This letter proposes a circular patch antenna with dual band circular polarization (CP) at the UHF-RFID and WLAN bands. Two perpendicular slots are etched on the patch to down-shift the first resonance to 915MHz (UHF-RFID band) and introduce a new resonance at 2.45GHz (WLAN band). Four slits are etched on the ground plane to improve axial ratio (AR) mainly in the first band. A dual band AMC reflector having 25 unit cells is placed a small distance below the patch to reduce the back lobe level and improve the gain at both bands. Measured 3dB AR bandwidths of 5.25% and 2% are achieved at UHF-RFID and WLAN bands respectively with gains of 3.1dBi (UHF-RFID) and 6.25dBi (WLAN). The antenna system can be used with RFID readers for detecting tags and sending information via the WLAN band.

This work presents a novel technique for miniaturization and bandwidth enhancement of a Rectangular Microstrip Antenna (RMA) operating at higher order TM03-like mode. The resonant length of a conventional RMA supporting the TM03 mode is reduced by λ/4 (λ is the operating substrate wavelength) by this design at the operating frequency. Consequently the conventional resonant length of 1.5λ for this mode is reduced to 1.25λ. Excitation of this TM03-like mode increases gain as well as antenna efficiency at the design frequency of 5.8 GHz. A wide slot is placed on the patch to reduce the side-lobes of the radiation pattern. Three meandered line linkages are placed inside the slot to miniaturize the structure maintaining current continuity. Resonance behaviour of the antenna is studied using Theory of Characteristic Modes and the impedance bandwidth is enhanced by controlling the excitation of the next higher order mode in the vicinity of TM03-like mode by appropriately choosing dimensions of the meander lines. The antenna is fed by a coaxial probe and is easy to fabricate. Measurement shows an impedance bandwidth of 8.5% and a peak gain of 10.5dBi. The overall size of the designed antenna is 1.31λ0λ1.31λ0λ0.03λ0 (λ0 is free-space wavelength at 5.8 GHz).

The design of a metamaterial-based tunable band elimination filter is described on silicon coplanar wave- guide (CPW) using complementary split ring resonators (CSRRs) and radio frequency microelectromechanical systems (MEMS) varactors to ensure compatibility with integrated circuit fabrication technology. CSRRs are patterned on both the active signal line and ground on both sides. A cantilever bridge is suspended on the signal line to realize variable capacitance. The rejection band of the filter is tuned by moving the MEMS bridge up or down using electrostatic actuation. A stopband around the center frequency of 35.32 GHz with a rejection ratio of ~ 20.19 dB is obtained when the bridge is pulled down. Another stopband around the center frequency 38.80 GHz is observed with a rejection ratio of ~ 18.29 dB when the bridge is allowed to remain in its up state without electrostatic actuation. Simulation for RF behavior is performed using ANSOFT High Frequency Structural Simulator v13. Numerical extraction of the filter parameters has been done using Agilent ADS (2009) and COVENTORWARE (2010) for mechanical and electromechanical characterization. This is the first reported tunable CPW filter having CSRR on the signal line and ground plane on silicon substrate using MEMS technology.

This letter introduces a miniaturized dual-band implantable antenna (volume of 21.53 mm3) to adapt C-Band 5G biotelemetry in Wireless Capsule Endoscopy (WCE). Open-ended slots were engraved on a patch to tune the antenna efficiently. The antenna along with the battery, PCB, camera, data-management system was placed within a biocompatible polyvinyl alcohol capsule. This antenna was communicating with fractional bandwidths of 20.42% and 13.85% and realized gains of -24.08 dBi and -26.11 dBi up to 12 m and 6 m distances at 2.45 GHz and 4.55 GHz within the human body phantom, respectively. The antenna system was fabricated and placed within two homogeneous body models to verify its performance at both frequencies. The proposed system shows the known best performance reported on wireless capsule endoscopic systems. Introduction of 5G facility in WCE biotelemetry is also a novel approach in this application to improve the quality of smart patient monitoring.

Theoretical and experimental investigation on isosceles θi-θi-φi Triangular Dielectric Resonator Antennas (TDRAs) are presented here for TM mode for the first time. Trilinear transformation is slightly modified to obtain the approximate solutions for eigenfunction and eigenvalue. Limitations of the theory are discussed. Closed form expression is given here to predict the resonant frequency with a maximum error of 4%. It is found that isosceles TDRA produces a peak in the broadside direction at fundamental TM 101z and higher order TM 103z modes. Three isosceles TDRAs having _i= 60∘, 70∘ and 75∘ are fabricated for experimental validation.

This letter presents an ultrathin planar bi-layered chiral metasurface which exhibits direction dependent reflection and direction dependent transmission of incident circularly polarized waves within five frequency bands. The five operational frequency bands lie within 5.55-5.78GHz, 6.1-6.23GHz, 10.42-10.68GHz, 11.06-11.17GHz and 12.03-12.18GHz respectively. The metasurface can therefore be used for C, X and Ku microwave band applications. Within the five asymmetric reflection bands, the metasurface acts as a meta-mirror where the handedness of the incident and reflected circularly polarized waves remain unchanged with respect to an observer. The response of the metasurface is stable for incident angles up to 45 degrees for the first four bands and 30 degrees for the final band. This makes it useful even for oblique incidence.