The fine frequency estimation of received signal is very important in Electronic Warfare and communication systems. The performance of radar classification depends on the accuracy of frequency measurements. Since frequency measurement accuracy in Digital Instantaneous Frequency Measurement receiver is highly dependent on corresponding pulse detection technique, here we propose an improved approach which is able to detect pulses as narrow as 50 nsec. Simulation results confirm that this receiver is capable of detecting pulses with 50 nsec width over 1.2 GHz bandwidth with a major error within 43 KHz.