Wave absorber of rubber sheet containing natural rubber and EPDM is designed, fabricated and measured for improving ETC environment. As a result, proposed absorption material has fine weatherability and wave absorption satisfied with ETC standard can be realized theoretically before and after the weatherability test if the thickness of absorber is fabricated at the ranging from 2.26 mm to 2.52 mm. Moreover, absorber sheet sample based on theoretical values is fabricated and are measured. As a result, 20 dB or more is also confirmed at the incident angle ranging from 5 to 55 degrees experimentally. Therefore, the wave absorber with fine weatherability being satisfied with ETC standard can be realized.

Utilization of electromagnetic absorbers under high power is increasing. The absorbers are used in anechoic chambers for performance estimation of high power radars. Variation of the absorption characteristics of the absorbers under such conditions is expected, due to the generation of heat or temperature change. In this paper, first the temperature distribution of a λ/4 type EM-wave absorber under high power injection is examined using the coupled method. The coupled method can calculate the electromagnetic field and all of the heat transmissions (heat transport, heat transfer and heat radiation). Next, the power injection experiment is examined using the absorber and high power instruments to get the temperature distribution experimentally. Finally the calculated and measured temperature distributions of the absorber are compared and discussed.

This paper presents an ultra-wideband (UWB) bandpass filter (BPF) with sharp attenuation slope characteristics. The circuit structure consists of an inter-digital finger resonator, parallel-coupled lines and phase matching line. The design of the bandwidth was described by using the even and odd mode characteristic impedances in the resonator structure. The parallel-coupled lines were also designed in the same manner. The parameters of the resonator and two parallel-coupled lines in combination as the BPF were then optimized by the simulation with HFSS. The designed BPF was experimentally fabricated and its measured performances showed the bandwidth from 3.6 to 10 GHz with the 20 dB outband rejection. For the U.S. UWB band design, the matching line was inserted between the two parallel-coupled lines. The matching at both band edges was then qualitatively analyzed on the smithchart. The HFSS simulation results of the structure realized the bandwidth from 3.1 to 10.6 GHz with sharp attenuation slope characteristics for SWR < 2.0. The measurement results agree well with the simulation results.

This paper focuses on the characteristics of tunable half-wavelength resonators and their applications to bandpass filters (BPFs). First, the resonance characteristics of various tunable half-wavelength resonators are examined for the tunabilities of transmission zeros and the center frequency of the proposed BPFs. We examine four types of tunable half-wavelength resonators, namely, an end-coupling resonator and three types of tap-coupling resonators. Secondly, the proposition and design of two types of BPFs using acquired resonators are carried out. The fabrication and experimental application of the resonators and designed BPFs are also performed based on coplanar waveguide (CPW) technologies. Their calculated and measured results are compared with each other. The results show that tunabilities of the transmission zero and the center frequency of the proposed BPF are obtained as expected.

It is known that the thickness of the λ/4 type EM wave absorber having a resistive film with the capacitive reactance is thinner than 1/4 wavelength. This paper investigates EM wave absorbers using the resistive film with capacitive reactance. We introduced the impedance into the resistive film, and then clarified the relationship between the impedance and the matching thickness in the single layer EM wave absorber. Practically, we carried out to grasp the impedance of the resistive films, which were prepared using the conductive flake powder. As the results, we have proven that the matching thickness in the single layer EM wave absorber could be realized 0.17 λ-0.09 λ in the frequency range from 2 GHz to 8 GHz by using these resistive films. We also fabricated the single resistive layer and the double resistive layers EM wave absorber using these resistive films for Dedicated Short Range Communications (DSRC) and wireless Local Area Network (LAN), in which the matching thickness could be reduced to 45% and 30%, respectively, as compared with the each absorber using the non-capacitive reactance.

Characteristics of a class of stepped-impedance resonators (SIRs) which is loaded with two dielectric rods, are investigated by a Finite-Difference Time-Domain (FDTD) method. Dielectric rods to be inserted between a strip conductor and the ground plane have higher relative permittivity than that of the substrate. When a tapped half-wavelength (λ/2) microstrip resonator is loaded with two dielectric rods, the electric length of a loaded λ/2 resonator becomes longer than λ/2, which makes its fundamental resonant frequency () to be generated on the region lower than that of an unloaded λ/2 resonator (fr) and its first spurious response (fsp1) is generated on the region higher than 2. Therefore, to shift back to fr, the resonator's length is to be reduced, and this, in turns, suppress the spurious responses. Then, the resonant characteristics of an SIR employing the proposed method has also been investigated, and it is found that this is capable of suppressing the spurious responses in wideband together with an attenuation pole in the stopband, and of further reducing the resonator's length. Therefore, wide exploitation of the presented method can be expected in the filter design based on the LTCC technique.

A free-space method is in wide spread use for the reflectivity measurement of electromagnetic wave absorbers (EMA) in VHF and UHF range. In the free-space method, the reflection levels from EMA and from the metal plate with same size as the EMA are measured, and the reflectivity is calculated from their ratio. The incident angle such as normal or oblique must be defined, and the polarization of electromagnetic (EM) wave must be specified to be TE, TM, or circularly-polarized mode. In this paper, a parallel EM wave beam method using dielectric lenses in front of horn antennas was studied experimentally. Electromagnetic wave absorption was measured with the vertical and the oblique incidence by using this parallel EM wave beam. This measurement system has following features:• It is compact because equiphase parallel EM wave beam was obtained in a short distance from the dielectric lens.• It requires no anechoic chamber because of little multi-reflection due to high directivity of parallel EM wave beam.• It allows a large oblique incident measurement by using high directive parallel EM wave beam.

The wave absorber which is formed by arranging cylindrical bars periodically composed of magnetic loss material and metallic bars is proposed for improving ETC environment, and characteristics of reflection loss and shielding effect are analyzed and measured. As a result, the change of various characteristics can be confirmed quantitatively by changing the thickness of magnetic loss material covering around a metallic bar and the pitch interval between bars. Furthermore, it is clarified that reflection loss of -9 dB and shielding effect of -25 dB are obtained at 5.8 GHz when the covering thickness of material is 1.5 mm and the pitch interval is 16.0 mm. Therefore, the wave absorber formed by arranging cylindrical bars that satisfies various characteristics required for the improvement of ETC environment can be realized.

In this paper, an ultra-thin wave absorber using a resistive patch array closely-placed in front of a back-metal is designed. The positively large susceptance is required for the patch array to cancel out the negatively large input susceptance of the short-circuited ultra-thin spacer behind the array. It is found that the array needs the gap of 1mm, sheet resistance of less than 20Ω/sq. and patch width of more than 15mm to obtain the zero input susceptance of the absorber with the 1/30 wavelength spacer. Moreover, these parameters were designed considering the electromagnetic coupling between the array and back-metal, and the square patch array absorbers with the thickness from 1/30 to 1/150 wavelength were designed.

We measured the complex permittivities of whole blood and blood plasma in quasi millimeter and millimeter wave bands using a coaxial probe method. The validity of these measurements was confirmed by comparing with those of a different measurement method, i.e., a dielectric tube method. It is shown that the complex permittivities of the blood samples are similar to those of water in quasi millimeter and millimeter wave bands. Furthermore, the temperature dependences of the complex permittivities of the samples were measured.

In this paper, first the temperature distribution of the pyramidal EM-wave absorber is calculated in the coupled method. Next, the injected power to the EM-wave absorber is changed to estimate the maximum power density that the EM-wave absorber can resist. As a result, the limitation of the injecting power density to a pyramidal EM-wave absorber is achievable.

In this paper we describe the investigation of design methodology of a planar duplexer consisting of BPFs using mixed tapped resonators. Firstly, we propose the planar duplexer consisting of bandpass filters (BPFs) using a tapped open-ended λ/2 resonator and a tapped λ/4 resonator. The duplexer is designed based on the general filter theory with narrow band approximation and tap-coupling technique. The actual duplexer is fabricated using a coplanar waveguide (CPW). Secondly, downsizing of the planar duplexer is carried out based on the BPF using stepped impedance resonators (SIRs). Lastly, another type of duplexer consisting of different BPFs using mixed tapped resonators is investigated in the same manner. The results of this study lead us to the conclusion that the design methodology is useful for realizing the high-performance planar duplexer fabricated without increasing the number of elements.

An epoxy-modified urethane rubber mixed with carbon particles is now chosen as the millimeter-wave absorber material in our study. The absorption characteristics of the absorber is measured under temperature changes. The weatherability of our absorber is also clarified based on absorption characteristics, thickness and hardness of the sample. As a result of the temperature characteristics of the absorber, the difference of the maximum absorption frequency under temperature changes is about 1 GHz, however the absorption of 20 dB or more is obtained between 54 and 58 GHz. The result of accelerated artificial exposure test is that 2.8% of the thickness of our sample is shrunk after 1000 hour exposure, and the hardness of rubber is hardened with increasing test time. It is also confirmed that the deterioration of the absorption ranges from 1 to 3 dB, although the absorption of about 20 dB is kept at the frequency range. As a consequence, it is confirmed that the wave absorber using the epoxy-modified urethane rubber mixed with carbon particles has good weatherability including our desired temperature characteristics, and it is suitable for outdoor use.

A can swells due to gas produced from an inner food caused by poor hermetic sealing of the can. This paper presents a measurement for the bottom shape to detect a swelled can by using the millimeter-wave imaging. For get higher spatial resolution and an adjustable focal distance, two collimated beam lenses were applied to the measurement system. First, a configuration of the system was studied with the electrical field intensity and focal distance by using full wave electromagnetic simulation. Next, the bottom shapes of cans with different pressure were evaluated quantitatively using the system. A shape change of 0.5 mm was detected with pressure difference of 50 kPa, and it is reasonable considering actual dimension of the can shape. A potential of the proposed detection method was presented.

This paper focuses on the realization of low spurious responses by various bandpass filters (BPFs) using open-ended λ/2 resonators. The first part of this paper gives the resonance characteristics of the open-ended λ/2 resonators when the excitation methods are chosen. Secondly, various BPFs obtained with our methodology are provided. For constructing the BPF, (1) point-coupled resonators, (2) comb-line resonators, (3) quasi comb-line resonators and (4) parallel-coupled resonators are used. It is verified that the presented BPFs can be used to obtain low spurious responses both theoretically and experimentally.

A compact and wide stopband low-pass filter (LPF) which consists of a hairpin structural resonator, a chip-capacitor, and inductor lines is proposed in this paper. With the capacitor loaded, the hairpin structure realized three transmission zeros in the stopband. The LPF with one hairpin unit was designed using the conventional prototype design procedure in the passband. To further improve the stopband characteristics, the LPF with three hairpin units was studied and designed with the same manner as in a one unit LPF. The finally designed three-hairpin LPF showed mostly 60 dB rejection characteristics in the conjunction with defected ground condition for avoiding the spurious response at the stopband. The measurement results agreed well with simulated ones.

In this paper, the method of locating multiple transmission zeros by the tap-coupling technique is described for bandpass filters (BPFs), using short-ended λ/2 resonators and its application to a duplexer. First, the method of locating the transmission zero using the short-ended λ/2 resonators is examined with various excitation methods. We focus on four types of short-ended λ/2 resonators: the end-coupling type, tap-coupling type, capacitive tap-coupling type and inductive tap-coupling type. Secondly, the BPFs based on the basic characteristics of the respective resonators are proposed and designed on the basis of a general filter theory with narrow band approximation. Lastly, we propose and design new duplexers consisting of the proposed BPFs. The results lead to the conclusion that the basic characteristics of the short-ended λ/2 resonators are useful for realizing a BPF with multiple transmission zeros and a high-performance duplexer fabricated without increasing the number of elements.

In this paper, we discuss an application of range Doppler imaging to measurement of reflected wave intensity from a moving object without using an anechoic chamber. The wave intensity reflected from a metal plate moving in the horizontal direction toward the antenna is typically 40-50 dB higher than that in the case without using the plate, and the estimated radar cross sections for a metal plate and sphere show good agreement with the theoretical value. The measurement of wave absorption by the present method suggests that frequency characteristics of the observed reflection loss are in close agreement with those of the calculated loss. These results show the reliability of the present experimental system and suggest that the method is applicable to wave reflection measurement not in an anechoic chamber but in an ordinary laboratory room.