Oscillator
Manufacturing
* Note: The following data applies to specific custom
made oscillators only.
Hy-Q International offer four standard types of oscillators:
SPXO - Simple Packaged
Quartz Crystal Oscillator - relies primarily on the
frequency temperature characteristics of its crystal for its stability performance. If any
frequency adjustment is provided it will be via a mechanical trimmer.
VCXO - Voltage Controlled
Quartz Crystal Oscillator - relies primarily on the
frequency temperature characteristics of its crystal for its stability performance.
Frequency adjustment is provided via an external voltage being applied to a varactor diode
in the oscillator circuit. This remotely changes the load capacitance of the circuit and
thus the output frequency.
 TCXO - Temperature Compensated
Quartz Crystal Oscillator - relies on accurately
compensating the frequency temperature characteristic of its crystal for its stability
performance. This is achieved by applying a voltage from a thermistor/resistor network to
a varactor diode in the oscillator circuit. The networks output voltage is precisely
matched to the oscillators output frequency so that any change in output frequency is
offset by the voltage applied to the varactor diode.
VCTCXO - Voltage Controlled
Temperature Compensated Quartz Crystal Oscillator
- relies on accurately compensating the frequency temperature characteristic of its
crystal for its stability performance as per the TCXO above. However, as with VCXO's,
frequency adjustment is also provided via an external voltage input, but adjustment is
restricted compared to that of a VCXO.
The basic oscillator manufacturing techniques begin with the surface mount
components being fitted to a panel of circuit boards via a process of screen printing,
automated pick-and-place and infrared reflow. Once the surface mount process is completed,
leaded components such as crystals, output connection pins or metal bases are added to the
assembly. A bench test is then carried out to ensure all units comply with their specific
electrical requirements such as output frequency and waveform, supply current, voltage
coefficient, pulling sensitivity, adjustment ranges, spurious response, phase noise,
calibration tolerance, etc.
 Upon completion of the assembly and first bench test,
a burn-in process is carried out. This burn-in process consists of holding at a high
elevated temperature for a period of between 72 and 240 hours depending on final
specification requirements. This burn-in helps alleviate stresses in the oscillator
assemblies and hence improves long term performance and stability. After burn-in, SPXO and
VCXO devices are again bench tested and fully aligned before being sealed, either by
solder seal or resistance weld methods. They are then tested over their full operating
temperature range in purpose built oscillator test systems to verify their frequency
stability and overall performance, bench tested again, and then finally labelled and
despatched to our customers.
TCXO and VCTCXO devices follow the same path as above, however an
additional compensation routine is required to obtain optimum frequency temperature
stability performance. This is achieved by characterising each oscillators output
frequency over its full operating temperature range in our oscillator temperature test
systems. Via computerised modelling techniques, utilising complex mathematical algorithms,
a series of precise resistor values are added to the thermistor network. This enables a
voltage to be applied to the oscillators varactor diode that accurately compensates for
any change in output frequency over the entire operating temperature range.
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