Two-Tone Phase Delay Control of Center Frequency and Bandwidth in Low-Noise-Amplifier RF Front Ends

This brief presents a two-tone system for controlling the center frequency and bandwidth of an RLC tank with an application to center frequency and bandwidth control in low noise amplifier (LNA) RF front ends. The circuit operates based on the fact that an RLC tank induces a phase difference with special properties between two frequencies. The system is demonstrated in hardware in the TSMC CMOS 0.18-μm process for a center frequency of 2.45 GHz and a bandwidth of 60 MHz. The LNA center frequency can be controlled with a precision of ≈0.2% while the bandwidth can be controlled with a precision of ≈8%. The tuning time is 3 μs multiplied by the number of tuning states. The tuning states are the circuit states set digitally and analyzed until the desired operating point is achieved.