A simple and novel reconfigurable dual-band dual-circularly polarized (CP) cavity backed high-gain antenna for vehicle global navigation satellite system (GNSS) is first reported in this paper. This ...design consists of a simple planar printed monopole with four branches, four pin-diodes and a modified cavity. Four pin-diodes are used to control the length of these four branches. By asymmetrically changing the states of these four diodes, this antenna can resonate both right-hand circular polarization (RHCP) wave and left-hand circular polarization (LHCP) wave at two bands. An elliptical cavity with a metal step is adopted to realize unidirectional radiation. To verify the concept, one prototype is fabricated and measured. The measured impedance bandwidths (|S 11 | < −10 dB) are 22.69% (1.055-1.325 GHz) and 5.68% (1.54-1.63 GHz), and the 3-dB axial ratio (AR) bandwidths are 7.4% (1.211-1.304 GHz) and 3.91% (1.554-1.616 GHz) with only 1.261 center frequency-ratio (CFR). The proposed antenna has advantages of simple structure, reconfigurability, higher gain, and smaller CFR.
This paper presents a novel shared-aperture dual-band dual-polarized (DBDP) high-gain antenna for potential applications in synthetic aperture radars (SARs). To reduce the complexity of SAR antennae, ...a DBDP high-gain antenna based on the concept of Fabry-Perot resonant cavity is designed. This antenna operates in both Cand X-bands with a frequency ratio of 1:1.8. To form two separate resonant cavities, two frequency selective surface layers are employed, leading to high flexibility in choosing desired frequencies for each band. The beam-scanning capability of this proposed antenna is also investigated, where a beam-scanning angle range of ±15° is achieved in two orthogonal polarizations. To verify this design concept, three passive antenna prototypes were designed, fabricated, and measured. One prototype has broadside radiation patterns, while the other two prototypes have frozen beam scanned to +15°. The measured results agree well with the simulated ones, showing that the high gain, high port isolation, and low cross-polarization levels are obtained in both the bands. Compared with the conventional high-gain DBDP SAR antennae, the proposed antenna has achieved a significant reduction in the complexity, mass, size, loss, and cost of the feed network.
This paper presents a novel method of designing the compact dual-sense circularly polarized (CP) microstrip antenna/array with improved impedance bandwidth, axial ratio (AR) bandwidth, and ...interpolarization isolation. The lefthand and right-hand CP characteristics are achieved simultaneously by conceiving a vertically coupled resonant structure for the first time. Different from traditional methods, the antenna shows a compact size but exhibits the wide impedance and 3 dB AR bandwidths. For each input, two coupling paths are purposely designed to excite the TM10 and TM01-mode of the patch, respectively. By composing different coupling units in the two paths, an intrinsic ±90° phase difference over a broadband can be obtained, resulting in the broadband CP characteristics. In addition, a novel method of using the neutralization line between the two feeds is investigated to improve the isolation between the polarizations. Based on the dual-sense CP element, a 1 × 4 dual-sense CP array is composed to exemplify its potential applications in large arrays. Compared with traditional CP antennas, the proposed antennas have the advantages of compact size, simplified feed, broad impedance and 3 dB AR bandwidths, and improved isolation. Experimental results verify the predictions.
A novel ultra-wideband (UWB) circularly polarized (CP) antenna array with sequential phase feed is proposed in this article. The element implements a multiresonance monopole to achieve UWB CP ...radiation. To investigate the CP operating mechanism, characteristic mode analysis is used to provide different modes at various frequencies. The simulated characteristic mode analysis results show that this element can realize good CP at three independently adjustable frequencies (2.4, 3.8, and 5.8 GHz). By combining these three frequencies, a UWB CP antenna element is realized from 2.02 to 6.03 GHz for axial ratio (AR) less than 3.0 dB. Because the main radiating region of this element changes at different frequencies, a compact 2 <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 2 array, whose profile is only <inline-formula> <tex-math notation="LaTeX">0.09\lambda </tex-math></inline-formula> (where <inline-formula> <tex-math notation="LaTeX">\lambda </tex-math></inline-formula> is the wavelength in free space at the lowest operating frequency), is designed and optimized to achieve higher realized gain and stable radiation pattern. Subsequently, a prototype of this array is fabricated and measured. Measured results demonstrate an overlapping bandwidth of 120.9% from 1.8 to 7.3 GHz, in terms of the −10 dB reflection coefficient bandwidth and 3 dB AR bandwidth. This array has the advantages of simple structure, compact size, high gain, and stable pattern within the entire operating band.
A novel concept of antenna design, termed differential mode/common mode (DM/CM) design, is proposed to achieve a highly integrated multi-input multi-output (MIMO) antenna unit in mobile terminals. ...The inspiration comes from a dipole fed by a differential line which can be considered a DM feed. What will happen if the DM feed is transformed into a CM feed? Some interesting features are provided in this article. By symmetrically placing one DM antenna and one CM antenna together, a DM/CM antenna can be achieved. Benefitting from the coupling cancellation of antiphase currents and the different distributions of the radiation currents, a DM/CM antenna can obtain high isolation and complementary patterns, even if the radiators of the DM and CM antennas are overlapped. Therefore, good MIMO performance can be realized in a very compact volume. To validate the concept, a miniaturized DM/CM antenna unit is designed for mobile phones. The 24.2 dB isolation and complementary patterns are achieved in the dimension of 0.330λ 0 × 0.058λ 0 × 0.019λ 0 at 3.5 GHz. One 8 × 8 MIMO antenna array is constructed by using four DM/CM antenna units and shows good overall performance. The proposed concept of DM/CM design may also be promising for other applications that need high isolation between closely packed antenna elements and wide-angle pattern coverage.
A novel low-cost, dual-polarized, two-dimensional (2-D) leaky-wave antenna (LWA) with four beams is proposed in this paper. The proposed 2-D LWA includes a 2-D leaky-wave radiation aperture and an ...orthogonal feeding network. The 2-D leaky-wave radiation aperture is evolved from two identical 1-D parallel-plate long-slot LWAs that are orthogonally placed within a shared radiation aperture. Based on the proposed feeding networks, two pairs of orthogonal in-phase excitations are provided for the proposed 2-D radiation aperture to realize four beams with orthogonal polarizations. Combining the frequency-controlled beam-scanning characteristic of 2-D LWA in elevation plane and the quad-beam radiation by the proposed feeding network in azimuth plane, a wide-angle beam-scanning characteristic can be realized. Besides, different from the conventional multi-beam antenna with multiple feeding ports or multiple radiation apertures, only a simple coaxial feeding port and single aperture are used, which greatly reduces the complexity and cost of the antenna. A prototype for verifying the design concept is manufactured and measured. The measurement results illustrate that the antenna supports a wide beam-scanning range around ±83° except for broadside direction in two orthogonal elevation planes with orthogonal polarizations. Furthermore, a wide operating bandwidth from 23 GHz to 33.6 GHz with a peak realized gain of 21.2 dBi is obtained by the antenna. The low-profile, quad-beam, dual-polarized, wideband, high-gain, low-cost, and wide-angle beam-scanning features make the proposed antenna suitable for various millimeter-wave applications.
This article presents the first report of a circularly polarized (CP) omnidirectional radiation antenna for wireless capsule endoscope (WCE) system applications. The proposed antenna incorporates an ...integrated design concept, and achieves operation at 0.915 GHz Industrial, Scientific, and Medical (ISM) band (0.902-0.928 GHz) with a compact size of <inline-formula> <tex-math notation="LaTeX">\pi \times 5.5^{2} \times 22 \text {mm}^{3} </tex-math></inline-formula>. The simulation is performed in Ansys HFSS, with the antenna being placed in the center of a cylindrical homogeneous muscle tissue with a size of <inline-formula> <tex-math notation="LaTeX">\pi \times 55^{2} \times 80\,\,\text {mm}^{3} </tex-math></inline-formula>. The simulated results show that the capsule antenna has an impedance bandwidth (BW) (<inline-formula> <tex-math notation="LaTeX">\vert S_{11} \vert < -10 </tex-math></inline-formula> dB) from 0.82 to 0.99 GHz and a CP BW (AR < 3 dB) from 0.84 to 1.09 GHz. Moreover, the omnidirectional CP radiation properties remain stable for a very wide <inline-formula> <tex-math notation="LaTeX">\theta </tex-math></inline-formula> range (49°-144°) in the elevation plane. The robust CP performance and the integrated design concept make the proposed antenna suitable for advanced WCE systems.
A novel self-diplexing aperture-shared dual-band dual-sense circularly polarized (CP) antenna array is proposed for transmitting/receiving (Tx/Rx) applications in X-band satellite communication ...systems. The antenna is capable of receiving the left-handed CP (LHCP) signals in the low band while transmitting the right-handed CP (RHCP) signals in the high band. First, a dual-port cavity-fed linearly polarized (LP) patch antenna with high isolation is developed as the element of the array. The element is composed of a slotted patch, a U-slot loaded substrate integrated cavity (SIC), and two groups of split-ring resonators (SRRs). The LHCP and RHCP operations are achieved by employing two sequentially rotated feeding networks which are isolated by a ground plane. To reduce the mutual coupling between the radiators, narrow slots are etched out in the center of the patches. Importantly, the sharing of patches at different bands (i.e., common aperture) enables a compact footprint to be achieved for the array, which is beneficial for suppressing undesirable grating lobes due to the reduced interelement spacing. The measured results of a fabricated prototype agree well with the simulations, showing an impedance bandwidth of 7.2-7.75 GHz (7.85-8.4 GHz), 3 dB axial ratio (AR) bandwidth of 7.4-7.7 GHz (7.95-8.32 GHz), and gain of 14 dBic (14.2 dBic) at the low band (high band). The channel isolation is over 27 dB and the sidelobe levels are below −15 dB in both bands. The demonstrated low-profile dual-band, dual-sense CP antenna array can be a good candidate for satellite communication.
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