Low Phase Noise Amplifiers
Low Phase Noise Amplifiers are essential for many of today’s defense platforms that require spectral fidelity. Low phase noise amplifier performance is especially important in clock circuits and receiver front-ends where low phase noise amplifiers are critical, as those oscillators require higher output power without comprising the noise floor of the LO.
Spectrum Control offers the only selection of over 100 guaranteed and fully tested low phase noise amplifiers in the industry. Our selection supports a range of output power levels from 0 dBm to +30 dBm; and frequencies of up to 6000 MHz for surface mount designs. Spectrum Control’s line of low phase noise amplifiers offers low phase noise performance down to -182 dBc/Hz at 100 kHz offset. These low phase noise amplifiers can offer increased outputs while not adding unwanted jitter or white noise to the LO circuit.
Spectrum Control’s low phase noise amplifiers are tested in-house using a variety of the industry’s latest test sets including multiple Rhode & Schwartz FSWPs, as well both a Keysight 5511 and an Agilent E5500. As an added benefit, if there is a Spectrum Control low phase noise amplifier design that would serve your application better with a slight tuning modification, Spectrum Control most times will make that modification at no charge. Visit our parametric search feature below (and select the Low Phase Noise drop-down) for some of the lowest phase noise performance in the industry.
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System Phase Noise Calculations
Correlated and Uncorrelated Components
When calculating the phase noise of a system there are many considerations. The following illustrates phase noise calculation of a system and the effects of correlated components verses uncorrelated components. Following these calculations there is an illustration
showing consideration of absolute power levels and how they affect the phase noise of a system. Let us assume the phase noise for each component at a single offset frequency, say 100 kHz is the following in dBc/Hz:
Phase Noise of each Component
| Source | S1=-150 | 2nd Doubler D2=-155 |
| 1st Doubler | D1=-155 | 3rd Doubler D3=-155 |
| 1st Amp. | A1=-165 | 2nd Amp. A2=-165 |
We will start off with a doubler and amplifier:
If we have a component preceding a doubler or any multiplier, its phase noise will be degraded by 20 log of the multiplication factor.
Let’s consider a mixer. If we have two uncorrelated sources with the same phase noise characteristics conditioned by these components and fed into a mixer the calculations and result would be as follows:
When the output of a single source is split, conditioned and mixed it is considered correlated. This would also be true if the two sources above were phase locked to each other. The calculations for the source would be correlated while the other components are not. The
result would be higher phase noise.
One can also conclude from this that the phase noise of a doubler made by splitting a source and then combining it in a mixer will be the same as using a passive doubler.
Thermal Noise Floor
If the phase noise measurement of a component
is made at the same power levels that will exist in the system the thermal noise floor is already in the result. If the data is recorded at much higher power levels than components will experience in the system or if the engineer would like to know what the power levels must be to maintain a particular phase noise result then the thermal noise floor must be a consideration. The thermal noise floor or kTB is ~-174 dBm/Hz. This is based on Boltzmann’s constant, the temperature, and the bandwidth of the signal.
Thermal noise is specified in dBm. If the phase noise of a component comes close to this power level it will be degraded and there is no method to correct the situation short of filtering for phase noise. The same rules for calculating correlated and uncorrelated components apply as before so let us consider the performance of the following cascade.
Therefore if the source in this system were ideal it would have a phase noise of –189 dBc/Hz (-174-15). Allowing the power level to drop significantly degrades the system noise performance.
Conclusion
When calculating the phase noise of a system one must pay close attention to power levels and precisely how the signal is used and reused.
About Amplifiers
Spectrum Control is a leading provider of high-performance RF amplifier solutions. We design, develop, and manufacture small signal amplifiers. Our standard and custom-designed, high-reliability amplifiers meet emerging military and commercial requirements.
Spectrum Control remains on the cutting edge of amplifier technology through out-of-the-box engineering and the manufacture of designs that reach increasing levels of complexity, power and performance. Spectrum Control can tailor a solution to your unique requirements.
Low phase noise, low noise, ultra high linearity, high frequency, and medium power RF amplifier products are available.