VOLTAGE-CONTROLLED SELF-TEMPERATURE COMPENSATED CRYSTAL-OSCILLATORS WITH NS-GT CUT QUARTZ RESONATORS

In this paper, voltage controlled self-temperature compensated oscilla tors made with NS-GT cut quartz resonators (VC-S-TCXOs in what follows ) are introduced and their frequency stability (obtained by controllin g input voltage to VC-S-TCXO) is discussed. An oscillator circuit cons ists of a CMOS inverter, a variable capacitor diode, resistors, and ca pacitors. The primary oscillator frequency of the coupled quartz reson ator is first derived from the electric equivalent circuit of the osci llator. The oscillator frequency is given by a function of the couplin g coefficient, which in turn is given as a function of the load capaci tance C-L. Since frequency stability by controlling the input voltage to VC-S-TCXO is dictated by the VC circuit, the VC circuit was investi gated in detail in order for the circuit independent of temperature to be obtained. Using the VC circuit, the oscillator frequency was contr olled by the input voltage and the temperature stability of the oscill ator frequency was less than 4 x 10(-9) at a temperature range of -30 to 85 degrees C. Furthermore, it has been demonstrated experimentally that the frequency stability of the VC-S-TCXO directly after voltage c ontrol does not depend on the frequency temperature characteristics of the quartz resonator, time interval between the voltage control, or r ate of temperature change.