Logarithmic Detector Amplifier System for Use as High Sensitivity Selective Receiver Without Frequency Conversion

A system for use in a receive chain of a communication device, the system comprising:

• a logarithmic detector amplifier (LDA), having a first LDA input and a first LDA output and a second LDA output, including:
• an amplifying circuit configured to receive a first LDA input signal at the first LDA input from a system input having a first frequency and to generate an oscillation based on the first LDA input signal;
• a sampling circuit coupled to the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation to generate a series of voltage spikes as a first LDA output signal at the first LDA output, wherein the series of voltage spikes have a frequency, wherein the frequency of the voltage spikes varies substantially with a logarithm of a power of the first LDA input signal;
• and
• a resonant circuit coupled to the amplifying circuit and configured to generate a second LDA output signal at the second LDA output;
• and
• a phase lock loop (PLL) coupled between the first LDA output, the second LDA output and a second LDA input, the phase lock loop including a comparator, a switch and a low pass filter, the comparator being configured to receive the second LDA output signal and a second system input signal (F_reference) that has been frequency divided by a factor M and to output a difference signal to the switch, the switch being configured to digitally shape the difference signal before the difference signal is input to the low pass filter, which drives the second LDA input.