (>4 kΩ) at the carrier frequency. Although the frequency response of the bias circuit impedance can only meet these conditions with difficulty, owing to the 20 MHz Tx signal bandwidth for 3G LTE, the proposed amplifier can achieve the impedance difference using the properties of a differential configuration where the difference frequency signal is the even-mode and the carrier frequency is the odd-mode. It has been demonstrated that the NF of the proposed amplifier, which has been fabricated in 0.18 µm SiGe BiCMOS technology operating at 2.14 GHz, can be kept to 1.6 dB or less and an OIP3 of 9.0 dBm can be achieved, which is 3 dB higher than that of a conventional amplifier, in the condition where the power gain is greater than 18 dB.

Cost down of millimeter wave components, especially antenna duplexer, is a key for spreading millimeter wave communication systems. An excellent cost-performance antenna duplexer is proposed. It consists of two E-plane filters and a wave-guide circulator. The performance fluctuations due to manufacturing accuracies are studied by simulations and experiments. These results are very useful for cost-down of the practical duplexer without performance degradation.

This paper presents a basic investigation of the power imbalance problem with regard to maximum ratio combining (MRC) array antennas for digital TV broadcast reception. First, the relationship between the decrease in the diversity gain and reduction in the received power was investigated using two-element and four-element dipole array antennas by means of a Monte Carlo simulation. The relationship between the decrease in the diversity gain and the number of branches imposed to reduce the received power was also investigated. Then, a simple method of predicting the reduction in the diversity gain under imbalanced power conditions is given using the simulation results. The objective is to determine a criterion associated with the gain reduction that allows us to achieve the required system performance. Finally, the proposed method is confirmed by analysis using a model representing a typical portable digital broadcasting TV set held with both hands that simulates the power imbalance condition.

In this paper, a method of calculating the mean channel capacity based on S-parameter of MIMO (Multiple-Input Multiple-Output) antenna is proposed. This method exploits the correlation matrix calculated from the antenna S-parameter matrix, and offers highly accurate estimates of the mean channel capacity without dependence on SNR (Signal-to-Noise Ratio). The numerical and experimental results revealed that the proposed method can calculate the channel capacity with fair accuracy independent of the number and spacing of the antenna elements if the radiation efficiency is sufficiently high.

This paper presents a spatial fading emulator for evaluating handset MIMO antennas in a cluster environment. The proposed emulator is based on Clarke's model and has the ability to control RF signals directly in spatial domain to generate an accurate radio propagation channel model, which includes both uniform and non-uniform angular power spectra (APS) in the horizontal plane. Characteristics of a propagation channel such as fading correlations, eigenvalues and MIMO channel capacities of handset antennas located in the vicinity of the emulator's ring can be evaluated. The measured results show that the fading emulator with 31 antenna probes is sufficient to evaluate fading correlation and MIMO channel capacity of handset antenna in the case of a narrow APS with the standard deviation of more than 20 degrees.

A simple method has been proposed for the measurement of the output power and phase characteristics of the 3rd-order inter-modulation distortion (IM3) components appearing in multistage power amplifiers. By adopting a unique definition of the phase for the IM3 components that is independent of the delay time caused by transmission lines and other instrument devices, it is possible to measure the phase, merely by using a vector signal analyzer. It is demonstrated that an accurate estimation of the IM3 characteristics of two-stage cascaded power amplifiers for cellular radio handheld terminals can be made by using the IM3 characteristics of the 1st and 2nd-stage amplifiers as measured by the proposed method. The results indicate that it is possible to reduce the dissipation power by 18% at 28 dBm RF output power with respect to conventional measurement methods. Further studies show that the error in the resultant vector of the estimated IM3 is less than 1 dB, when the asymmetry characteristics of the IM3 sidebands in the 2nd-stage amplifier are less than 7.3%.

In this paper, we present a weighted-polarization wearable multiple-input multiple-output (MIMO) antenna that is based on radio-frequency (RF) signal processing to realize ultra-high-speed and high-capacity mobile communications. The proposed antenna is comprised of three orthogonal dipoles, two of which can be selected according to a weight function in different usage scenarios. The weight function is determined by considering the variation in the cross-polarization power ratio (XPR) and the antenna inclination angle which depend on the radio-propagation environment and human motion. To confirm the suitability of the proposed antenna, we perform preliminary experiments to evaluate the channel capacity of a weighted-polarization wearable MIMO antenna with an arm-swinging dynamic phantom. The measured and analytical results are in good agreement, which verifies the effectiveness of the proposed antenna. We demonstrate that the proposed antenna is suitable for realizing gigabit mobile communications in future wearable MIMO applications.

A variable phase shifter using a movable waffle iron metal plate comprised of iron rods a quarter-wavelength in length is proposed. A study of the waffle iron structure was carried out and the design method for creating a structure that would achieve large phase changes, small loss, and good isolation between adjacent phase shifters is discussed. Experiments on 1-port and 2-port phase shifters operating in the 5 GHz band show that they not only have low loss characteristics but also wide phase changes. Furthermore, the application to phased array antennas using the proposed phase shifter and its principle are demonstrated.

Coupling effects between resonators on a laminated Band Elimination Filter (BEF) is studied. The coupling degrades the filter attenuation performance. A new equivalent circuit of coupled-line BEF with loaded capacitors is investigated. The performance is simulated and the improvement by staggered resonators is confirmed. An experimental filter made of Low Temperature Co-fired Ceramics (LTCC) is constructed. It shows good performance.

Practical design procedure of a four-pole dual-mode cavity filter is explained in the details. Coupling matrix M of an elliptic function filter is derived analytically. The effects of septum thickness is studied experimentally. The dimensions of the aperture have to be modified due to the effects. This attempt had made the filter design very elegant, because no complicated calculation is required. A four-pole filter and a multiplexer are designed and constructed experimentally. They show very excellent performances in the 23 GHz band.

This paper presents the shadowing analysis of a body area network (BAN) diversity antenna based on the statistical measurements of the human walking motion. First, the dynamic characteristics of the arm-swing motion were measured using human subjects, and a statistical analysis was then carried out using the measured data to extract useful information for the analysis of a BAN diversity antenna. Second, the analytical results of the shadowing effects of the BAN antenna were shown based on the statistical data of the swing motion. The difference between the typical and the realistic arm-swinging models significantly affected the bit error rate (BER) characteristic of the BAN antenna. To eliminate the shadowing caused by the movement of the arms, a BAN diversity antenna was used. Particular emphasis was placed on the evaluation of the spatial separation of the diversity antennas to attain reduction of the signal-to-noise ratio (SNR) required to achieve a specific BER performance, considering the combined outcome of shadowing and multipath fading unique to BAN antenna systems. We determined that an antenna angle separation of greater than 80° is required to reduce the shadowing effects when the diversity antenna is mounted at the left waist in a symmetrical configuration. Further, an antenna angle separation of 120° is required when the diversity antenna is mounted in an asymmetric configuration.

A new beam tilt dipole array antenna in a simple structuer has been developed for indoor base stations in the 1.9 GHz band. The antenna comprises a radiator and skewed off-center parasitic elements placed around the radiator. With this stucture, the main beam of the array antenna can be tilted for mobile terminals reception by the effect of mutual coupling. Studies on tilt characteristics for antenna dimensions and tilt mechanism by precise current measurements have clarified the operating principle. The antennas with a fan beam and an omnidirectional pattern have been designed. The measured tilt angle was varied in the range of 0 to 26 with little alteration of the horizontal radiation patterns.

This paper presents a new methodology for realizing a Rice channel in BAN Over-The-Air (OTA) testing using a fading emulator with a dynamic phantom. For the proposed apparatus to be effective, the fading emulator must be provided with an appropriate K-factor that represents the actual propagation environment indoors. Further, an implementation of the Rice channel to the proposed fading emulator in a BAN situation is presented. Thereafter, a calibration method for the fading emulator to adjust the actual K-factor of the on-body Rice channel is advanced. This calibration method is validated by analyzing the variations in the instantaneous K-factor attributed to the arm-swinging motion. Finally, an experiment is conducted for a continuous human walking motion with the fading emulator using an arm-swinging dynamic phantom. The results show that the developed fading emulator allows BAN-OTA testing to replicate the actual Rice channel propagation environment with the consideration of the dynamic characteristics of human walking motion.

This paper presents a new methodology of the over-the-air (OTA) assessment for vertically arranged multiple-input multiple-output (MIMO) array antennas. Particular emphasis is placed on how well handset MIMO antennas with a vertically arranged structure are characterized using the limited number of scatterers implemented in a fading emulator. First we studied the mechanism of the arrangement of scatterers on the variation of channel responses using a proposed three-dimensional analytical model. It is shown that the condition of a 3D-OTA with the prescribed parameters allows the correlation to be reduced, which permits the channel capacity to increase in the same manner that sufficient scatterers are distributed over the entire solid angle. Then the appropriate scatterers arrangement for a 3D-OTA instrument considering the number of DUT antenna elements and multipath characteristics is investigated. The analytical results show that a suitable scatterers arrangement can be determined for various conditions of multipath environments and numbers of array elements, and that the arrangement can be employed for designing an actual 3D-OTA apparatus.

This paper presents a simple abdomen model of pregnant women and the evaluation of the specific absorption rate (SAR) inside the proposed model close to normal mode helical antennas (NHAs), which are replacing the portable radio terminals for business at 150 MHz. First, dielectric properties of amniotic fluid and those of fetus of rabbit, which have about the same electrical properties as human, are measured. As a result, the conductivity of amniotic fluid is 1.8 times and that of fetus is 1.3 times higher than that of adult muscle at 150 MHz. The result also suggests the modeling of pregnant women including the amniotic fluid and the fetus is necessary. Next, a simple abdomen model of pregnant women based on the measurements of magnetic resonance (MR) images of Japanese women in the late period of pregnancy is proposed. Finally, the SAR inside the proposed abdomen model close to 0.11λ and 0.18λ NHAs is calculated using the finite-difference time-domain (FDTD) method. As a result, we have confirmed that the 10-g average SAR in the fetus is sufficiently less than 2 W/kg, when the output power of NHAs is 5 W, which is the maximum power of portable radio terminals in Japan.

This paper addresses the variation of the attenuation characteristics of the Specific Absorption Rate (SAR) in a lossy medium as a function of the distance between an antenna and the medium with different EM-source sizes. Analysis and measurements were performed using a dipole antenna at 900 MHz and a COST244 cubic phantom. From this, an empirical equation has been derived, representing the attenuation characteristics of the SAR. The equation takes into consideration an energy loss due to the spatial spread of electromagnetic waves. In the case where an antenna is placed more than λ/2π away from the medium, the attenuation characteristics of the SAR are those obtained from plane waves in the lossy medium. In the case where a half-wavelength dipole antenna is located close to the medium, at a distance of less than λ/2π, the attenuation characteristics of the SAR are calculated from an equation that includes a loss caused by the spread of energy as a cylindrical wave. Moreover, when the length of antenna is short, it is found that a spatial attenuation factor appropriate to a spherical wave should be taken into account.

A simple but efficient method for evaluating the channel capacity of 2×2 multiple-input multiple-output (MIMO) antenna systems is proposed. First, the channel capacity of a half-wavelength dipole array antenna is calculated using the Monte Carlo method by changing the incident-wave signal-to-noise power ratio, the power difference between two elements, and the correlation coefficient. Using the calculated results, a polynomial function is derived by multivariate regression analysis to estimate the channel capacity. The validity of the developed function is confirmed by comparing the channel capacity estimated by the developed function with that calculated by the Monte Carlo method using a MIMO array antenna operated under various scenarios, including antenna-human body electromagnetic interactions and radio-wave propagation environments, for future MIMO systems. The function is also validated by means of two experimental approaches: the use of radiation patterns measured in an anechoic chamber and the use of a spatial fading emulator that can create a two-dimensional fading environment.