Now that we have our measurement equipment and an antenna range, we can perform some antenna measurements. We will use the source antenna to illuminate the antenna under test with a plane wave from a ...
Testing of real antennas is fundamental to antenna theory. All the antenna theory in the world doesn't add up to a hill of beans if the antennas under test don't perform as desired. Antenna Measuremen ...
One of the earliest methods of optimizing array geometry dates back to around 1960 and is known as "thinning arrays" or "array thinning". This method is relatively simple. A large uniformly sp ...
The basic geometry of a 7-element hexagonal array is shown in Figure 1.
Figure 1. Hexagonal Two-Dimensional Antenna Array.
The hexagonal structure is such that each element is a fixed distance ( ...
We've discussed the basics of antenna arrays and weighting methods in arrays. The performance of an array will depend on the number of elements in the array (generally more elements yields better perf ...
Antennas (and antenna arrays) often operate in dynamic environments, where the signals (both desired and interfering) arrive from changing directions and with varying powers. As a result, adaptive ant ...
In this section, we'll look at an example using MMSE weights, given by:
We'll consider an array with N=3 elements, with uniform half-wavelength spacing oriented along the z-axis. We'll assume the d ...
We're deriving the optimal MMSE weights. Recall from the previous page:
Multiplying the terms above, the MSE becomes
(1)
Because the weights are constant (don't vary wi ...
In this section, I'm going to move on to a (relatively) more advanced weighting scheme, one that is statistically based instead of deterministic. This weighting method minimizes the Mean Square Error ...
In the previous page on Dolph Weights, the Dolph-Tschebysheff method was introduced. On this page, we'll run through an example. Consider a N=6 element array, with a sidelobe level to be 30 dB down fr ...
You may have noticed that the antenna array factors for arrays with uniform weights have unequal sidelobe levels, as seen here. Often it is desirable to lower the highest sidelobes, at the expense of ...
In this section, we'll look at two-dimensional or planar arrays with uniform spacing and with phased weights. Fortunately, two-dimensional phased arrays are not much more difficult to understand than ...
In the previous page, the general form of the antenna Array Factor for an N element array with uniform spacing of d and phased tapered weights steered towards was shown to be:
Let's begin by maki ...
In this page, we'll derive a general equation for the array factor or antenna array response for an N element uniformly spaced linear antenna array. The weights will be simple phased weights; when the ...
We saw previously that a uniformly-spaced array with weights selected to be:
(1)
will have the array steered towards the desired direction, . In equation (1), k is the wave num ...
