Wenquan Cao

Broadband Circularly Polarized Microstrip Antenna Array Using Sequentially Rotated Technique

In this letter, a broadband circularly polarized microstrip antenna array with a separate feed network layer is presented. A Wilkinson power divider that provides high isolation between elements and subarrays is employed in constructing the non coplanar corporate feed network of the array. The corporate-fed 4×4 antenna array composed of sequentially rotated 2×2 subar rays is designed and fabricated. The measurement results indicate that the proposed array exhibits a 1-dB axial-ratio (AR) bandwidth of 47.8% in which the return loss is below -10 dB.

Single-Feed Dual-Band Dual-Mode and Dual-Polarized Microstrip Antenna based on Metamaterial Structure

A novel single-feed dual-band dual-mode and dual-polarized microstrip antenna based on metamaterial structure is proposed. The composite right/left-handed transmission line (CRLH TL) theory is used to design this antenna. Dual-mode can be obtained by exciting the antenna with a monopolar radiation in the n = 0 mode and a patch-like radiation pattern in the n = +1 mode, respectively. As the geometry of the radiating patch does not affect the infinite wavelength mode, circular polarization (CP) is obtained for the n = +1 mode by truncating the square radiating patch with the n = 0 mode, linear polarization (LP) staying unchangeable. Results of a fabricated one illustrate that this antenna is valuable in practical application for its low-profile, easy fabrication, radiation pattern selectivity and polarized diversity.

A Low-Cost Compact Patch Antenna With Beam Steering Based on CSRR-Loaded Ground

A novel low-cost compact patch antenna with capability of beam steering is presented in this letter. The complementary split-ring resonators (CSRR)-loaded ground structure enables the property of wide-scale steering range and can greatly reduce the cost of a phased-array system to meet the requirement of the wireless communications. Parameter extraction for the CSRR structure is investigated to analyze the effect of the loading metamaterial on the radiation pattern of the antenna. It is shown that the refractive index of the loading part affects the beam direction. Both of the single and double CSRR-loaded antennas are fabricated to verify the design. Measured results show that the beam of the double CSRR-loaded antenna can scan from -51° to 48° via changing the parameters of CSRR structure.

A High-Isolation Dual-Polarization Patch Antenna With Omnidirectional Radiation Patterns

In this letter, a high-isolation dual-polarization microstrip patch antenna with omnidirectional radiation patterns is proposed. The radiation elements of the antenna are a combination of an annular-ring patch and four curved branches. The annular-ring patch is fed by a modified capacitive coupling structure to radiate a vertically polarized omnidirectional pattern, while the four curved branches that are set around the annular-ring patch with a suitable distance for high isolation are fed in phase to radiate a good horizontally polarized omnidirectonal radiation pattern. The isolation between the two ports is better than a high degree of - 40 dB to limit the interference of the signals. A prototype of the proposed antenna is fabricated and measured to verify the predictions, and the measured results are in good agreement with the simulated ones. The proposed antenna is a good candidate for wireless communication for its extremely low profile, high port isolation, and omnidirectional radiation property.

A Single-Feed Broadband Circular Polarized Rectangular Microstrip Antenna With Chip-Resistor Loading

A single-feed circular polarized (CP) rectangular microstrip antenna (MPA) is proposed. Capacitive disk coupling feed is used in the design. By connecting a resistor load to another capacitive disk at the opposite position, CP radiation over a wide frequency range is realized. Experimental results show that the fabricated antenna has an impedance bandwidth (S11 return loss) of 78.7% and a 3-dB axial ratio (AR) bandwidth of 27.5%. The peak gain level is about 6.8 dB. As a result, this antenna can be used in occasions when wide AR CP performance is desired.

A Dual-Band Microstrip Antenna with Omnidirectional Circularly Polarized and Unidirectional Linearly Polarized Characteristics Based on Metamaterial Structure

A novel single-feed dual-band microstrip antenna with omnidirectional circularly polarized (CP) and unidirectional linearly polarized (LP) characteristics for each band is proposed in this paper. The function of dual-band dual-mode is realized based on loading modified mushroom structure. By employing curved branches in the radiating patch, CP property for the omnidirectional zeroth-order resonance (n = 0 mode) is achieved. As the curved branches have little effect on the radiation pattern of patch mode, LP property for n = +1 mode stays the same. A prototype is fabricated to verify the properties of the antenna. Both simulation and measurement results illustrate that this antenna is valuable in practical application for its low-profile, radiation pattern selectivity and polarization diversity.

Multi-Band Multi-Mode Microstrip Circular Patch Antenna Loaded With Metamaterial Structures

Abstract A microstrip circular patch antenna with multi-band multi-mode function is presented in this paper. Metamaterial structures including four curved lines added around the circular radiating patch and a circular ring of modified mushroom cells loaded under the radiating patch enable this property. Two monopole modes with omnidirectional radiation patterns in the azimutal plane and one patch mode with patch-like radiation pattern between them are excited by a single probe feed for this novel antenna. A prototype was designed and fabricated for verification. Both simulation and measurement results verify that this antenna is valuable in wireless communications for its low-profile structure and radiation pattern selectivity.

Low-Profile Patch Antennas With Vertical Monopole-Like Radiation Patterns Based on Modified Capacitive Coupling Structures

A low-profile linearly polarized (LP) patch antenna with a vertical monopole-like radiation pattern is proposed in this letter. Modified capacitive coupling structure (MCCS) that is introduced to feed the patch antenna compactly enables the polarization flexibility without changing the near- and far-field characteristics much. Then, four curved branches are added around the circular radiating patch to employ a horizontal wave of the same amplitude and 90° phase difference, thus an antenna with circularly polarized (CP) characteristic is realized. In order to decrease the resonant frequencies of both the LP and CP antennas to the GPS l1 band, four shorted pins are adopted to connect the patch with the ground. Antenna prototypes are fabricated to verify the designs; the measured and simulated results are in good agreement. Both the LP and CP antennas own the feature of low profile (less than 0.05λ), which is a good candidate for GPS communication.

A forward narrow-wall double-slot 3 dB coupler based on hybrid HSIW/GCPW guided-wave structure

Based on a novel hybrid guided-wave structure of half-mode substrate integrated waveguide (HSIW) and ground coplanar waveguide (GCPW), a forward narrow-wall double-slot 3 dB coupler with the center operating frequency of 18 GHz is proposed. The narrow-wall double-slot coupling mechanism between TE10 mode of SIW and TEM mode of GCPW is studied and efficient coupling is achieved by using triangle-shaped slots. Such coupler takes the advantages of low profile, low insertion loss of HSIW and flexibility of GCPW. The coupler is fabricated and the measured results are in agreement with the simulated ones. A relative bandwidth over 20% is achieved with 0.5 dB amplitude imbalance excited at different ports.

Microstrip antenna with radiation pattern selectivity and polarized diversity based on modified metamaterial structure

In this paper microstrip antenna with linear polarization (LP) for monopolar radiation pattern mode and circular polarization (CP) for patch-like radiation pattern mode is presented. The introduction of modified metamaterial structure enables antenna with this function. Equivalent evolutionary approximation of the proposed antenna from CRLH TL theory is used to analyze the operating principle. Both simulated and measured results of a proposed one confirm the predictions of the theory. Comparing to the former dual-mode and dual-polarized antennas, this one owns compact structure and good radiation properties besides radiation pattern selectivity and polarized diversity.