Polyphase Filter for MM-Wave Frequencies Featuring Symmetric Layout
AssigneeST-Ericsson SA
InventorsPatrick Reynaert, Shailesh Kulkarni, Dixian Zhao
Life of this patent
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Abstract
A two-stage, passive, RC polyphase filter for mm-wave quadrature LO generation is presented. The filter features an innovative, symmetrical layout structure, which is more robust to parasitics than the conventional layout. Layout parasitics which become important at mm-wave frequencies are identified and a compensated. Impedance variations and transfer functions are evaluated considering these dominant parasitics. More than 15 dB improvement in image rejection ratio is achieved in comparison with conventional layouts. Using the inventive techniques more than 35 dB of image rejection ratio over a bandwidth of 6 GHz is demonstrated in an outphasing transmitter at 60 GHz in 40 nm CMOS.
Claims15
A passive, quadrature, RC polyphase filter (PPF) stage operative at Extremely High Frequencies (EHF), comprising:
- first, second, third, and fourth inputs;
- corresponding first, second, third, and fourth outputs;
- a resistor interposed between each respective input and output;
- a first capacitor coupled between the first input and second output;
- a second capacitor coupled between the second input and fourth output;
- a third capacitor coupled between the third input and first output;
- a fourth capacitor coupled between the fourth input and third output;
- wherein the conductor connecting the second input to the second capacitor has substantially equal length to the conductor connecting the third input to the third capacitor;
- and
- wherein the conductors connecting each capacitors to its respective output all have substantially equal length.
Dependencies are inferred from the claim text.