The Instantaneous Frequency Measurement (IFM) receiver has become a point of interest to the RF system design engineer upon its frequent application in electronic warfare (EW) purposes. Correlator is the most important part in an IFM receiver. The microwave correlator that acts as the frequency measurement mechanism of the IFM receiver was designed at 4GHz, to perform instantaneous RF input frequency measurement from 2GHz to 5GHz. The correlator components, such as the delay line, the Wilkinson power divider, the 90° hybrid and 180° hybrid were designed using the Agilent’s Advanced Design System (ADS). The design were realized in microstrip form. The 90° hybrid and 180° hybrid were fabricated on the separate printed circuit board as the connector crossing constraint. In simulation, the designed correlator managed to track instantaneously the RF input signal from 2GHz to 5GHz. However, the physical prototype cannot be tested for the frequency required, due to several problems highlighted in the discussion. There was a reasonable agreement between the physical measurement and the simulation results. Therefore, the prototype of the correlator is considered acceptable but need further research for improvement.