Re: Airspy architecture

Siegfried Jackstien

Hello alberto

I would guess the if n and if p means if negative and if positive (balanced
output) and NOT be I/Q signals

The r820t tuner does only have low if out and not 0hz if (i/q)




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Von: []
Gesendet: Montag, 2. Februar 2015 11:26
Betreff: [airspy] Airspy architecture

A few naive questions, originated from my attempt to understand the
architecture of the Airspy.

The tuner is an R820T2, which converts in the analog domain down to a low
IF, just above 4 MHz.

First question : from the simplified block diagram of that chip, it
doesn't seem to use a quadrature
mixer. That notwithstanding, the image rejection reported from its data
sheet is 65 dBc... how is
that possible ?

A more detailed look shows that it has two IF outputs, pin 12 and pin 13,
marked as IF N and IF P.
In the unconfirmed hypothesis that those outputs are actually I and Q, in
other words the mixer
is as a matter of facts a quadrature mixer, then those two outputs must be
digitized by the
12-bit, 80 MHz high speed ADC of the NXP LPC-4370 processor, which is a
single ADC.
So it should work in a time interleaved fashion... is this correct ?

A bit of light on the Airspy architecture would be welcome, thanks.

73 Alberto I2PHD
Credo Ut Intelligam


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