Qualcomm Incorporated

University of Washington

Xiaoyong Li

Rahul A Apte

Yi Zeng

David Allstot

Luca Blessent

Cormac S Conroy

Sang-Oh Lee

Tzu-Wang Pan

Sunghyun Park

Pushp Trikha

Haitao Gan

A circuit used in a mixer configured to receive a signal made up of a relatively small modulation signal and a relatively large carrier signal is described. The mixer includes multiple switches. A balancing circuit configured to receive a supply voltage and a clocking signal is provided, and the balancing circuit provides a control signal to a switch in the mixer. The balancing circuit includes a capacitor configured to receive and selectively dissipate charge as a gate voltage along a gate path. The control signal causes switching of the switch in the mixer at times in accordance with the clocking signal according to a voltage difference value between a source voltage and the gate voltage, wherein the voltage difference value between the source voltage and the gate voltage is approximately a predetermined voltage value greater than a turn on voltage level of the switch.

Linearity in passive mixer circuits

Techniques to improve low noise amplifiers (LNAs) with noise canceling are described. LNA includes a first and a second amplifier which work together to noise cancel the noise generated at an input stage circuit. The input stage circuit receives an RF signal and is characterized by a first node and a second node. The first amplifier converts a noise voltage at the first node into a first noise current at an output of the first amplifier. The second amplifier is directly coupled to the output of the first amplifier and provides noise canceling by summing the first noise current with a second noise current generated by the second amplifier as a function of the noise voltage at the second node. The proposed techniques eliminate the need for large ac coupling capacitors and reduce the die size occupied by the LNA.

Wide band LNA with noise canceling

A cellular telephone includes cellular telephone circuitry and an FM receiver. An FM signal being received is downconverted by a mixer. The downconverted signal is processed to generate an FM signal that is supplied to a digital IF filter. If a blocker emitted by the cellular telephone circuitry would interfere with receiving of the FM signal due to interaction of an LO harmonic with the blocker if a conventional LO frequency were used, then a different LO frequency is used. Subsequent processing of the downconverted FM signal (for example, by a digital complex conjugate selector and an IF rotator) results in the signal supplied to the digital IF filter having the same center frequency as the digital IF filter despite the use of the different LO frequency. In some embodiments, the LO is shifted by different amounts depending on cellular telephone mode and on the FM signal.

Using LO shifting to prevent a local transceiver from interfering with an FM radio

An active analog filter () having a MOS capacitor device () with improved linearity is proposed. In an exemplary embodiment, dc bias voltage sources () alter the capacitance of MOS varactors () connected in anti parallel so that the total capacitance of the MOS capacitor device remains constant or within a range over the voltage range of the filter and the filter linearity is set. In a further exemplary embodiment the output stage () of the operational amplifier circuit () of the active analog filter () is modified so that the dc bias voltage is provided by resistors () connected to a current source () already existing in the filter. Thus the linearity is set and the die area is significantly reduced.

Active analog filter having a MOS capacitor device with improved linearity

Techniques to improve low noise amplifiers (LNAs) with noise canceling are described. LNA includes a first and a second amplifier which work together to noise cancel the noise generated at an input stage circuit. The input stage circuit receives an RF signal and is characterized by a first node and a second node. The first amplifier converts a noise voltage at the first node into a first noise current at an output of the first amplifier. The second amplifier is directly coupled to the output of the first amplifier and provides noise canceling by summing the first noise current with a second noise current generated by the second amplifier as a function of the noise voltage at the second node. The proposed techniques eliminate the need for large ac coupling capacitors and reduce the die size occupied by the LNA. The elimination of ac coupling capacitors between amplification stages of the LNA allows current reuse resulting in reduced current consumption.

Techniques for improving the linearity of a cascode amplifier. In an exemplary embodiment, an auxiliary common-gate amplifier is provided in parallel with the principal cascode branch. The auxiliary common-gate amplifier samples a cascoded node in the principal cascode branch. The auxiliary common-gate amplifier generates a current which, when combined with the current generated by the principal cascode branch, cancels a distortion component to generate an output current with improved linearity characteristics. In an exemplary embodiment, a phase shifting network couples the cascoded node to the auxiliary common-gate amplifier, and may include, e.g., a capacitor coupled to an inductor.

Techniques for improving amplifier linearity

Techniques for integrating a common-source and common-gate amplifier topology in a single amplifier design. In one aspect, an input voltage is provided to both a common-source amplifier and a common-gate amplifier. The output voltages of the common-source amplifier and the common-gate amplifier are provided to a difference block for generating a single-ended voltage proportional to the difference between the output voltages. When applied to the design of, e.g., low-noise amplifiers (LNA's), the disclosed techniques may offer improved noise performance over the prior art.

Common-gate common-source amplifier

Embodiments of the present invention include a common-gate amplifier having an input terminal and an output terminal, a transistor having a source, a drain, and a gate, four inductors, and two capacitors, and a negative amplification circuitry. The negative amplification circuitry has an input terminal to receive an RF signal. The negative amplification circuitry applies negative or zero amplification to the RF signal and outputs the negative or zero amplified signal on an output terminal. Alternative embodiments include a Colpitts differential oscillator, which includes two Colpitts single-ended oscillators. Each Colpitts single-ended oscillator includes a transistor. The source of the transistor in one Colpitts single-ended oscillator may be capacitively coupled to the gate of the transistor in the other Colpitts single-ended oscillator.

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Santa Clara, CA, United States of America

Xiaoyong Li