New high frequency OCXO delivers impressive phase noise performance

Launching at IMS 2013, IQD’s has unveiled the IQOV-200 series Oven Controlled Crystal Oscillator (OCXO), which has been designed from the ground up in order to optimise low phase noise performance. Phase noise is caused primarily by semiconductor thermal noise but noisy resistors, capacitors and inductors can all have an effect, as can poor signal transfer paths due to circuit layout and design.

Good oscillator design consideration allows the IQOV-200 series to deliver phase noise performance of -172dBc/Hz at 100kHz offset and -160dBc/Hz at 1kHz offset based on a nominal oscillating frequency of 100MHz.

Available at any frequency in the range 80MHz to 130MHz, the new model is housed in an industry standard 36 x 27mm IEC C008 Euro package although other package styles including surface mount variants can be considered to suit specific customer applications. The oscillator nominally operates from a 12 Volt power supply and consumes just 1 Watt of power at steady state, incorporating a very high level of internal voltage regulation so proving somewhat immune to external voltage variations. Drive capability is quoted at +6dBm into 50 Ohms.

Operating over a standard temperature range of -20 to 60 degrees C with an initial frequency stability of ±50ppb (parts per billion), other temperature ranges and stabilities can also be considered.

The key component within any quartz oscillator is the quartz crystal and the IQOV-200 series’ long term aging rates are particularly low due to the very high quality and processing of the quartz crystal.The new model incorporates a SC-cut (Stress Compensated) HC43 cold welded crystal as research has shown that this style of package offers much less stress on the crystal than the more commonly used multiple mounting point systems. This has a direct effect in improving the oscillator’s close-in phase noise. The actual drive circuitry has its most direct influence on the far-out phase noise performance. Inevitably both aspects are somewhat interactive so a fine engineering balance has to be struck.

Among the potential applications for this high specification OCXO are: ground and airborne radar equipment (both military and commercial); military digital communications systems; satellite communications such as ‘Very Small Aperture Terminal (VSAT) – for data transfer from a remote ground terminals to high orbiting satellite such as the Inmarsat system with minimal distortion; high performance Global Positioning Systems (GPS); phase locked microwave signal sources and frequency synthesisers and signal generators.

Phase noise or phase jitter is of particular importance because it reduces the signal quality and hence increases the bit error rate of a communications system. Indeed, in complex communications systems the amplitude noise caused by high signal levels is often of less importance than the phase noise content. While phase noise is an unwanted addition to all signals, its presence must be accounted for in many applications. Phase noise is an important aspect of synthesizer design as a further example and levels of phase noise must therefore be considered at the earliest design stages.

Test equipment is another key application for the IQOV-200 series. A very clean signal source is required for the reference source since any fluctuations will manifest themselves as side bands on the main signal and since the test equipment is the reference then in simplistic terms you will not actually measure what you think you are measuring.


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