A Wide-Range Multiport LC-Ladder Oscillator and Its Applications to a 1.2–10.1 GHz PLL

This brief presents a wide-range multiport LC-ladder resonator and its application to phase-locked loop (PLL). The multiport LC-ladder structure provides a high-order resonator, which has multiple resonance frequencies. The output frequency can be discretely altered from these resonance frequencies through enabling or disabling the active devices of various ports. The capacitor bank provides continuous frequency tuning to cover the gaps between the resonance frequencies. Thus, the oscillator seamlessly achieves a wide frequency coverage. The ports of the LC-ladder resonator are series connected with inductors. The oscillator can be a single output port, and avoids output multiplexing. The structure and behavior of the resonator are discussed and analyzed in this brief. A PLL with a three-port LC-ladder oscillator is fabricated with 65-nm CMOS technology to demonstrate this concept. The core circuit occupies a silicon area of 0.4 mm². The measured output frequency ranges from 1.2 to 10.1 GHz. Phase noise at 1 MHz of all frequencies is below -96 dBc/Hz. The proposed voltage-controlled oscillator consumes less than 8 mW from a 1.2 V supply voltage in all of the operational modes.