An-Shyi Liu

A Dual Wideband Filter Design Using Frequency Mapping and Stepped-Impedance Resonators

A dual-wideband filter design implemented by stepped-impedance resonators, which involves the frequency mapping approach, is presented in this paper. The dual-band filter can be divided into two parts: the wideband virtual passband filter and the narrowband virtual stopband filter. Both filters are designed by conventional synthesis methods, under the assumption that the common connecting lines serve as J- and K-inverters simultaneously. The basic building resonators formed by paralleling open- and shorting-stubs are implemented by unbalanced stepped-impedance resonators, exhibiting the desired resonating frequencies and susceptance slope parameters at these two bands. Two filters are tested to validate this design.

Bandwidth enhancement on waveguide transition to conductor backed CPW with high dielectric constant substrate

This paper proposes a broadband transition design between conductor-backed coplanar waveguide (CB-CPW) and rectangular waveguide based on the concept of the multisection transformer. The genetic algorithm (GA) was adopted to efficiently optimize the multisection transformer for achieving wideband performance. Using a multisection of order 3, a V-band transition realized on an Al/sub 2/O/sub 3/ substrate could achieve 25% bandwidth with a return loss better than 20 dB. Two transitions connected back to back were realized to demonstrate the feasibility of the transition. Also, a tolerance analysis was performed via the simulation to verify the robustness of this transition design.

Ka-band 32-GHz planar integrated switched-beam smart antenna

This paper presents an integrated planar switched-beam antenna based on rectangular waveguide antenna and Butler matrix network for beamforming, which is implemented by complementary-conducting-strip transmission line (CCS TL). The 32-GHz waveguide antenna with size of 71.5 mm by 4.1 mm, consisting of 20 slots in the broadside wall, is built on the Rogers RO4003 (/spl epsiv//sub r/ = 3.38) substrate. For a compact and reliable design of the Butler matrix beamformer, the branch-line coupler and the crossover of the Butler matrix are designed by CCS TLs with characteristic impedance of 60 and 85 /spl Omega/, respectively. The proposed 4-beam smart antenna shows the steered beams in orthogonal direction at 38/spl deg/, 76/spl deg/, 106/spl deg/, and 136/spl deg/, respectively, and demonstrates a great potential for planar integration of smart antenna for wireless communication application. Measured results agree well with theoretical predictions, validating the design concepts employed in the millimeter-wave smart antenna design.

Frequency Tunability of Terahertz Photonic Transmitters

In this study we investigated the frequency tunability of an edge-coupled membrane photonic transmitter. Its frequency tunability was found to be determined, not only by the radiation loss of the device and antenna pattern, but also by the frequency response of the photodetector. With a properly designed device pattern with a slot dipole antenna, which is known to have a strong resonant peak, both high-power conversion efficiency and a broadband response can be achieved. A wide frequency tuning range from <100GHz up to 1.1THz is demonstrated from a single terahertz photonic transmitter. Combined with coherent-controlled quasicontinuous-wave optical excitation, this optoelectronic-based device also exhibits a record-high light-THz power-conversion efficiency of 0.33%.

A wide-stopband low-pass filter design based on multi-period taper-etched EBG structure

Electromagnetic bandgap (EBG) microstrip structures have been proposed in the application of antenna and microwave filter design. The paper demonstrates a design procedure for the EBG structure to achieve a wide stopband low-pass filter, by combining tapered etched holes and multi-period EBG structure. The measurement result shows the rejection band is from 5.2 GHz to 25 GHz, which meets the simulation result.

Synthesis of nonuniformly spaced linear array for GSM/DCS/WCDMA base station application using genetic algorithm

The design of a nonuniformly spaced linear array suitable for a GSM/DCS/WCDMA base station application is presented. In the design, both the interspacing between array elements and the feeding Wilkinson power divider for a triband antenna array are facilitated using a genetic algorithm. The simulation results show the nonuniformly spaced linear array fed by an 8-way Wilkinson power divider is suitable for a triband antenna array design. The performances of radiation patterns and impedance bandwidth meet the specifications of base station antennas.

Design of X-band complementary metal-oxide semiconductor-based frequency-modulation continuous-wave sensor

This study presents an X-band complementary metal-oxide semiconductor-based frequency-modulation continuous-wave (FMCW) sensor system for transportation management. The proposed sensor system has two antennas, one to transmit signals and the other to receive them. The complete radio frequency (RF) transceiver is based on standard 0.18 µm one-poly six-metal (1P6M) CMOS technology with a chip area of 1.68 mm×1.6 mm. Two planar leaky-mode antenna arrays with a gain of 18 dB are also designed. Experimental results indicate that the isolation between two antenna arrays that are 5.0 mm apart exceeds 42.0 dB at 10.5 GHz. The prototype of the FMCW sensor system is used in the range measurement of multiple lanes for the transportation management system (TMS). The major contribution of this study is that it integrates a 0.18 µm CMOS transceiver and antenna arrays into an FMCW RF front end, and employs an IF amplifier and a digital signal processor to demonstrate that the beat frequencies are linear. Measurements made in field tests agree closely with the simulation results.

Highly Directed Radiation Pattern From a THz Photonic Transmitter With a Two-Dimensional Rampart Slot Array Antenna

In this study, we investigate the directivity of the terahertz (THz) radiation pattern from a newly designed two-dimensional rampart slot array antenna integrated in an edge-coupled membrane photonic transmitter. The antenna design is based on the array theory which is well-developed in the microwave regime. By means of the array arrangement of rampart slot antennas, we demonstrate that the 3-dB beam width of the THz radiation pattern at 907 GHz is successfully confined within 30 in both and planes.

A two-phase full-wave GA optimization for W-band image rejection waveguide filter design

The feasibility of a new two-phase design approach for image rejection waveguide filters, using a genetic algorithm, is demonstrated in this paper. The design approach is capable of minimizing the number of simulations required in the full-wave analysis, without sacrificing the accuracy of the final design. In addition, it has been employed for a high-pass waveguide filter design at the W-band and yields a satisfactory performance.

Modeling antenna array elements and bandwidth enhanced by genetic algorithm

A systematic approach for optimal design of broadband antenna arrays is proposed. The method is based on circuit modeling of the antenna array and optimization with genetic algorithm. An optimal design of a printed dipole antenna array is demonstrated.