Mitigation of Oscillator Pulling in SoCs

Abstract

This paper presents a novel method to mitigate undesirable oscillator pulling effects in wireless transmitter architectures. In practice, coupling of the power amplifier (PA) signal caused by inductive or electromagnetic crosstalk, inevitably leads to injection pulling. Particularly, for nonconstant envelope modulation schemes such as Bluetooth enhanced data rate (EDR), GSM-EDGE, or WiFi, the pulling is extremely troublesome due to the amplitude-to-frequency (AM–FM) conversion effect. The difficulty to cope with this undesirable effect stems from the fact that the pulling is largely dependent on process spread and environmental factors like temperature and antenna load mismatch. This paper proposes a novel method based on stochastic-gradient algorithms to resolve the pulling effect. It can be realized inexpensively in digital design and does not rely on knowledge of the unpredictable crosstalk path which makes it extremely efficient to mitigate the pulling effect. To verify the novel idea, a prototype IC has been fabricated in 65 nm CMOS technology.