The long, microwave-photonic variable delay of the impulse response of linear frequency-modulated (LFM) waveforms is proposed and demonstrated experimentally. The delay method is based on the application of a variable frequency offset to one side-band of an LFM-modulated optical carrier. Due to the time-frequency ambiguity properties of the LFM signal, the effect of the frequency offset on the impulse response is nearly equivalent to that of a group delay. Numerical simulations suggest negligible degradations in the resolution, peak-to-side-lobe ratio and integrated side-lobe ratio of the processed LFM waveform. Experiments demonstrate the delay of a 500-MHz-wide LFM signal by up to 250 ns. The method is applicable to LFM waveforms of arbitrary bandwidth and central radio-frequency. The long delays make the method attractive for optical beam-steering in large phased-array radars.
|Number of pages||3|
|Journal||IEEE Photonics Technology Letters|
|State||Published - 2012|
Bibliographical noteFunding Information:
Manuscript received October 5, 2011; revised October 21, 2011; accepted November 9, 2011. Date of publication November 18, 2011; date of current version January 18, 2012. This work was supported in part by the German-Israeli Foundation under Grant I-2219-1978.10/2009.
- Linear frequency modulated (LFM) waveforms
- Optical beam forming
- Variable optical delay