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

To reduce DC offset caused by local-oscillator-signal self-mixing in a direct-conversion receiver, an active balanced harmonic mixer with second-order intermodulation (IM2) canceler was proposed, and a direct downconverter containing the mixer and a 45/spl deg/ phase shifter was fabricated on a BiCMOS chip. The dc offset caused by the self-mixing was measured and found to be 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 direct conversion receivers for quadrature phase-shift keying signals containing an amplitude modulation component.