[Premium-Rx] The new R&S EM510 Direct-Sampling HF Receiver

[Clemens Paul]

Hi Pieter,

> I should have a 16 bit front end prototype in the next couple of
>days. We'll see how it works. I am also preceding the ADC with a 10dB gain
>preamp with 47dBm IP3 and 1.75dB noise figure that I developed this last
>year.

Are you using some kind of bandpass filtering ahead of the preamp like R&S?
Are you talking about IIP3 or output IP3?
What is the IIP2 of the preamp?


73
Clemens
DL4RAJ

----- Original Message ----- 
From: Pieter Ibelings
To: cpaul at gmx.net ; premium-rx at mailman.qth.net
Sent: Sunday, February 18, 2007 9:31 PM
Subject: Re: [Premium-Rx] The new R&S EM510 Direct-Sampling HF Receiver


Hi John,

The additive phase noise of the ADC is very small. Most of the phase noise
comes from the reference oscillator driving the ADC. These can be really
really good. If the R&S uses the Analog Devices part, they are probably
using the 16 bit AD9446 which is one of their best parts. I have been
playing with the LTC2208 part from Linear devices. The one thing I like
about this part is that it has build in dithering. This dithering is needed
when you are doing measurements on the receiver since the spurs are very
obvious in that scenario. Once you connect the HF antenna, the ADC has
enough noise from the HF spectrum to dither itself and the spurs are not
visible. I should have a 16 bit front end prototype in the next couple of
days. We'll see how it works. I am also preceding the ADC with a 10dB gain
preamp with 47dBm IP3 and 1.75dB noise figure that I developed this last
year. I have also come to the conclusion that to build a radio that displays
both wide spectrum scans and receives, the best is to have two paths (one
filtered and one non filtered). The non filtered path goes to a 14 bit ADC
that can be used to display up to 100 MHz of bandwidth. The other path goes
though a band of 10 hi-Q filters and to a 16 bit ADC. This ADC is used for
the demodulation. That way you get the best of both worlds. I think I am
going to get some incredible performance on this prototype.

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