what is ideal scan angle for phased array?

Is 45-degrees the ideal scan angle for most phased arrays?

The reason I think so (and I need someone to agree or disagree with me) is because at 45-degrees there is a good balance between gain and beamwidth. If I want my array to have a wide enough beamwidth and good gain, 45-degrees is the happy medium. If I go up in scan angle to say 90 degrees (broadside), I get much wider beam and low gain. If I go down in scan angle to say 0 degrees (endfire), I get excellent gain, but narrower beam.

Thanks.

It really depends on the type of element that you use. you really can't scan an array past 60° and depending on the element, coupling, and spacing you can get scan blindness in different areas. Once again it is fully dependent on the element but I have seen designs where you get more gain at 45° than you get at 0° even thought the element itself has more gain at 0°. if you are looking for an element type that has good gain at 45° and 0° I would recommend either a end fire Helix or a dipole.

great thanks. I am using dipole and I am getting good gain at 45 and 0 degrees.

just for kicks, I changed the phase angle (not the scan angle) to 45 degree phase excitation angle, and I got huge gain. I am not sure what the 45-degree phase excitation angle corresponds to scan angle (theta) wise as when I plug it in the equation beta = -kd cos(theta), beta=45 and d=0.1lambda, then I get errors for theta? I wonder what the theta for 45-degree phase is?

Also, my array is not exactly linear and doesn't have equal inter-element spacing (d). The array is semi-circular and the interelement spacing varies between 0.1lambda and 0.4lambda. I wonder what formula to use to find the correct phase excitation angle?

just for clarification, what do you mean by "you really can't scan an array past 60° "?
Do you mean 60° scan angle or 60° phase excitation angle? The two are different. 90° scan angle which is broadside has a 0° phase excitation angle.

Thanks.

I mean scan angle. If you have an array even if it has a perfect element you will start to see grating lobes and other problems when you scan past 60°. This is due to element spacing (you can only get the elements so close), element to element coupling at high scan angles, radiation blockage from neighboring elements, scan blindness from the said things, and in practical antennas (look at a dipole or a helix) there is very little element radiation past 60° scan and therefore you can't scan that far. All these things show that in practical applications you cannot scan more than 60° from boresight.