Any body know about Low Phase Noise Amplifier?

时间：04-08 整理：3721RD 点击：

Hi All,
I need help from you guys,We all know design of Low Noise Amplifier but i wants to knwo something about Low phase Noise Amplifer.
Can any body coach me how to design or from where to get the design clue about Low Phase Noise Amplifier.

Low phase noise is a signal rather than an amplifier property. Using a lower noise amplifier also means adding less phase noise to a signal.

All passive and active components contribute to the phase noise of the system.

If the phase noise of a component is close to the thermal power level, this will be degraded and there is no method to correct the situation.

Unlike measuring phase noise in a VCO, amplifiers require a much more sensitive measuring system with an extremely low noise floor.

Thanks for your help..
But i wants to know if i wants to design Low Phase noise Amplifier than what would be approach?...Bcos now a days so many RF vendors coming with Low Phase Nosie Amplifer. what is difference in design between LNA & LPNA

Thanks!

When you design an amplifier for low noise figure, you are designing it so that the TOTAL added noise power of the amplfier is low. You integrate over a wide frequency range, say 1 Hz to 20 MHz offset from the carrier, and the total integrated noise power yields your amplifier noise figure.

When you design a low phase noise amplifier, while you should also have a low noise figure when you are done, you ALSO need to worry about what the additive noise is at ANY offset to the carrier frequency. To do this you have to be very careful about what type of device you are using. If you chose a CMOS fet, which has poor 1/f noise, you might have a pretty good total noise figure, but as you got close to the carrier the measured phase noise would go up very quickly. If you instead chose a bipolar transistor with a very low 1/f corner frequency, you would have a slightly higher noise figure when you are done, but close to the carrier you would have much lower phase noise.

In general, if I were designing a low phase noise amplifier I would:
1) choose the best family of active devices that have the best overall phase noise
2) in that family of devices, I would actually test individual device part numbers for the best phase noise. Then I would use the best device found.
3) I would investigate the optimum bias point for the device selected, and run the device there
4) I would have some sort of active bias network design to degenerate any audio frequency fluctuations in device current
5) I would have a boat-load of power supply noise filtering, including things like 1000 uF capacitors, etc

Thanks for your valuable input....
While designing LNA we match Fmin to 50Ω in the Smith chart and Fmin is the control parameter for LNA design
Do we have any control parameter for LPNA, so while designing we mainly concentrate on that parameter to get the Ultra low phase noise.
Do you any papper,book or any resource is available on LPNA so that i can read more and proceed on designing LPNA.

what are you trying to amplify? Signal frequency, power, any modulation, etc? Rich

tomhive,

The theory behind the additive phase noise of a amplifier is determined by the type of amplifier used. An amplifier decides to swing the voltage higher or lower depending upon the input signal. The input signal is the voltage that is on the gate or base of the transistor. When we use a FET, the gate current is very low, and this can bee seen as a high impedance resistor. This is good for high gain but the high impedance leads to high Johnson noise ( {v^2} = 4 k_B T R ) which can cause jitter on the output of the amplifier since there is some uncertainty in the input signal. A BJT amp on Si or SiGe has a higher base current therefore less resistance and Johnson noise on the input signal. Unfortunately there is no universally published parameter that will help you.

Si will go a few GHz, SiGe will go to 6 GHz, if you need to go higher i am not an expert on the technologies available. I did order 10GHz amps with low phase noise years ago and they were designed with HBT on GaAs. Those were the material limts a few years ago.

In addition, if you make a balanced amplifier the combined jitter can be less assuming the input signal splitter did not add more jitter. To determine the risk benefit of a balanced amplifer approach, you will need to analyze the noise on the inut and output.

Good Luck

last time I looked, SI bipolar was king, HBT was 10 dB worse, and GaAs FET was 10 dB worse again. Not sure where SiGe fits in in that lineup.