Abstract: Certain aspects of the present disclosure are directed to a circuit for signal processing. The circuit generally includes a first transformer having a first inductive element magnetically coupled with a second inductive element, and a second transformer having a third inductive element magnetically coupled with a fourth inductive element, wherein the first inductive element is coupled in series with the third inductive element. In certain aspects, the circuit also includes a first switch coupled in parallel with the third inductive element, a capacitive element coupled in parallel with the fourth inductive element, wherein a notch is formed at least by the capacitive element and the fourth inductive element, the notch circuit coupled in series with the second inductive element, and a second switch coupled in parallel with the fourth inductive element.

Abstract: Certain aspects of the present disclosure are directed to a circuit for signal processing. The circuit generally includes a first transformer having a first inductive element magnetically coupled with a second inductive element, and a second transformer having a third inductive element magnetically coupled with a fourth inductive element, wherein the first inductive element is coupled in series with the third inductive element. In certain aspects, the circuit also includes a first switch coupled in parallel with the third inductive element, a capacitive element coupled in parallel with the fourth inductive element, wherein a notch is formed at least by the capacitive element and the fourth inductive element, the notch circuit coupled in series with the second inductive element, and a second switch coupled in parallel with the fourth inductive element.

Abstract: Amplification with post-distortion compensation is disclosed. In an example aspect, an apparatus includes a voltage rail and a cascode amplifier. The cascode amplifier includes an amplification node, a cascode node, and a common-source node. The cascode amplifier also includes at least one cascode transistor, an input transistor, and a compensation transistor. The cascode transistor is coupled between the amplification node and the cascode node. The input transistor is coupled between the cascode node and the common-source node. The compensation transistor is coupled between the voltage rail and the cascode node.

Abstract: Amplification with post-distortion compensation is disclosed. In an example aspect, an apparatus includes a voltage rail and a cascode amplifier. The cascode amplifier includes an amplification node, a cascode node, and a common-source node. The cascode amplifier also includes at least one cascode transistor, an input transistor, and a compensation transistor. The cascode transistor is coupled between the amplification node and the cascode node. The input transistor is coupled between the cascode node and the common-source node. The compensation transistor is coupled between the voltage rail and the cascode node.

Abstract: This disclosure provides systems and apparatuses for converting a single-ended analog signal into a differential analog signal. In some implementations, a single-ended to differential signal converter may include an N-path filter to generate a 180 degree phase-shifted version of a single-ended input signal. The single-ended input signal and the 180 degree phase-shifted version of the single-ended input signal together may form a differential signal. In some implementations, the N-path filter may delay the single-ended input through a series of switched capacitors.

Abstract: Certain aspects of the present disclosure generally relate to a circuit for signal processing. The circuit generally includes a first transformer having a first inductive element magnetically coupled with a second inductive element, and a second transformer having a third inductive element magnetically coupled with a fourth inductive element. In certain aspects, the first inductive element may be coupled in series with the third inductive element. In certain aspects, the circuit also includes a capacitive element coupled in parallel with the fourth inductive element, the capacitive element and the fourth inductive element forming a notch circuit, the notch circuit coupled in series with the second inductive element.

Abstract: 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.

Abstract: Amplifiers with inductive degeneration and configurable gain and input matching are disclosed. In an exemplary design, an apparatus includes a gain transistor, an inductor, and an input matching circuit for an amplifier. The gain transistor has a variable gain determined based on its bias current. The inductor is coupled between the gain transistor and circuit ground. The input matching circuit is selectively coupled to the gain transistor based on the variable gain of the gain transistor. For example, the input matching circuit may be coupled to the gain transistor in a low-gain mode and decoupled from the gain transistor in the high-gain mode. In an exemplary design, the input matching circuit includes a resistor, a capacitor, and a second transistor coupled in series. The resistor is used for input matching of the amplifier. The second transistor couples or decouples the resistor to or from the gain transistor.

Abstract: 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.

Abstract: Amplifiers with inductive degeneration and configurable gain and input matching are disclosed. In an exemplary design, an apparatus includes a gain transistor, an inductor, and an input matching circuit for an amplifier. The gain transistor has a variable gain determined based on its bias current. The inductor is coupled between the gain transistor and circuit ground. The input matching circuit is selectively coupled to the gain transistor based on the variable gain of the gain transistor. For example, the input matching circuit may be coupled to the gain transistor in a low-gain mode and decoupled from the gain transistor in the high-gain mode. In an exemplary design, the input matching circuit includes a resistor, a capacitor, and a second transistor coupled in series. The resistor is used for input matching of the amplifier. The second transistor couples or decouples the resistor to or from the gain transistor.