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Optical Cancellation of RF Interference

By converting radio frequency (RF) signals into the optical domain, it is possible to 'cancel' user-generated signals from the spectrum. For example, this system allows an aggressor to jam the communications of others while remaining unjammed. Waves from (a) the jamming signal (red) and (b) the surrounding environment (green+red) are converted into optical intensity fluctuations and subtracted from one another, resulting in the desired signal (green).

 

Illustration of an integrated photonic opto-cancellation system ready to be implemented in portable devices or cellphone radio towers. The footprint of an integrated system would be less than several square millimeters.

 

As the number of wireless devices grows exponentially in the coming decades, technologies will need to address the shrinking bandwidth availability of the radio frequency (RF) spectrum. One problem experienced by almost all RF devices is interference. A particular class of radio frequency (RF) interference, called co-site interference, occurs when a receiver cannot lock onto signals of interest because it is being overwhelmed by a much stronger simultaneous transmission from its own transmitting antenna. The problem is the reason why most of our communications today are half-duplex, leading to spectral and power inefficiencies. Interference cancellation is needed to realize the full potential of wireless communications.
 
Traditional interference cancellation techniques are electronics-based, but their performance is consequently bandwidth-limited and precision-limited by the RF components. Electronic interference cancellation is also inhibited by the inability to cancel in-band interference. Our group has developed an optical technique for interference cancellation by using light to carry the RF information. The optical system, called the Opto-Cancellation System (OCS), is capable of cancelling both in-band interference as well as broadband signals over a huge bandwidth due to the low loss and high bandwidth of optics. To date, the OCS has demonstrated >70 dB cancellation of narrowband interference signals, as well as >30 dB cancellation over 40 MHz bandwidth in both the popular WiFi 900MHz and 2.4GHz frequency bands. This is 10x better than electronic methods while across a significantly broader bandwidth. The OCS is being developed for commercial applications with industry partner L3 Communications.
 

Journal Papers

J. Chang and P. R. Prucnal, "A novel analog photonic method for broadband multipath interference cancellation", IEEE Microwave and Wireless Component Letters, vol. 23, no. 7, pp. 377–379, Jul. 2013.

J. Bruno, M. Lu, Y. Deng, and P. R. Prucnal, “Broadband optical cosite interference cancellation,” Optical Engineering, vol. 52, no. 5, pp. 053001–053001, May. 2013.

M. Lu, M. P. Chang, Y. Deng, and P. R. Prucnal, “Performance comparison of optical interference cancellation system architectures,” Applied Optics, vol. 52, no. 11, pp. 2484–2493, Apr. 2013.

M. P. Chang, M. P. Fok, A. Hofmaier, and P. R. Prucnal, “Optical analog self-interference cancellation with electro-absorption modulators,” IEEE Microw. Wireless Compon Lett., vol. 23, no. 2, pp. 99–101, Feb. 2013.

Conference Papers

M. P Chang, D. Fisher, J. Wang, M. Lu, B. Chen, and P. R. Prucnal, “Microwave photonic self-interference cancellation system using a slow and fast light delay line,” in Proc. IEEE Photonics Conference (IPC), San Diego, CA, USA, Oct. 2014, paper TuC2.3.

M. Chang, A. Tait, J. Chang, and P. R. Prucnal, “An integrated optical interference cancellation system,” in Proc. Wireless Optical Communications Conference (WOCC), Newark, NJ, USA, May 2014. Paper O5.4.

M. P. Chang and P. R. Prucnal,“Amplitude-invariant fast light in a semiconductor optical amplifier for microwave photonics,” in Proc. Conference on Lasers and Electro-Optics (CLEO), San Jose, CA, USA, paper QM4E.3.

M. Lu, J. Bruno, Y. Deng, and P. R. Prucnal, and A. Hofmaier “Co-site interference mitigation using optical signal processing”, in Proc., vol. 8397, Baltimore, MD, USA, Apr. 2012, paper 839705.

Group Members: 
  • Paul Prucnal, Professor of Electrical Engineering
  • Matt Chang, Graduate Student