A logarithmic detector amplifier, LDA, system for use in a receive chain of a communication device, the system comprising: an amplifying circuit (A81) configured to receive an input signal and to generate an oscillation based on the input signal; a quadripole resonant circuit coupled to an output of the amplifying circuit and configured to establish a frequency of operation of the system wherein the quadripole resonant circuit is a four-terminal network having parallel and series resonant circuits where the parallel and series resonant circuits are coupled between an output of the amplifier and ground and are designed to be a bandpass filter having a transfer function including a passband with a null phase; a first low pass filter circuit configured to filter signals exiting the parallel resonant circuit or filter signals entering the parallel and series resonant circuits, and configured to output a first RF output signal from a first output; a sampling circuit (C83, R81) coupled to an input of the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation, thereby generating a series of voltage spikes, wherein a repetition frequency of the voltage spikes carries frequency modulation, FM, and amplitude modulation, AM, information of the input signal transposed to an intermediate frequency, IF, band and is output as a second output signal from a second output; and a second low pass filter circuit (D81) coupled between the amplifier circuit and the sampling circuit to isolate the second output signal from the input signal and the oscillation generated by the amplifying circuit. an amplifying circuit (A81) configured to receive an input signal and to generate an oscillation based on the input signal; a quadripole resonant circuit coupled to an output of the amplifying circuit and configured to establish a frequency of operation of the system wherein the quadripole resonant circuit is a four-terminal network having parallel and series resonant circuits where the parallel and series resonant circuits are coupled between an output of the amplifier and ground and are designed to be a bandpass filter having a transfer function including a passband with a null phase; a first low pass filter circuit configured to filter signals exiting the parallel resonant circuit or filter signals entering the parallel and series resonant circuits, and configured to output a first RF output signal from a first output; a sampling circuit (C83, R81) coupled to an input of the amplifying circuit and configured to terminate the oscillation based on a predetermined threshold so as to periodically clamp and restart the oscillation, thereby generating a series of voltage spikes, wherein a repetition frequency of the voltage spikes carries frequency modulation, FM, and amplitude modulation, AM, information of the input signal transposed to an intermediate frequency, IF, band and is output as a second output signal from a second output; and a second low pass filter circuit (D81) coupled between the amplifier circuit and the sampling circuit to isolate the second output signal from the input signal and the oscillation generated by the amplifying circuit. <EOS>