A wide-band low phase noise LC-tuned VCO with constant K_(VCO)/ω_(osc) for LTE PLL

摘要

A wideband LC-tuned voltage-controlled oscillator (LC-VCO) applied in LTE PLL frequency synthesizerswith constant KVCO/ωosc is described. In order to minimize the loop bandwidth variations of PLL, a varactorarray is proposed, which consists of a series of differential variable capacitor pairs and a series of single-poledouble-throw (SPDT) switches to connect V_(tune) or V_(DD). The switches are controlled by switching bits. With thisscheme, the ratio of K_V= θC_(var)/θV_(tune) and the capacitance value of the capacitor array maintains relatively constant;furthermore, the loop bandwidth of the PLL fluctuation is suppressed. The 3.2–4.6-GHz VCO for multi-bandLTE PLL is fabricated in a 0.13-μm RF-CMOS process. The VCO exhibits a maximum variation of K_(VCO)/ω_(oscof) only ±4%. The VCO also exhibits a low phase-noise of –124 dBc/Hz at a 1-MHz offset frequency and a lowcurrent consumption of 18.0 mA with a 1.2-V power supply.