Transformer with integrated notch filter

摘要

Techniques for providing low-cost and effective jammer rejection for a radio receiver. In an aspect, a notch filter is provided between a transformer and a differential mixer in the receiver. The notch frequency of the notch filter may be selected to correspond to an expected jammer frequency to effectively attenuate the jammer signal prior to down-conversion mixing by the mixer. The notch filter may be implemented using various techniques, e.g., an L-C combination having adjustable capacitance, and/or elliptic or Chebyshev filters.

主权项

1. An apparatus comprising:
a transformer comprising a single-ended portion and a differential portion, the differential portion defining a differential voltage between a first node and a second node; and a plurality of notch filters coupled in parallel with each other, each notch filter coupled between the first node and the second node, each notch filter comprising an inductor coupled in series with at least one capacitor, each notch filter having a different notch frequency than all other notch filters of the plurality of notch filters.