Circuit and method for receiving and mixing radio frequencies in a direct conversion receiver

A frequency mixer comprising:

• a first differential amplifier for amplifying a first pair of input signals having a first frequency (f1) for outputting a first differential output signal;
• a second differential amplifier for amplifying a second pair of input signals orthogonal to the first pair input signals having the first frequency (f1) and for outputting a second differential output signal;
• a subtracter for subtracting the second differential output signal from the first differential output signal and for outputting a subtracted output signal;
• and
• a mixer for mixing the subtracted output signal and a pair of drive signals having a second frequency (f2) in a double balanced mixing mode for outputting a pair of output signals orthogonal to each other wherein at least one harmonic is cancelled.

A frequency mixer comprising:

• a differential amplifier for amplifying a first pair of radio frequency (RF) input signals having a first frequency (f1) and for generating a first current signal at a first node and a second current signal at a second node;
• a harmonic rejection circuit for processing a second pair of input signals orthogonal to the first pair of input signals and for generating a third current signal at the first node and a fourth current signal at the second node, the second pair of input signals having a substantially same frequency as the first frequency (f1);
• and
• a mixer for mixing the current signals applied to the first and the second node with a first pair of drive signals and a second pair of drive signals being orthogonal to each other and having a second frequency (f2), in a sub-harmonic double balanced mixing mode, adapted to output a pair of output signals orthogonal to each other, a harmonic being cancelled from the output signals.

A method comprising:

• providing a first differential signal having a first frequency;
• providing a second differential signal orthogonal to the first differential signal, and having a substantially same frequency as the first frequency;
• subtracting the second differential signal from the first differential signal to output a subtracted signal;
• and
• mixing the subtracted signal, and a first pair of drive signals and a second pair of drive signals orthogonal to each other having a second frequency, in a sub-harmonic double balanced mixing mode, to output a pair of output signals being orthogonal to each other, a harmonic being cancelled from the output signals.

A method comprising:

• amplifying a first pair of input signals having a first frequency to output a first differential signal;
• amplifying a second pair of input signals orthogonal to the first pair of input signals to output a second differential signal, the second pair of input signals having a substantially same frequency as the first frequency;
• subtracting the second differential signal from the first differential signal to output a subtracted signal;
• and
• mixing the subtracted signal with a pair of drive signals having a second frequency, in a sub-harmonic double balanced mixing mode, to output a pair of output signals orthogonal to each other, wherein a harmonic is cancelled in the output signals.

A method comprising:

• amplifying a first pair of input signals, having a first frequency, to output first and second input signals;
• subtracting respectively a third and fourth current signals from a first and second current signals to output a first and second subtracted signals wherein a second pair of input signals orthogonal to the first pair of input signals have a substantially same frequency as the first frequency;
• and
• mixing the first and the second subtracted signals, and a first pair of drive signals and a second pair of drive signals orthogonal to each other, in a sub-harmonic double balanced mixing mode, to output a pair of output signals orthogonal to each other, wherein the first pair of drive signals and the second pair of drive signals have a second frequency.

A frequency mixer comprising:

• a first amplifier for amplifying a first input signal having a first frequency, to output a first amplified signal;
• a second amplifier for amplifying a second input signal orthogonal to the first input signal, to output a second amplified signal, the second input signal having a substantially same frequency as the first frequency;
• a subtracter for subtracting the second amplified signal from the first amplified signal, and for outputting a subtracted signal;
• and
• a mixer for mixing the subtracted signal with a drive signal having a second frequency, in sub-harmonic double balanced mixing mode, to output a output signal, a harmonic being cancelled from the output signal.