Giuseppe Li Puma

Mitigation of Oscillator Pulling in SoCs

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.

Analysis of distortion effects on differential EVM

The impact of transmitter imperfections on the modulation accuracy is analyzed for devices supporting Bluetooth (BT) modulation types with differential phase shift keying (DPSK). Such modulation accuracy is measured in terms of Differential Error Vector Magnitude (DEVM). Impairments such as thermal noise, phase noise, power amplifier (PA) nonlinearity, LO leakage, quantization noise are considered, and simulation results are compared to the analysis.

Adaptive Techniques to Mitigate Oscillator Pulling in Radio Transmitters

This brief presents novel methods to resolve the long persisting oscillator pulling effect for the two most important radio transmitter categories, namely, the polar and Cartesian transmitters. In practice, oscillator injection arises from the coupling of the power-amplifier output signal. In particular, for nonconstant envelope modulation schemes, e.g., enhanced data rates for GSM evolution (GSM-EDGE), Bluetooth enhanced data rate (EDR), WiFi, or universal mobile telecommunications system (UMTS), the pulling is extremely troublesome due to the conversion of the amplitude to frequency, which happens in the oscillator. What renders the pulling most severe is the fact that the crosstalk path is unpredictable and, moreover, extremely dependent on the process as well as environmental factors like temperature and antenna impedance. To mitigate the pulling, novel predistortion techniques with self-learning capabilities are presented. These methods are based on algorithms from adaptive filter theory that can be realized inexpensively in digital submicrometer complementary metal-oxide semiconductor technologies.