Key Technology For Magnetic Field Measurement Based On Diamond Nitrogen Vacancy Color Center

In recent years,diamond NV(Nitrogen-Vacancy)color center has attracted wide interest due to its high sensitivity and high spatial resolution in the field of magnetic field measurement.The research on diamond NV color center magnetometer mainly focuses on improving fluorescence contrast by optical methods.This thesis mainly improves the microwave part of the circuit,mainly completed the antenna,filter and microwave switch,integrated assembly part of the photodiode noise reduction circuit and card slot design.This thesis mainly improved the microwave part of the circuit,and completed the design of antenna,filter,microwave switch,besides the photodiode noise reduction circuit and groove in integrated assembly.The first part of the work is the antenna design.The energy of microwave source needs to radiate to diamond NV color center through antenna,so antenna design is necessary.Firstly,a circular loop antenna is designed,which has a return loss greater than10 dB and a gain of 3.7dB in the 2.4-3.1GHz frequency band.However,the antenna does not have a filtering function,and a filtering antenna was designed later.The return loss of the filter antenna is more than 10 dB in the 2.5-2.7GHz frequency band,and the gain curve is steep,and there are two radiation nulls.The gain in the passband reaches 2.1dB and the gain out of the band is only-6dB,which can realize the filtering function.Both the loop antenna and filter antenna are processed.The loop antenna has been applied to the system,and the filter antenna will be applied in the future.The second part of the work is the filter design.For the final miniaturization,it is necessary to use the point frequency microwave source,and the higher harmonics generated by it may affect the quantum detection results,so it is necessary to design a pre-selected bandpass filter.A bandpass filter with a passband frequency of 2.5-4.0GHz is designed and processed in practice.The measured results show that the in-band interpolation loss is better than 2.9dB,the in-band flatness is less than 1.3dB,and the inband return loss is better than 14.1dB.For lower sideband suppression,no less than23.0dB in the 1.0-1.8GHz range.For upper sideband suppression,no less than 18.2dB in the 5.5 to 8.0GHz range.It meets the design requirements and can be applied to quantum detection systems.The third part of the work is the design of microwave switch.Corresponding to the diamond NV color center has four axes,four microwave channels need to be selected,so a single-pole four-throw switch needs to be designed.A PIN diode is used as the switching body,and lumped parameter elements and microstrip lines are used for circuit design.Four channels are selected for different bias voltage combinations.Simulation results show that the insertion loss of the four channels is less than 1.5dB,and the isolation is greater than 20 dB.The simulation results meet the system requirements.The fourth part of the work is assembly design.The RC low-pass filter is designed to denoise the photodiode working circuit,filter out the noise generated by the power supply,and the circuit was processed.Then the antenna groove,filter groove and photodiode noise reduction circuit groove are designed respectively,and the actual processing and assembly are carried out.The last part of the work is system testing.After connecting the laser module,microwave module,integrated assembly module and data acquisition module,the experimental platform was built.The quantum state control data acquisition based on diamond NV color center is preliminarily completed,which lays a foundation for the follow-up magnetic field detection.