Akira Saitou

Ultra-Wideband, Differential-Mode Bandpass Filters with Four Coupled Lines Embedded in Self-Complementary Antennas

SUMMARY A design method for an ultra-wideband bandpass filter (BPF) with four coupled lines has been developed. For demonstration purposes, 50 Ω-matched self-complementary antennas integrated with the ultra-wideband, differential-mode BPF with four coupled lines, a notch filter, and a low-pass filter (LPF) were prepared and tested. An optimized structure for a single-stage, broadside-coupled and edge-coupled four-lines BPF was shown to exhibit up to 170% fractional bandwidth and an impedance transformation ratio of 1.2 with little bandwidth reduction, both analytically and experimentally. Using the optimized structure, 6stage BPFs were designed to transform the self-complementary antenna’s constant input impedance (60πe −1/2 e (Ω)) to 50 Ω without degrading bandwidth. In addition, two types of filter variations — a LPF-embedded BPF and a notch filter-embedded BPF — were designed and fabricated. The measured insertion loss of both filter systems was less than 2.6 dB over the ultra-wideband (UWB) band from 3.1 GHz to 10.6 GHz. The filter systems were embedded in the wideband self-complementary antennas to reject un

Practical realization of self-complementary broadband antenna on low-loss resin substrate for UWB applications

Practical realizations of self-complementary ultra-wideband antennas on low-loss resin materials are demonstrated. Dependences of broadband characteristics on sizes and shapes are clarified by simulations and experiments. The self-complementary antennas impedance-matched to a 50-ohm system, utilizing a 3-stage Chebyshev transformer over the UWB band, were designed and fabricated on a resin material (the relative permittivity; /spl epsiv//sub r/=3.6). A measured return loss of less than -9.8 dB and a measured absolute gain of 0-3 dBi over a frequency range from 3.1 to 10.6 GHz (the UWB band) were obtained with a 30 mm/spl times/60 mm sized antenna. A reduced sized antenna (20 mm/spl times/40 mm), designed and fabricated on a resin material of /spl epsiv//sub r/=10.2, delivered a return loss of less than -7.8 dB with an isotropic radiation pattern.

Design Considerations on the Minimum Size of Broadband Antennas for UWB Applications

The practical realization of Chus minimum-sized antenna is investigated using self-complementary antennas. Rigorous bandwidth formulas for broadband antennas are derived for broadband antennas based on Chus fundamental mode equivalent circuit. By comparing input impedances and radiation patterns, the fabricated self-complementary antenna used for Japans ultra-wideband higher band (7.25-10.25 GHz) is found approximated by the minimum-sized antenna. Using the rigorous bandwidth formulas above, the fabricated antenna is shown to be smaller than the minimum-sized antenna. This breakthrough is achieved by using a more complicated matching circuit for broadband antennas instead of the single-stage inductor used in bandwidth estimation with the Q factor.

Ultra-wideband differential mode bandpass filters embedded in self-complementary antennas

A 50 /spl Omega/. matched self-complementary antenna integrated with a four coupled-line ultra-wideband differential mode bandpass filter (BPF), a notch filter and a lowpass filter (LPF) is demonstrated. Broadside- and edge-coupled four coupled-line BPFs were found to exhibit up to 170% fractional bandwidth and to exhibit impedance trans-formation ratio of 1.2 with little bandwidth reduction. Thus, 6-stage BPFs were utilized concurrently to transform the self-complementary antennas constant input impedance (60 /spl pi/ /spl epsiv//sub e//sup - 1/2 //spl Omega/) to 50/spl Omega/. In addition, LPFs with the BPF and notch filters with the BPF were designed and fabricated. Measured insertion losses of the total filter systems were less than 2.6dB over the ultra-wideband (UWB) band (3.1GHz to 10.6GHz). The filters were embedded in wideband self-complementary antennas to reject the radiation over the next passband and the 5GHz wireless LAN band.

Multi-band reconfigurable antennas embedded with lumped-element passive components and varactors

Frequency reconfigurable dual-band antennas with varactor diodes have been demonstrated. An equivalent circuit that takes both coupling with free space and an antenna conductor embedded with lumped-elements into consideration is proposed for the design of reconfigurable antennas. By means of the equivalent circuit, reconfigurable antennas that independently control dual-band resonant frequencies were designed and fabricated with a parallel circuit with an inductor and a varactor. The lower resonant frequency was successfully controlled between 1.60 and 1.91 GHz, and the upper resonant frequency was controlled between 3.32 and 3.71 GHz. Measured gains were more than -9.8 dBi in the lower band, and more than -7.3 dBi in the upper band, respectively. To improve the gain, a reconfigurable antenna with a series circuit of an inductor and a varactor was also fabricated for the lower band. Measured gains have been improved to more than -4 dBi in the lower band.

Analytical expression of linear antenna's characteristics using multipole expansion and Chu's equivalent circuit

Analytical expression including higher-order modes for a linear dipole antenna is derived with the multipole expansion and Chus equivalent circuits. Current distribution on the antennas conductor and loss caused by the radiation are consistently combined. Input power at the port is approximated to be guided totally on the conductor up to an effective antennas radius, and to propagate in free space beyond the radius. The circuit for the power to propagate in free space is expressed by Chus equivalent circuits for all the TM modes. With the derived formulae, numerical estimations of the current distributions and input impedances are shown up to 3rd-order-modes resonant frequency. The numerical data are compared with measured data for the antennas with different line widths, and the data are shown to agree well.

Microwave-Circuit-Embedded Resin Printed Circuit Board for Short Range Wireless Interfaces

Microwave circuits embedded in a multi-layer resin PCB are demonstrated using low loss resin materials. Resin materials for microwave frequencies were compared with conventional FR-4 with respect to dielectric and conductor loss factors, which proved that losses could be reduced drastically with the low loss material and design optimizations. Baluns, switches and BPFs were designed and fabricated to estimate microwave performances. Measured and simulated insertion losses of the circuits for 2.5 GHz band, were 0.3 dB for a switch, 0.4 dB for a balun and 2.0 dB for a 3-stage Chebyshev BPF. An integration of a switch, a BPF and two baluns was successfully implemented in a multi-layer PCB. Insertion losses of the fabricated integrated circuit were less than 3 dB with 0.1 dB additional loss compared with a sum of individual circuit losses. With estimated results of temperature characteristics and reliability as well as low loss performances, microwave circuits in resin PCBs can be considered as a viable candidate for microwave equipments.

Miniaturized Ultra-Wideband Self-Complementary Antennas Using High Permittivity Thick Resin Material

A miniaturized self-complementary antenna for Japanese UWB higher band (7.25 GHz-10.25 GHz) is demonstrated. Input impedances of four antennas in the size of 30 mm, 20 mm, 15 mm, 10 mm each on 1 mm and 2 mm thick high permittivity (epsivr = 10.2 ) resin substrates were measured and extracted. With the extracted input impedance, 50 Omega-matched self-complementary antennas in the size of 10 mm were designed and fabricated. The measured return loss was less than -10 dB between 5.9 GHz and 13.8 GHz and the fractional bandwidth was 80%. The fabricated antenna size is almost equivalent with the broadband antennas minimum size Chu showed [1]. Measured radiation patterns were almost omni-directional between 6 GHz and 12 GHz.

Group delay analysis of differential-mode coupled four lines bandpass filters

In this paper, the analytic formula of the group delay of one-stage coupled four lines BPF is proposed. The analytic formula agrees well with measured group delay of one-stage BPF, except for at band-edges. In case of multi-stage BPF, the sum of analyzed group delay of each stage is quite agrees with measured result in UWB band (3.1 GHz - 10.6 GHz). A 6-stage BPF with impedance transformation from 50 Omega to 172 Omega, the input impedance of the self-complementary antenna, is shown as an example.

Four-value multiplexing orbital angular momentum communication scheme using loop antenna arrays

A four-value multiplexing orbital angular momentum (OAM) communication scheme is demonstrated using loop antenna arrays. Considering the radiated fields of loop antennas, MIMO communication without signal processing is shown to be realized by controlling the current distribution in a single Fourier expansion coefficient. Through numerical analysis on the current, a single coefficient is shown to be dominant, where the loop perimeter is approximately the integral multiple of the wavelength. For long-range OAM communication, diffraction patterns of the collimated fields with paraboloids are analyzed, and the diffraction is shown to have a greater effect on the higher OAM modes. For short-range communication, four-element loop antenna arrays are estimated by simulations and measurements. The transmission coefficient between the antennas of the same perimeter is shown to be larger by more than 12 dB than those of a different perimeter for a 1-cm distance. For long-range communication, a collimating configuration is proposed, and the transmission coefficient between the antennas of the same perimeter is shown to be larger by more than 11 dB for a 1-m distance.