St-Ericsson Sa

Stmicroelectronics Belgium N.v.

Dieter Joos

Steven Terryn

A mixer is described having a Gilbert cell structure including a first input and a second input for inputting an RF signal, a third input and a fourth input for inputting a local oscillator signal, a first output and a second output for outputting an IF signal, a plurality of switches for converting the RF signal to an IF signal, and a dynamic bleed circuit for dynamically reducing the dc-current of the switches at the switching-point. As the dc-current of the switches is reduced at the point of commutation, the 1/f-noise is also strongly reduced without degrading the linearity. The switching happens at twice the local oscillator frequency. The mixer also includes a common mode feedback circuit that feeds the common mode signal, optionally amplified, to a common mode feedback control device that is in series between the dynamic bleed circuit and the supply voltage.

Mixer cell with a dynamic bleed circuit

An active RC filter has an op-amp and a biasing circuit arranged to bias the op-amp to set a gain bandwidth product of the op-amp according to a desired pole frequency of the filter. The biasing circuit is operable according to an output of an RC calibration circuit. The op-amp can be an OTA transconductance amplifier, and the biasing circuit can be arranged to maintain a constant product of R and transconductance at an input of the transconductance amplifier. This biasing can help to set the pole frequency more accurately and can thus reduce the need for bandwidth margin to be provided to allow for manufacturing process variations.

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Mechelen, Belgium

Dieter Joos