LOGARITHMIC AMPLIFIER WITH UNIVERSAL DEMODULATION CAPABILITIES

摘要

A logarithmic amplifier (LDA) is described that includes an amplifier configured to oscillate a modulated input signal, a feedback establishing a 180 degree phase shift between the amplifier input and the output and maintaining oscillation of the input signal, a parallel resonant circuit connected to the amplifier output causing the amplifier to resonate at or around a center frequency, and a controller connected to the amplifier input cyclically terminating oscillation of the input signal each time a pre-determined threshold of current is detected, the controller including a low pass filter configured to generate a second output signal having a repetition frequency. The LDA may be used for AM with or without a PLL and/or a superhetrodyne. The LDA may be implemented as a mixer and used for phase demodulation. The LDA may be used for phase demodulation. The LDA may be used in place of a low noise amplifier.

主权项

1. A logarithmic amplifier, comprising:
an amplifier circuit configured to receive an input signal at an amplifier input, oscillate the input signal, and generate a first output signal at an amplifier output, wherein the input signal includes a modulated signal to be detected and electrical noise; a feedback circuit coupled to the amplifier output and the amplifier input and configured to establish a 180 degree phase shift between the input signal and the first output signal, the feedback circuit including a single capacitor configured to maintain oscillation of the input signal; a parallel resonant circuit connected to the amplifier output and configured to cause the amplifier circuit to resonate at or around a center frequency; and a controller circuit connected to the amplifier input and configured to cyclically terminate oscillation of the input signal each time a pre-determined threshold of voltage is detected, the controller circuit including a low pass filter configured to generate a second output signal having a repetition frequency.