Re: [Discuss-gnuradio] Analog Devices RF RX/TX subsystems for Spartan-3AN FPGA

[Jeffrey Lambert]

Hello,

An RF Front-end can take many forms, depending upon the application. For 
use with the USRP or similar hardware, a direct-conversion approach is 
probably adequate.  This type of front-end typically consists of low 
noise amplifier (LNA), mixer, and perhaps a baseband/IF amplifier or 
automatic-gain control (AGC) amplifier.  Determing the requirements for 
amplifier gains will be based on mixer conversion loss and the receiver 
sensitivity desired.

Designing the RF front-end requires knowledge of RF and microwave 
circuits and perhaps impedance matching skills and amplifier design 
depending upon how low-level you want to get into the design process. 
This is not a simple task.  That said, however, coaxial components are 
available from manufacturers such as Mini-circuits that are relatively 
easy to work with provided you are working relatively low frequency (~7 
GHz or less).

Also, it is worth pointing out that the ADC and DACs that you choose are 
part of the analog front-end, and they have an associated noise figure 
and power requirements.  As such, if you are looking to design an RF 
front-end, choosing an ADC/DAC might not be the way to go.

~Jeff

On 6/17/2010 12:58 PM, Elvis Dowson wrote:
> Hi,
>           I would like to design a custom board based on the Spartan-3AN FPGA, 
> based on the Spartan-3AN FPGA Starter Kit, but would like to build my own RF 
> front-end.
>
> http://www.analog.com/en/rfif-components/rxtx-subsystems/products/index.html
>
> If I look at the AD9874 IF-to-Bits RX subsystem component
>
> http://www.analog.com/en/rfif-components/rxtx-subsystems/ad9874/products/product.html
>
> it contains an ADC and a whole bunch of other stuff.
>
> Could someone help me by pointing out what other components or parts I should 
> be looking at to build the RF receiver front-end to start with, assuming that I 
> am going to learn from the USRP2 design, and the fact that it already has the 
> Spartan-3AN FPGA, and I'm going to build my own RF front-end?
>
> Best regards,
>
> Elvis Dowson
>
>