Suppression of VCO pulling effects using even-harmonic quiet transmitting circuits

Abstract

VCO TX pulling could seriously degrade transmitter performance. Unlike previous works that focus on alleviating the problem on the victim side(i.e. VCO or LO generator), we explored methods on suppressing the pulling tone generation at the transmitter side both magnetically and electrically. Magnetic differential structures and harmonic notch are employed for TX inductor/transformer and active circuits to reduce the pulling. Measurement results showed > 25dB reduction of pulling tone at +7dBm output power with <;10.5% DEVM_pk for 8-DPSK bluetooth modulation.