Reduction of noise in impedance measurement circuits

A method of flicker noise reduction in an impedance measurement circuit, the method comprising:

• transmitting a carrier signal to a sample under test;
• and
• receiving sidebands of the carrier signal in response to modulation of the carrier signal from the sample under test;
• suppressing the carrier signal in the reception of the sidebands using compensation impedances coupled between transmission ports and receive ports of the impedance measurement circuit;
• mixing the carrier signal with a version of the received sidebands of the carrier signal;
• generating a value of impedance of the sample under test in a non-modulated state from impedance information about the compensation impedances that suppress the carrier signal;
• and
• combining the value of the impedance of the sample under test in the non-modulated state with a measured impedance of the sample under test from the received sidebands.

A device having an impedance measurement circuit, the device comprising:

• a means to transmit a carrier signal to a sample under test;
• a means to receive sidebands of the carrier signal in response to modulation of the carrier signal from the sample under test;
• and
• a means to suppress the carrier signal in the reception of the sidebands, with the means to suppress the carrier signal coupled between the means to transmit the carrier signal and the means to receive the sidebands of the carrier signal;
• a means to mix the carrier signal with a version of the received sidebands of the carrier signal;
• and
• a means to process information to:
• generate a value of impedance of the sample under test in a non-modulated state from impedance information about the means to suppress the carrier signal;
• and
• combine the value of the impedance of the sample under test in the non-modulated state with a measured impedance of the sample under test from the received sidebands.