Garry , I understand what you are trying to say.
With respect Austin... I don't think you do.
Designers don't just choose a radar frequency for fun.
Specific frequencies have different properties which leads to different advantages and disadvantages.
If you want to spot objects on the ground then a very high frequency radar can give an almost photo like view of things like terrain... that is why we get such a detailed view of the world, but the cost is processing power. Flash still images in front of a human at the pathetically slow rate of 25 frames per second and we think we are seeing normal live moving action... when in fact we are seeing still images flashed before our eyes at a rate of 25 frames per second.
If you just want to detect the presence of a target then a long wave radar will ignore clouds and shaping of the object.
Different frequencies have different performances in different conditions, so looking down yo might find changing frequency gives you better performance, while looking up a different frequency again might be better.
The point is that the missiles seeker in an Active Radar Homing missile is a transmitter and receiver so it can choose the frequency to transmit... the fact that it can transmit, means it can also receive it, so it sends a pulse and listens for the signals it gets in return... using doppler shift (which is a property of the returning wave) it can separate moving objects from those that are still in comparison with their background).
I have rarely seen radar designed in more than one band and i am talking of more capable bigger radar , the missile has small radar with limited power and processing capability.
Size of the radar, processing power, and level of power have nothing to do with it. A transistor radio can detect several bands at once, in fact I have a short wave radio that can detect AM frequency radio waves from 530KHz to 1600KHz, plus short wave 1 from 2.3 MHz to 7 MHz, and Short Wave 2 from 7 MHz to 22MHz.
In the case of a radio it only receives and does not transmit... in the case of this ARH missile its antenna both transmits and receives.
The radio and Radar bands are not based on antenna capabilities.
The radio transmitter for the Shturm and ATAKA missile operates in the 35GHz range which is high K or Ka band... and a very similar frequency to speed camera radar... very hard to jam.
What makes it so impossible?
Having a single radar antenna that can transmit and receive HF (10-100m wavelength) and MMW radar (7.5mm to 0.1mm wavelength) would be near impossible.
Having a single antenna that can transmit and receive X (25mm-37.5mm wavelength) and Ka (16.7mm-25mm wavelength) Band radar signals is not that big a deal!
Processing and power and radar size doesn't come in to it.. basically a radar that can operate in frequency ranges of 20mm to 30mm... which is a pathetic 1cm range of bandwidth is technically an X/Ku band radar. In fact a radar antenna designed to operate in the 24-26mm range is technically an X/Ku band radar... how can a radar with a 2mm bandwidth be impossible to make?