UAA2073M

UAA2073M contains both a receiver front-end and a high frequency transmit mixer intended for GSM (Global System for Mobile communications) cellular telephones. UAA2073M is designed in an advanced BiCMOS process it combines high performance with low power consumption and a high degree of integration, thus reducing external component costs and total front-end size.

The main advantage of the UAA2073M is its ability to provide over 30 dB of image rejection. Consequently, the image filter between the LNA and the mixer is suppressed and the duplexer design is eased, compared with a conventional front-end design.

Image rejection UAA2073M is achieved in the internal architecture by two RF mixers in quadrature and two all-pass filters in I and Q IF channels that phase shift the IF by 45° and 135° respectively. The two phase shifted IFs are recombined and buffered to furnish the IF output signal.

For instance, signals presented at the RF input at LO + IF frequency of UAA2073M are rejected through this signal processing while signals at LO - IF frequency can form the IF signal.An internal switch allows to reject the upper or lower image frequency. Image rejection of UAA2073M is at an optimum when the IF is 71 MHz and local oscillator is above the wanted signal.

The receiver section UAA2073M consists of a low-noise amplifier that drives a quadrature mixer pair. The IF amplifier has on-chip 45° and 135° phase shifting and a combining network for image rejection.The IF driver UAA2073M has differential open-collector type outputs.

The LO UAA2073M part consists of an internal all-pass type phase shifter to provide quadrature LO signals to the receive mixers. The all-pass filters outputs are buffered before been fed to the receive mixers.

The transmit section UAA2073M consists of a down-conversion mixer and a transmit IF driver stage. In the transmit mode an internal LO buffer is used to drive the transmit IF down-conversion mixer.

All RF and IF inputs or outputs of UAA2073M are balanced to reduce EMC issues.

Fast power-up switching UAA2073M is possible. A synthesizer-on (synthon) mode enables LO buffers independent of the other circuits. When SYNTHON pin is HIGH, all internal buffers on the LO path of the circuit are turned on, thus minimizing LO UAA2073M pulling when remainder of receive chain is powered-up.