A photonic instantaneous frequency measurement system capable of measuring both RF frequency and power simultaneously, is conceived and practically demonstrated. This system employs an RF photonic Hilbert transformer together with low-cost, low-frequency photo-detectors to obtain two orthogonal DC measurements. This system exhibits a frequency range of 1-10 GHz. Wider frequency range can be achieved through integration.

A photonic implementation of a practical broadband RF Hilbert transformer is demonstrated by using a four-tap transversal system. An almost ideal 90 degrees phase shift with less than 3 dB of amplitude ripple has been achieved from 2.4 to 17.6 GHz. An efficient method to realize both transformed (quadrature-phase) and reference (in-phase) signal has been achieved by using a coarse wavelength division multiplexing coupler. Extension of the transformer bandwidth and further improvements of its implementation are discussed.

A broadband photonic instantaneous frequency measurement system utilizing four-wave mixing in highly nonlinear fiber is demonstrated. This new approach is highly stable and does not require any high-speed electronics or photodetectors. A first principles model accurately predicts the system response. Frequency measurement responses from 1 to 40 GHz are demonstrated and simple reconfiguration allows the system to operate over multiple bands.

A new low cost method for implementing an Instantaneous Frequency Measurement (IFM) system is presented in this paper. The proposed method is based on dividing the incoming RF signal into four signals and filtering each one by an appropriate band-pass filter. The frequency is then estimated from the power level of the filtered signals. A closed form for the Standard Deviation (STD) and the bias of the frequency estimator is derived. A design example for an IFM system with a working frequency band of 2 to 4 GHz is presented with simulated and measured results. The design is implemented on a commercial FR4 (DE104) substrate using printed circuit board technology. Experiments in a laboratory show a maximum error of about 15 MHz in estimating the frequency value.