ASN9 - 3rd Harmonic & QSD

Back to my home page 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.)

Third Harmonic Sampling $\sum _{n=1}^{\infty }{\frac {1}{n}}cos(n\omega t)=cos(\omega t)+{\frac {1}{2}}cos(2\omega t)+{\frac {1}{3}}cos(3\omega t)+{\frac {1}{4}}cos(4\omega t)+\cdots$ Third harmonic sampling is used in some applications, such as the SoftRock-40 software defined radio, to divide the local oscillator frequency by three.