This paper presents a novel 2D meta-surface wall to increase the isolation between microstrip patch radiators in an antenna array that is operating in the teraherz (THz) band of 139-141 GHz for applications including communications, medical and security screening systems. The metasurface unit-cell comprises conjoined twin 'Y-shape' microstrip structures, which are inter-digitally interleaved together to create the meta-surface wall. The proposed meta-surface wall is free of via holes and defected ground-plane hence easing its fabrication. The meta-surface wall is inserted tightly between the radiating elements to reduce surface wave mutual coupling. For best isolation performance the wall is oriented orthogonal to the patch antennas. The antenna array exhibits a gain of 9.0 dBi with high isolation level of less than −63 dB between transmit and receive antennas in the specified THz-band. The proposed technique achieves mutual coupling suppression of more than 10 dB over a much wider frequency bandwidth (2 GHz) than achieved to date. With the proposed technique the edge-to-edge gap between the transmit and receive patch antennas can be reduced to 2.5 mm. Dimensions of the transmit and receive patch antennas are 5 × 5 mm 2 with ground-plane size of 9 × 4.25 mm 2 when being constructed on a conventional lossy substrate with thickness of 1.6 mm.

A novel miniature ultrawideband antenna is proposed that exhibits excellent radiation characteristics. The antenna is based on the simplified composite right/left‐handed transmission‐lines (SCRLH‐TLs) that are implemented using F‐shaped and T‐shaped slits on the antenna's ground‐plane and radiating arms, respectively. The coplanar waveguide feed‐line is impedance matched to the radiating patches using H‐shaped microstrip stub. The antenna operates between 0.65 and 9.2 GHz, which corresponds to an impedance bandwidth of 173.6%. The maximum gain and efficiency measured are 3.5 dBi and 70% at 4.5 GHz, respectively. The antenna dimensions are 25 × 15 × 1.6 mm3 or 0.054λ0×0.032λ0×0.003λ0, where λ0 is free‐space wavelengths at 0.65 GHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:69–71, 2016

This study presents the empirical results of a low-profile light-weight antenna based on a periodic array of the complementary artificial magnetic conductor metamaterial structure, which is realised by loading the antenna with Eshaped slits and inductive microstrip lines grounded using metallic via-holes. The finalised prototype antenna operates over a broadband of 0.41-4.1 GHz, which corresponds to a fractional bandwidth of 165.84%, and has dimensions of 40 × 35 × 1.6 mm 3 or 0.054l 0 × 0.047l 0 × 0.0021l 0 , where l 0 is free-space wavelength at operating frequency of 410 MHz. The finalised antenna has a peak gain and radiation efficiency of 4.45 dBi and 85.8%, respectively, at 2.76 GHz. At the lower operating frequency of 410 MHz, the gain and radiation efficiency are 1.05 dBi and 32.5%, respectively, which is normally highly challenging to realise with very small antennas. The planar nature of antenna enables easy integration with wireless transceivers.

New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The results illustrate that by loading the conventional monopole antennas with an asymmetrical meander lines SRR, a lower resonance frequency mode can be excited. The dimensions of the SRR have been selected to provide a resonance close the resonance of the monopole antennas. The results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced. The length and width of the antennas are 25 × 10−2λ0 × 11 × 10−2λ0 and 25 × 10−2λ0 × 21 × 10−2λ0 at 4 GHz for monopole antennas, and 29 × 10−2λ0 × 21 × 10−2λ0 at 2.9 GHz for both monopole antennas loaded with SRR. For antennas without SRR loading, maximum of measured gains and efficiencies are 3.6 dBi and 78.5% for F‐antenna, and 3.9 dBi and 80.2% for T‐antenna, hence they appear at 5 GHz. For antennas with SRR loading, these parameters are 4 dBi and 81.2% for F‐antenna, and 4.4 dBi and ∼83% for T‐antenna, which appeared at 6 GHz. By implementing the meander lines SRR as a matching load on the monopole antennas, the resulted antennas cover the measured frequency bandwidths of 2.9–6.41 GHz and 2.6–6.6 GHz (75.4 and ∼87% fractional bandwidths), which are ∼2.4 and 2.11 times more than monopole antennas with an approximately same in size.

A novel backfire‐to‐endfire leaky‐wave antenna is presented with ability to scan from −25° to +45°. The antenna is based on metamaterial transmission‐lines and is implemented using monofilar Archimedean spiral and rectangular slots, spiral inductors, and metallic via‐holes. The slots act as series left‐handed capacitances, and the spirals with via‐holes provide the shunt left‐handed inductances to realize the metamaterial antenna. A prototype antenna was fabricated prototype on FR4 dielectric substrate, which has an electrical size of 0.0302λ0 × 0.0357λ0 × 0.0008λ0, where λ0 is free space wavelength at 165 MHz. Measured bandwidth of the antenna is 710 MHz (165–875 MHz) corresponding to a fractional bandwidth of 136.5%. The main advantage of the antenna is its ability to scan over a wide angle from −25° to +45° with acceptable gain and radiation efficiency of 1.2 dBi and 50.1%, respectively, measured at 400 MHz. The wide scanning attributes of the antenna make it suitable for passive radar applications to scan across the VHF–UHF bands for FM‐Radio, television, mobile phones, and GPS applications.