Simulated e-field distribution on series-fed antenna sub-array
The elevation pattern of the sub-array with 20º half power beamwidth
When the sub-array is placed in the full size array the proximity of the neighbouring sub-arrays tends to distort the radiation pattern. While the elevation pattern shown above hardly changes, the azimuth pattern does, so it is necessary to check the radiation patterns through detailed simulation.Depending on the array spacing and the inevitable mutual coupling which arises, the azimuth pattern may get better or worse. Typically, a flattened main lobe is seen.
Sub-array azimuth pattern influenced by coupling of neighbouring sub-arrays
This can be helpful, depending on the required range of azimuth scan. In other cases, a ripple on the lobe would lead to significant variations in antenna gain as the beam is scanned (i.e. scan loss). In the above design we will scan the radar beam to 45º so the sub-array will work well. Beyond about 50º the array would exhibit increasing scan loss because the pattern then rolls off pretty sharply.Words of advice I have proffered on more than one occasion have been:“Do not just procure a set of individual antennas, mount them in an array and hope for the best.”
x-band patch antenna array
Vector network anaylser Measured reflection coefficient
Simulated scanned forward and back lobes