From this diagram, it is easy to see that the maximum allowable phase noise in order to achieve an adjacent channel rejection (or selectivity) of S dB (S 0) is given by L(fm) = C(dBm)S(dB) I(dBm)10log(B), (dBc/Hz), ( 13.50) where C is the desired signal level (in dBm), I is the undesired (interference) signal level (in dBm), and B is the bandwidth of the IF filter (in Hz). Derive Equation (13.50) giving the required phase noise for a specified receiver selectivity