Hello All,
I have gone through a few research documents where I came across a term "Spatial Frequency" which is basically the sin of theta where theta is the azimuth angle ranging from -90 to 90 degrees. Therefore, spatial frequency ranges from -1 to 1.
However, I am a bit confused on what is the significance of this term spatical frequency. In terms of an antenna radiation pattern, what observations can be made from spatial freq vs antenna radiation strength which can not be made from theta (azimuth angle vs antenna radiation strength.
Many Thanks
Anum
Hello Anum,
not knowing the documents you have read, my guess is:
In the theory dealing with antenna arrays, the sin of theta (multiplied by distance between antennas / wavelength) usually appears in a term denoting the phase delay between adjacent antennas; theta = 0 => no delay, theta = +/-90° => maximum delay, provided all antennas are located in a plane.
While the concept of spatial frequency might be the topic of the resp. article, the sin of theta itself does not denote spatial frequency nor the spatial spectrum.
To go beyond this guess would require links to the documents.
Hope this helps a bit.
If you use sine theta instead of theta the lobe width remains constant so some of the properties of the pattern can be more obvious.
Spatial frequency is proportional to how many cycles there are across the aperture. Spatial frequency is proportional to sin theta. Zero spatial frequency is zero phase across the aperture. Very high spatial frequency corresponds to radiation into imaginary space (sine theta greater than 1).
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