a1 Department of Information Engineering, University of Pisa, via Caruso 16, 56122 Pisa, Italy. Phone: + 39 0502217673.
a2 CNIT-RaSS (National Inter-University Consortium for Telecommunications – Radar and Surveillance System Research Center), via Moruzzi 1, 56124 Pisa, Italy.
a3 Scuola Superiore Sant'Anna, via Moruzzi 1, 56124 Pisa, Italy.
a4 CNIT-NLPN (National Inter-University Consortium for Telecommunications – National Laboratory of Photonics Network), via Moruzzi 1, 56124 Pisa, Italy.
In this paper we propose a photonic technique for a reconfigurable microwave signal generation based on the beating of two laser modes coming from a regenerative fiber mode-locked laser (FMLL) into a photodiode. The excellent performance of this kind of pulsed laser guarantees high stability on the directly generated microwave signal even at ultrahigh frequencies (up to W band). Therefore, by using the proposed architecture, the performance of a reconfigurable full digital coherent radar system can be enhanced for example in terms of moving target indicator (MTI) improvement factor and analog to digital converter maximum signal to noise ratio. Differently from the conventional radar oscillators, whose performance strongly deteriorate with increasing frequencies, the photonic radio frequency (RF) generation always shows an excellent spectral purity. Moreover, thanks to the achievable high repetition rates and the coherence properties of the FMLL, this laser scheme has also been proposed for digitizing, directly at RF, the received signal by electro-optical sampling. Thus the advantage of using just one device for signal generation in both the transmitter and receiver chain, makes the proposed solution a cost-effective architecture for microwave signal generation.
(Received October 14 2010)
(Revised January 11 2011)
(Online publication March 25 2011)