Masataka Ohira

Multiband single-layer frequency selective surface designed by combination of genetic algorithm and geometry-refinement technique

This paper proposes an optimization-design method for the frequency selective surface (FSS) based on the genetic algorithm (GA) incorporated with a geometry-refinement technique. The present method takes the connectivity condition of the elements into consideration, thereby resulting in an easy fabrication. As an example, we design the multiband single-layer FSS for transmitting L band (1.5 GHz band) and S band (2.5 GHz band) and also reflecting Ka band (20/30 GHz band). The designed FSS has bandwidths broader than previous FSSs. Finally, the validity of the present method is proved by the agreement between the calculated and the measured transmission responses for the designed FSS.

Novel waveguide filters with multiple attenuation poles using dual-behavior resonance of frequency-selective surfaces

This paper develops novel waveguide filters consisting of frequency-selective surfaces (FSSs) in order to realize both the drastic size reduction and multiple attenuation poles in stopbands at both sides of passband. The FSS provides not only a passband but also attenuation-pole frequencies in stopbands since the FSS has both the aperture-element and the patch-element behaviors. In the present design method, the shape of each FSS is designed by a genetic algorithm so that the resonant curve of FSS can be fitted to that obtained from an equivalent-circuit approach. By using such FSSs and quarter-wavelength waveguides, a bandpass filter with six attenuation poles like an elliptic-function filter has been constructed. Furthermore, a technique of the size reduction by controlling adequately the resonant response of each FSS is presented. In this filter, the FSSs are closely located at the interval of the length much shorter than a quarter wavelength. It is shown from the design example that the half longitudinal length of the former example can be obtained, keeping both the passband response and attenuation poles in stopbands. The effectiveness of the waveguide filters with FSSs is validated by good agreement between the calculated and the measured results.

60-GHz Wideband Substrate-Integrated-Waveguide Slot Array Using Closely Spaced Elements for Planar Multisector Antenna

A new wideband waveguide slot array is proposed for covering a wide elevation-angle range with a planar sector antenna of a multigigabit wireless LAN in the 60-GHz band. The requirement of millimeter-wave sector antennas is to realize both wide bandwidth of 11.2% and wide elevation-angle coverage with a required gain of over 10 dBi. To satisfy both the required gain and bandwidth, the important structural features of the proposed antenna are that multiple slot elements are successively arranged at an interval of the length less than one quarter guide wavelengths and that the slot length increases from the shorted waveguide end to the feed end. The operational principle of the slot array is based on multisection quarter-wavelength reflection cancellation, so the slot array can achieve the required bandwidth. Furthermore, this antenna produces a unidirectional radiation pattern by using the radiators and the reflectors, resulting in the required gain over a wide elevation-angle range. In the design, the structural parameters of the slot array are selected to meet the requirements for 60-GHz-band sector antenna. The developed substrate-integrated-waveguide (SIW) slot array achieves both the 10 dB return-loss bandwidth of 15% and the specified gain in 88-96% of the one-sector coverage range of 59-66 GHz. The effectiveness of the proposed slot array for a sector antenna is verified by the good agreement between the simulated and measured results.

Experimental Characterization of Microwave Radio Propagation in ICT Equipment for Wireless Harness Communications

The wireless harness is a new emerging short-range communication to replace wire harness implemented in devices with wireless communications between internal components. In such an in-device wireless harness, the communication distance is up to a couple of meters at most. Through the challenge to apply this wireless communication technology to information and communication technology (ICT) equipment, we found that the radio channel inside the ICT equipment deeply depends on its internal structure more than we expected. In order to understand the radio propagation characteristics inside such equipment, we propose a new modeling technique with using a frequency- dependent path loss exponent expressing the near- and far-field propagation, which enables us to successfully extract attenuation factors for the frequency and the propagation distance from the measured data. The results shows the path loss characteristics can be divided into three regions; line-of-sight (LOS), non-line-of-sight (NLOS), and a transition range. The transition range, which appears between the LOS and the NLOS, is caused by a blocking due to the densely-packaged internal components. These findings and equations can be criteria to design a wireless harness communication link.

A new dual-behavior FSS resonator for waveguide filter with multiple attenuation poles

This paper proposes a new element shape of frequency selective surface (FSS) for designing a waveguide filter with multiple attenuation poles like an elliptic-function filter. The FSS is a dual-behavior resonator by the combination of the aperture-type and the patch-type FSSs. Introducing such FSSs can realize high skirt selectivity by utilizing anti-resonances (full reflection) in stopbands at both sides of passband in addition to resonance (full transmission) in a passband. To design the waveguide filter, the resonant characteristics for various geometrical parameters of the FSS are investigated. As a design example, we demonstrate the bandpass filter with 4% bandwidth at the center frequency 10 GHz. The effectiveness of the waveguide filter with the FSSs proposed here is validated by good agreement between the calculated and the measured results.

A Parameter-Extraction Method for Microwave Transversal Resonator Array Bandpass Filters With Direct Source/Load Coupling

A new simple and straightforward parameter-extraction method for a general transversal resonator array filter, which consists of parallel connected resonators in a circuit model, is proposed. Using this method enables one to effectively extract a direct source/load (S/L) coupling, as well as the external quality factor and the resonant frequency of each resonator path only from input reflection phase characteristics of the singly terminated even- and odd-mode networks, without using any complicated optimization techniques and coupling matrix calculations. One of the advantages noted here is that a frequency-dependent S/L coupling in practical physical filter models can be handled with this method. Furthermore, dissipation effects due to unloaded quality factors of the resonator paths is investigated based on a new closed-form formula derived in this paper. The effectiveness of the proposed extraction technique and equations is verified by the comparison with the optimization method results through applications to three planar filter examples. The proposed extraction technique is indispensable for recent advanced filter designs using a transversal array filter synthesis theory for quasi-elliptic function filters having multiple transmission zeros.

Novel waveguide filters with multiple attenuation poles using frequency selective surfaces

This paper proposes a waveguide filter consisting of frequency selective surfaces (FSS) with an arbitrarily-shaped element, which can control not only a passband characteristic but also attenuation-pole frequencies at stopbands. In the present design method, the shape of each FSS is designed by a genetic algorithm (GA) so that the resonant curve of the FSS can be fitted to that obtained from an equivalent-circuit approach. By using such FSSs, we have constructed the bandpass filters with 4% bandwidth at the center frequency 10 GHz, in addition to multiple attenuation poles like an elliptic-function filter. The effectiveness of the waveguide filter with FSSs proposed here is validated by good agreement between the calculated and the measured results.

A NEW FREQUENCY SELECTIVE WINDOW FOR CONSTRUCTING WAVEGUIDE BANDPASS FILTERS WITH MULTIPLE ATTENUATION POLES

This paper presents a novel frequency selective window for waveguide fllters. It has a resonant characteristic with two attenuation poles on both sides of a passband, that is, a dual-behavior resonance. Such frequency selective windows make it possible to construct a compact bandpass fllter having multiple attenuation poles without any additional coupling structures. As design examples, we show 3-pole Chebyshev waveguide fllters with six attenuation poles in both the microwave and the millimeter-wave regions. The validity of the present fllters is proven by the comparison of the frequency characteristics between the calculated and the measured results.

Optimized Multiband Single-layer Frequency Selective Surface and Its Experimental Verification

This paper has developed a multiband single-layer frequency selective surface (FSS) designed by using the optimization technique (micro-genetic algorithm). The characteristics of the designed FSS are superior to those of the Fractal FSS in the close dual-band separation and to those of the convoluted double square loop FSS in the bandwidth. We design the FSS for transmitting L and S bands and reflecting Ku and Ka bands. The agreement between the calculated and measured transmission responses for the designed FSS proves the validity of the present method.

Eigen-mode analysis of a novel three-mode microstrip/slot-line resonator and the development of a compact bandpass filter with multiple transmission zeros and wide stopband property

A novel compact three-mode resonator is proposed, which consists of a parallel-coupled microstrip line resonator embedded with a slotline resonator. Resonance mechanism and properties of these three modes are analyzed and verified by using an electromagnetic simulator. Four transmission zeros are produced because of multi-paths between the input/output stub lines formed by the three resonant modes and the direct source-load coupling. A circuit model is proposed and a very compact bandpass filter is developed, which has three reflection zeros in the passband and four transmission zeros near the passband, showing sharp skirt property and a wide stopband.