Photonic time stretch channelizer for broadband microwave spectrum sensing

Microwave spectrum sensing is of critical importance in wireless communications,

radars and electronic warfare. Measuring high-frequency and broadband RF signals in a high-

speed and high-resolution while low-cost manner is challenging. Photonically assisted techniques

have shown superior performance over their electronic counterpart. Particularly, optical spectral

channelizer based technique has attracted great interest as it enables lost-cost spectrum mea-

surement for multi-tone microwave signals. One di±culty of this technique is its relatively poor

measurement resolution, limited by the channel spacing.

Based on photonic time-stretch technique, which mirrors the spectrum shape of a largely chirped

optical pulse to its temporal waveform, here we propose to use an optical channelizer to equiva-

lently sample the modulated optical pulse. Since no high-speed photodetector is required, system

cost is greatly reduced. More importantly, the method features greatly improved measurement

resolution, which is more than two orders of magnitude higher than the channel spacing. The

technique was veriØed by experimental demonstrations. Means to further improve the measure-

ment resolution and operational bandwidth will be discussed as well