Mediatek Corporation

Ralink Technology Corporation

Mediatek Singapore Pte. Ltd.

Philips Electronics North America Corporation

Philips Electronics North Amercia Corporation

Keng Leong Fong

I-Chang Wu

Jenwei Ko

YuenHui Chee

John Wong

Chungwen Dennis Lo

Jianhan Liu

Thomas Edward Pare, Jr

Osama K A Shana'a

Fei Song

Chiyuan Lu

Bryan Liangchin Huang

Dai Sieh

Neric Fong

Wei-Kai Hong

Ming Chung Liu

Hsing-ting Yu

Chung Wen Lo

Systems and methods of transmitting a multi-user (MU) wake-up packet in WLAN including wake-up signals to activate main radios on multiple communication devices via the wake-up radios (WURs). In the multi-user wake-up packet, a frequency channel can be divided into several sub-channels for transmitting multiple wake-up signals in FDMA. Each wake-up signal is modulated in ON/OFF Key modulation. Two adjacent wake-up signals are adequately spaced apart by a certain frequency spacing to reduce adjacent channel interferences. Once a WUR on a receive device receives the packet, it generates a wake-up indication to wake up the main radio for active data communication. The MU wake-up packet may also include a sequence of multiple wake-up signals transmitted using the same sub-channel and cascaded in a time-domain. A reconfiguration window may be inserted between consecutive wake-up signals on the same sub-channel, and between a legacy preamble and the following wakeup signals.

Multi-user (MU) wake-up signal transmission by using FDMA scheme in WLAN

Methods and apparatus for providing adaptive biasing to power amplifiers. Adaptive bias circuits are configured to provide sharp turn on and/or current clamping to improve the efficiency of a power amplifier over a wide input signal bandwidth. Sharp turn on may be achieved using a subtraction technique to subtract outputs from multiple detectors. Clamping may be achieved using MOSFET device characteristics to pull the device from the triode region into the saturation, subtraction techniques to subtract the outputs from multiple detectors, and/or by using circuit devices, such as diodes.

Wideband adaptive bias circuits for power amplifiers

An amplifier circuit that includes a first power amplifier configured to drive a load and a second power amplifier configured to drive the load through an impedance step-up network. The impedance step-up network is connected to an output of the second power amplifier. The impedance step-up network is configured to switch into a first mode to present an increased impedance to the first power amplifier, and switch into a second mode in which the impedance step-up network steps-up an impedance seen by the second power amplifier looking into the impedance step-up network.

Matching network for load line change

Some embodiments relate to a method and circuit for gain compensation. The method includes detecting a strength of an output signal generated by a power amplifier of a transmitter in response to a commanded transmission signal. The method also includes comparing the detected strength of the output signal to a delayed version of a detected strength of the commanded transmission signal to obtain an error signal. The method further includes compensating for gain drop of the output signal by adjusting a gain of the transmitter based on the error signal.

Active compensation for power amplifier gain droop

A radio frequency receiver is provided. The receiver can be employed in a low power (or ultra-low power) receiver architecture to generate a baseband signal or an intermediate frequency signal. In addition, the receiver includes capabilities of gain control to provide different gain settings as well as providing better/improved impedance matching control.

Radio frequency receiver front-end with gain control capability as well as improved impedance matching control capability

A method and system for synchronizing the output signal phase of a plurality of frequency divider circuits in a local-oscillator (LO) or clock signal path is disclosed. The LO path includes a plurality of frequency divider circuits and a LO buffer for receiving a LO signal coupled to the plurality of frequency divider circuits. The method and system comprise adding offset voltage and setting predetermined state to each of the frequency divider circuits; and enabling the frequency divider circuits. The method and system includes enabling the LO buffer to provide the LO signal to the frequency divider circuits after they have been enabled. When the LO signal drives each of the frequency divider circuits, each of the frequency divider circuits starts an operation. Finally the method and system comprise removing the offset voltage from each of the frequency divider circuits to allow them to effectively drive other circuits.

Method and system for synchronizing the phase of a plurality of divider circuits in a local-oscillator signal path

Phase-locked loop charge pump driven by low voltage input. In one aspect, a phase-locked loop circuit includes a phase frequency detector operating at a low voltage and providing low-voltage sourcing control signals and low-voltage sinking control signals at the low voltage. A charge pump operates at a high voltage and includes a sourcing control circuit coupled to the low-voltage sourcing control signals and selectively causing the charge pump to source the sourcing current to an output of the charge pump based on the low-voltage sourcing control signals. The charge pump also includes a sinking control circuit that receives the low-voltage sinking control signals and selectively causes the charge pump to sink the sinking current from the output of the charge pump based on the low-voltage sinking control signals.

Fast-response phase-locked loop charge-pump driven by low voltage input

A differential-pair amplifier comprising a transistor pair. The differential-pair amplifier includes a current source coupled to the transistor pair for providing a bias current to the transistor pair. The differential-pair amplifier also includes a switching mechanism coupled to the transistor pair for steering the bias current away from the transistor pair when disabling the amplifier operation. A system and method in accordance with the present invention allows fast enabling and disabling of a differential-pair amplifier. This fast switching technique can be used in the signal paths where the switching time is critical.

Fast switch for controlling a differential-pair amplifier

Phase-locked loop charge pump driven by low voltage input. In one aspect, a charge pump for a phase-locked loop circuit includes a sourcing current transistor providing a sourcing current, wherein the sourcing current transistor is coupled to a high-voltage operating voltage supply. A sourcing control circuit uses low-voltage sourcing control signals to selectively cause the charge pump to source the sourcing current to an output of the charge pump, and a sinking control circuit uses low-voltage sinking control signals to selectively cause the charge pump to sink the sinking current from the output.

Fast response phase-locked loop charge-pump driven by low voltage input

One embodiment of the present invention includes a frequency generation circuit including a control module, an oscillator circuit coupled to the control module, the oscillator circuit having a start-up time defined by the time required to reach a desired frequency. The oscillator circuit includes an amplifier having an input and an output and being programmably-alterable by the control module, a first capacitor coupled to the input of the amplifier and being programmably-alterable, in capacitance, by the control module, a second capacitor coupled to the output of the amplifier, a crystal resonator coupled to the first and second capacitors for generating an output signal having a desired frequency, wherein fast start-up time is achieved.

Method and apparatus for a crystal oscillator to achieve fast start-up time, low power and frequency calibration

A circuit includes a transconductance stage which converts an input signal power into a signal current and supplies it to an output of the circuit. A current diverting circuit branch is coupled to selectively divert the current from the transconductance stage away from the output. A feedback network feeds back a portion of the current diverted away from the output to the input of the transconductance stage. When implemented as a variable gain amplifier, the current diverting branch functions to change a gain of the circuit from a high level to one or more lower levels. The feeding back of a portion of the diverted current to the input improves the linearity of the circuit in the lower gain mode(s).

Variable gain amplifier with improved linearity

A shunt-feedback technique is provided for improving noise figure and linearity of electronic circuits, such as amplifiers and mixers. An input common-emitter transconductance stage of an electronic circuit has a transistor, and a degeneration impedance provided between the emitter of the transistor and a ground terminal. A feedback capacitor is connected between the collector and the base of the transistor. A feedback resistor is coupled between the collector of the transconductance stage transistor and the emitter of a transistor in the next stage of the electronic circuit. The feedback capacitor and the feedback resistor form a shunt-feedback network.

Noise figure and linearity improvement technique using shunt feedback

A circuit includes a transconductance device which converts an input signal voltage to a signal current. An output terminal is coupled to receive signal current from the transconductance device. A gain-control circuit has an impedance network coupled to the output terminal to maintain a constant impedance at the output terminal and selectively steers current from the transconductance device through at least first and second different nodes of the impedance network to vary the current supplied to the output terminal. The circuit has reduced noise figure degradation as compared to known current steering circuits by controlling gain without dumping signal current directly to the supply and without changing the impedance at the output terminal. The circuit is particularly useful in the RF section of radio receivers and transmitters, such as in cellular phones.

Growing community of inventors

Sunnyvale, CA, United States of America

Keng Leong Fong