The paper presents a highly efficient, low cost, ultra-wideband, microstrip monopole antenna for microwave imaging and wireless communications applications. A new structure (z-shape, ultra-wideband (UWB) monopole) is designed, which consists of stepped meander lines to achieve super-wide bandwidth and high efficiency. Three steps are used to design the proposed structure for the purpose to achieve high efficiency and wide bandwidth. The antenna bandwidth is enhanced by varying the length of meander line slots, optimization of the feeding line and with the miniaturization of the ground width. The simulated and measured frequency bands are 2.7–22.5 GHz and 2.8–22.7 GHz (156% fractional bandwidth), respectively. The dimensions of the antenna are 38 mm × 35 mm × 1.57 mm, and its corresponding electrical size is 2.41 λg × 2.22 λg × 0.09 λg, where guided wavelength λg is at the center frequency (12.75 GHz). This antenna achieved a high bandwidth ratio (8.33:1). The realized gain is varying from 1.6–6.4 dBi, while that of efficiency is 70% to 93% for the whole band. Radiation patterns are measured at four operating frequencies. It has an acceptable group delay, fidelity factor, and phase variation results that satisfy the limit of ultra-wideband in the form of the time domain.

This paper presents a new shape (s-shape monopole) of a super wideband antenna using stepped meander lines, a quarter waveguide transformer feeding line, and a defected ground structure (DGS). The antenna will be used for multiple wireless communication applications like WIMAX/WLAN/ISM/UWB, and also for several wireless communication applications. The total dimensions of the proposed antenna are 35 mm × 35 mm × 1.57 mm or 0.36 λo × 0.36 λo × 0.016 λo, which are the corresponding electrical dimensions with free-space wavelength (λo) at the lower operating frequency. The antenna is designed and simulated into two steps: the first (Antenna 1) covers a bandwidth of 18.2 GHz, while the second (Antenna 2, using DGS) covers a super wide bandwidth of 37.82 GHz (3.08–40.9 GHz). The measured fractional bandwidth and bandwidth ratio of the antenna are 174.68% and 13.009:1, respectively, which is operating from 3.09–40.2 GHz. The maximum calculated gain and efficiency are 5.9 dBi and 92.7%, respectively. The time-domain performance is good due to the calculation of the system fidelity factor, group delay, and its linear and constant phase variation.

In this letter, a null-filled shaped beam planar monopole antenna for aerial platform applications is presented. Proposed antenna consists of a slot and a loop hybrid to give vertically-polarized monopole configuration, which is overlapped by a curl to control current distribution that leads to filling of radiation null and shaping the beam. Antenna possesses different gain amplitudes at different yaw and pitch angles, as being required by aerial platforms to cover variant distance ranges in various directions. Simulated and measured results exhibit that antenna retains null-filled pattern in vertical-plane, along with high, stable and linear peak gains (6.4 $\times$ .4 dBi), over the entire operation band that is from 2.54 GHz to 2.69 GHz (Measured reflection coefficient less than -10 dB). Proposed antenna displays an omni-directional radiation characteristics and a good gain in azimuth-plane, having the minimum horizontal gain of -2.85 dBi. Furthermore, flaunted antenna is rigid, planar, aero-dynamically stable and surface-mount that makes proposed antenna prospective and worthy candidate for aerial platforms.

Circularly-polarized planar antenna with a shaped pattern for airborne applications, is proposed in this letter. The proposed antenna consists of vertically-polarized formation and horizontally-polarized stubs to provide circularly-polarized configuration, which is loaded by a copper curl based top layer to control current distribution for beam shaping and filling of zenith null. The antenna also contains split ring resonators beside partial ground to make it deployable over larger ground planes (metallic bodies) without distorting circular polarization by controlling phase of reflected waves. The power density of presented airborne shaped pattern antenna differs for variant elevation and azimuth angles, to have uniform wireless coverage over the earth’s surface by managing variations of the signal strength because of different path lengths. The demonstrated antenna also possesses circular polarization and direction based circular polarization diversity at angles against the greatest path-lengths. Antenna retains a null-filled pattern in the vertical plane along with having high absolute peak gain (5.5 ± 1 dBi) and adequate peak polarization gain (2 to 4 dBi) through-out the operational bandwidth from 2.82 GHz to 2.89 GHz (Measured reflection coefficient less than -10 dB). Moreover, the radiating element exhibits omnidirectional radiation characteristics, with good horizontal gain (greater than -3.6 dBi).

In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall. The use of the modified ground structure causes a more than 28 dB (measured value) mutual coupling reduction. The modified ground structure has been optimized and validated with a finite spaced planar 2 × 1 antenna array operating at 4.16 GHz, intended for unmanned aerial vehicle radar altimeter applications. The patch antennas built with the MGS exhibit high gain (greater than 6 dBi throughout the operational band), along with inter-element coupling as low as −65 dB. Mutual coupling reduction at lower contours is beneficial for altimeter applications.

A rugged metal protected antenna that produces an omnidirectional radiation pattern is proposed in this letter. The omni-directionality is achieved by using a cavity enclosed PCB (Printed Circuit Board) with /4 transformers and ground shortening pins combination. The slotted cavity filled with ablative material is designed to maintain the radiation characteristics of the enclosed PCB and provide strength for the antenna arrangement, which can be effectively used on high-speed aerial platforms. The simulated and measured results demonstrate that the proposed antenna possesses a stable omnidirectional radiation pattern, its horizontal gain is higher than -1.5 dB, the azimuthal gain ripple is within 0.7 dB, and the antenna efficiency exceeds 85%, over the entire operational frequency band. In addition, the conformal, tapered, non-protruding, low-profile and DC-grounded design makes winged antennas superior candidate for supersonic (Mach> 1) airborne applications.