Research And Design Of Ultra-small Oven Controlled Crystal Oscillator

Crystal oscillator has been widely used as a frequency source since it was discovered.Compared to the LC oscillators,the frequency stability and quality factor have been greatly improved.Now the base stations,electronic equipments,satellite communications,weapons and other fields are inseparable from the crystal oscillator.The performance of crystal oscillator is often a limiting factor in the performance of electronic systems.Oven Controlled Crystal Oscillator(OCXO)as a crystal oscillator with better performance gets more attention and welcome.At present,foreign products in the OCXO market account for the vast majority of the market share,so the study of better performance of OCXO becomes increasingly urgent,which is of great theoretical and practical significance to achieve the nationalization of important equipments.In this paper,the background and related progress of OCXO are summarized.Then,the basic theory of the piezoelectric effect,the frequency temperature characteristic,the impedance frequency characteristic and the phase noise are introduced.The influence of oscillator's parameters on performance is analyzed and simulated to realise the low phase noise.The power gain,stability of the amplifier circuit and the noise figure of the output are simulated and analyzed.The function of the frequency selection network is also analyzed.The low-pass filter is designed based on parameter caculation and ADS simulation.The principle of temperature control circuit and design issues are also explored.Ultimately through protel 99 SE,the design of schematic diagram and PCB board of the sample are completed.As a circuit composed entirely of crystal resonators,capacitors,resistors,inductors,operational amplifier and triodes,it is necessary to start from the integrated circuit--part of the device packaged into a chip--to reduce the space occupied by the components.But for the packaging circuit it should be taken into consideration that components like capacitance and the thermistor can not be in the chip.The design of the package chip is based on the oscillation circuit,the transistor,its bias circuits and temperature control circuit,leaving an external port to adjust some circuit parameters.The size of AT4X4 chip designed by the project team is 4mm ? 4mm,and the size of the PCB board is only 18 mm ? 10 mm.Thus the design of OCXO's size compared to the mainstream market products has been significantly reduced to achieve the purpose of ultra-small OCXO.The frequency meter-Agilent 53131A-can be used to test the frequency-temperature stability of the experimental prototype and the frequency-temperature stability reaches ? 0.19 ppm from-30 C to 70 C.Agilent E5052 B signal source analyzer can be used to test its phase noise which reaches-106dBc/Hz@10Hz?-136dBc/Hz@100Hz?-160dBc/Hz@1kHz?-170dBc/Hz@10kHz?-173dBc/Hz@100kHz.After measuring its size,it can be found that the volume reaches 20 mm ? 12 mm ? 10 mm.Finally,it could be found that the designed OCXO has achieved the desired goal in the volume,phase noise,etc.