Frequency-sensitive High-field ESR using CMOS LC Tank Oscillators

Frequency-sensitive High-field ESR

The main objective of the this project is to develop fully-integrated CMOS detectors for combined amplitude- and frequency-sensitive ESR experiments at B0-field strengths between 1.25 and 3 T in order to improve the state-of-the-art in spin sensitivity by at least one order of magnitude and thereby enable a speed-up of the analysis of mass limited biological samples.

The targeted improvements in spin sensitivity for the frequency-sensitive detectors can be achieved because the achievable spin sensitivity in frequency-sensitive ESR detection scales quadratically with the B0-field strength. Since the required oscillator operating frequency and the employed static B0-field are proportional to each other with the constant of proportionality given by the gyromagnetic ratio (about 28 GHz/T for an electron), working at higher magnetic fields requires the design of integrated oscillators with larger operating frequencies.

One of the key advantages of the proposed method is the fact that the LC-tank oscillator itself both excites the spin ensemble through the magnetic field of its tank inductor and at the same time detects the ESR effect as a change of the oscillation frequency. In this way, the ESR effect can be measured at elevated B0-field strengths without the need for bulky and expensive high-power EM-sources such as Gyrotrons, which are used in most conventional high-field ESR setups.

Overall the proposed approach of using integrated CMOS ASICs for ESR detection exploits two intrinsic properties of  modern CMOS technologies – miniaturization capabilities and operating speed – in order to design miniaturized, high sensitivity ESR detectors in a relatively simple, reproducible and yet – assuming high volume production – cost-effective manner.


M.Sc. D. Djekic