GTEM cell method based comparative analysis of performance degradation in integer and fractional frequency synthesizer based direct conversion CDMA transmitters

Oscillator injection pulling as presented in R. Adler (1973) and K. Kurokawa (1973), is a phenomena that may have significant impact on the performance of modern direct conversion transmitters, that is today almost exclusively applied for the architecture in the cell phone design. Oscillator injection pulling affects crucial CDMA transmitter parameters like waveform quality factor (rho) and in severe cases adjacent channel power ratio (ACPR), due to the in-channel integrated phase noise degradation and increased phase noise at adjacent channel frequency offset. Comparative study presents analysis of rho, ACPR and phase noise parameters degradation obtained in measurements of fractional and integer N synthesizers based direct conversion CDMA transmitters. Relations between phase noise, rho and ACPR parameters are formulated. Advantages of fractional N frequency synthesizer are explained based on measurements result analysis. Assuring repeatable and consistent measurement of oscillator injection pulling in ASIC based transmitters is challenging. In order to assure consistent and repeatable measurements of oscillator pulling, a method based on GTEM as stated in J. Nadolny (1995) and A. Nothofer et al. (2003) cell - variety of transverse electromagnetic mode cell, was developed. Details of the measurement method are presented in this study