In this paper, an extremely sensitive microwave sensor is designed based on a complementary symmetric S shaped resonator (CSSSR) to evaluate dielectric characteristics of low-permittivity material. CSSSR is an artificial structure with strong and enhanced electromagnetic fields, which provides high sensitivity and a new degree of freedom in sensing. Electromagnetic simulation elucidates the effect of real relative permittivity, real relative permeability, dielectric and magnetic loss tangents of the material under test (MUT) on the resonance frequency and notch depth of the sensor. Experiments are performed at room temperature using low-permittivity materials to verify the concept. The proposed design provides differential sensitivity between 102% to 95% as the relative permittivity of MUT varies from 2.1 to 3. The percentage error between simulated and measured results is less than 0.5%. The transcendental equation has been established by measuring the change in the resonance frequency of the fabricated sensor due to interaction with the MUT.

Polarization converters play an important role in modern communication systems, but their wide and multiple band operation to facilitate volume and size reduction is quite challenging. In this letter, a dual-band Linear Polarization to Circular Polarization (LP-to-CP) converter is presented using a novel design procedure based on geometric parameters optimization of a meta-array. For dual-band operation, the concept of mutual interaction of two distinct resonators is used. Step by step design procedure is proposed and an example is presented to convert incident x(y) polarization into transmitted LHCP(RHCP) in Ku band (15.15~19.5 GHz) and RHCP(LHCP) in Ka band (33.1~39.05 GHz). After performing model-based theoretical paradigm analysis, and full-wave simulation and optimization, the converter is fabricated and the measurements are performed with a vector network analyzer. The measured results, close to simulation results, depict the validity and reliability of the design. The proposed meta-array is ultrathin, wideband and polarization diverse which is very suitable for wide range of applications including millimeter wave communication.

Satellite communication systems require dual-band circularly polarized (CP) waves to integrate receiving and transmit antennas into one dual-band terminal. Polarization converters play an important role in such a scenario to convert the incoming linearly polarized (LP) signal into the transmitted CP signal. Wide-band and wide-angle performance for the transmission based dual-band polarization converters has been a challenge. In this paper, a transmission-based linear polarization to circular polarization (LP-to-CP) converter is presented using a very simple and thin metasurface based structure. The proposed metasheet is uni-layered, patterned with a circular diagonal split ring enclosed in the square ring. The idea for dual-band polarization conversion is verified with an example in which x(y) polarization is converted into LHCP(RHCP) in Ku-band (15.25~18.9 GHz), and RHCP(LHCP) in Ka-band (29.7~36.7GHz). The converter performs polarization conversion for both bands over 21% of bandwidth which is very wide. Moreover, it maintains performance over wide-angled oblique incidences. Dual-band performance is analyzed theoretically, numerically, and experimentally. The equivalent circuit model is also presented for the unit cell. This metasheet has simple and low-cost design, wide polarization conversion bandwidths, polarization diversity, and wide-angle performance which are very promising for future communication systems.

Polarization converters play an important role in modern communication systems, but their wide and multiple band operation to facilitate volume and size reduction is quite challenging. In this paper, a triple-band Linear Polarization to Circular Polarization (LP-to-CP) converter is presented using a novel design procedure based on geometric parameters optimization of a metasheet. The proposed converter is ultrathin, wideband, stable over a wide range of incident angles, and polarization diverse. The conductor layer of metasheet is patterned with a square ring and five square-patches diagonally intersecting each other. To validate the proposed method, an LP-to-CP convertor in X-band (7.3~9.6 GHz) and dual Ka-bands (25.4~31.4 GHz, 35.4~42.2 GHz) is presented. The performance is quite stable in wide range of frequencies and against the variation of incident angles from −25° to 25°. After performing model-based theoretical paradigm analysis, and full-wave simulation and optimization, the converter is fabricated and the measurements are performed inside the anechoic chamber. The measured results, close to simulation results, depict the validity and reliability of the proposed design.

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.

Transmissive metasurface-based dual-wide-band dual circular polarized operation is needed to facilitate volume and size reduction along with polarization diversity for future THz wireless communication. In this paper, a novel dual-wide-band THz linear polarization to circular polarization (LP-to-CP) converter is proposed using transmissive metasurfaces. It converts incident X polarized waves into transmitted left-hand circular polarized (LHCP) and right-hand circular polarized (RHCP) waves at two frequency bands. The structure consists of bi-layered metasurfaces having an outer conductor square ring and three inner conductor squares diagonally intersecting each other. The proposed converter works equally well with incident Y polarizations. Operational bandwidths for the dual-band LP-to-CP are 1.16 THz to 1.634 THz (34% fractional bandwidth) and 3.935 THz to 5.29 THz (29% fractional bandwidth). The electromagnetic simulation was carried out in two industry-standard software packages, High Frequency Structure Simulator (HFSS) and Computer Simulation Technology (CST), using frequency and time domain solvers respectively. Close agreement between results depicts the validity and reliability of the proposed design. The idea is supported by equivalent circuits and physical mechanisms involved in the dual-wide-band dual polarization operation. The impact of different geometrical parameters of the unit cell on the performance of LP-to-CP operation is also investigated.