Carrier-voltage control for improved dynamic range in rectifier modulators

A technique for increasing the dynamic range of a balanced modulator by automatic adjustment of the carrier amplitude is described. A peak detector is used to sense the amplitude of input signals, and to control a variable-gain amplifier which reduces the carrier amplitude¿and hence the carrier leak¿for small inputs. It is shown that some commercially available modulator diodes are satisfactory for use in the system, although ideally bilinear diodes are required. Some experimental results on a phase-sensitive detector are included.