A direct conversion IC for digital satellite TV

A direct conversion IC for digital satellite TV applications is described. The incoming pre-selected satellite IF band is converted into two quadrature base band signals. This is achieved by mixing the gain controlled RF input signal with two orthogonal local oscillator signals. These signals are generated by an internal delay cell oscillator that is controlled by a PLL. An externally tuned reference oscillator is working at half the RF input frequency. After off-chip base band filtering the I and Q signals are fed back for amplification in order to meet the requirements of the succeeding AD converters. Measurement results indicate an overall phase noise figure better than -72dBc @ 10kHz and I/Q mismatching of less than 1dB in amplitude and 3 degrees in phase. The direct conversion IC has been implemented in a bipolar 20GHz process.