A low-profile aperture-coupled microstrip patch antenna (MPA) using the TM10 and TM30 resonant modes to enhance the impedance bandwidth is proposed in this paper. Based on the cavity model for a square MPA, the TM10 and TM30 modes as well as both higher odd-order and even-order modes between them can be characterized. In order to combine the dual radiative resonant modes for a wide impedance bandwidth, a rectangular radiating patch with an aperture-coupled feeder is employed and theoretically investigated at first, aiming to demonstrate that all of the undesired modes between them can be removed effectively. After that, by loading the shorting pins properly underneath the patch, the resonant frequency of TM10 mode is shown to progressively turn up with slight effect on that of TM30 mode. As a result, these two radiative modes can be allocated in proximity to each other, resulting in a wide impedance bandwidth with a stable radiation pattern and the same far-field polarization. Moreover, the principal parameters of the MPA have been extensively studied in order to investigate the sensitivity in input impedance of the aperture-fed patch antenna. Finally, the proposed antenna is fabricated and measured. Simulated and measured results are found in good agreement with each other and illustrate that the antenna achieves a wide impedance bandwidth of about 15.2% in fraction or 2.32-2.70 GHz under |S ₁₁ | <; -10 dB, while keeping a low profile property with the height of 0.032 free-space wavelength. Besides, a stable gain varied from 3 to 6.8 dBi within the whole operating band is also obtained.

A differential-fed microstrip patch antenna (MPA) with bandwidth enhancement is proposed under the operation of TM ₁₀ and TM ₃₀ resonant modes in a single patch resonator. Initially, a rectangular differential-fed MPA is theoretically investigated so as to demonstrate that all of the undesired modes between the TM ₁₀ and TM ₃₀ modes are suppressed or removed out effectively. Then, by symmetrically introducing two pairs of shorting pins, the resonant frequency of TM ₁₀ mode is progressively turned up. After that, with the help of two long slots, the resonant frequency of TM ₃₀ mode is decreased with slight effect on that of TM ₁₀ mode. Furthermore, a short slot is inserted at the center of the patch to cancel the parasitic inductances of the shorting pins and probe feeds. With this arrangement, these two radiative resonant modes are moved in proximity to each other for wideband antenna. Finally, the proposed differential-fed MPA is fabricated and measured. Experimental results illustrate that the impedance bandwidth (| _Sdd11 | <; -10 dB) of the antenna has gained a tremendous increment up to about 13% (1.88-2.14 GHz), while keeping a low profile property with the height of 0.029 free-space wavelength. Additionally, the antenna has achieved a stable gain varied from 5.8 to 7 dBi over the operating band.

Pin-loaded circularly polarized (CP) patch antennas with wide 3-dB axial ratio beamwidth (ARBW) are proposed in this paper. The ARBW of a CP patch antenna is mainly dependent on its electrical width at a frequency, while the patch size at resonance is fully controlled by the shunt inductive load. First of all, four shorting pins are introduced along the diagonals of the dual-fed square patch, so as to exhibit that the 3-dB ARBW can be significantly extended if the shorting position and pin radius are properly chosen. Next, the two degenerate modes in a single-fed CP patch antenna are slightly separated in resonant frequencies by loading another pair of shorting pins along the central line of the patch, so as to excite CP radiation. After extensive analysis is executed, two patch antennas with and without shorting pins are fabricated and measured. Simulated and measured results show good agreement, and both of them demonstrate that the 3-dB ARBW is tremendously improved from 50° to 140° or gets nearly 90° increment by means of the proposed method.

A novel design concept of enhancing the impedance bandwidth of a single-layer shorted microstrip patch antenna (MPA) is proposed under simultaneous radiation of the one- and three-quarter wavelength resonant modes (TM _0,1/2 and TM _0,3/2 modes). Initially, a conventional MPA with the shorting wall is studied to demonstrate that none of the redundant modes can be excited between the dual-resonant modes. Then, a pair of shorting pins are appropriately installed underneath the patch to progressively turn up the resonant frequency of TM _0,1/2 mode without significant influence on that of TM _0,3/2 mode. After that, a V-shaped slot is etched out on the patch to dramatically reduce the resonant frequency of TM _0,3/2 mode with little effect on that of TM _0,1/2 mode. With the use of these arrangements, the dual-desired radiative resonant modes are gradually moved in proximity to each other, thus widening the impedance bandwidth under emergence of dual resonant poles. In order to validate the principle and design method, the proposed antenna is designed, fabricated, and measured. The measured results demonstrate that the impedance bandwidth of the proposed shorted patch antenna has been extended to about 11.8%, and it is about 1.82 times of 6.5% of the traditional shorted MPA. Meanwhile, the fabricated antenna exhibits other attractive performances including stable radiation pattern, same polarization, and a low-profile property with the height of 0.042 free-space wavelength.

A dual-band single-layer microstrip patch antenna (MPA) with simultaneous improvement of impedance bandwidth and radiation beamwidth is proposed in this communication. The performances of the MPA are implemented by resonating its radiative TM10 and TM12 modes at the lower and upper bands, respectively. Initially, the far-zone radiated fields of the MPA working in the TM10 mode are theoretically investigated. It demonstrates that its E-plane half-power beamwidth (HPBW) in the lower band is significantly widened by removing the array factor between dual equivalent slots. After that, the MPA working in TM12 mode is deeply studied and analyzed. The results depict that its wide E-plane HPBW and low H-plane sidelobe level (SLL) in the upper band could be obtained by reshaping radiation patterns of its improved TM12 mode via the shorting pins. Additionally, a linear slot is cut on the core radiator so as to achieve a good impedance matching. With these arrangements, the E-plane HPBW, H-plane SLL, and impedance bandwidth of this designed MPA can be simultaneously enhanced in the dual bands. Finally, the proposed antenna is fabricated and measured. Experimental results show that the antenna has gained an improved-bandwidth (|S11|<−10 dB) ranging from 3.45-3.77 GHz and 5.75-6.04 GHz with two attenuation poles. Most importantly, the HPBW of its E-plane radiation patterns is successfully widened to around 135: over these dual operating bands. Moreover, the high H-plane SLL of the antenna is decreased to about −10 dB in the upper band.

A two-dimensional (azimuth and elevation) beam steering partially reflective surface (PRS) antenna is proposed in this paper. It consists of a probe-fed square patch antenna acting as the radiator and a reconfigurable PRS structure serving as the beam steering superstrate. The reconfigurable superstrate employs 6×6 reconfigurable unit cells and is equally divided into four sections. By controlling the states of the PIN diodes inserted in each unit cell, four sections have diverse biasing combinations, which can generate 10 different radiation models. As a result, the proposed antenna can radiate a boresight beam or a ±22° tilted beam in the plane of phi=0°, 45°, 90°, 135°. To verify the design feasibility, an antenna prototype operating at 5.5 GHz is fabricated and measured. The simulated and measured results for the input reflection coefficients and radiation patterns are in good agreement. The measured realized gains are around 10 dBi for all states. Moreover, the gain variation from the broadside direction to the tilted direction (22°) is less than 0.8 dBi. Compared with some reported two-dimensional beam steering PRS antennas, the proposed design can achieve a much wider beam tilting range with a more stable radiation performance and fewer tunable diodes.