97 VCO Based on Parallel Connection of Varactors Applied to Magnetometer

VCO is the core device of optically pumped magnetometer. To make sure that optically pumped magneto- meter can measure the entire range of the geomagnetic field effectively, we need a VCO which should have a wide output frequency range, wide band coverage coefficient and can scan the entire magnetic field range in a relatively short period of time. In this paper the principle of the VCO is analyzed, and a VCO based on paralleling of multiple varactors is designed, it uses the form of Seiler oscillator circuit and with the function of amplification. The results show that the output frequency range of this VCO is greater than 8MHz to 20MHz, its band coverage coefficient is 2.5, the amplitude of output waveform in the entire frequency range reached more than 3V, and they fully meet the requirements of the optically pumped magneto-meter. The VCO has the advantages of simple hardware and stable performance.