hi jyoti raina…
as clear from the screen shot it is clear that you are getting signal only in the lower region that means the filter is only passing that much band and i think increasing power will not help you in this. Also you have not mentioned the type of filter your are using in your design and i think the filetr you have used has aa very narrow passband. so you sholud try to use a filter with a wider passband.
with regards