María Vera Isasa

Microstrip antenna for 5G broadband communications: Overview of design issues

In this contribution we present two practical implementation cases of single patch antennas at 28GHz and 60GHz. We describe the design challenge of conciliating the antenna performance specifications and fabrication restrictions. Over this basic element of an array antenna we discuss the influence of three different categories of design issues.

Linear polarization parallel plate slot antenna

We show the design of a linearly polarised flat antenna. The main goal is getting a low cost antenna to use for the reception of Hispasat satellite emissions in the 12 GHz band. The gain needed for the antenna is around 30 dBi. A rectangular array of slots in the upper side of a parallel plate waveguide form the main antenna structure. The guide is excited by one planar feeding structure consisting of an array of rectangular microstrip patches. We also modify the feeding network the design procedure and the materials used to build of the radiation surface.

3×3 Microstrip beam forming network for multibeam triangular array

The design of a beam forming network (BFN) for a triangular cell of three elements is considered. A useful relation between phase excitation of the elements of the cell, beam direction, wavelength and distance is given. The BFN is studied based on a Butler matrix, using balanced and unbalanced hybrid couplers to obtain a three inputs and three outputs network which is used to develop a multibeam structure. A system of three equations is also presented to calculate the lengths of the transmission lines which connect the couplers of the network. These equations allow a flexible design of the network depending on the needed specifications. Finally, a microstrip BFN circuit that demonstrates the utility of the design has been developed.

Synthesis of circularly polarised multiprobe feed radial line slot array

In previous articles, we presented an easy way to analyze a slot array fed through a radial line and the design of an array of slots placed in an Archimedes spiral. The analysis was based on a circuit approach where the circuit parameters have been estimated using the first propagation mode in the radial line and the far field theory. The Archimedes spiral design, obtained with only one probe, has an efficiency problem due to the reflected field, that can be solved with this multiprobe design. The paper describes the antenna design method, giving the slot position and angle to obtain a radial line slot antenna having circular polarisation and broadside main beam.

Circular array with dual conical beam pattern for emergency communications

This paper presents the design of a circular array working at 2 GHz capable of generating two conical beam patterns with a semiangle of 30° and 90° respectively. The genetic algorithm was employed in order to obtain the characteristics of the array. Four parameters were optimized by using this method: number of rings, ring radius, number of elements in each ring and phase excitations. As a result, three arrays formed by 1, 2 and 4 rings (12, 33 and 66 elements) were selected.

Synthesis of Circularly Polarised Radial Line Slot Array

In previous articles, an easy way to analyse a slot array fed through a radial line was presented. The analysis was based on a circuit approach where circuit parameters have been estimated using the first propagation mode in the radial line and the far field theory. Here we study the design of a particular application for circularly polarised broadside antenna. The design defines the length, position and orientation of the slots in the antenna surface. The final analysis of the antenna gives a good behaviour in field diagrams and gain.

Antenna Cross-Polar Requirements for 3-PolD Weather Radar Measurements

The analysis and correction of the bias occurring in weather radar polarimetric measurements is a challenging problem. Polarization coupling due to the cross-polar radiation pattern of the radar’s antenna is known to be responsible for errors in the estimation of the polarimetric covariance matrix, and consequently in the hydrometeor classification and quantification, either when using the ATSR or the SHV method. An alternative method for Doppler and polarimetric measurements based on transmitting three different polarizations (3-PolD) has been proven to provide accurate polarimetric covariance matrix estimates without making any hypothesis about the target polarimetric response or its Doppler spectrum. This method does not reduce the Doppler capabilities or the unambiguous range of the radar despite alternately transmitting 3-PolD. These characteristics have encouraged evaluating the polarimetric parameter biases due to cross-polar radiation when this method is used. Biases are calculated considering reflector antenna systems as well as phased-array antenna systems. The results show that this method may guarantee a tolerable bias level even with a poor co- to cross-polar antenna pattern ratio.

A compact microstrip feeding network for circular arrays with conical beam pattern

In this paper the design in microstrip technology of two 12-port compact feeding networks working at 2 GHz for a circular array is presented. The series-parallel transmission line theory was employed to obtain the design parameters. Both structures provide equal power to each output port and generate a constant phase shift between adjacent ports of 30° and 120° respectively. This kind of network is employed for feeding arrays capable of generating two conical beam patterns, which are very useful in mobile applications.

Analysis and design software for radial slot antennas

A software for the analysis and design of radial slot antennas excited by one or several coaxial probes is presented. This tool has two main different blocks: analysis and design. The software has been improved with a file input/output options and a graphic display of radiation patterns, impedance, directivity and other antenna parameters. Everything is compiled in C++ for Windows. The second part of the paper includes some designs and results.