A Local Oscillator Leakage Signal Eliminating Circuit for Direct Quadrature Up-conversion Transmitters

In this paper, we described a method to solve the local oscillator (LO) leakage problem of direct quadrature upconversion transmitters (DCTs). Comparing to traditional superheterodyne transmitters, DCTs have made great breakthroughs in dimension, power consumption and cost, but its performance will be worsened critically by LO leakage signal. To solve the DCT LO leakage problem, we provide a set of circuits which is uniquely based on I,Q signal DC offsets adjustments. The circuits can be applied in the field of multi-carrier and multi-mode transmitters of mobile phone and wireless area networks etc. The experiment results indicate that after the application of the LO leakage signal eliminating circuit, the LO leakage signal is suppressed to the level of -47 dBc with the improvement of 9 dB comparing to the case without the eliminating circuit.