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# Limited field of View Array

## Limited field of View Array

(OP)
Hey everybody,

has somebody of you experience in building LFOV (Limited Field of View) arrays?

My design has a 4x8 patch matrix with lambda/2 spacing.

The patch element has a 3dB beamwidth of around 105°.

Which field of view you would expect by assuming a very clever amplitude and phase distribution?

Are there any guidelines for a clever amplitude and phase distribution?

Thanks.

### RE: Limited field of View Array

Limited Field of View, never heard that phrase. Does it mean narrow beam, non scanned array?

4x8 isn't a large array. So you can't get magic by varying the amplitude and phase distributions much. You either have them all the same for highest gain, or make the center ones stronger than the edge ones.

Your array is 2x4 wavelenghts, so -3 dB beamwidths with all antennas at equal power is 51 degrees/2 wavelengths = 25 degrees and
51 degrees/4= 13 degrees.

If you make the center antennas stronger than the edge antennas, and say you have alot of them and taper the edge antennas to be very weak in a cosine function amplitude taper, the beamwidth formula is 68/# wavelengths, (as opposed to 51/# wavelengths) and the sidelobes get lower and your gain drops a bit because the beamwidths are wider.

### RE: Limited field of View Array

I'd also never heard of "Limited Field of View" either.

Googling it (with 'antenna') reveals that it's an approach where the steering angle requirement is narrowed to allow slight improvement of other characterictics.

### RE: Limited field of View Array

The further you steer an array, the worst it's active VSWR gets and the worse the sidelobes get.
I'd expect an LFOV array to be larger based on VE1BLL's Google description.

### RE: Limited field of View Array

LFOV means the steering angle requirement might be narrowed (for example) 10° instead of 45°. Presumably this makes things easier in all other respects.

### RE: Limited field of View Array

(OP)
All of you know, that the scan angle of the phased array antenna is depending on the element pattern of a single element.

By building a subarray we would get a new element pattern, with a main lobe and sidelobes.As a general rule , the beamwidth is very narrow.

But if I design now a subarray with LFOV I am able to create a defined beam shape with larger reactaguar beamwidth. In the end it is a way to decrease the phase control units in a large antenna array of subarrays.

The phase tilt in the large antenna array would be generated by changing the phase distributiion of the subarrays. Inside the subarray a feeding network will be used to define the clever amplitude an phase distribution for the LFOV subarray pattern.

### RE: Limited field of View Array

Thanks for the explanation DenVo.

So the reason you need a clever subarray amp/phase control is to primarily lower the subarrays sidelobes thereby minimizing the large array grating lobes while scanning, or so I guess. Is this for efficiency, full array beam shape, or array scan blindness protection?

I believe I've read Pozar's discussion that you can eliminate scan blindness fears in large arrays by subarraying as you are doing (I think).

It seems like you need a MatLab routine to optimize your desired subarray pattern shape based on amp/phase distributions that are realizable.

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