By further analysis of the receiver diagram, following considerations were made.
• The sensitivity or the MDS is assumed to be -100 dBm.
• The sampling rate of an ardiuno board, which is to be used for data acquisition can be set to
2 MHz with a corresponding prescale factor. Thus, according to Nyquist sampling theorem,
the bandwith frequency could be considered as 1 MHz.
• Thus, using the equation MDS (dBm) = -174 dB + 10 log10 BW +NF,
NF = 14 dBm.
• Since the reflecting target is assumed to be stationary, there is no any doppler effect. Thus
with having a differential mixer, the output through the mixer would be almost zero. In order
to filter out this output signal , a low pass filter must be added instead of band pass filter.
The low pass filter prior to I and Q channel acquisition has to be designed so that the
receiver path has a cumulative Noise figure of 14 dBm.
• More over,this low pass filter is considered to be designed as an active filter. It is because
since active filers are easier to design, possess good performance characteristics, much
accurate , has a steep roll-off , low noise.
• The 90 degree phase shift is achieved using a 3dB coupler which is already designed as for the balanced amplifier configuration.