Sheng-Ming Deng

A WIDEBAND WIDE-STRIP DIPOLE ANTENNA FOR CIRCULARLY POLARIZED WAVE OPERATIONS

A thin dipole antenna is a well-known antenna with linearly polarized wave operation. In this work, a wide-strip dipole antenna is proposed for circularly polarized wave operations. To obtain circularly polarized (CP) wave operations, there are two conditions to be satisfled. One is that the antenna must have two degenerated orthogonal modes with difierent resonant frequencies. The other is that the phase difierence of two orthogonal modes is 90 degrees. To match the flrst condition, the slab width W is tuned to generate current distributions directed in two difierent directions. In addition, the second condition is matched by asymmetric feeding point by adjusting the overlapped square width C. The parametric study is completed by the Ansoft HFSS simulator. Simulated results reveal that the CP wave is mainly in∞uenced by the slab width W. The in∞uences of the parameters C and d on the performances of the proposed antenna are also investigated in this paper. Taking i8dB as reference, there are two working bands for this proposed antenna and the measured center frequencies are 0.66GHz and 2.04GHz, respectively, and the corresponding bandwidths are 0.27GHz (40%) and 1.78GHz (87%), respectively. In addition, the measured center frequencies and bandwidths of the axial ratio are 1.94GHz and 0.53GHz (27%), respectively.

CPW-fed PIFAS with a Capacitively Coupling Slot for Dual Wide-Band Operations

CPW-fed planar inverted-F antennas (PIFAs) with small ground plane for dual-band performance are proposed. The lower band and upper band can be selected independently: PIFA is for the lower band, and capacitively coupling slot is for the upper band. Moreover, the frequency ratio of upper band to lower band can be obtained from 1 to 3.1. The proposed antenna with wider frequency ratio will enable antenna engineer to design dual-band antenna easily. The radiation patterns for the lower band are decided by the PIFA with the quarter-wavelength electric L-shaped monopole patterns, and those for the upper band are dominant over the coupling slot with the half-wavelength magnetic dipole patterns. Hence, both patterns in the dual-band are near omni-directional. An antenna example is given for WLAN dual-band applications. Simulated data are consistent with the measured ones. Measured impedance bandwidth for 2.4 GHz band is 1090 MHz (47.9%), and that for 5 GHz band is 1180 MHz (20.6%). Additionally, through a suitable adjustment in antenna parameters, a wider bandwidth of 1970 MHz (51.2%) can be obtained with center frequency at 3.845 GHz. The radiation patterns and gains are also studied and analyzed.

CPW-fed dual rectangular ceramic dielectric resonator antennas through inductively coupled slots

CPW-fed dual rectangular ceramic dielectric resonator antennas through inductively coupled slots have been studied by experiment. A better bandwidth is achieved if these compare with only single dielectric resonator as antennas. Also, these antennas can be easily do the input impedance matching using several parameters like adjusting the length of inductive slots, the space between dielectric resonators, and the offset distance of DR center to the center of end inductive slots.

Antennas with Two Shorted Rectangular-ring Slots Coupled by Microstrip Line for the Opposite Sense CP in the Wide-Band Operations

The two shorted rectangular-ring slots antenna fed by a microstrip line is presented to achieve the novel characteristic of wide impedance bandwidth with the opposite sense circular polarizations (CP). If the two rectangular-ring slots are arranged to be shorted in the opposite direction, reversely circular polarization will be obtained in the different frequency band. A microstrip line is used to feed power and to couple to the two shorted rectangular-ring slots. Meanwhile, the impedance and axial-ratio (AR) matching are done by adjusting lines parameters. An antenna example is given to result in the lower and upper bands in the 1575 MHz and 1.8 GHz bands. The measured impedance bandwidth is 27.54% which covers the 1575 MHz and 1.8 GHz band. But the polarization for the lower and upper bands is right- and left-hand CP, respectively. The frequency ratio of opposite sense CP band can be lowered to 1.13 and then, give a good choice to design the low frequency ratio with opposite sense CP. The measured ARs center frequency and bandwidth for the lower band is 1.602 GHz and 2.81% respectively, and the minimum AR and antenna gain is 0.987 dB and 3.8 dBic for RHCP, respectively. Meanwhile, the ARs center frequency, bandwidth, antenna gain for the upper band are 1.820 GHz, 3.24%, and 2.43 dBic for LHCP, respectively. Radiation patterns in both bands are broadside radiations and similar to each other except the opposite sense CP characteristic.

A Novel Shorted Rectangular-Loop Antenna for Circularly Polarized Wave Operations

A shorted rectangular-loop antenna is presented for circular polarization applications. The proposed antenna is connected to feeding pin in one end of rectangular-loop metal and shorted to ground in the other end of rectangular-loop metal. It can own wide impedance bandwidth, wide AR bandwidth, and high gain performances in the low profile configuration, especially, without a balanced feeding structure. It is well-known situation of open-loop antenna with circular polarization. The proposed antenna in this paper is interesting for shorted-end of loop antenna, and then, it still has the similar antenna performances as open-loop antenna. An example of WLAN 2.4 GHz application is given. The antenna height is adjusted to fit the required AR bandwidth. The measured impedances center frequency and bandwidth are 2.56 GHz and 17.5%, respectively. Also, the ARs center frequency and bandwidth are 2.44 GHz and 4.1%, respectively. Both impedance and AR bandwidths satisfy the specification of WLAN 2.4 GHz applications. Besides, radiation patterns are broadside radiation and antenna gain in the operating band is about 8 dBic. The proposed shorted rectangular-loop antenna can be applied to high gain antenna or become the elements of higher gain antenna by its good performances and simple feeding structure in a low profile configuration.

A Dual-Port Antenna for GPS and UWB Operations

A dual-port antenna is proposed to operate in the two frequency bands of global positioning system (GPS) and ultrawideband (UWB). First, the shorted ring-slot antenna is etched on the top surface of the FR4 substrate to radiate circularly polarized (CP) waves in the GPS band. Second, a monopole antenna, which is responsible for operation in UWB, is constructed on the bottom surface. In order to reduce the coupling coefficient, the monopole antenna is located in the center region of the bottom surface and the microstip line is placed in the specific region, whose reverse side is grounded. The measured data for impedance and axial ratio (AR) bandwidths in the GPS band are 320 MHz (21.1%) and 80 MHz (5.0%), respectively. As for UWB, experimental results show that the reflection coefficient is below – 10 dB between 2.93 GHz and 10.7 GHz. The antenna gain in GPS is 4.74 dBic and those in UWB are between 4.4 and 5.8 dBi. Moreover, the measured coupling coefficient is below –14 dB between 1.5 GHz and 10 GHz, which implies that the proposed antenna can operate independently in the bands of GPS and UWB.

A broadband CPW-fed planar inverted-F antenna

The paper presents the simulation results for a CPW-fed planar inverted-F antenna. With a suitable arrangement for the distance between the center of the open-ended slot and the feeding pin, a 20.8% (540 MHz) wideband impedance bandwidth can be obtained at 2.6 GHz. The optimal impedance bandwidth corresponding to the height of the inverted-F antenna is analyzed. The radiation patterns are broadside radiation but the main beam is split into two beams with 3.5 dBi gain in any plane, including the z-axis.

An internal multiband inverted-F antenna for laptop applications

A novel multiband antenna which can be integrated into a laptop computer is reported in this conference. The antenna evolved from a dual-band inverted-F antenna vertically mounted on a ground plane of LCD panel. By adding four parasitic resonators which are shorted quarter-wavelength elements, the antenna can achieve wideband performance to cover GSM850/GSM900/DCS/PCS/UMTS and 802.11a/b/g. Simulation was performed here by HFSS to optimally design the antenna and then practical structure was also fabricated to verify the simulation results. The measured antenna parameters as well as radiation efficiency are presented to validate the proposed antenna.

A CPW-fed suspended, low profile rectangular dielectric resonator antenna for wideband operation

An open-ended CPW-fed suspended rectangular dielectric resonator antenna with an air gap between the antenna and substrate is presented, and a lower Q value is obtained than that without an air gap. In the meantime, by experimental results, a wider impedance bandwidth of 15.3% is enhanced to be a fivefold bandwidth of that without an air gap. Additionally, the higher gain performance is achieved to over 6 dBi. Although such kind of antenna configuration has an an air gap, it is still equivalent to the horizontal magnetic dipole antenna. Besides, the front-to-back ratio is 16 dB, and co-polarization to cross-polarization is 23 dB at 4.8 GHz.

CPW-fed rectangular ceramic dielectric resonator antennas with high profile

This work presents the performance of rectangular ceramic dielectric resonator antennas with high profile coupled by an open-ended CPW. Dielectric resonators with dimensions of 18.66 mm /spl times/18.66 mm /spl times/ 6 mm and relative dielectric coefficient of 36 are used to apply to the frequency band of 2.5 GHz. The measured results show the high profile DRA have lower frequency and better bandwidth than those of DRA with low profile.