Patents by Inventor Sheldon Xu

Sheldon Xu has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 7248111
    Abstract: A power amplifier with a multi-mode digital bias control circuit is provided. The power amplifier utilizes a complementary reference voltage generation circuit and a bias current-control circuit to generate a plurality of bias current levels for different output power levels. In an embodiment of the present invention, the power amplifier circuit is connected to a reference voltage and two control signals. Depending on the desired output power level, the control signals set the corresponding bias current in the amplifying transistors, to ensure sufficient linearity. The power amplifier is capable of operating at a very low quiescent current level, for example, 5 mA. As a result, a significant improvement in the power amplifier's overall efficiency is achieved, and the battery talk time of a wireless communication device is increased. The invention finds application in wireless communication devices such as CDMA, WCDMA, EDGE and WLAN mobile devices.
    Type: Grant
    Filed: April 14, 2005
    Date of Patent: July 24, 2007
    Assignee: Anadigics, Inc
    Inventors: Sheldon Xu, Thomas William Arell, Mahendra Singh, Mohammed Ali Khatibzadeh
  • Patent number: 6759922
    Abstract: The present invention discloses a miniature high directivity multi-band coupled-line coupler for RF power amplifier module application. The coupler utilizes a three-coupled-line structure, with a first RF line designated coupled line for the GSM 900 MHZ band, a second RF line designated coupled line for the DCS/PCS 1800/1900 MHZ band, and a common coupled line. A first capacitor is connected between the center of the first line and the center of the common line and a second capacitor is connected between the center of the second line and the center of the common line. The coupler has a length considerably less than the length of a quarter wave length coupler while achieving directivity requirements for both GSM band and DCS/PCS band.
    Type: Grant
    Filed: May 20, 2002
    Date of Patent: July 6, 2004
    Assignee: Anadigics, Inc.
    Inventors: Aharon Adar, Sheldon Xu
  • Publication number: 20030214365
    Abstract: The present invention discloses a miniature high directivity multi-band coupled-line coupler for RF power amplifier module application. The coupler utilizes a three-coupled-line structure, with a first RF line designated coupled line for the GSM 900 MHZ band, a second RF line designated coupled line for the DCS/PCS 1800/1900 MHZ band, and a common coupled line. A first capacitor is connected between the center of the first line and the center of the common line and a second capacitor is connected between the center of the second line and the center of the common line. The coupler has a length considerably less than the length of a quarter wave length coupler while achieving directivity requirements for both GSM band and DCS/PCS band.
    Type: Application
    Filed: May 20, 2002
    Publication date: November 20, 2003
    Inventors: Aharon Adar, Sheldon Xu