Yen-Ju Lu

A Differential-Mode Wideband Bandpass Filter With Enhanced Common-Mode Suppression Using Slotline Resonator

A novel design of a differential-mode (DM) wideband bandpass filter (BPF) with enhanced common-mode (CM) suppression using a slotline resonator is presented. The BPF consists of two pairs of parallel microstrip transmission lines, a pair of transverse microstrip sections connected to the transmission lines, and a longitudinal slotline resonator placed in the ground plane. With proper placement of the slotline resonator, the mode coupling between the slotline mode and the (DM) signals can be maximized, while that between the slotline mode and the CM signals can be minimized. It is found that throughout the (DM) passband, the insertion loss of the CM signals is higher than 47.5 dB, the fractional bandwidth defined by the 10 dB return loss for the (DM) signals is about 105%, and the insertion loss for the (DM) signals ranges from 1.22 to 5.82 dB over the fractional bandwidth. Good agreement between simulated and measured results is obtained.

Capacitively-Loaded Loop Antenna for Multi-Band Mobile Handsets

Due to the low profile and the simple structure, the planar monopole antennas and the planar inverted-F antennas (PIFA) have been very attractive in the mobile handset applications. Although the planar loop antennas possess similar features, they have not been discussed extensively. Moreover, the urging requirement for multi-band operations makes the handset antenna design more and more challenging. In this paper, we present a capacitively-loaded loop antenna with a low profile, simple structure, and multi-band capabilities. The operation principles are discussed. A prototype antenna is designed, fabricated, and tested. The impedance and radiation performances are shown to be satisfactory throughout the designed operating bands.

Harmonic Suppressed Slot Loop Antenna Fed by Coplanar Waveguide

A harmonic suppressed coplanar waveguide (CPW)-fed slot-coupled circular slot loop antenna is proposed. Two coupling slots placed inside the radiating slot loop and connected directly to the CPW are used for the harmonic suppression. By properly adjusting the coupling slot lengths, the second and third harmonics can be suppressed separately or simultaneously. The principle of harmonic suppression is discussed, and simulation and measurement results are also presented and discussed.

Finite-width conductor-backed coplanar waveguide-fed side-plane antenna

A novel miniaturized finite-width CBCPW-fed side-plane antenna has been presented. The proposed antenna utilizes two shorting strips at the slots of the finite-width CBCPW to excite the side-plane ground conductors properly and a broadside radiation pattern has been achieved. The measured 10-dB return loss bandwidth of the proposed antenna is 5.8 %. The measured peak antenna gains in band range from 5.38 dBi to 6.33 dBi. The proposed antenna has a simple structure, compact size, unidirectional radiation pattern, and moderate antenna gains. The simulated and measured results are in good agreement.

CBCPW-Fed Side-Plane Patch Antenna

A side-plane patch antenna fed by a conductor-backed coplanar waveguide (CBCPW) is proposed. By etching a slotline pair on the side planes in the transverse direction of the CBCPW, the surface currents on the two side planes can be made the same phase and a 4.8-dBi antenna gain is achieved. This antenna is compared to a two-element patch antenna array fed by a microstrip line. Similar return loss response, antenna gain, and radiation mechanism are observed.

A Hybrid Design of Printed Antenna Fed by Coplanar Waveguide With and Without Back Conductor

A hybrid design of coplanar waveguide (CPW)-fed printed antenna with and without back conductor (BC) is presented. An E-shaped strip protruded from the signal strip of the feedline is used to connect the two side (ground) planes of the antenna, and a pair of thin slits cut in the side planes adjacent to the two side arms of the E-shaped strip is employed to tune the input impedance of the antenna with BC. When BC is placed, the antenna is a conductor-backed CPW (CBCPW)-fed side-plane patch antenna, while when BC is removed, the antenna becomes a CPW-fed slot dipole antenna. The antenna is designed to have the side-plane patch and the slot dipole operate at the same frequency, so that it can adapt itself to the presence or absence of a BC. Resonant behaviors and radiation characteristics of the proposed hybrid antenna with and without a BC are presented. Design details and simulation and measurement results are also presented and discussed.

A dual-band CPW-fed stepped-impedance slot antenna with wide range of frequency ratio

A capacitively excited coplanar waveguide-fed dual-band stepped-impedance slot antenna with wide range of frequency ratio is proposed. The wide range of frequency ratio is achieved by the first two modes of the stepped-impedance slot. The stepped-impedances are characterized by the slotline of different sizes, and the lower and upper bounds of the frequency ratio for the proposed slot antenna are presented and discussed. Simulation and measurement results are also presented.

Metamaterial-inspired circularly polarized slot dipole antenna fed by coplanar waveguide

A novel metamaterial-inspired circularly polarized slot dipole antenna fed by coplanar waveguide is proposed. Two slot dipoles are placed perpendicular to each other to get two orthogonal polarizations and a shunt inductor is inserted in the right-hand-side slotline of the coplanar waveguide to have 90° phase advance than the left-hand-side one, such that the circularly polarized radiation is achieved. Simulated and measured results are presented and good agreement between them is observed.

Design of an EBG-backed CPW-fed slot antenna

Design of an electromagnetic-bandgap-backed coplanar waveguide-fed slot antenna is presented. The antenna is formed by placing a coplanar waveguide-fed slot dipole on top of an electromagnetic bandgap structure. A leaky wave mode of the electromagnetic-bandgap-backed slotline is found and utilized to design the antenna. Characteristics of the leaky wave mode and simulated and measured results of the antenna are presented and discussed. Good agreement between simulated and measured results is obtained.

Finite-width conductor-backed coplanar waveguide-fed circularly polarized side-plane antenna

The coplanar waveguide with a lower ground plane forms the conductor-backed coplanar waveguide (CBCPW). Due to the lower ground plane, the mechanical strength and heat-sinking capability of the conventional coplanar waveguide are improved [1]. In practice, the substrate and the ground planes of the CBCPW are usually of finite width. The CBCPW mode and the microstrip-like mode coexist in the finite-width CBCPW. Both of them have zero cutoff frequency [2]-[3]. The phase velocity of the microstrip-like mode (MSL) is slower than the CBCPW mode. Therefore, the MSL mode takes power away all the time. The leaky MSL mode causes the resonances of the side-plane conductors. The transmitted power is reduced by the reflected and radiated power when the side-plane conductors resonate [4]. The unwanted radiation maybe degrades the performance of the finite-width CBCPW-fed antenna unless through-plated vias are placed at the inner edges of the side-plane conductors [5]. Using through-plated vias increases the manufacturing cost. With proper design, the side-plane conductors fed by finite-width CBCPW can form a simple, vialess, unidirectional, and linearly polarized antenna [6]. In this paper, a compact finite-width CBCPW-fed circularly polarized (CP) side-plane antenna is proposed.