Envelope-detecting circuit and receiver incorporating this circuit

A circuit for detecting an envelope of a signal modulated in a high-frequency band located above 30 GHz, this circuit comprising:

• an input port able to receive the signal modulated in the high-frequency band, this modulated signal comprising an envelope modulated by a carrier at a preset frequency fc comprised in the high-frequency band, the envelope comprising a constant v1 added to a desired signal sf1(t), portion of the power of the desired signal sf1(t) being comprised inside a desired frequency band centered on an intermediate frequency f1 and of width Lu,
• an output port via which the detected envelope is delivered,
• wherein this envelope-detecting circuit comprises:
• a first multiplier connected to the input port and able:
• to multiply a first sample of the signal received on the input port by itself, and
• to deliver on an output this first sample of the received signal multiplied by itself,
• a modifier connected, in parallel to the first multiplier, to the input port, this modifier being able:
• to modify an amplitude of the power spectrum, of a second sample of the signal received on the input port, at the frequency fc without modifying the amplitude of this power spectrum in the desired frequency band, and
• to deliver on an output the modified signal,
• a second multiplier connected to the output of the modifier and able:
• to multiply the modified signal by itself, and
• to deliver on an output the modified signal multiplied by itself,
• a subtractor comprising first and second inputs connected to the outputs of the first and second multipliers, respectively, this subtractor being able:
• to subtract the signal received on its first input from the signal received on its second input, and
• to deliver on an output the result of this subtraction,
• a filter able to remove frequency components higher than or equal to 2fc in a signal obtained from the signal delivered by the output of the subtractor, this filter comprising to this end a −3 dB cut-off frequency comprised between f1+Lu/2 and 2fc, this filter being able to deliver the result of this filtering on an output connected to the output port of the envelope-detecting circuit.