Noise cancellation system

A system comprising:

• an I-channel mixer configured to receive a radio frequency signal from an antenna and an intermediate frequency signal from a local oscillator;
• a Q-channel mixer configured to receive the radio frequency signal from the antenna and a phase-shifted intermediate frequency signal from the local oscillator;
• a first noise cancellation apparatus connected to the I-channel mixer, wherein the first noise cancellation apparatus comprises a trans-impedance amplifier stage coupled to an output of the I-channel mixer, a noise reduction stage coupled to the trans-impedance amplifier stage and a feedback loop stage coupled to the noise reduction stage, and wherein the noise reduction stage comprises a first adjustable resistor and a second adjustable resistor connected in series with the first adjustable resistor, and wherein the first adjustable resistor and the second adjustable resistor are configured such that an I-channel differential mode second-order intermodulation component and an I-channel common mode second-order intermodulation component cancel each other in the first noise cancellation apparatus, and wherein a common node of the first adjustable resistor and the second adjustable resistor is directly connected to both an input and an output of a buffer;
• and
• a second noise cancellation apparatus connected to the Q-channel mixer, wherein the second noise cancellation apparatus and the first noise cancellation apparatus have a similar structure.

A system comprising:

• an I-channel mixer configured to receive a radio frequency signal from an antenna and an intermediate frequency signal from a local oscillator;
• a Q-channel mixer configured to receive the radio frequency signal from the antenna and a phase-shifted intermediate frequency signal from the local oscillator;
• a first noise cancellation apparatus having an input directly connected to an output of the I-channel mixer, wherein the first noise cancellation apparatus comprises:
• a first trans-impedance amplifier stage coupled to an output of the I-channel mixer;
• a first noise reduction stage coupled to the first trans-impedance amplifier stage;
• and
• a first feedback loop stage coupled to the first noise reduction stage, and wherein the first noise reduction stage comprises a first adjustable resistor and a second adjustable resistor connected in series with the first adjustable resistor, and wherein the first adjustable resistor and the second adjustable resistor are configured such that an I-channel differential mode second-order intermodulation component and an I-channel common mode second-order intermodulation component cancel each other, and wherein a common node of the first adjustable resistor and the second adjustable resistor is connected to a reference voltage through a buffer, and wherein an output of the buffer is directly connected to the common node of the first adjustable resistor and the second adjustable resistor;
• and
• a second noise cancellation apparatus having an input directly connected to an output of the Q-channel mixer, wherein the second noise cancellation apparatus comprises:
• a second trans-impedance amplifier stage coupled to an output of the Q-channel mixer;
• a second noise reduction stage coupled to the second trans-impedance amplifier stage;
• and
• a second feedback loop stage coupled to the second noise reduction stage, and wherein the second noise reduction stage comprises a third adjustable resistor and a fourth adjustable resistor connected in series with the third adjustable resistor, and wherein the third adjustable resistor and the fourth adjustable resistor are configured such that a Q-channel differential mode second-order intermodulation component and a Q-channel common mode second-order intermodulation component cancel each other.