An I/Q active balanced harmonic mixer with IM2 cancelers and a 45 degrees phase shifter

To reduce dc offset caused by local-oscillator-signal self-mixing in a dire ct-conversion receiver, an active balanced harmonic mixer with second-order intermodulation (IM2) canceler was proposed, and a direct downconverter co ntaining the mixer and a 45 degrees phase shifter was fabricated on a BiCMO S chip. The de offset caused by the self-mixing was measured and found to b e smaller than the noise level. A second-order intercept point at the input of +37 dBm was achieved with the IM2 canceler, which is suitable for direc t conversion receivers for quadrature phase-shift keying signals containing an amplitude modulation component.