Yuan-Ming Cai

Compact-Size Low-Profile Wideband Circularly Polarized Omnidirectional Patch Antenna With Reconfigurable Polarizations

A compact-size low-profile wideband circularly polarized (CP) omnidirectional antenna with reconfigurable polarizations is presented in this communication. This design is based on a low-profile omnidirectional CP antenna which consists of a vertically polarized microstrip patch antenna working in TM01/TM02 modes and sequentially bended slots etched on the ground plane for radiating horizontally polarized electric field. The combined radiation from both the microstrip patch and the slots leads to a CP omnidirectional radiation pattern. The polarization reconfigurability is realized by introducing PIN diodes on the slots. By electronically controlling the states of the PIN diodes, the effective orientation of the slots on ground plane can be changed dynamically and the polarization of antenna can be altered between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The proposed antenna exhibits a wide-operational bandwidth of 19.8% (2.09-2.55 GHz) with both axial ratio below 3 dB and return loss above 10 dB when radiates either LHCP or RHCP waves. Experimental results show good agreement with the simulation results. The present design has a compact size, a thickness of only 0.024λ and exhibits stable CP omnidirectional conical-beam radiation patterns within the entire operating frequency band with good circular polarization.

Broadband Circularly Polarized Printed Antenna With Branched Microstrip Feed

A novel broadband circularly polarized antenna is presented in this letter. It consists of a triangular monopole and a slot etched on the ground plane. By employing a branched microstrip feedline to excite the monopole and the slot in parallel, the broadband circular polarization performance of the proposed antenna is realized with overall size of 38 × 54 mm 2. The measured 3-dB axial-ratio bandwidth is 46.8% ( 2.13 ~ 3.43 GHz), and the impedance bandwidth for S 11leqslant -10 dB is 73.0% ( 1.99 ~ 4.28 GHz). Good agreement between the simulated and measured results is also achieved, validating our design concept. The surface current analysis and a parametric study of the design are also carried out to explain the mechanism of circular polarization .

Dual-Band Circularly Polarized Antenna Combining Slot and Microstrip Modes for GPS With HIS Ground Plane

A dual-band circularly polarized antenna for GPS L1 and L2 bands is proposed and investigated in this letter. The dual-band design is realized based on the strategy of combining the microstrip mode and annular slot mode. The proposed antenna consists of an annular slot radiator printed on a square substrate and a high impedance surface (HIS) ground plane. The HIS, working as ground plane for microstrip mode and reflector for slot mode radiation, is settled under the square substrate to realize unidirectional radiation with low profile. Experimental results show that the proposed antenna exhibits two overlapped impedance and axial ratio bandwidth of 40 MHz (1.210-1.250 GHz) and 50 MHz (1.555-1.605 GHz) and the measured gains are about 8.0 dBic and 7.5 dBic, respectively. Very low backward radiation can also be observed in both operating bands.

A Novel Design of Low-Profile Dual-Band Circularly Polarized Antenna With Meta-Surface

A low-profile dual-band circularly polarized (CP) antenna applied for WiMAX (2.5 and 3.5 GHz) is proposed in this letter. With a well-designed meta-surface placed atop a slot antenna, two circularly polarized bands can be excited. The annular folded slot antenna resonates at 2.5 GHz while the meta-surface is designed to excite another CP band around 3.5 GHz, and the meta-surface can also effectively enhance the front radiation. Two CP operation bands are 2.48-2.56 GHz and 3.48-3.63 GHz, with the low frequency ratio (FR) of 1.4 (2.5 GHz/3.5 GHz). The antenna is compact with a low profile of 3 mm, which can be easily integrated in the wireless communication system.

Single-Feed Circularly Polarized Annular Slot Antenna for Dual-Broadband Operation

A novel dual-broadband circularly polarized folded slot antenna with single-feed is presented. The proposed antenna consists of two folded annular slots. By adjusting the asymmetric widths of the two slots, circularly polarized radiation can be achieved in two difierent bands. By optimizing the parameters of the proposed antenna, two wide impedance bandwidths of 35.0% (1.91{2.72GHz) and 46.5% (4.36{7.00GHz) can be obtained, and two axial ratio bandwidths are 2.36{2.56GHz and 5.68{6.04GHz, respectively. The antenna with simple structure is fabricated and measured. Good agreement between the simulated and measured results is also achieved.

Polarization-Reconfigurable Circularly Polarized Planar Antenna Using Switchable Polarizer

A novel polarization-reconfigurable planar antenna is presented. The antenna consists of an electronically reconfigurable polarizer integrated with a printed slot. By changing the states of the p-i-n diodes on the polarizer, the linearly polarized (LP) waves radiated by the slot can be converted into either right-hand circularly polarized (RHCP) or left-hand CP (LHCP) waves. The polarizer contains 16 unit cells arranged as a

DESIGN OF A NOVEL WIDEBAND LOOP ANTENNA WITH PARASITIC RESONATORS

4times 4

Design of a Miniaturized Zeroth- and First-Order Resonant Antenna with Mushroom Cells and Interdigital Capacitors

array. The antenna radiates RHCP waves if the p-i-n diodes on the top side of the polarizer are switched ON, while LHCP waves are radiated if the p-i-n diodes of the bottom side of the polarizer are switched ON instead. The physical mechanisms of the antenna are discussed and the parametric study is carried out by full-wave simulations. To verify the concept, one prototype at 2.5 GHz is designed, fabricated, and measured. Good agreement between the measured and simulated results is obtained. The antenna achieves a gain ≥8.5 dBic in both RHCP and LHCP with an aperture efficiency of 70%. Advantages of the proposed design include electronically reconfigurable polarizations for RHCP or LHCP, low profile, low cost, high isolation between the dc bias circuit and RF signals, high power handling capability, and easy extension to large-scale arrays without increasing the complexity of the dc bias circuit. To the best of our knowledge, this is the first report of an electronically polarization-reconfigurable CP antenna with a single-substrate polarizer.

A Meta-Surface Antenna Array Decoupling (MAAD) Method for Mutual Coupling Reduction in a MIMO Antenna System

A novel coax-fed wideband loop antenna loaded with rectangular patches and U-shaped elements is presented and studied. By inserting a pair of rectangular patches inside the strip loops and employing a pair of U-shaped elements as the parasitic resonators, two additional resonances are excited and a good performance of bandwidth enhancement can be obtained. The measured results indicate that the impedance bandwidth (VSWR•2) is about 87.1% from 1.58 to 4.02GHz, which covers the required operating bands of DCS1800 (1710{1880MHz), PCS1900 (1850{1990MHz), UMTS2100 (1920{ 2170MHz), WLAN2400 (2400{2484MHz), LTE2300/2500 (2300{ 2690MHz) and WiMAX3500 (3300{3690MHz). In addition, good radiation characteristics such as symmetrical radiation pattern, moderate peak gain, low back radiation, and low cross-polarization are observed over the entire operating band.

An Ultra-Wide-Band Tightly Coupled Dipole Reflectarray Antenna

A novel design of miniaturized dual-band antenna based on mushroom cell and interdigital capacitor is presented in this paper. Four transmission line (TL) elements are loaded in a microstrip antenna, and each one is composed of a mushroom cell and interdigital capacitors. The interdigital capacitors contribute to the series capacitance and metallic via-hole of mushroom structures result in the shunt inductance in the equivalent circuit model. The antenna works as a zeroth-order (f0 = 2:51GHz) and flrst-order (f1 = 3:78GHz) resonant antenna with varied radiation patterns. Omnidirectional radiation pattern and unidirectional radiation pattern are obtained at 2.51GHz and 3.78GHz, respectively. The overall size of the antenna is only 0:25£0:25£0:017‚ 3 (at f0 = 2:51GHz). The proposed antenna features compact structure, low proflle and easy fabrication. Good agreement between the simulated and measured results is also achieved, validating our design concept.