Highly Ruggedised Radio Transceiver

2009-11-07

Resilient and reliable

A customer providing a wide area training system required a radio transceiver that would be very resilient to vibration and temperature effects.   Previously the customer had used a commercially available private mobile radio device but this placed physical and technical restrictions on the final design and would not meet the stringent operational environmental parameters.

A synthesised radio transceiver is dependent for many of its key dynamic specification parameters on the design of the voltage controlled oscillator (VCO).   This critical piece of circuitry generates the transmit signal and also the local oscillator that is mixed with incoming received signals to allow the signals to be processed.   The VCO is a free running oscillator which is locked in a phase locked loop and digital divider combination to the frequency of operation.    Even a poorly designed oscillator can be made to lock in this way but it is the quality of the signal that it generates that is critical.   If the signal is noisy it will degrade receiver performance and cause interference to other users when transmitting.  If it has poor mechanical design it will be upset by vibration and in extreme will kick out of lock causing other problems and poor reliability.

W&D is familiar with these issues having worked with phase locked loop systems at very high frequencies for over 30 years.  A combination of good mechanical and electronic design must be brought to bear in these circumstances.  The mechanical aspects are perhaps the most critical.

The Electronic and Mechanical design teams in conjunction with Production Engineering group perfected a way of fitting a mechanical screening ‘fence’ to the pcb module as part of the reflow process in the surface mount oven.   This bonded the ‘fence’ which was chosen to be of shallow height and resilient material such that once the unit was fully assembled it was highly immune to any physical distortions and therefore the VCO was very stable and clean.
The resulting module met the customer requirements in all respects.  Its compact and resilient nature meant the customer could integrate it successfully into their training node and it could be used on all manner of personnel and vehicles with no degradation in radio link performance.

Since completion of the design process over 20,000 pieces have been and will continue to be produced through the W&D surface mount production line.