the real space noise map by doing two-dimensional inverse Fourier transform of the reduced noise in Fourier space at each frequency channel.

The right-hand panel of Figure \[image\_p4tbsins\_nosmt\] shows the simulated noise map at the central frequency channel for an angular resolution 2 for 2000 h of observation time and the parameters listed in Table \[tab1\]. The rms noise per beam of the corresponding map is $\sim$ 19 $\mu$Jy. The amplitude of the signal as shown in the middle panel of Figure \[image\_p4tbsins\_nosmt\] is significantly smaller the rms noise for 2000 h of observation, thus the signal is not detectable without further reducing the noise using some other techniques like “smoothing”, which we will discuss later part of the paper (in section \[RES\_SI\_NS\_FG\]).

Foreground maps {#FG_map}
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The cosmological signal will be contaminated by other astrophysical foregrounds which have significantly larger amplitude [@2008MNRAS.385.2166A; @ghosh12]. In this study, we consider the Galactic synchrotron radiation and emission from unresolved extragalactic point sources as the major contributors to these foregrounds. Among these two, the Galactic synchrotron radiation contributes $\sim 70\%$ of the total foregrounds [@2006ApJ...650..529W; @jelic08]. In addition to these, the Galactic free-free emission, supernova remnants, and extragalactic radio clusters may also provide 