communication principal (Please help)
时间：04-08
整理：3721RD
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A mixer of an AM radio receiver converts the carrier frequency fc to a fixed
intermediate frequency (IF) of 455 kHz by using a local oscillator of frequency fLO. The broadcast band frequencies range from 540 kHz to 1600 kHz.
a) Determine the range of tuning that must be provided in the local oscillator and the respective image frequencies when high-side injection is used.
b) What is the range of tuning in the local oscillator if low-side injection is used?
c) Which of these injection (high or low) methods would be highly recommended for designing this AM radio receiver? Explain why
intermediate frequency (IF) of 455 kHz by using a local oscillator of frequency fLO. The broadcast band frequencies range from 540 kHz to 1600 kHz.
a) Determine the range of tuning that must be provided in the local oscillator and the respective image frequencies when high-side injection is used.
b) What is the range of tuning in the local oscillator if low-side injection is used?
c) Which of these injection (high or low) methods would be highly recommended for designing this AM radio receiver? Explain why
a) fLO = 455K + 540K --> 455K + 1600K, fIMAGE = 2*455K + 540K --> 2*455K + 1600K
b) fLO = 540K - 455K --> 1600K - 455K
c) High side injection is recommended because in this case the ratio fLOmax / fLOmin is smaller
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