公开(公告)号：US3775689A

公开(公告)日：1973-11-27

申请号：US3775689D

申请日：1970-12-18

Applicant: ITT

Inventor： GREENWALD C

IPC: H03D7/02 ,  H04B1/06

CPC classification number: H03D7/02

Abstract: A balanced mixer and crystal oscillator translates a baseband signal upward in frequency just below the passband of a crystal filter at the output of the mixer. The filter passes only the noise in its passband to a logarithmic amplifier-detector. The DC output of the detector is coupled to a recorder calibrated directly in signal-to-noise ratio of the translated baseband signal. Different width baseband signals (different number of FDM channels) are handled by changing the crystal of the oscillator so that the translated baseband signal remains just below the filter passband.

Abstract translation: 平衡混频器和晶体振荡器将基带信号的频率上升到正好低于混频器输出端的晶体滤波器通带的频率。 滤波器将其通带中的噪声仅传递给对数放大器检测器。 检测器的直流输出耦合到直接以转换的基带信号的信噪比校准的刻录机。 通过改变振荡器的晶体来处理不同宽度的基带信号（不同数量的FDM通道），使得转换的基带信号保持在滤波器通带的正下方。