Wei-Kuo Chia

A Novel Approach for Realizing 2.4/5.2 GHz Dual-Band BPFs using Twin-Spiral Etched Ground Structure

This paper proposes a simple approach for realizing a dual-band response bandpass filter (BPF) comprising two strip feed lines on the upper layer and a twin-spiral etched ground structure (EGS) on the lower layer. It is shown that by moving the two strip feed lines from the center of the EGS toward the upper-left and lower-right corners of the EGS unit, respectively, a 5.2-GHz passband can be excited in addition to the original 2.4-GHz passband. Moreover, by carefully controlling a dimension of the EGS, the second passband can be tuned in such a way as to realize a 2.4/5.7 GHz BPF. The experimental results show that the dual-band 2.4/5.2 GHz BPF has a good passband selectivity and an excellent out-of-band noise suppression capability. Consequently, the device provides an ideal solution for both Industrial-Scientific-Medical (ISM) and Wireless Local Area Network (WLAN) applications.

Compact Etched Ground Structure Ultra-Wideband Bandpass Filter with Adjustable Bandwidth

A bandwidth adjustable ultra-wideband (UWB) bandpass filter is investigated using a simple meander-typed etched ground structure (EGS) unit on the lower ground plane. On the upper layer, the feed line of characteristics 50Ω is modified by attaching a two-directional open-circuited stub to form a modified symmetrical T-shaped microstrip line, which is proposed to achieve wide upper stopband. Three similar EGS morphologies with different dimensions are designed for comparison. We will show that a novel compact EGS UWB filters with adjustable bandwidth can be easily investigated. The center frequency and the bandwidth increase with decreasing effective length of EGS unit. The experimental results show that a EGS unit with an effective length of 23.6 mm yields a UWB filter with the bandwidth of 3.01 ∼ 10.6 GHz. The measured results also show that the fabricated UWB filter has a high out-of-band rejection and a low group delay variation.

Improvement of out-of-band rejected and spurious response for BPF using fourth-order cross-coupling resonator structure

This paper proposes a novel 2.4-GHz fourth-order cross-coupled bandpass filter (BPF) with an electric coupling open-loop stepped impedance resonator (SIR) configuration. The performance characteristics of three BPF configurations are compared, namely a conventional electric open-loop BPF, a conventional second-order SIR electric open-loop BPF, and the proposed fourth-order cross-coupled SIR BPF. Moreover, the coupling coefficients and external quality factors of the proposed filter are systematically derived. A good agreement is observed between the numerical and experimental characterization results. Overall, it is shown that compared to the conventional electric coupling and SIR electric coupling open-loop resonator structures, the proposed fourth-order cross-coupled SIR BPF increases the spurious frequency response to more than 8 GHz and improves the out-of-band rejection capability by more than 20 dB.

Print a small size U-shape-modified broadband slot antenna on ceramic substrate

A microstrip-line-fed U-shaped modified slot antenna is designed and fabricated on AI2O3 ceramic substrate using the printing method. The influences of the length of microstrip-fed line and the thickness of AI2O3 ceramic on the characteristics of designed antennas are well defined in this study. As compared to other available current designs, the proposed structure of the fabricated antennas would offer the advantages of large bandwidth, large return loss, low profile and easy fabrication. Due to the larger dielectric constant of AI2O3 ceramic, the fabricated antenna has a small ground plane size of 30 mm x 30mm, and that is smaller than the slot antennas fabricated on a FR4 substrate. The fabricated slot antenna has a broad bandwidth of 275 MHz/8.9%, a high return loss of -28.0 dB and a maximum gain of 2.77 dBi at 3.12 GHz.

Improving the Coupling Characteristics of Bandpass Filters by Using Multilayer Structure and Defect Ground Units

This paper proposes a novel multi-layer microstrip 2.4 GHz bandpass filter fabricated on two bonded substrates. The multi-layer filter has a symmetrically-bent, open-loop, square- ring stepped impedance resonator (SIR) structure on the top surface of the upper substrate, a similar SIR pattern rotated through 90deg on the lower surface of the upper substrate, and a pair of L-shaped symmetrical defected ground units on the bottom surface of the lower substrate. The simulation results demonstrate that the multi-layer structure improves the electromagnetic coupling characteristics of the bandpass filter and increases both the return loss by more than 30 dB at the center frequency compared to that achieved using a conventional two-layer (SIR-ground) structure, hi addition, the defected ground units etched onto the metallic ground plane beneath the feed lines yield a significant reduction in the spurious harmonics at a frequency of 5.2 GHz. Experimental results are presented to show the performance of the proposed filters.

Development of dual-frequency CPW-fed monopole antennas on the Al 2 O 3 substrates

A simple and compact dual-frequency monopole antenna is presented and investigated and which is suit for the applications of WLAN IEEE802.11b/g (2400-2484 MHz) and IEEE802.11a (5150-5350 MHz). The screen-print technology is used, to print the CPW-fed dual-frequency antennas on AI2O3 ceramic substrates. The proposed antennas have the advantages of small size (29 mmx20 mmxl mm), dual-frequency operation (2.4 and 5.2 GHz), good radiation characteristics (near omni-directional radiation pattern in y-z plane) and large gain (1.29 dBi at 2.35 GHz and 3.96 dBi at 5.27 GHz).

Fabrication of Wide-Band Microstrip Line T-shaped Antenna on the Al2O3Substrate

Recently, due to the rapid developments in the wireless communications, low cost, small size (low profile) and easy fabrication are the major goals of the wireless communication devices. In this paper, the resonant frequency of the purposed antenna is 5.77 GHz, which could be applied for the use of IEEE802.11a WLAN (5725 MHz-5825 MHz) and RFID. However, Al2O3 ceramic is adopted to be the substrates of the antenna in this research because of its high dielectric constant (epsivr=9.8). Therefore, the size of the purposed antenna will be reduced. In this paper, the optimum microwave characteristics of the purposed antenna are: small size (14.18 mm times 20 mm), wide bandwidth (560 MHz/9.71%) at the resonant frequency of 5.77 GHz, and high return loss S11 of -40.92 dB, and enough gain of 2.8 dBi for real use. For that the fabricated antennas can be used in the microwave communication circuits.

Improvement the Characteristics of a Simple Antenna by Using the Tuning Slits and Stub

The major structure of designed monopole antenna is planar form and the operation band is single frequency for LAN and Bluetooth system, which are usually defined as the band from 2400 to 2484 MHz. For the designed antennas, a rectangular antenna pattern is printed on the FR4 substrate, the ground plane is printed on the other side of the substrate. Two different parameters are used to find the designed antennas with the optimum characteristics. The first is to change the length of stub, which is connected on the fed-microstrip-line. The second is to change the length of slits, which are digging in the patch. The IE3D electromagnetic simulator is used to find the optimum characteristics. As compared to other available current designs, the proposed structure of the fabricated antennas would offer the advantages of large bandwidth, large return loss, and low profile. However, the proposed antennas have been successfully designed, optimized, and fabricated in this research.

Designed Wide-Band Microstrip Line-Fed T-shaped Antenna on the Al 2 O 3 Substrate

Recently, there have been rapid and great developments in wireless communication, the operation frequency increase and the size of the microwave devices reduces gradually. Substrates play an important role in the design and fabrication of the small-size microwave devices, especially the dielectric constant and quality factor. In this study, we are tried to design the wide-band microstrip line antenna on ceramic substrate in order to reduce the size of fabricated antenna. High quality factor AI2O3 ceramic is adopted as the substrate and the influences of the structure (the metal of covering and the length of ground) are also investigated in this thesis. Due to the larger dielectric constant of AI2O3 ceramic (epsivr = 9.8), the size of this antenna is small (25 mm x 20 mm). For the designed antenna, the resonance frequency is near 4.2 GHz, the optimum bandwidth is 760 MHz (18.1%), and the return loss (S11) is -36.77 dB. The gain of fabricated antenna is acceptable for the application in the communication.