A dual-beam filtering patch antenna consisting of a slotted patch, a metal strip underneath the patch, two pins, and a ground plane are proposed for wireless communication application. A wide operation band with stable symmetrical dual-beam far-field radiation pattern is obtained, and two radiation nulls at the lower and the upper band edges, respectively, are controlled to ensure a sharp roll-off rate at the band edges for both reflection coefficient and realize gain. Undesired higher modes can be suppressed over the stopband by changing the spacing between the patch and ground pane. With entire height of 0.058λ0, the proposed antenna is implemented to show a -10 dB bandwidth of 3.0-3.8 GHz, a consistent realized gain of about 6.8 dBi within the passband for both two radiation beams directed at ±30°, out-of-band radiation suppression level of higher than 17dBi, and good band-edge selectivity.

A shared-radiator dual-band dual-sense circularly-polarized (CP) microstrip antenna with duplexing and filtering functions is presented. For each band, there is a coupling network, which consists of a hairpin resonator, a straight slot, and a U-slot, and thus two paths with an inherent 90o or -90o phase difference are available for the input signal to couple to the patch, left-handed CP (LHCP) characteristic and right-handed CP (RHCP) characteristic are respectively realized at different bands for the proposed antenna with a single patch. Such a dual-band dual-sense CP patch antenna is highly integrated and outperform other traditional CP antennas state-of-the-art. Moreover, the duplexing and filtering functions are seamlessly integrated in the dual-band patch antenna with a low-profile (0.044λo), and application of such an integrated device in wireless systems can potentially reduce the volume, complexity, and cost of RF front-ends. Based on resonator-based topologies, the principles of achieving the dual-sense CP, duplexing, and filtering functions are illustrated. As a proof-of-concept, an antenna working at C-band is prototyped and tested. Good agreements between the measured and simulated results are achieved, showing a LHCP radiation characteristic for the low-band operation and a RHCP radiation characteristic for the high-band operation, respectively. The antenna also exhibits very good frequency selectivity, and out-of-band rejection performance. At the low-band, the impedance and 3-dB axial-ratio (AR) bandwidths are 4.7% and 1.1%. At the high-band, the impedance and AR bandwidths are about 7.3% and 3.2%. The isolation between the two channels/bands is over 24 dB.

A dual-beam filtering patch antenna with two absorptive band-edge radiation nulls and four reflective stopband radiation nulls is proposed. By loading a pair of T-shaped metallic strip underneath the radiating patch, a modified TM ₂₂ mode with TM ₂₀ -like radiation pattern is obtained, which combines with the TM ₂₀ mode of the radiating patch, generating a wide operating band with symmetrical dual-beam radiation pattern. Two reflective radiation nulls are generated in both upper and lower stopbands for suppressing the out-of-band radiation. Through embedding two pairs of shorted small patch in the radiating patch, one absorptive radiation null combining with one absorptive resonant mode is produced at each band edge to absorb the band-edge incident energy, leading to a reduced reflection and sharp roll-off at both band edges, and therefore, the transceiver can be protected. With a total height of $0.038~\lambda _{0}$ , a prototype is designed, fabricated, and measured, showing a −10 dB impedance bandwidth from 4.63 to 6.10 GHz with sharp band-edge roll-off, two radiation beams directed at ±40° with an in-band gain of 6.0 dBi, and high out-of-band suppression of over 15 dB.

This communication presents an ultra-wideband dual-polarized antenna consisting of a main radiator, parasitic elements, and a ground plane. The main radiator is composed of two pairs of dual-dipoles, which are cross-arranged and fed by coplanar-strip lines in order to achieve ±45° dual-polarization within a wide frequency band. Parasitic elements including a circular patch and four pairs of dipole strips are employed for improving the radiation performance in the high frequencies, which is very essential for stabilizing the radiation pattern over the entire bandwidth. The proposed antenna can cover the frequency range from 1.7–5.1 GHz for both polarizations, corresponding to an ultra-wide bandwidth of 100%. The gain and half-power beamwidth (HPBW) are very stable within the entire bandwidth, which are 8.2±0.7 dBi and 65°±5°, respectively. Measured results agree well with simulated ones, indicating that the proposed antenna is a very promising candidate for the future base station communication system.

In this paper, a stacked circular polarization (CP) patch antenna with broad impedance bandwidth, axial-ratio (AR) bandwidth, and flat gains is investigated. The antenna is composed of a square ring, double layers' stacked patches, and four vertical patches. The corner truncated loop served as a sequential phase feeding structure for four driven patches. To improve the impedance matching, four square patches are stacked on the bottom layer. Furthermore, four vertical patches are introduced on the ground plane to broaden the AR bandwidth. Simulated and measured studies are conducted on an antenna prototype to validate the proposed design. The proposed design shows that the measured impedance bandwidth is 4.65-7.21 GHz (43.2%), measured 3-dB AR bandwidth at broadside is 4.9-6.4 GHz (26.5%) and the 1-dB gain bandwidth is 4.75-6.6 GHz (32.6%). Compared with other similar CP stacked patch antennas, the antenna owns advantages of wide bandwidth, compact size, and flat gain.

With wide impedance bandwidth (IBW), wide axial-ratio bandwidth (ARBW), stable AR beamwidth, and stable half-power beamwidth (HPBW), a dual-circularly-polarized (DCP) crossed-dipole antenna is proposed. Each dipole consisting of two patches is fed by a pair of parallel transmission line, leading to a wide IBW. To enhance the ARBW and AR beamwidth, a quadrature wideband coupler is used, and the overlapping bandwidth of IBW and ARBW is up to 100%. The quadrature coupler is integrated with two pairs of parallel transmission line, and are printed on two substrates, which are squeezed into the space between the radiators and reflector, resulting into a compact antenna structure. With a total height of 0.016 λ _L , a prototype is fabricated and measured, showing 1.5-VSWR IBW of larger than 104% for both Left-handed CP (LHCP) and Right-handed CP (RHCP), 3-dB ARBW of up to 100% both for LHCP and RHCP, and port-to-port (polarization) isolation of lager than 30 dB in 1.70 - 2.82 GHz, so the effective bandwidth (EBW) is about 50% (1.70 - 2.82 GHz). 3-dB AR beamwidth of 76° ± 5°, stable DCP characteristics with average gain of 7.2 dBi and HPBWs of 67° ± 4° are achieved.