Background:
Patch antennas are composed of the substrate material with patch and ground plane on the both
sides of the substrate. The dimensions and performance characteristics of the antenna are highly influenced by the choice
of the appropriate substrate depending upon the value of their dielectric constant. Generally, low index substrate materials
are used to design the patch antenna but there are also some of the applications, which require the implementation of patch
antenna design on high index substrate like silicon and gallium arsenide.
Objective:
The objective of this article is to review the design of antennas developed on high index substrate and the
problems associated with the use of these materials as substrate. Also, main challenges and solutions have been discussed
to improve the performance characteristics while using the high index substrates.
Method:
The review article has divided into various sections including the solution of the problems associated with the
high index substrates in the form of micro-machining process. Along with this, types of micro machining and their
applications have discussed in detail.
Results:
This review article investigates the various patch antennas designed with micro-machining technology and also
discusses the impact of micro-machining process on the performance parameters of the patch antennas designed on high
index substrates.
Conclusion:
By using the micro-machining process, the performance of patch antenna improves drastically but
fabrication and tolerances at such minute structures is very tedious task for the antenna designers.
Grape yield estimation has traditionally been performed using manual techniques. However, these tend to be labour intensive and can be inaccurate. Computer vision techniques have therefore been developed for automated grape yield estimation. However, errors occur when grapes are occluded by leaves, other bunches, etc. Synthetic aperture radar has been investigated to allow imaging through leaves to detect occluded grapes. However, such equipment can be expensive. This paper investigates the potential for using ultrasound to image through leaves and identify occluded grapes. A highly directional low frequency ultrasonic array composed of ultrasonic air-coupled transducers and microphones is used to image grapes through leaves. A fan is used to help differentiate between ultrasonic reflections from grapes and leaves. Improved resolution and detail are achieved with chirp excitation waveforms and near-field focusing of the array. The overestimation in grape volume estimation using ultrasound reduced from 222% to 112% compared to the 3D scan obtained using photogrammetry or from 56% to 2.5% compared to a convex hull of this 3D scan. This also has the added benefit of producing more accurate canopy volume estimations which are important for common precision viticulture management processes such as variable rate applications.
Efficient yield estimation of multiband patch antennas by polynomial chaos‐based Kriging
