Homework Nine

1. How does Third Harmonic Sampling work? (The Soft Rock receiver uses it.)
2. How does the quadrature sampling detector (QSD) work? (Look at the SDR-1000 QEX articles.)

Nick Christman

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The Softrock 40 software defined radio (SDR) uses a special technique when sampling the data -- this technique is referred to as 3rd Harmonic Sampling. The purpose of 3rd Harmonic Sampling is to eliminate the need to use a high frequency oscillator which is useful economically and physically. (In other words, a high frequency oscillator is expensive and is often incompatible with "cheaper" switches.) However, nothing in this world is perfect and because of this imperfection, Third Harmonic Sampling have a signal loss of $\textstyle 20\log _{10}({\frac {1}{3}})=-9.54db$ (Max Woesner).