Advanced Cepstral Filtering - Introduction to Imaging from Scattered Fields - page 163

table 10.11 A Comparison of Reconstructed Images for Circular Targets with
Radius λ Using the Method of Processing Each Source Separately and Then
Combining Them in Cepstrum Space after Filtering for Three Different Permittivity
Value s

Reconstructed image Processing each source separately and combining in the
cepstrum Domain

ε r no subtraction subtracting Ψ inc

1.1

1.5

1.9

Note: These images compare the results of subtracting the cepstrum version of the incident ( Ψ inc ).

Circumference
# of Receivers

= 2
90

π r

Spacing = (10.4)

For the case mentioned above, the spacing is 53 mm. This is still smaller than
the wavelength, which corresponds to the highest spatial frequency, but as the
receivers are further reduced in number, this spacing increases to be greater