Why parabolic antenna is often chosen for MMW seeker?

[Vanessa1402]

I observe that on missile with X band radar seeker, the type of antenna they often use is flat slotted array

but on missile with MMW seeker, they always use parabolic antenna. Why?

 

[overscan (PaulMM)]

My gut feeling is that for the much smaller wavelengths of MMW, the parabolic antenna performance is good enough to not need the expense of a slotted waveguide antenna, especially given it is disposable.

 

[stealthflanker]

Because it's simple and provides enough performance.

Making array/slotted planar array for mmw appears to be quite challenging due to manufacturing tolerance for the each elements, which can be costly. The following is simple tradeoff Of seeker frequency selection. As can be seen shorter wavelength indicates increase in cost

 

[Nik]

Perhaps also that AGM needs to get very close to its target ? Mission-kill a jet with a little shrapnel, but needs a lot more damage to ruin a big antenna ??

 

[stav]

Probably because of the bandwidth.
Slotted arrays have relatively narrow bandwidth and are suitable for active (with self generated and well known Tx/Rx frequency) applications.