Newly designed OCXO from IQD delivers class leading ultra low phase noise performance

TRX1890.TIFIQD’s new IQOV-200F OCXO delivers exceptional phase noise performance with a close-in measurement of
-130dBc @100Hz and a noise floor better than -180dBc across a high frequency range of 80 to 130MHz.

Phase noise is the term used to quantify signal noise in the frequency domain and such phase noise measurements and specification limits are common to most RF engineers in their work. In the time domain, signal purity is described in terms of jitter so measurements and specification limits on jitter are common to digital signal engineers. The root causes of phase noise and jitter are essentially the same and so the design and production techniques used to optimise both are the same.

The IQOV-200F uses a specially designed circuit to allow optimisation of these parameters during production. There is a complex relationship between the crystal, the oscillator circuit, the internal voltage regulation circuit and the output buffer which all contribute to noise in the system. Designing a circuit which isolates these elements and allows specific tuning to optimise each has been a key part of IQD’s research and development work for this new product range and a critical success is the ability to apply this to our automated production line. We are now able to offer this low phase noise product range with the same level of consistent production control which has been a hallmark of IQD’s success.

In addition to the challenges of the oscillator circuit, the crystal is a critical component in any OCXO design and especially where close-in phase noise performance is of high priority. IQD’s engineering team have developed a predictive test system to allow the phase noise of crystals to be measured before mounting in the oscillator circuit. This has allowed the team to focus research specifically on the effects of changes in the crystal production process and tighter control of plating, bonding and sealing processes have been key areas of improvement within our SC-cut crystal production to deliver such class leading performance.

Combining the high performance expected from an IQD SC-cut crystal based OCXO, the IQOV-200F delivers a frequency stability of ±50ppb over the standard -20 to 70 degrees C operating temperature range. Housed in a 36 x 27mm ‘Eurostyle’ package and running off a 12V supply, the new model offers a sinewave output of 13dBm min. The new model is in production now and any frequency from 80 to 130MHz can be ordered whilst optional pulling can also be specified. Furthermore, the IQOV-200F offers comparatively low power consumption of just 150mA max at 25 degrees C and 350mA max during warm up.

The product is suitable for any application were phase noise is a critical design consideration. Test and measurement systems have by nature, always required the best signal purity to ensure that internal references are above that of measured signals. The latest high frequency measurement systems operating in the GHz range require internal references to be multiplied up and to preserve a suitable signal to noise ratio the initial reference source must have exceptionally good noise qualities.

Radar applications are another area where a low phase noise floor contributes to clarity of detection of fast moving objects and the low phase noise close to the carrier contributes to clarity of slow moving objects. Military systems such as communication, friend or foe detection, guidance and jamming all depend on low phase noise for improved capability.

Other examples of applications where low phase noise is a key parameter include Dielectric Resonator Oscillators (DRO) where the very high frequency and large pulling needs to be tied to a reference with very high spectral purity. Again the OCXO signal is multiplied up to the GHz range.

The phase noise performance of the IQOV-200F represents IQD’s current capability based upon our latest research & development work and the production optimisation necessary for volume manufacture of this product. However, our engineering team confidently predict even better phase noise performance in the coming months as design and production techniques are further optimised. Even better results can be offered now where customers are able to compromise on parameters such as output power, current draw, ageing and of course price. Where phase noise is a key parameter in proposed designs, customers should discuss with IQD’s Application Support Team who can tailor specifications to suit specific system requirements.