JoeN:
I am going to supply my first reply here. Are there any radio / data conversion experts out there? Here is what he gives as HackRF project goals:•transmit and receive
•operating frequency: 100 MHz to 6 GHz
•maximum sample rate: 20 Msps
•resolution: 8 bits
•interface: High Speed USB
•power supply: USB bus power
•portable
•open source hardware and software
•low costOK, it all makes sense to me. But one question, how can a 20Msps 8 bit ADC/DAC be sufficient when working at these frequencies? That's all it takes? I wonder if you could do more with some of the (admittedly more expensive) faster high resolution ADCs on the market. There are 16 bit ADCs now with 100msps data conversion rates or faster and obviously far faster 8 bid ADCs. How can this be enough? Thanks.
I think most wide range and very high frequency RF applications working at these frequencies utilize hardware based DDS ICs (Analog Devices is a leader) to generate the low level RF frequencies of interest that are used both in receive applications (via the DDS as local oscillator that is mixed down to a lower frequency for fixed IF frequency that is more easily processed with a ADC that operates at base band or at lower fixed IF frequency for the demodulation or modulation of the signal in upconversion for transmitting applications.
Do to answer your question more simply a ADC that works at these very high RF frequencies is not required, the ADC is just used at lower frequencies to generate or to demodulate the information that will then be mixed with and upconverted to the desired RF frequencies.
The modern DDS chips available have tremendous capabilities.
Lefty