In this study, a thin coaxial antenna for microwave ablation (MWA) is proposed. A helical slot is added between two slots in order to overcome the disadvantage of the radiation range extending to the unwanted part in the conventional single-slot and double-slot applicators. By adding a helical slot, the specific absorption rate (SAR) pattern is more concentrated near the slot as compared with. Booker in 1946, from Babinet's principle in optics a slot in a metal plate or waveguide has the same radiation pattern as a driven rod antenna whose rod is the same shape as the slot, with the exception that the electric field and magnetic field directions are interchanged; the antenna is a magnetic dipole instead of an electric dipole; the magnetic field is parallel to the. Slot antenna is a best choice for such type of applications due to its low profile planar structure with simple and low-cost fabrication 1. The concept of printed slot antenna was first introduced by Y. Yoshimura in 1972 2. Printed slot antenna consists of a slot etched on the. Slot Antenna is an example of Aperture antenna. A rectangular slot is made on the conducting sheet. A rectangular slot is made on the conducting sheet. These slot antennas can be formed by simply making a cut on the surface, where they are mounted on. Abstract: A high-isolation eight-antenna multi-input multi-output (MIMO) array operating in the 3.5 GHz band (3.4-3.6 GHz) for future smartphones is proposed. Here, a novel balanced open-slot antenna is designed as an array antenna element, in which this antenna design can yield a balanced slot mode (with reduced ground effects) that can enhance the isolation between two adjacent input ports.

H-guide slot antenna shrinks sidelobes

Abstract

For antennas with low sidelobes, a radiator is proposed that uses a slot symmetrically cut or etched in the upper plate of an H-guide (a dielectric-loaded parallel plane waveguide) that supports the dominant mode and has a zero cutoff frequency. The H-guide radiator is linearly polarized, conformal, easy to integrate, and very efficient (more than 80 percent). Its bandwidth is about 20 percent. Unlike current microstrip antennas, the H-guide slot antenna does not emit parasitic radiation from lines feeding the radiating elements. The measured radiation pattern of the H-guide antenna conforms well with the calculated pattern of a linear magnetic current for a wide frequency range (8.0 to 12.4 GHz). Means to boost efficiency and achieve better 'equal ripple' response are considered. A radiator with a guide height of 9 mm is shown to be 80 percent efficient in an 18 percent bandwidth, with 26 percent bandwidth achievable theoretically by decreasing guide height to 4.5 mm.

• Antenna Radiation Patterns;
• Microwave Antennas;
• Sidelobe Reduction;
• Slot Antennas;
• Waveguide Antennas;
• Antenna Arrays;
• Equivalent Circuits;
• Gallium Arsenides;
• Integrated Circuits;
• Microstrip Antennas;
• Millimeter Waves;
• Phase Shift;
• Radar Antennas;
• Ultrahigh Frequencies;
• Communications and Radar

The standard rectangular microstrip patch is a narrowband antenna and provides 6-8 dBi Gain with linear polarization. This example based on the work done in [1],[2], models a broadband patch antenna using a slot in the radiator and develops a dual-band and a tri-band variation from it. In the process, the single wide response has been split into multiple narrow band regions catering to specific bands in the WiMAX standard. These patch antennas have been probe-fed.

Building the Single U-Slot Patch

Define Parameters The basic U-slot patch antenna consists of a rectangular patch radiator within which a U-shaped slot has been cut out. As discussed in [1], the patch itself is on an air substrate and thick so as to enable higher bandwidths to be achieved. The presence of the slot structure achieves additional capacitance within the structure which combines with the inductance of the long probe feed to create a double resonance within the band. The geometry parameters based on [2] are defined and shown in a drawing below.

Define radiator shape - Single U-slot

H Slot Antenna Mounts

Use the rectangle shape primitives in Antenna Toolbox™ to create the U-slot patch radiator shape. Boolean subtraction operation is used among the shape primitives for this purpose.

Define ground shape

Create the ground plane shape for the antenna. The groundplane in this case is rectangular and 71 mm x 52 mm in size.

Define stack

Use the pcbStack to define the metal and dielectric layers and the feed for the single U-slot patch antenna. The layers are defined top-down. In this case, the top-most layer is a metal layer defined by the U-slot patch shape. The second layer is a dielectric material, air in this case, and the third layer is the metal ground plane.

Calculate and Plot Reflection Coefficient

Mesh the structure by using a maximum edge length which is one-tenth the wavelength at the highest frequency of operation which is 6 GHz for this example. Compute and plot the reflection coefficient for this antenna over the band. The reflection coefficient is plotted with a reference impedance of 50 ohms.

Calculate and plot pattern

Plot the radiation pattern for this antenna at the frequencies of best match in the band.

Dual-band U-Slot Patch Antenna

Define Parameters

To achieve dual-band behavior as shown in [1], [2], the double resonance is modified such that the two contributing resonances, i.e. from the patch and from the slot do not merge. To do so the existing slot parameters are adjusted and a second slot is introduced into the structure. The parameters for the double U-slot are listed below as per [2] and a figure annotated with the variables used is shown.

Create Double U-slot radiator

As before use the shape primitives, to create the geometry by using Boolean operations.

Modify Layers in Stack

Modify the existing stack by introducing the new radiator in the Layers property.

Mesh and Plot Reflection Coefficient

H Slot Antenna Booster

Mesh the structure at the highest frequency of operation and calculate the reflection coefficient.

Triple-Band U-slot Patch Antenna Parameters

For triple-band operation a third U-slot is introduced and the existing slot parameters are adjusted. The parameters are shown below based on [2].

Create Triple U-slot radiator

Modify Layers in Stack

Mesh and Plot Reflection Coefficient

Conclusion

The models of the multi-band single layer U-slot patch antenna as discussed in [1], and [2] have been built and analyzed and agree well with results reported.

Reference

[1] K. F. Lee, S. L. S. Yang and A. Kishk, 'The versatile U-slot patch antenna,' 2009 3rd European Conference on Antennas and Propagation, Berlin, 2009, pp. 3312-3314.

[2] W. C. Mok, S. H. Wong, K. M. Luk and K. F. Lee, 'Single-Layer Single-Patch Dual-Band and Triple-Band Patch Antennas,' in IEEE Transactions on Antennas and Propagation, vol. 61, no. 8, pp. 4341-4344, Aug. 2013.