The design of GALFA Quadrature Downconverter
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چکیده
Specifications: The goal of the project is to design a quadrature downconverter (QD) that will demodulate an intermediate frequency (IF) signal in the range from 100MHz to 400MHz to base band. There will be a total of 14 QD boards for 7 beams, 2 polarizations per beam, coming from Galactic Arecibo L-band Feed Array (GALFA). The power of the IF signal will be in the range from -25dBm to -10dBm (50Ω load) and will need to be amplified to 0dBm (50Ω load). The demodulated I and Q signal from QB are to be followed by 40 MHz (3dB point) low-pass image rejection filters with no pass-band ripple, and high stop band attenuation. It is essential that the phase difference between the I and Q demodulated signals at the output does not exceed 3 degrees. The QB will drive 8 bit ADC that will sample at 100Msamples/s.
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