A compact dual mode wideband antenna is presented in this paper which operates from 24.8 to 31.6 GHz (suitable for 5G applications). The antenna is based on substrate integrated waveguide (SIW) and consists of a two-element array of half-bow-tie slots. Each slot excites two modes (slot mode and half patch mode) in the antenna due to its geometry. The resonant frequencies in these modes are optimized to achieve wide impedance bandwidth using Ansys HFSS. A prototype is fabricated and its measured impedance bandwidth is 6.8 GHz, which is in close agreement with the simulated one. It also has a peak gain of 8.5 dBi at 30.4 GHz and its physical size is 2.4λ g × λ g , where λ g is the guide wavelength at center frequency.
In this paper, a novel branch line coupler with improved bandwidth and reduced size is presented. The size reduction is achieved by means of capacitive loading. The capacitive loaded transmission line implemented in the proposed design eliminates the need of open stubs. The mechanism of size reduction and bandwidth enhancement of the coupler is discussed analytically with the help of its equivalent circuit. A prototype is fabricated and tested to validate the concept. The measured fractional bandwidth is 40%, ranging from 2.8 GHz to 4.2 GHz which is suitable for 5G systems. Moreover, the obtained phase imbalance between the output ports is less than ±5 • for the entire operating range.
The analysis of traveling-wave electrooptic modulator on z-cut and x-cut lithium-niobate substrates is carried out using the finite element method based on a quasi-TEM approximation. The microwave effective index, characteristic impedance, and frequency dependent attenuations are calculated. Optical frequency response is also calculated and hence the bandwidth is estimated for velocity matching and impedance matching conditions. Bandwidth increases significantly for simultaneous velocity and impedance matching but is limited by the microwave losses in the dielectric material. Optical 3-dB bandwidth of more than 140 GHz can be achieved with x-cut LiNbO 3 substrate, when two slots are incorporated in the structure.
A rectangular monopole antenna with an extended ground, excited by Coplanar Waveguide (CPW) and backed by a 6 × 6 array of fractal artificial magnetic conductor (AMC) unit cells, resonating at 5.8 GHz in Industrial, Scientific, and Medical (ISM) band, is presented in this manuscript. To attain the objective of proposing a compact and economical antenna solution for employment in wearable biomedical domain, a novel approach of utilizing both surfaces of the same dielectric for engraving antenna element as well as AMC array is adopted. It results in the elimination of layers of expensive substrate (RO3003) and of thick separator (foam) between antenna and AMC array. During measurement in open space, the proposed antenna system exhibited an impedance bandwidth of 570 MHz with a gain of 7.9 dBi. While a total realized gain of 7.5 dBi, amounting to a gain enhancement of about 3 dB as compared to that of monopole alone, is observed when the integrated antenna system is placed just over a three-layer rectangular human body equivalent model. Specific absorption rate values, as calculated at 5.8 GHz and averaged over 1 and 10 g of human tissue, are 0.0117 and 0.00244 W/kg, respectively. Obtained results strongly advocate the use of the proposed antenna system in smart wearable healthcare devices.
In this article, empirical design formulae for a unit cell of series‐fed substrate integrated waveguide power divider for a wide range of power division ratio from 1:1 to 1:40 are presented. These formulae are determined through extensive simulations carried out in Ansys HFSS. The physical dimensions of the power divider for any given power division ratio can be directly determined through the design formulae presented in the article. A simple design procedure is discussed and verified with the help of experimental and simulation results. For experimental verification, a power divider is designed to operate in X band, and its prototype is developed on RT Duroid 5880, the measured results for this power divider are in close agreement with simulated as well as predicted results. Also, for validating the design procedure over a wide range of frequencies, many power dividers are designed with different power division ratios, different operating frequencies and different cut‐off frequencies of TE10 mode. The cut‐off frequency (fc) of TE10 mode is varied from 15 to 25 GHz, and the operating frequency is adjusted in between 1.2fc and 1.8fc. That is, 18–40 GHz, which is suitable for many microwave and millimeter wave applications. The obtained results are very close to the desired power division ratios.
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