1GHz tuning range, low phase noise, LC oscillator with replica biasing common-mode control and quadrature outputs

The paper presents a low phase noise LC oscillator with 1GHz tuning range suitable for fiber optic transceivers and SDH/SONET (STM16/OC48 applications. In order to reduce power supply pushing and to have a well controlled common-mode with temperature and process, a replica biasing circuit regulates the common-mode voltage. The guaranteed tuning range covered with process and temperature variations is 2.2GHz-3.2GHz. A new concept of quadrature generation has been introduced. Measured results show a phase noise of -128dBc @ 3MHz @ 2.5GHz oscillation frequency. The measured quality factor of the coil is better than 20 @ 4GHz. Statistical analysis give 1 σ deviation in the oscillation frequency of 12MHz (1% from the tuning range). The variation over temperature in the range (-45 °C,+85°C) is only 20MHz. The typical power consumption of the VCO core is 18mW from a 3.3V power supply.