Comparison among precision temperature compensated crystal oscillators

Abstract

There are different precision temperature compensated crystal oscillators showing the frequency-temperature stability better than 1 /spl times/ 10/sup -6/ in a very wide temperature range. To choose the suitable oscillator one should consider its frequency-temperature stability, power consumption, size, cost, phase noise and other specifications. According to a lot of experiments and comparisons, as the precision TCXO, double compensated TCXO which combines analog and digital compensation approaches together is more competitive in cost, size, stability and mass production compared with ordinary precision TCXO, DTCXO and MCXO based on AT cut crystals. It is difficult to use ordinary TCXO to get very good frequency-temperature stability, but its repeatability can be good with suitable components and circuits, and quantization error does not exist in it. Therefore it is possible to be compensated further. TCXO production technology is very mature and it is easy to obtain VCTCXO with low phase noise, simple structure and good frequency-temperature repeatability. Double temperature compensated crystal oscillator divides the request to compensation accuracy into two parts, and every part is not very high. To the first compensation, analog one, only good repeatability and low phase noise are necessary. To the second compensation, digital one, only simple structure is necessary. Therefore the double compensated TCXO can combines two low compensation. In this way the high precision is easy to be obtained and mass production too.