Zhou Du

Antenna Pattern Retrieval from Reflection Coefficient Measurements with Reflective Loads

This paper presents a new method for antenna pattern retrieval from reflection coefficient measurements. A reflective load with known reflective properties is placed close to the aperture of the antenna under test. The reflection coefficient of the antenna is measured at the antenna feed with multiple different reflective loads. The antenna pattern is then solved from the measurements with an inversion method. This paper derives and verifies the analytical foundations needed to implement the method, and demonstrates the method both by simulations and experiments for a pyramidal horn antenna at 30 GHz.

Generation of Free Space Radiation Patterns From Non-Anechoic Measurements Using Chebyshev Polynomials

Generally, antenna radiation patterns are measured in an anechoic condition so that the presence of undesired reflections does not skew the final measurements. The objective of this communication is to search for methodologies which can extract meaningful approximate results from non-anechoic measurements. In other words, how to process the reflection contaminated data and extract valuable information when one does not have a good anechoic room and performs measurements with various undesired reflections present in the data. The Chebyshev polynomials are used to extract from the data collected under non-anechoic environment and generate a radiation pattern for the same antenna radiating in free space conditions. The problem with this method is that some a priori information is required about the environment. Measured data has been used to illustrate the applicability of this new methodology and its improved performance over the FFT based methods.

Radiation pattern retrieval from impedance measurement with a reflective object in the antenna near field

A recently proposed antenna measurement technique based on impedance or reflection coefficient measurements with varying reflective objects in front of an antenna is reviewed. The method allows radiation pattern determination without moving cables which are subject to changes in their electrical length and attenuation during conventional antenna measurements. In addition, a modification to the method is introduced in order to speed up the involved iterative optimization process.

Beam-steering antennas at millimeter wavelengths

In many emerging applications of millimeter waves, electronic focusing and beam steering is needed. We present a survey of mm-wave beam steering antennas, where the necessary phase change for antenna elements is achieved using various electronically tuneable elements, e.g. microelectromechanical systems (MEMS), such as tuneable leaky-wave antennas, shaped lens antennas with integrated switched feed array, active reflectarray, tuneable high-impedance surface, and dielectric rod waveguides with integrated phase shifters. Some early results of our own relevant investigations are also presented.

Realization of wideband hologram compact antenna test range by linearly adjusting the feed location

Hologram-based compact antenna test range (HCATR) is very attractive for antenna measurement at mm/sub-mm wave frequencies. However, as the hologram is a frequency sensitive element, the operation of a HCATR is usually limited to a narrow band. This paper describes a wideband HCATR: It can be realized by linearly adjusting the feed location. The position needs to be adjusted for approximately compensating the wave front curve of the feed, which is proportional to the operating frequency. The theory can be conformed under the paraxial condition. For the acceptable quiet zone field quality over a wide band, the aperture needs to have a large focal ratio. The idea is verified and the wideband performance of the quiet zone is studied with the simulated and measured results at W band (95 GHz) and D band (170 GHz).

Antennas for electronic beam steering and focusing at millimeter wavelengths

This paper discusses the prospects of millimeter-wave beam steering antennas, such as tuneable high-impedance surface, dielectric rod waveguide with an integrated phase shifter, tuneable leaky-wave antenna, active reflectarray, and shaped lens antenna with an integrated switched feed array. In these antennas the necessary phase change for antenna elements can be achieved using various electronically tuneable elements, but in our case MEMS are used. Some early results of our investigations are presented.