Reduced Cost Photonic Instantaneous Frequency Measurement System

Abstract

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.

All optical measurement of an unknown wideband microwave frequency

“…The estimation of an unknown test frequency for the range of 5 to 30 GHz, with the help of a four−wave mixing power is done with the measurement ac− curacy of ±0.3 GHz. The measurement accuracy achieved here is comparable to that of the previous works [4][5][6][7][8][9][10], but substantial increment in the measurement range is the main advantage of this approach, which is acceptable for applica− tions where a rough but an instantaneous microwave fre− quency measurement is required.…”

“…All optical techniques for processing the microwave signal have been considered as a reliable solution [2][3][4] which overcomes limitations of conventional techniques. Recently, few methods have been proposed to measure the unknown microwave frequency in an optical domain [5][6][7][8][9][10][11][12][13]. In the intensity modulation based method [5] of detecting microwave signal, power received from a dispersive fibre is correlated with an unknown RF frequency signal as dissimilar modulating RF signals suffer different chromatic dispersions.…”

“…7 and 8. Measurement of an unknown microwave frequency with an experimental set up consisting of two cascaded Mach−Zehnder Modulators (MZM), a RF delay line and a single photodetector has been also reported [9,10], but it requires sophisticated electrical circuitry to control DC bias drifting. However, microwave frequency measurement by power distribution using two laser sources, phase modulator and highly dispersive fibre is independent of bias drifting problem [12].…”

Sensitivity improved photonic Instantaneous Frequency Measurement receiver

“…The factor G is defined as G=rG PD L 1 L 2 where r and G PD are the photo-detector responsivity and gain respectively and L 1 and L 2 are the MZM1 and MZM2 insertion loss respectively [8]. Fig.…”

“…The cost of multiple broadband photo detectors would be prohibitive expensive [5]. Recently we have explored a frequency measurement system where frequency detection is achieved via D.C measurement [8]. However the sensitivity of the receiver was poor due to high noise floor.…”