UAA2077AM

UAA2077AM contains a high frequency low noise receiver front-end intended to be used in DECT mobile telephones. UAA2077AM 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 UAA2077AM is its ability to provide over 25 dB of image rejection. Consequently, the image filter between the LNA and the mixer is suppressed.Image rejection 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 of UAA2077AM are recombined and buffered to furnish the IF output signal.

For instance, signals presented at the RF input at LO + IF frequency are rejected through this signal processing while signals at LO - IF frequency can form the IF signal. An internal switch enables the upper or lower image frequency to be rejected.

The receiver section UAA2077AM 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 UAA2077AM has differential open-collector type outputs.The LO part consists of an internal all-pass type phase shifter to provide quadrature LO signals to the receive mixers.The centre frequency of the phase shifter is adjustable for maximum image rejection in a given band.

The all-pass filters outputs of UAA2077AM are buffered before being fed to the receive mixers. All RF and IF inputs or outputs are balanced.Two pins RXON and SXON are used to control the different power-down modes. A special mode of operation
called synthesizer-on mode (SX mode), controlled by pin SXON can be used to minimize the LO UAA2077AM pulling when the receiver is turned on. When SXON is HIGH, all internal buffers on the LO path are turned on. Pin SBS UAA2077AM allows a selection of whether to reject the upper or lower image frequency. Special care has been taken for fast power-up switching.