High Swing VCO with Current-Reused Frequency Doubler and Darlington Amplifier

Abstract

This letter proposes a current-reused frequency doubler-Darington amplifier (FD-DA) aiming at enlarging the doubler signal. Conventional active balanced frequency doubler can output a signal with the frequency beyond <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{max}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\mathrm{t}}$</tex> of transistor, but the output strength is small. Normal transistor amplifier can't amplify this signal. Darlington amplifier (DA) is also called <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\mathrm{t}}$</tex> -doubler can amplify the signal at a frequency beyond <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{\mathrm{t}}$</tex> . In the proposed circuit, the DA stacks on a frequency doubler (FD). The current-reused circuit accepts an input signal from a voltage-controlled-oscillator (VCO). To reduce the power consumption and to improve the phase-noise performance, a capacitance-splitting and a gate–drain impedance-balancing technique are realized with an inductive divider. The 16 GHz frequency source has been designed and fabricated in the TSMC <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.18\ \mu\mathrm{m}$</tex> 1P6M CMOS technology. The measured output power of the fundamental signal and second-harmonic signal are −4.61 and −4.95 dBm, respectively. The measured tuning ranges of the fundamental signal and second-harmonic signal are from 7.52 to 7.885 and 15.04 to 15.77 GHz, respectively. The measured phase noise of the fundamental signal and second-harmonic is −104.96 and −105.12 dBc/Hz at 1MHz offsets, respectively. The frequency source total power consumption is 8.74 mW. The whole chip occupies a small area of 1.07×1.19 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .