Analysis of impairments in direct conversion receivers and their effects in GMSK signaling

A very important source of errors in a direct conversion receiver is the quadrature mixer that is used to remove the carrier and convert the RF signal directly to baseband. The quadrature mixer distorts the received signal through four basic mechanisms: gain imbalance, phase imbalance, DC offset and cross-coupling. Here, the effect of the first three mechanisms on the phase of a demodulated GMSK signal is considered. Performance degradation of a digital receiver is also presented by means of computer simulations