A Wide Band VCO with Automatic Frequency, Gain, and Two-Step Amplitude Calibration Loop for DTV Tuner Application

摘要

This paper presents a wide tuning range VCO with an automatic frequency, gain, and two-step amplitude calibration loop for Digital TV (DTV) tuner applications. To cover the wide tuning range, the fully digital automatic frequency calibration (AFC) loop is used. In addition to the AFC loop, a two-step negative-G_m tuning loop is proposed to provide the optimum negative-G_m to the LC tank in a wide frequency range with a fine resolution. In the coarse negative-G_m tuning loop, the number of active negative-G_m cells is selected digitally based on the target frequency. In the fine negative-G_m tuning loop, the negative-G_m is tuned finely with the bias voltage of the VCO. Also, the digital VCO gain calibration scheme is proposed to compensate for the gain variation in a wide tuning range. The VCO tuning range is 2.6 GHz, from 1.7 GHz to 4.3 GHz, and the power consumption is 2 mA to 4 mA from a 1.8 V supply. The measured VCO phase noise is -120dBc/Hz at 1 MHz offset.