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

From: Jeffrey Lambert
Subject: Re: [Discuss-gnuradio] Analog Devices RF RX/TX subsystems for Spartan-3AN FPGA
Date: Fri, 18 Jun 2010 00:26:10 -0400
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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.


On 6/17/2010 12:58 PM, Elvis Dowson wrote:
          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 


If I look at the AD9874 IF-to-Bits RX subsystem component


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

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