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