Tomoki Uwano

A shoulder-mounted planar antenna for mobile radio applications

A new planar antenna, suitable for use on a shoulder, has been studied for police and fire service portable radios in the 350-MHz band. This shoulder-mounted antenna, which is a type of planar inverted F antenna (PIFA), features extreme compactness while maintaining a higher gain than that of a conventional whip antenna and small impedance changes in the presence of a human body. The low-profile structure enables the antenna to be unseen when the operator wears a jacket. A prototype of the antenna has been built and tested, and the measured impedance characteristics and the radiation patterns are presented. Emphasis is placed on the effect of the human body. The antenna provides a gain of -5.5 dBd, which is 3.5 dB higher than that of a whip antenna. Field measurements verified the excellent performance under a multiple propagation environment.

A compact LPF with broad stopband characteristics using hairpin structure and chip-capacitor

A compact microstrip lowpass filter is proposed in this paper. The LPF consists of hairpin type inductor lines as quasi-lumped elements, coupled lines and a chip-capacitor. Firstly, using the equivalent circuit, the transmission zero frequencies are investigated. As a results, the proposed filter has two attenuation poles at a stopband. Then, cascaded LPF is cross examined with the simulated and experimental results. The measured results show that the experimental LPF has sharp attenuation slope at the cut-off frequency and wide rejection characteristics.

Ultra-wideband bandpass filter using matching-lines and interdigital filter with close-coupled resonators

This paper presents an ultra-wideband bandpass filter (UWB BPF) using quarter-wavelength inverter-lines at both sides of a three-pole interdigital filter. The relations between the impedances of the inverter-line with the load and those of the interdigital filter connected to the inverter-line were studied. From these, the design procedures for the impedance matching at the UWB passband edges were shown. Then the designed BPF from the above results showed that the bandwidth was 24% wider than that of the sole interdigital filter by additional two conjugate matching poles. The fabricated BPF achieved the performances of the required passband by the five matching poles.

A study on the UWB BPF using the hairpin-type LPF and the Parallel-coupled Lines

A compact ultra wide-band bandpass filter is proposed in this paper. The BPF consists of a hairpin-type LPF with a chip capacitor and a HPF using parallel-coupled lines. Firstly, the circuit model of LPF is investigated. Next, the characteristics of the HPF is also examined, and the results show the broad bandpass characteristics. Then the performances of UWB BPF composed of the LPF and the HPF are simulated and measured. As the results, the filter show the performance close to the FCC-Full band. In addition, UWB BPF using high dielectric rod by LTCC technology is simulated which has the similar performance without the chip capacitor.

A compact microstrip BSF using quasi-lumped elements

A compact microstrip BSF using quasi-lumped elements is proposed in this paper. The filter consists of inductor lines and inter-digital-type gap capacitors as quasi-lumped elements. The resonator using the above elements is represented by a series LC resonator. The design of the resonator was performed by changing the structural parameters so that the reactances of the inductor (positive) and the gap capacitor (negative) have the same absolute values. The measured results of the combination of the resonators for the BSF agreed well with the simulated ones.

26 GHz TM/sub 11/spl delta// mode dielectric resonator filter and duplexer with high-Q performance and compact configuration

A novel structure of 26 GHz bandpass filters using TM/sub 11/spl delta// rectangular-mode dielectric cavity resonators is introduced. The resonator of high-permittivity ceramics shows a high quality factor (Q) value of 2600, which is roughly comparable to that of waveguide type ones, in spite of its small structure. A three-stage Tchebyscheff bandpass filter with 0.4% relative bandwidth was fabricated and the passband insertion loss was measured to be 1.7 dB. The filter has input/output ports of microstrip lines for the surface mounting. A duplexer, consisting only of two TM/sub 11/spl delta// mode filters and a microstrip T-junction, is also presented. These filter and duplexer have a configuration compact and easy to manufacture as well as the high-Q performance.