Hua-Ming Chen

Miniature Internal Penta-Band Monopole Antenna for Mobile Phones

A compact T-slit monopole antenna with slotted ground plane in the mobile phone for penta-band operation is proposed. In this configuration, the antenna comprises a T-slit monopole printed on the top ungrounded portion of an FR4 substrate of small size of 47 × 5.4 mm2 and a slotted ground plane etched on the back side of the substrate of size of 47 × 10 mm2. In addition, an inverted-L copper strip is soldered to the end edge of the monopole for extending the electrical length of the antenna for GSM band; that is, the proposed antenna occupies a small volume of 47 × 10 × 5 mm3 inside the mobile phone and is suitable to operate as an internal antenna. By controlling the related parameters, the proposed antenna can resonates at different operating bands to cover GSM850/900 and DCS/PCS/UMTS operations independently.

Microstrip-Fed Circularly Polarized Square-Ring Patch Antenna for GPS Applications

A novel coupling technique for circularly polarized square-ring patch antenna is developed and discussed. The circular polarization (CP) radiation of the square-ring patch antenna is achieved by a simple microstrip feed line through the coupling of a square patch on the same plane of the antenna. Proper positioning of the coupling square patch excites two orthogonal resonant modes with 90deg phase difference, and a pure circular polarization is obtained. The dielectric material is a square block of ceramic with a permittivity of 58 and that reduces the size of the antenna. The prototype has been designed, fabricated and found to have an impedance bandwidth of 1.1% and a 3-dB axial-ratio bandwidth of about 0.03% at GPS frequency of 1573 MHz. The characteristics of the proposed antenna have been studied by simulation software HFSS and experiments. The measured and simulated results are in good agreement.

A Compact Dual-Band Dielectric Resonator Antenna Using a Parasitic Slot

A compact dual-band dielectric resonator antenna (DRA) using a parasitic c-slot fed by a microstrip line is proposed. In this configuration, the DR performs the functions of an effective radiator and the feeding structure of the parasitic c-slot in the ground plane. By optimizing the proposed structure parameters, the structure resonates at two different frequencies. One is from the DRA with the broadside patterns and the other from the c-slot with the dipole-like patterns. In order to determine the performance of varying design parameters on bandwidth and resonance frequency, the parametric study is carried out using simulation software High-Frequency Structure Simulator and experimental results. The measured and simulated results show excellent agreement.

Broadband CPW-Fed Circularly-Polarized Slot Antenna With an Open Slot

A novel broadband CPW-fed circularly-polarized slot antenna with an open slot is presented. The broadband circular polarization can be achieved simply by opening the radiation slot at the lower left of slot. From the experimental results, the 3-dB axial-ratio bandwidth can reach as large as 1000 MHz (27% relative to the center frequency of 3700 MHz) which can cover the 3.3-3.8 GHz WiMAX band. In addition, the proposed design has the VSWR ≤ 2 impedance bandwidth of 5330 MHz (111% relative to the center frequency of 4795 MHz) which can cover the 2-6 GHz WiMAX band. The proposed antenna also has a peak antenna gain of about 5.3 dBic and gain variations can be less than 1 dBic for frequencies within the CP bandwidth.

Circularly Polarized Crossed Dipole Antenna With Phase Delay Lines for RFID Handheld Reader

To produce circularly polarized (CP) radiation, a small, double-sided, crossed dipole antenna with two metal strips loaded for phase delay is proposed. The proposed antenna uses two orthogonal, unequal length dipoles, connected in parallel to a coaxial probe feed. It requires no matching network. The required power and phase relationships are obtained by proper choice of dipole lengths and the metal strips attached to them. The antenna also operates at its half wavelength orthogonal modes, for the UHF band. The phase delay metal strip generates the two resonant modes for CP radiation. Simulated and measured results indicate that the crossed dipole structure can produce CP radiation. An impedance bandwidth (VSWR ≤ 2) of about 11.8% and a 3-dB axial-ratio (AR) bandwidth of about 3.3% around the center frequency of 925 MHz were measured.

Compact Dual-Band Hybrid Dielectric Resonator Antenna With Radiating Slot

A miniature independent dual-band hybrid dielectric resonator antenna (DRA) fed by a coplanar waveguide (CPW) inductive slot is proposed. In this configuration, the CPW inductive slot performs the functions of an effective radiator and the feeding structure of the DR. By optimizing the structure parameters, the hybrid structure resonates at two different frequencies independently. One is from the DRA with the broadside patterns and the other from the inductive slot with the dipole-like patterns. In order to determine the performance of varying design parameters on bandwidth and resonance frequency, parametric study is carried out using simulation software HFSS and experimental results. The measured and simulated results show excellent agreement.

Proximity-Fed Circularly Polarized Slotted Patch Antenna for RFID Handheld Reader

A novel, compact X-shaped slotted square-patch antenna is proposed for circularly polarized (CP) radiation. A cross-strip is embedded along the X-shaped slot for a novel proximity-fed technique to produce CP radiation in the UHF band. In the proposed design, two pairs of T-shaped slots are etched orthogonally on the square patch, connected to the center of the X-shaped slot for CP radiation and antenna size reduction. Proper adjustment of the length and coupling gap of the cross-strip will excite two orthogonal modes with 90 ° phase difference for good CP radiation. Simulated and measured results indicate that the proposed structure can achieve circular polarization. A measured impedance bandwidth (VSWR ≤ 2) of about 3.0% (909-937 MHz) and a 3-dB axial-ratio (AR) bandwidth of about 1.3% (917-929 MHz) were obtained.

Design of an Omnidirectional Polarized RFID Tag Antenna for Safety Glass Applications

An UHF RFID tag antenna which is comprised of a trapezoidal loop and a dual-dipole radiator with an L-slit for omnidirectional polarized reading patterns is designed, fabricated and measured. For a conjugate match to the Monza 3 microchip impedance of 44-j231 at 915 MHz, an orthogonal dual-dipole tag antenna (91 mm × 91 mm) with L-slit on each dipole arm was designed. Simple size adjustments of the L-slit and dipole radiator of the antenna allow for easy control of the antenna resistance and inductive reactance, from which the microchip impedance requirement may be readily satisfied. The read range of the prototype attached on a different glass can reach more than 9 m, which has been tested for an RFID reader with 4.0 W of EIRP. Good tag sensitivity and near omnidirectional radiation patterns were obtained in the desired frequency band.

Miniature Folded Patch GPS Antenna for Vehicle Communication Devices

A novel miniature folded square patch antenna is proposed and developed for Global Positioning System (GPS) receivers. Four different lengths of meander strips connected to the four edges of the square patch of a single coaxial-feed square patch antenna are folded to obtain a circularly polarized antenna. Properly positioning the coaxial feed on the square patch excites two orthogonal resonant modes with a 90 ° phase difference and achieves a pure circular polarization. Conventional antennas for roof-mounted vehicle communication devices use commercially available ceramic corner-truncated patches whereas the proposed GPS antenna is designed to use a less expensive and more compact FR4 patch. Experiments also showed that mounting the proposed GPS antenna in different locations on the roof of a vehicle had little effect on circular polarization radiation. The fabricated prototype revealed an impedance bandwidth of 2.1% and a 3-dB axial-ratio bandwidth approximating 0.76% at a GPS frequency of 1575 MHz. Experiments confirmed that the characteristics of the proposed antenna were consistent with the simulation results.

Single-layer circularly polarized patch antenna for RFID reader application

Radio frequency identification (RFID) system in the ultra-high frequency (UHF) band has gained much interest in several service industries, purchasing and distribution logistics, manufacturing companies and goods flow system [1]. The RFID system generally consists of the reader and the tag, and the UHF RFID system operates at the bands of North America (902–928 MHz), Taiwan (920–928 MHz) and Europe (865–867 MHz). The RFID reader antenna is one of the important components in RFID system and has been designed with CP operation. Circularly polarized antennas can reduce the loss caused by the multi-path effects between the reader and the tag antenna. A CP antenna with a low profile, small size, and light weight is required in portable RFID reader. A typical technique for producing circular polarization is to excite two orthogonal linearly polarized modes with a 90° phase difference. Single-fed circularly polarized annular-ring, square and circular patch antennas with perturbation elements are reported [2–4]. Using perturbation cuts or strips to suitably differentiate the two orthogonal modes at resonant frequency, the antenna can easily radiate CP wave. However, these antennas provide small impedance bandwidth and narrow axial ratio (AR) bandwidth. To enhance an AR bandwidth, a single-fed slot-coupled microstrip antenna for circular polarization operation is preferred [5–7]. The CP antenna is achieved by using an inclined nonlinear coupling slot or unequal arm of crosss-lot. However, a common slot coupling patch antenna in its basic structure consists of two substrates separated by a ground plane. Two substrates increase the volume of the antenna and the complexity of fabrication. Another drawback is that a multi-layered substrate with the coupling slot on the ground plane can result in coupled surface-wave modes, which will lead to distorted radiation patterns.