Analysis of analog WDM links for radar applications

Active phased array with low power multiple transmit/receive modules is a radical change over conventional arrays with single high power transmitter section. Hence these radar systems demand the distribution of a number of signals including Radio Frequency (RF) phase reference, Local Oscillator (LO) signals and digital signals used for control and monitoring. Generally, coaxial cables are used for the distribution of these signals, which makes the overall systems bulky, costly, massive and inflexible. This paper presents a feasibility study on using optical fibres links to replace the coaxial cables for signal distribution. Wavelength Division Multiplexing (WDM) technique is used to multiplex the different radar signals into an optical fibre, used for the distribution network. The manifold advantage of optical fibre links, like low loss, light weight, large bandwidth and immunity to EMI makes this system very attracted for radar applications. In this work, WDM links are validated for Continuous Wave RF (CWRF), Pulsed RF and Non-Linear Frequency Modulated (NLFM) waveforms. The measured results are compared for losses incurring in these links. The results are thus verified with total losses occurring in a WDM system based on the loss budgeting results obtained using WDM component specifications.