# Photonic-Assisted Scanning Receivers for Microwave Frequency Measurement  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2  
[PERSON]  
1 School of Electrical and Information Engineering, The University of Sydney,  
Camperdown, NSW 2006, Australia; [EMAIL_ADDRESS] (S.S.); [EMAIL_ADDRESS] (W.Y. ); [EMAIL_ADDRESS] (L.N. ); [EMAIL_ADDRESS] (S.X.C. ); [EMAIL_ADDRESS] (L.L. ); [EMAIL_ADDRESS] (R.A.M.) 2 College of Engineering, Design and Physical Science, Brunel University, London UB8 3 PH, UK; [EMAIL_ADDRESS]
precision for estimating an unknown frequency, it is more often limited by its inadequacy to measure multiple microwave frequencies simultaneously in a spectrally cluttered environment. To enable the measurement of multiple microwave frequencies, a variation of this approach was presented based on stimulated Brillouin scattering (SBS) with the use of multiple optical modulators. Photonic frequency scanning approaches, on the other hand, form the third class for implementing microwave frequency measurement [12; 13; 14; 15; 16; 17; 18; 19; 20]. This technique can be realized in a simple configuration with a single laser, an electro-optic modulator (EOM), an optical filter, and a low-speed photodetector whilst demonstrating the capability to perform single and multiple frequency measurements. Frequency scanning can be easily achieved via tuning the carrier frequency of the laser or the center wavelength of the optical filter. Current developments in integrated optical filters have demonstrated a fast-swept filter based on an interior-ridge micro-ring with a mean sweep rate of 22,600 nm/s, which makes a monolithically integrated on-chip scanning receiver with compact size and low power consumption possible [21]. Classical scanning receivers implement RF sensing via measuring the time delay occurring relative to a reference time of filter shaped pulses detected by a photodetector. However, due to the bandwidth of the filter, each single RF frequency component will spread out, thus forming a broader distribution which mimics the filter shape in the time domain. With the reduction in separation between closely spaced RF frequency components, the dip between two pulse peaks slowly merges and eventually disappears, leading to a limited measurement resolution. In [12], a scanning receiver with a resolution of about 5 GHz is experimentally demonstrated via a micro-ring resonator with a bandwidth of 5 GHz, which shows the limitation of the measurement resolution governed by the bandwidth of the optical filter employed in the scanning receiver.