The following are a list of whitepapers and articles prepared by Rakon in answer to various questions from customers. They are presented here for your reference, should you have any specific questions please contact us at any time.
Measurement of Phase Noise for the Ultra Low Noise Surface Acoustic Wave (ULN SAW) oscillators
Rakon ULN SAW oscillators exhibit exceptional phase noise performance at frequencies above 300 MHz. This application note gives best practice advice on how to measure the phase noise in ultra low noise surface acoustic wave (ULN SAW) oscillators.
Guidelines for use of Mercury™ and Mercury+™ OCXOs in Network Timing
This application note gives best practice advice on how to optimise the performance of Rakon's miniature Mercury™ and Mercury™+ OCXOs in network timing and synchronisation applications (date of issue: 2016-09-14).
Guidelines for use of 7x5 mm Network Timing TCXOs
This application note gives best practice advice on how to optimise the wander performance of applications using Rakon’s 7x5 mm ‘Pluto’ TCXOs.
Rakon DCPSS: Radar Upgrade Solution
Military Embedded Systems magazine article Jan/Feb 2013 Radar Special Feature Q & A:
Will there be more opportunities for embedded Commercial-Off-the-Shelf suppliers in radar upgrades and new platforms?
Single Transistor Crystal Oscillator Circuits
For an electronic circuit to oscillate there are two criteria which must be satisfied. It must contain an amplifier with sufficient gain to overcome the losses of the feedback network (Quartz Crystal in this case) and the phase shift around the whole circuit is 0o or some integer multiple of 360o. To design a crystal oscillator the above has to be true but there are a myriad of other considerations including crystal power dissipation, unwanted mode suppression, crystal loading (the actual impedance the crystal sees once oscillation has started) and the introduction of a non-linearity in the gain to limit the oscillation build-up.
IC Crystal Oscillator Circuits
The majority of ICs with built in crystal oscillator circuits use the Gated Pierce design where the oscillator is built around a single CMOS inverting gate. For oscillator applications this is usually a single inverting stage comprising one P channel and one N channel enhancement-mode MOSFET, more commonly known in the digital world as an Un-Buffered Inverter (see Fig.1). It is possible to use a Buffered Inverter (usually comprising three P-N MOSFET pairs in series) but the associated gain of many thousands will lead to a potentially less stable finished oscillator.
Time Keeping with Quartz Crystals
“The only reason for time is so that everything doesn't happen at once only assume he wasn’t talking about synchronised global networks when he made this comment!
Phase Noise and Jitter in Crystal Oscillators
Before we can cover the sources of Phase Noise / Jitter in Crystal Oscillators we need to de-mystify some of the wording associated with the measurement, so let’s start with a simple description of Phase Noise and Jitter.
Relationship between Phase Noise and Jitter
Phase Noise and Jitter are both ways of describing the stability of an oscillator. Phase Noise describes the stability in the frequency domain whilst jitter describes the stability in the time domain. The choice of which domain to consider the oscillators stability is usually application dependant. RF (Radio Frequency) Engineers working in Radar, Base Station design etc. will be interested in Phase Noise as poor Phase Noise performance will affect up/down conversions and channel spacing. Digital Engineers working in Time Division Multiplexing (the majority of modern Telecoms infrastructure) will be interested in jitter as poor jitter performance will result in network slips and excessive re-send traffic.
Relationship Between PN and Jitter
Relationship between Phase Noise and Bit Error Ratio (BER)
As stated in the article ‘relationship between phase noise and jitter' the Phase Noise of a stable crystal oscillator can be converted to an Rms jitter figure. This Rms jitter figure can be analysed further to show the contribution the crystal oscillator makes to the overall system Bit Error Ratio.
Variance as applied to Crystal Oscillators
Before we can discuss variance as applied to crystal oscillators we need to understand what a Variance is, or is trying to achieve. In simple terms variance tries to put a meaningful figure 'to what actually receive’ against ‘what we expect to receive'. It is, simply, a mathematical formula applied to a set of data points / samples / readings which are usually collected over a specified period of time.