Six-port Direct Conversion Receiver

The applicability of the known six-port receiver structure for mobile phones was studied. The six-port receiver is typically used in high frequency microwave analyzers where a wide bandwidth is required. In these applications the unperfections of the six-port structure can be canceled by using calibration. In direct conversion receivers a severe problem is to achieve the required AM suppression characteristics. This is known as a DC problem. Strong adjacent channel signals cause interference in the baseband through second order effects. To evaluate the suitability of a six-port receiver to achieve the required AM suppression level a discrete component six-port receiver operating at 2GHz frequency area was implemented and measured. The results were compared against traditional mixer structures.