Phase noise performance of low voltage surface transverse wave oscillators in the 0.9 to 2.4 GHz range

This paper presents the performance and verifies the expected improvement in phase noise of GHz range surface transverse wave (STW) oscillators operating at very low supply and tuning voltages, in the 1.2 to 3.3V range, according to the nonlinear "step-up" converter principle. The oscillators operate at 0.9, 1.0 and 2.4 GHz, are stabilized with low-loss, medium-Q STW based two-port resonators and use single-transistor sustaining amplifiers operating in the self limiting AB-class mode. Tuning is achieved with varactor based phase shifters in the loop. These low-voltage, voltage controlled surface wave oscillators (LWCSOs) generate output power levels in the 9 to 13 dBm range at 14 to 22% RF/DC efficiency. Phase noise levels ranging from -102 to -119 dBc/Hz at 1 kHz carrier offset and thermal noise floors in the -169 to -178 dBc/Hz range were measured. Design considerations, important to achieving low phase noise performance and maximum tuning range and power efficiency are discussed in detail.