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High Performance Cellular Receivers in Very Advanced CMOS

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A direct-conversion receiver topology often used for cellular receiver, due to its good configurability.




Benjamin Sporrer


ETH Zurich




A state-of-the-art receiver covers a large number of services and therefore has to receive signals over a wide frequency range. Using one input pin for every frecuency band to cover is not feasible for a transceiver that operates on latest cellular communication standards like LTE. Also the count of external components must be kept as low as possible, although the complexity of the transceiver is increasing.

To solve this problem wideband receiver chains can be employed. A small number or even a single wideband receiver front-end then cover the whole range of receive frequencies. Wideband frontends come at the cost of a much higher sensitivity to out-of-band blocking signals. Interferers outside the actual service-band may desensitize the receiver. The exact characterisation of the surrounding frequency contents around the input signal is therefore of high importance in this project.

A very advanced CMOS technology (28nm technology from ST Microelectronics) offers several benefits to receiver design. The fast transistors of advanced CMOS may make it possible to use feedback structures for gain stages at radio frequency. The biggest advantage however lies in the fact, that all digital parts following the analog-to-digital converter of the RF receiver baseband part. On the other side drawbacks for analog circuits also do exist in ultra-scaled CMOS. They include high parasitic capacitances, very low supply voltages, high leakage currents and increased thermal channel noise.