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.