Design of a Ku-band Low-Phase-Noise VCO Using the Dual $LC$ Tanks

Abstract

A Ku-band voltage-controlled oscillator (VCO) using dual LC tanks, together with feedback, is proposed and designed by using a 0.18-µm Bipolar compatible Complementary Metal Oxide Semiconductor (BiCMOS) process. A triple-coil transformer is employed to provide strong coupling between the two LC tanks and simultaneously introduce a transformer-based feedback. The parameters of the transformer are optimized to provide the required inductance ratios and reduce unwanted parasitic. The phase noise improvement for the proposed VCO is analyzed theoretically and verified by circuit and full-wave electromagnetic simulators. A benefit from the strong coupling between the two LC tanks, the proposed VCO achieves a low phase noise of −117.4 dBc/Hz at 1-MHz offset from an operation frequency of 12.64 GHz with a 4.3-mW power consumption of the VCO core.Index Terms-Dual LC tanks, low phase noise, low power, transformer-based feedback, voltage-controlled oscillator (VCO).

Methods and techniques for improving the figure of merit for wide tuning range quadrature voltage controlled oscillators

“…An example of reciprocal mixing is shown in Fig. 1 For wide tuning and low phase noise purposes in cognitive radio applications, three prominent types of oscillators have been heavily targeted in the recent literature, ring [6][7][8][9][10][11][12][13], active inductor-based [14][15][16][17], and LC [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] oscillators.…”

“…There have been noticeably successful attempts in the literature [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] to expand the tuning range of LC oscillators beyond capacitive tuning. For example in [20], a new inductor switching technique is proposed in which the parasitic series resistance of the switch is added in parallel to the oscillation tank.…”

“…This approach reuses the same inductor for two separate ranges of oscillation frequencies, which is an economical way to use the expensive on-chip area. Two additional approaches that have started gaining popularity in the area of wide tuning range LC oscillators for apparently achieving high FOMs are: inductive current tuning [22][23][24][25][26] and multi-mode transformer-based (T-based) oscillators [24][25][26][27][28][29][30][31][32][33][34][35]. The tuning range ).…”

“…Another popular scheme that researchers have moved to in the recent years in both single phase and quadrature oscillators is coupled inductors oscillators ( Fig. 3.1) [24][25][26][27][28][29][30][31][32][33][34][35]. Coupled inductors allow the oscillator to make use of the coupling between inductors instead of avoiding it when building on-chip LC oscillators with different frequency ranges.…”

“…Dual-state implementation using transformers is the most commonly used form of coupled inductors [24][25][26][29][30][31][32][33][34][35]. The reason is that more on-chip coupled inductors are likely to have more parasitic capacitance.…”