[hpsdr] Companding in SDR RX Front End

[T.W.H.Fockens]

Dear Guido,

Companding is just a (dynamically controlled) attenuator in front of the
ADC. This means that it works on the whole received bandwidth and not just
on the selected channel. It just shifts the input range up and down. The
realtime dynamic range is not altered!

Further, be aware of possible intermodulation effects in the (analog)
attenuator circuit. This circuit needs a real high third order intercept
point!

73,
Koos
PA0KDF


On 05 Jan, Guido <threeme3 at gmail.com> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> Companding increases the dynamic range of a channel. So, could this 
> advent the performance of our SDR receivers ?

> Applying companding just in front of the ADC could increase the dynamic
> range of the overall system. I understand that companding goes at the 
> cost worse distortion for small signals, but is this effect really
> noticable (the harmonic products of a small signal are also small) and 
> scarifying the receiver performance ?

> Any thoughts?

> 73,
> Guido
> PE1NNZ

-- 
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

 1199616535.0