This paper presents a novel kind of patch antenna with high-selectivity filtering responses and high-gain radiation performance. The proposed antenna is mainly composed of a driven patch and a stacked patch, with its entire height being ${0.09\lambda }$ . Three shorting pins and a U-slot are embedded in the driven patch to enhance out-of-band suppression levels and skirt selectivity near the lower band-edge, whereas the stacked patch provides a sharp roll-off rate at the upper band-edge and also an enhanced gain. Without using extra filtering circuits, the proposed antenna exhibits a quasi-elliptic boresight gain response with three radiation nulls. For demonstration, an antenna is implemented covering the LTE band (2.3–2.7 GHz). The antenna achieves an average gain of 9.7 dBi within passband, and out-of-band suppression levels of more than 21 dB.

High-Gain Filtering Patch Antenna Without Extra Circuit

A low-profile, high-gain, and wideband metasurface (MS)-based filtering antenna with high selectivity is investigated in this communication. The planar MS consists of nonuniform metallic patch cells, and it is fed by two separated microstrip-coupled slots from the bottom. The separation between the two slots together with a shorting via is used to provide good filtering performance in the lower stopband, whereas the MS is elaborately designed to provide a sharp roll-off rate at upper band edge for the filtering function. The MS also simultaneously works as a high-efficient radiator, enhancing the impedance bandwidth and antenna gain of the feeding slots. To verify the design, a prototype operating at 5 GHz has been fabricated and measured. The reflection coefficient, radiation pattern, antenna gain, and efficiency are studied, and reasonable agreement between the measured and simulated results is observed. The prototype with dimensions of 1.3 $\lambda_{0}\times1.3\ \lambda_{0}\times0.06\ \lambda_{0}$ has a 10-dB impedance bandwidth of 28.4%, an average gain of 8.2 dBi within passband, and an out-of-band suppression level of more than 20 dB within a very wide stop-band.

A Low-Profile High-Gain and Wideband Filtering Antenna With Metasurface

A novel differentially-driven dual-polarized antenna is proposed in this communication. It is a magneto-electric dipole antenna whose gain and beamwidth keep constant along frequency within the operation bandwidth. If the antenna is ideally symmetrical, its differential port-to-port isolation is theoretically infinite. Due to the differentially-driven scheme, its cross-polarization level can be very low. Measurement shows that the proposed antenna achieves a wide impedance bandwidth of 68% (0.95 to 1.92 GHz) for differential reflection coefficients less than -10 dB and high differential port-to-port isolation of better than 36 dB within the bandwidth. The 3-dB-gain bandwidth of the proposed antenna is 62% (1.09 to 2.08 GHz), and the radiation pattern across it is stable and unidirectional. The broadside gain within the 3-dB-gain bandwidth ranges from 6.6 to 9.6 dBi. The cross-polarization level is lower than -23 dB across the 3-dB-gain bandwidth. The proposed antenna is the first differentially-driven dual-polarized magneto-electric dipole antenna. A feeding structure is specially designed to fit the differentially-driven scheme, and also to achieve wide impedance and gain bandwidths.

A Differentially-Driven Dual-Polarized Magneto-Electric Dipole Antenna

Design, fabrication, and measurement of a new compact filter-antenna for modern wireless communication systems are presented in this letter. Two microstrip square open-loop resonators, a coupled line, and a Γ-shaped antenna are used and integrated to be a filter-antenna. The Γ-shaped antenna is excited by a coupled line that is treated as the admittance inverter in filter design. The Γ-shaped antenna performs not only a radiator, but also the last resonator of the bandpass filter. Therefore, near-zero transition loss is achieved between the filter and the antenna. The design procedure follows the circuit approach-synthesis of bandpass filters. Measured results show that the filter-antenna achieves an impedance bandwidth of 16.3% (over 2.26-2.66 GHz) at a reflection coefficient |S11 | <; - 10 dB and has a gain of 2.41 dBi.

A New Compact Filter-Antenna for Modern Wireless Communication Systems

A compact circularly polarized (CP) co-designed filtering antenna is reported. The device is based on a patch radiator seamlessly integrated with a bandpass filter composed of coupled stripline open-loop resonators, which are designed together as a system. In the proposed design, the patch functions simultaneously as the radiator and the last stage resonator of the filter, resulting in a low-profile integrated radiating and filtering module with a small overall form factor of $\mathbf{0.53{\lambda _0} \times 0.53{\lambda _0} \times 0.07{\lambda _0}}$ . It is shown that the filtering circuit not only ensures frequency selectivity but also provides impedance matching functionality, which serves to broaden both the impedance and axial ratio bandwidths. The designed filtering antenna was fabricated and measured, experimentally achieving an $\mathbf{{S_{11}} , an axial ratio of less than 3 dB and a gain higher than 5.2 dBi over a bandwidth from 3.77 to 4.26 GHz, i.e., around 12.2%, which makes it an excellent candidate for integration into a variety of wireless systems. A linearly polarized version of the integrated filtering antenna was also demonstrated. In addition, further full-wave simulations and experiments were carried out to verify that the designed CP filtering antenna maintains its properties even when mounted on different positions of the human body with various body gestures. The stable impedance and radiation properties also make it a suitable candidate as a wearable antenna for off-body wireless communications.

A Compact, Wideband Circularly Polarized Co-designed Filtering Antenna and Its Application for Wearable Devices With Low SAR

In this letter, a co-designed antenna-filter is presented. The antenna-filter is composed of a microstrip patch antenna and a hairpin filter, both of which share the same ground plane to reduce the size. Instead of using the traditional 50-Omega interfaces, the impedance between the filter and antenna is optimized to improve the performance. The simulated and measured results have demonstrated that co-designed antenna-filter has a better bandwidth (4.7%, 4.064.26 GHz) and a larger gain (4.3 dBi) than the traditional version with 50-Omega interfaces impedance.

An Integrated Approach to RF Antenna-Filter Co-Design

A compact differential dual-frequency antenna with stacked configuration is described. Compared with the conventional stacked dual frequency antenna, the radiating element with a half guided wavelength is distributed on two layers and connected through via holes, thus the dimension of the antenna is reduced effectively. In order to improve the bandwidth at the first resonant frequency (f1), a reflecting board is introduced and connected with the ground plane through three via holes. As a result, a new resonant frequency closing to f1 can be excited and the bandwidth at fx is enhanced. Both differential antennas with and without the reflecting board are fabricated and measured. The realized antennas have a compact size of 15 mm × 15 mm, which equals to 0.23?1 × 0.23?1 (?1, the guided wavelength at f1). Experimental results show that the proposed antenna can operate at 2.4 GHz and 5.2 GHz bands. Good agreement between the simulated and measured results is obtained.

Design of Compact Differential Dual-Frequency Antenna With Stacked Patches

A beam-sweeping antenna utilizing a novel active frequency-selective surface (FSS) is developed in this letter. It is comprised of a simple dipole and a cylindrical FSS formed by six columns of unit cells. The dipole used as a radiating source is situated at the center of the cylindrical FSS. The radiation pattern of the antenna could be reconfigured by controlling the states of the PIN diodes in the FSS. The dimension of the whole antenna is 0.75 λg × 0.75 λg × 1.57 λg (λg is the guided wavelength at its resonant frequency). Experimental results demonstrate that the presented beam-steering antenna can operate at 2.45 GHz and the main beam can be swept across the whole azimuth plane with a peak gain of 8.15 dBi.

Electronically Beam-Steering Antenna With Active Frequency-Selective Surface

A novel circularly polarized (CP) antenna realizing omnidirectional radiation in the wider azimuth planes is proposed in this letter. By introducing curved branches at both the patch and ground plane and making an angle of α between them, the amplitude and phase characteristic of the antenna are improved. Meanwhile, the omnidirectional CP field is obtained in the wider azimuth planes. The measured results show that the proposed antenna has a −10-dB impedance bandwidth of 19.6% and a 3-dB axial-ratio bandwidth of 27.4%. Moreover, the omnidirectional CP fields can be obtained in the azimuth planes of $\theta \,= \,50^\circ{-}\text{130}^\circ $ .

Wideband Circularly Polarized Antenna Realizing Omnidirectional Radiation in the Wider Azimuth Planes

A balanced dual-band bandpass filter based on λ/2 stepped-impedance resonators and open-loop resonators is proposed in this letter. By employing a type of self-feedback structure, an extra transmission zero is introduced near the common-mode resonance .frequency, and the common-mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common-mode suppression is achieved.

Guorui Han

Papers

An Integrated Approach to RF Antenna-Filter Co-Design

Design of Compact Differential Dual-Frequency Antenna With Stacked Patches

Electronically Beam-Steering Antenna With Active Frequency-Selective Surface

Wideband Circularly Polarized Antenna Realizing Omnidirectional Radiation in the Wider Azimuth Planes

Design of Balanced Dual-Band Bandpass Filter with Self-Feedback Structure