Radioware from Notre Dame

Radioware project from Notre Dame University:
http://radioware.nd.edu/documentation/basic-gnuradio/entering-the-world-of-gnu-software-radio

Introduction to GNURadio

Software radio is the technique of getting the code as close to the antenna as possible. It turns radio hardware problem into software problems. The fundamental characteristic of software radio is that software defines the transmitted waveforms and demodulates the received waveforms. This is in contrast to most radios in which the processing is done with either analog circuitry or analog circuitry combined with digital chips.

Analog to Digital  Converter (ADC)
ADC has two primary characteristics: sampling rate and dynamic range.
Generally speaking, device physics and cost impose trade-offs between the sample rate and dynamic range.

In GNURadio
USRP Board servers as above part which is developed by Matt  Ettus and Eric Blossom.

The RF Front-End
How can we listen to broadcast FM Radio at 92.1 MHz with ADC runs at 20 MHz. The answer is the Radio Frequency (RF) front-end. The receive RF front end translate a range of of frequencies appearing at its input (RF) to a lower range intermediate frequency (IF) range at its output.
For example RF side 90 - 100 MHz range down to 0 - 10 MHz range (IF).

Mostly we can treat the RF front-end as a black box with a single control, the center of the input range that's to be translated.

Center frequency of the output range is called the intermediate frequency, or IF

Typical RF front-end structure:

Antenna -> Low Noise Amplifier (LNA) -> Low Pass Filter (LPF) -> Mixer -> LPF -> ADC 
                                                                   ^
                                              Local Oscillator ----|

In the explaining context of Notre Dame, they use "different frequency" to explain this.
About structure above more information can be found through searching :
direct conversion receiver architecture
More detail information from EE times about RF circuit design.
http://www.eetimes.com/design/microwave-rf-design/4018954/What-s-in-an-RF-Front-End-


FAQ about Hardware Front end :
http://www.ettus.com/faq#norf

Can I create a radio system with just a USRP motherboard and BasicTX/BasicRX, but no RF frontend?

The most direct and easy way to create a complete radio system is to use one of our complete RF frontend daughterboards, the TVRX2, DBSRX2, WBX, SBX, RFX-series, and XCVR2450.




Collaborative Hardware?
MiniCircuits?
GNURadio Introduction Guides Written by Dawei Shen
http://www.snowymtn.ca/gnuradio/gnuradiodoc-1.pdf
Series Documents


Another Hardware introduction Document Created by VT (Virginia Tech)
http://www.ece.vt.edu/swe/chamrad/crdocs/CRTM09_060727_USRP.pdf


ASSA GNU Radio Page
http://www.radio-assa.org.au/sdr/gnu-radio