Hello,
I am looking for an example of a schematic of a space antenna receiver or LNB. I am interested what tricks they use to reduce the noise of the amplifier.
I want to mention here the phono-amp of Stuart Yanninger and how smart and cool he used a diode as a low noise current source.
Now I want to see how e.g. NASA reduce noise.
Could anybody give an example of it or describe it?
I am looking for an example of a schematic of a space antenna receiver or LNB. I am interested what tricks they use to reduce the noise of the amplifier.
I want to mention here the phono-amp of Stuart Yanninger and how smart and cool he used a diode as a low noise current source.
Now I want to see how e.g. NASA reduce noise.
Could anybody give an example of it or describe it?
They are digital so there is no "noise" as mathematically it is removed. Same as a compact disc algorithm does. The math is very extensive.
Your home TV satellite dish uses the same techniques, just not as many at once.
They do start with the lowest noise receiver they can make, but the signal is often below the noise level, and so incredibly complex processing digs a coherent signal out of that. The tricks they use are mainly other than in the receiver. Also look at their antenna. They use dishes that are larger than your house, gathering signal.
Getting a signal from something in orbit around the earth is easy. But those probes to the outer planets and beyond need every trick they can devise.
They do start with the lowest noise receiver they can make, but the signal is often below the noise level, and so incredibly complex processing digs a coherent signal out of that. The tricks they use are mainly other than in the receiver. Also look at their antenna. They use dishes that are larger than your house, gathering signal.
Getting a signal from something in orbit around the earth is easy. But those probes to the outer planets and beyond need every trick they can devise.
the front ends of the older analog C and Ku band satellite dishes used and LNA or later an LNB that used GAs Fets. Gallium Arsenide FETs. As time went on they became lower and lower noise. Originally to get them quiet enough they were bathed in some very cold stuff, like liquid nitrogen, iirc.
Their ought to be some schematics for LNAs online by now...
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Their ought to be some schematics for LNAs online by now...
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Multiple antennas provide noise canceling thus no need to strain low noise amplifier with 'impossible' specs. Low noise blocks at antenna are a must to ensure fragile signal is not contaminated as it makes its way along conductors or wave guides
They got better over time because of special construction techniques (eg, the HEMT) and dirt cheap because MMICs used in cell phones increased production volume of GaAs. Today, L and C band FETs have noise figures lower than that of the 50-ohm source impedance. Ku is getting close. And devices that cost $200 back in the heyday of C-band satellite can be found in the Digi-Key catalog for a song.
The "shematic" for an LNA is actually quite simple, and complex at the same time. Most are just a simple FET biased into class A with chokes for current sources. The techniques in general are NOT applicable to audio. The magic is in the RF traces on the PCB which do the impedance matching. It's dirt simple if you know how to do it - black magic if you don't.
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