Abstract: The invention provides a means for determining rapidly and accurately frequency information of electromagnetic radiation. It combines the operation of an Instantaneous Frequency Measurement receiver with the operation of an Instantaneous Fourier Transform receiver which utilizes a Laser-Bragg cell-photodetector array. The operational characteristics of the two receivers are such that, when they are controlled by signal processing elements, including a programmable frequency memory screen to enable or inhibit data transfers, they complement each other to provide the combined advantages of both receiver types, namely broad RF bandwidth, rapid response, ability to deal with high pulse densities, multiple CW signals, combined CW and pulse signals. The complementary IFM/IFT system operates under conditions for which either receiver operating separately would fail.