This paper reports on an effective mutual coupling suppression technique in which a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array. Modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects. A detailed analysis of this proposed scheme is carried out on a low as well as on a high-permittivity substrate. Coupling suppression of 27 and 11 dB is achieved experimentally on the low- and high-permittivity substrates, respectively, with an element separation of λ _o /8. The design is compact and easy to realize and it removes drawback of poor front-to-back ratio previously reported in other decoupling techniques. In addition to high-coupling suppression, the decoupling slab can be added or removed in real time which makes this technique versatile for various applications having stringent performance requirements.

This paper presents the design of compact and low profile multi-band/reconfigurable planar monopole antennas using a 1.6 mm-thicker FR4 substrate and a truncated ground-plane. One of the proposed structures (Antenna2) is reconfigured using optical switch. The proposed antennas can operate in single- and dual-band modes depending on the STATE of the switch. Antenna1 operates in dual-band mode (Wi-Fi @ 2.45 GHz and WLAN @ 5.4 GHz). Antenna2 gives two distinct dual-band modes depending on the state of the switch, i.e. (Wi-Fi @ 2.45 GHz and WLAN @ 5.13 GHz) and (WiMAX @ 3.49 GHz and WLAN @ 5.81 GHz), when the switch is ON and OFF, respectively. The proposed structures achieve bandwidths ranging from 11% to 36% at respective centred frequencies. The antennas are designed with input impedance in the range of 45–53 Ω having VSWR < 1.27 for operating frequency bands. Gain values from 1.6 to 3 dBi and radiating efficiencies from 76.4% to 92% are attained at required operating bands. The proposed antennas are light-weight, low-profile, and easily fabricated. Therefore, they are potential candidates for use in portable and intelligent mobile phones, laptops, PDAs, and iPads as well as for military, rescue, safety, and medical applications. Using a numerical Finite Integration Technique employed in Computer Simulation Technology Microwave Studio, the antennas far-field, scattering, and gain parameters are evaluated. The antennas are fabricated and a good agreement between the measured and simulated results is observed.

A novel and compact design of a dual-band filter with widely separated passbands is proposed. Applications of such a device can be found in systems where a single device is responsible for both transmission and reception. The proposed filter is composed of resonators working on two distinct modes. The proposed dual-mode structure offers a good rejection of unwanted resonances, producing a widely separated dual-band response. The idea is demonstrated with the design of a four-pole filter comprising two dual-mode structures and the concept is verified experimentally by the measurement of a fabricated prototype. Finally, a six-pole filter is proposed, showing the possibility of designing higher order filters.

This article reports on a simple yet efficient miniaturization technique of substrate integrated waveguide cavity resonators through stub loading. The stubs are attached to the cavity side edges and they are coupled with the magnetic fields of the cavity. This setup allows the stub loaded cavity to operate below its fundamental resonant frequency. This miniaturization technique is demonstrated by developing a two pole filter in horizontally and vertically coupled configurations. The potential to incorporate electronic tuning and various possible applications of these miniaturized cavities in low frequency system-in-package designs make them an excellent choice as compared to their conventional counterparts.

Orbital Angular Momentum (OAM) for radio communications has the potential of simultaneously transmitting multiple signals at the same frequency and time resources. This multiplies the achievable channel capacity at a given bandwidth by increasing the available number of simultaneous data streams. One downside of OAM radio communication is the requirement of multi-mode radio frequency (RF) hardware at both ends of a link i.e. transmitter as well as the receiver. This is not always practically viable, especially as we move towards low profile receivers in future communication devices. In this work, we present a novel method of OAM-based radio communication with enhanced physical layer security that requires only a single antenna receiver. We first present the system architecture, then we design and realize a Rotman lens-based circular antenna array transmitter operating at 5.8 GHz. We then experimentally verify the capability of the hardware to create multiple modes. As a proof-of-concept, we propose a communication system that simultaneously uses mode 0 and +1 of the OAM beamformer and in doing so show how a single receive antenna can be used for data recovery. We first identify a general analogue modulation expression and use the proposed system to transmit digitally modulated data stream to a single antenna equipped receiver. A pre-communication training sequence is required to realize the proposed approach. Experimental results verify the simulated predictions.