Dual-mode Microstrip Patch Research Articles

Miniaturized Dual-Band Dual-Mode Microstrip Patch Antenna with Defected Ground Structure for Wearable Applications

This work presents the performance of a miniaturized dual-band dual-mode microstrip patch antenna with Defected Ground Structure (DGS) at 2.45 GHz and 5.8 GHz on the stacked substrate configuration in the order of FR-4 – PDMS- FR-4. The antenna offers a promising solution for wearable applications in the ISM bands. The first substrate is a flexible Flame Retardant 4 (FR-4) and the other substrate is a highly flexible Polydimethyl Siloxane (PDMS). The size of the antenna was reduced from 50 × 50 mm2 to 30 × 30 mm2, by introducing DGS on the ground plane. A single U-slot on the rectangular radiating patch was introduced to produce the upper resonant frequency of 5.8 GHz while the existing square patch is to generate the lower resonant frequency of 2.45 GHz. The simulations on the dual-band dual-mode microstrip patch antenna shows the reflection coefficient, S11 at 2.45 GHz is -17.848 dB with a bandwidth of 278.8 MHz and -13.779 dB with a bandwidth of 273 MHz at 5.8 GHz. A unidirectional radiation pattern observed in the E-plane shows that the antenna could be applied for off-body communication while an omnidirectional radiation pattern in the H-plane showed that the antenna can be used for on-body communication. Bending investigation were performed for the antenna over a vacuum cylinder with varying diameters of 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm and 120 mm in the CST MWS® software. From the graph of reflection coefficients, the performance of the antenna were not affected in bending condition. The SAR simulations showed that the SAR limits obey the guidelines as stipulated by the Federal Communication Commission (FCC) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for 1 mW of input power. The 2.45 GHz SAR limit for 1 g of human tissue is 0.09007 W/kg (FCC standard: < 1.6 W/kg) while for 10 g is 0.01867 W/kg (ICNIRP standard: < 2 W/kg). For 5.8 GHz, the SAR limit for 1 g of human tissue is 0.115 W/kg and for 10 g is 0.03517 W/kg. Based on the performance of the antenna in bending condition and the SAR limits, it is safe to conclude that the antenna can be used for wearable applications at 2.45 GHz and 5.8 GHz of the ISM bands.

Principles of adaptive element spacing in linear array antennas

A novel approach to linear array antennas with adaptive inter-element spacing is presented for the first time. The main idea is based upon electronically displacing the phase center location of the antenna elements, which determine their relative coordinates in the array configuration. This is realized by employing dual-mode microstrip patch antennas as a constitutive element, whose phase center location can be displaced from its physical center by simultaneously exciting two modes. The direction and the amount of displacement is controlled by the amplitude and phase of the modes at the element level. This in turn facilitates reconfiguring the inter-element spacing at the array level. For instance, a uniformly-spaced array could be electronically transformed into a non-uniform one without any mechanical means. The proposed idea is demonstrated in two- and three-element linear antenna arrays. The technique has the potential to control the radiation characteristics such as sidelobe levels, position of the nulls, and the beamwidths in small arrays, which are useful for adaptively controlling the array performance in emerging wireless communication systems and radars.

A Self-Nulling Single-Layer Dual-Mode Microstrip Patch Antenna for Grating Lobe Reduction

A single-layer, dual-mode microstrip patch antenna with self-nulling patterns is proposed. The antenna consists of a circular microstrip patch antenna, surrounded by a shorted concentric ring patch, exciting the TM11 and TM21 modes, respectively. Adaptive radiation patterns with self-scanning and nulling capabilities are realized by concomitantly exciting these two modes. To attain the mode purity, four symmetrical arc slits, inspired by the surface current distribution of the TM21 mode, as well as two horizontal slits are placed in the ring patch. For the miniaturization purpose, the circular patch is loaded by three vertical slits. A prototype of the proposed antenna is fabricated and tested. The measured results are in good agreement with the simulation results. To showcase the effectiveness of the proposed self-nulling dual-mode antenna, it is employed as an antenna element in a linear scanning array with element spacing greater than one-wavelength to reduce its unwanted grating lobes.

Tunable dual‐mode microstrip patch resonators and filters

In this study, tunable dual-mode microstrip patch resonators are presented and utilised to design microstrip bandpass filters (BPFs). The novelty of the designs lies in that the performance of frequency agility can be realised by using either the signal line or the return path (the ground) of microwave transmission line. For the proposed resonators, the resonant frequencies of two coupled degenerate modes can be tuned using a square-loop slot with loaded tunable capacitors on the ground plane or on the patch. The locations of the capacitors are determined according to the electric field distributions of the two orthogonal modes. The variations of the modes in spectrum are studied. Finally, two types of demonstration compact tunable BPFs are designed and fabricated, and the simulated and measured results show good agreement.

Investigation of new nondegenerate dual-mode microstrip patch filter

A new nondegenerate dual-mode microstrip patch filter structure is introduced. The proposed filter is based on a square microstrip patch with four slots etched in symmetrical form. Besides its simple structure, the filter has the advantages of small size and low loss. The full-wave IE3D package is used to analyse the proposed structure. Design curves that relate the mode resonance frequencies and fractional bandwidth against slot parameters are presented. A bandpass filter is designed, analysed and tested at 2.15 GHz. Experimental results show good agreement with theoretical results.

Theory and Experiment of Dual-Mode Microstrip Triangular Patch Resonators and Filters

In this paper, we report on the results of an investigation into dual-mode operation of microstrip triangular patch resonators and their applications for designing dual-mode bandpass filters. It has been found theoretically that the dual modes can result from the rotation and superposition of a fundamental mode. The characteristics of the dual modes and their mode splitting are described. The applications of this new type of dual-mode microstrip patch resonator in the design of microwave planar filter are presented. A circuit model for operation of this type of filter is proposed. Two- and four-pole filters of this type are demonstrated for the first time. Both theoretical and experimental results are presented.