Automation of control voltage correction to compensate a non-linear VCO tuning characteristic

摘要

Voltage controlled oscillators (VCOs) are used in numerous types of radio engineering systems, such as communication systems, radars, phase locked loops and others. Generally, the VCO tuning characteristic is non-linear. In many real-world applications, changing output frequency of the VCO linearly makes it possible to achieve noticeably better performance. This article discusses a method to compensate the tuning characteristic nonlinearity in a device, which contains DAC-driven VCO, as well as a programmable digital circuit that generates signal codes for the DAC. Interpolation of function inverse to VCO tuning characteristic is used to generate correction function for VCO control voltage. It is proposed to use automatized system to correct VCO tuning characteristic for mass production purposes and an example of such a system introduced. Test results show that the maximum deviation from linear frequency change with corrected control voltage is 139.63 times less than without correction.