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A wideband LC-tuned voltage-controlled oscillator(LC-VCO) applied in LTE PLL frequency synthesizers with constant AVco/ω_(osc) is described.In order to minimize the loop bandwidth variations of PLL,a varactor array is proposed,which consists of a series of differential variable capacitor pairs and a series of single-pole double-throw(SPDT) switches to connect V_(tune) or V_(dd).The switches are controlled by switching bits.With this scheme,the ratio of K_V =(?)C_(var)/(?)V_(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-band LTE PLL is fabricated in a 0.13-μm RF-CMOS process.The VCO exhibits a maximum variation of A_(VCO)/ω_(osc) of only±4%.The VCO also exhibits a low phase-noise of-124 dBc/Hz at a 1-MHz offset frequency and a low current consumption of 18.0 mA with a 1.2-V power supply.
A wideband LC-tuned voltage-controlled oscillator (LC-VCO) applied in LTE PLL frequency synthesizers with constant AVco / ω_ (osc) is described.In order to minimize the loop bandwidth variations of PLL, a varactor array is proposed, which consists of of a series of differential variable capacitor pairs and a series of single-pole double-throw (SPDT) switches to connect V_turn or V_dd. The switches are controlled by switching bits. With this scheme, the ratio of K_V = (?) C_ (var) / (?) V_ (tune) and the capacitance value of the capacitor array maintaining relatively constant; band LTE PLL is fabricated in a 0.13-μm RF-CMOS process. The VCO exhibits a maximum variation of A_ (VCO) / ω_ (osc) of only ± 4%. The VCO also exhibits a low phase-noise of -124 dBc / Hz at a 1-MHz offset frequency and a low current consumption of 18.0 mA with a 1.2-V power supply.