Patents by Inventor Raghu Challa

Raghu Challa 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: 6950841
    Abstract: In one embodiment, the invention is directed toward techniques for generating results in a logarithmic domain. The techniques may exploit properties of a logarithmic function to reduce the memory requirements needed to implement lookup tables. For example, the techniques may utilize non-uniform sampling over a logarithmic or logarithmic-like function to reduce the number of entries needed for a given lookup table. In particular, the techniques may involve separating a number into an exponent component and a mantissa component. Each of these different components can then be converted from a first domain to a second domain using different lookup tables.
    Type: Grant
    Filed: September 14, 2001
    Date of Patent: September 27, 2005
    Assignee: Qualcomm Incorporated
    Inventors: Raghu Challa, Nagabhushana Sindhushayana, Arun Raghupathy
  • Patent number: 6912244
    Abstract: Techniques to acquire the frequency of a signal instance based on a window of data samples covering a time period shorter than the time needed to achieve frequency lock. The window of data samples is initially captured and stored to a sample buffer. A segment of data samples is then retrieved from the sample buffer for processing. The retrieved data samples are rotated by a current frequency error estimate to provide frequency-translated data samples, which are further processed to provide one or more pilot symbols. An updated frequency error estimate for the frequency-translated data samples is then derived based on the pilot symbols using a frequency control loop. The window of data samples is processed for a number of iterations until frequency acquisition is achieved for the signal instance or termination is reached. For each iteration, one segment is processed at a time and typically in sequential order.
    Type: Grant
    Filed: January 30, 2003
    Date of Patent: June 28, 2005
    Assignee: Qualcomm Inc.
    Inventors: Raghu Challa, Mark Charles Roh, Shimman Patel
  • Patent number: 6813478
    Abstract: Techniques to search for a gated pilot reference in a wireless communication system. In one method, an overall code space in which the pilot may be found is partitioned into a number of groups of code sets, with each code set representative of all possible chip offsets of a specific PN sequence. The groups are ordered based on the likelihood of detecting the pilot in each of the groups. The groups of code sets are then used to search for the pilot, one group at a time, starting with the group most likely to result in successful pilot acquisition and ending with the group least likely to result in successful pilot acquisition. The search is terminated upon successful acquisition. The pilot search may be performed using detect, dwell, and pull-in substages. The detect substage for one group may be performed in parallel with the pull-in substage for another group.
    Type: Grant
    Filed: May 1, 2001
    Date of Patent: November 2, 2004
    Assignee: Qualcomm Inc
    Inventors: Serguei A. Glazko, Peter J. Black, Raghu Challa
  • Publication number: 20040184569
    Abstract: The invention is directed toward a digital VGA that is implemented in the logarithmic domain. The digital VGA exploits logarithmic properties to replace a complex multiplier of a conventional digital VGA with a simple and inexpensive adder. Moreover, additional techniques are described to significantly reduce the size of one or more lookup tables (LUTs) implemented within the digital VGA. In this manner, the invention can realize a simple, low cost digital VGA.
    Type: Application
    Filed: January 30, 2004
    Publication date: September 23, 2004
    Inventors: Raghu Challa, Nitin Kasturi, Nikolai Schlegel
  • Publication number: 20040110525
    Abstract: Systems and techniques for controlling transmission power involve receiving a first to second channel power ratio, receiving a first to second channel power ratio, adjusting the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and computing gain of the first channel as a function of the power ratio.
    Type: Application
    Filed: June 16, 2003
    Publication date: June 10, 2004
    Inventors: Peter J. Black, Nagabhushana Sindhushayana, Raghu Challa, Rashid Attar
  • Patent number: 6748201
    Abstract: Systems and techniques for gain control include amplifying a signal with an amplifier having a gain represented by one of a plurality of gain curves depending on a value of a parameter, the signal being amplified at a first one of the parameter values, and controlling the gain of the amplified signal from a predetermined gain curve relating to the gain curve of the amplifier for a second one of the parameter values by adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of the first one of the parameter values, and applying the adjusted gain control signal to the amplifier. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure.
    Type: Grant
    Filed: March 28, 2002
    Date of Patent: June 8, 2004
    Assignee: Qualcomm Inc.
    Inventors: Peter J. Black, Nagabhushana Sindhushayana, Raghu Challa, Kevin Seltmann
  • Patent number: 6707865
    Abstract: The invention is directed toward a digital VGA that is implemented in the logarithmic domain. The digital VGA exploits logarithmic properties to replace a complex multiplier of a conventional digital VGA with a simple and inexpensive adder. Moreover, additional techniques are described to significantly reduce the size of one or more lookup tables (LUTs) implemented within the digital VGA. In this manner, the invention can realize a simple, low cost digital VGA.
    Type: Grant
    Filed: September 14, 2001
    Date of Patent: March 16, 2004
    Assignee: Qualcomm Incorporated
    Inventor: Raghu Challa
  • Patent number: 6704555
    Abstract: According to a disclosed embodiment, a receiver comprising a digital rotator in combination with a frequency error discriminator in a digital automatic frequency control loop is used to arrive at accurate digital values used to calibrate a local oscillation frequency. A frequency error in the oscillation frequency of a local frequency generation loop causes a change in the baseband input signal frequency. The change in the baseband input signal frequency related to the frequency error in the local frequency generation loop can be detected as a phase rotation by the frequency error discriminator. By using the digital automatic frequency control loop, the frequency error introduced by the local frequency generation is determined with accuracy. The frequency error and corresponding control bits are entered into a calibration table. The calibration table may be used to adjust the local oscillation frequency for temperature changes, pilot frequency searching, and quick paging.
    Type: Grant
    Filed: March 12, 2001
    Date of Patent: March 9, 2004
    Assignee: Qualcomm, Incorporated
    Inventors: Gilbert C. Sih, Raghu Challa
  • Patent number: 6700922
    Abstract: A spread spectrum wireless device (100) may include a receiver (110), a searcher (128), a search controller (130) and other features. The search controller (130) selectively generates control signals to control the searcher (128), which searches for a spread-spectrum signal. In one embodiment, the architecture of the searcher (128) is dynamically configurable by the search controller (130) to selectively search multiple channels using multiple frequency bins for the signal.
    Type: Grant
    Filed: April 30, 2003
    Date of Patent: March 2, 2004
    Inventors: Raghu Challa, Farrokh Abrishamkar, Ian Fevrier, Serguei Glazko, Way-Shing Lee, Christopher Patrick, Gil Sih
  • Publication number: 20030193992
    Abstract: A spread spectrum wireless device (100) may include a receiver (110), a searcher (128), a search controller (130) and other features. The search controller (130) selectively generates control signals to control the searcher (128), which searches for a spread-spectrum signal. In one embodiment, the architecture of the searcher (128) is dynamically configurable by the search controller (130) to selectively search multiple channels using multiple frequency bins for the signal.
    Type: Application
    Filed: April 30, 2003
    Publication date: October 16, 2003
    Inventors: Raghu Challa, Farrokh Abrishamkar, Ian Fevrier, Serguei Glazko, Way-Shing Lee, Christopher Patrick, Gil Sih
  • Publication number: 20030186665
    Abstract: Systems and techniques for gain control include amplifying a signal with an amplifier having a gain represented by one of a plurality of gain curves depending on a value of a parameter, the signal being amplified at a first one of the parameter values, and controlling the gain of the amplified signal from a predetermined gain curve relating to the gain curve of the amplifier for a second one of the parameter values by adjusting a gain control signal corresponding to a point on the predetermined gain curve as a function of the first one of the parameter values, and applying the adjusted gain control signal to the amplifier. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure.
    Type: Application
    Filed: March 28, 2002
    Publication date: October 2, 2003
    Inventors: Peter J. Black, Nagabhushana Sindhushayana, Raghu Challa, Kevin Seltmann
  • Patent number: 6608858
    Abstract: A method and apparatus for frequency tracking is described. The present invention provides a tracking mechanism for removing the effects of error due to frequency offset as well as compensation for frequency error due to doppler in a plurality of multipath signals. Each finger of a RAKE receiver utilizing the present invention will compute a frequency error for that finger. The weighted average of all of these frequency errors is calculated and filtered to provide a control signal for varying the frequency of IF and RF frequency synthesizers, accounting for the common frequency offset seen at each finger. Additionally, each finger is equipped with a rotator for providing frequency adjustment specific to that finger. The frequency of each finger is adjusted through feedback of the frequency error for that finger.
    Type: Grant
    Filed: January 26, 2000
    Date of Patent: August 19, 2003
    Assignee: Qualcomm Incorporated
    Inventors: Gilbert C. Sih, Avneesh Agrawal, Mark Roh, Brian K. Butler, Raghu Challa
  • Publication number: 20030144020
    Abstract: Various techniques for improving a wireless communication device are described. The techniques may include reducing power in a wireless communication device for a first sleep period and then increasing power in the wireless communication device for an intermediate wake period after the first sleep period to estimate an error of the sleep clock. The method may further include reducing power in the wireless communication device for a second sleep period after the intermediate wake period. The intermediate wake mode implemented during the intermediate period can be used to estimate the error of the sleep clock without performing one or more tasks associated with an awake mode, such as demodulation. The techniques may facilitate the effective use of low frequency low power clocks for sleep mode, even when relatively large slot cycles are defined within a slotted paging system.
    Type: Application
    Filed: July 26, 2002
    Publication date: July 31, 2003
    Inventors: Raghu Challa, Baaziz Achour, Robbin D. Hughes
  • Publication number: 20030143951
    Abstract: Techniques to acquire the frequency of a signal instance based on a window of data samples covering a time period shorter than the time needed to achieve frequency lock. The window of data samples is initially captured and stored to a sample buffer. A segment of data samples is then retrieved from the sample buffer for processing. The retrieved data samples are rotated by a current frequency error estimate to provide frequency-translated data samples, which are further processed to provide one or more pilot symbols. An updated frequency error estimate for the frequency-translated data samples is then derived based on the pilot symbols using a frequency control loop. The window of data samples is processed for a number of iterations until frequency acquisition is achieved for the signal instance or termination is reached. For each iteration, one segment is processed at a time and typically in sequential order.
    Type: Application
    Filed: January 30, 2003
    Publication date: July 31, 2003
    Inventors: Raghu Challa, Mark Charles Roh, Shimman Patel
  • Publication number: 20030142734
    Abstract: Techniques for deriving interpolated pilot symbols for a gated pilot in a wireless (e.g., IS-856, cdma2000, or W-CDMA) communication system. In one method, first and second recovered pilot symbols for first and second time instances, respectively, are initially obtained (e.g., derived based on pilot bursts for the gated pilot). A phase change induced in the received signal at a third time instance between the first and second time instances is estimated. First and second phase-rotated symbols are next derived based on the first and second recovered pilot symbols and the estimated induced phase change. Interpolated pilot symbols between the first and third time instances are then derived (e.g., using linear interpolation) based on the first recovered pilot symbol and the first phase-rotated symbol. Similarly, interpolated pilot symbols between the third and second time instances are derived based on the second phase-rotated symbol and the second recovered pilot symbol.
    Type: Application
    Filed: January 31, 2002
    Publication date: July 31, 2003
    Inventors: Peter J. Black, Raghu Challa
  • Publication number: 20030137996
    Abstract: Systems and techniques are disclosed detecting an embedded signal which includes producing a plurality of first correlated values from a portion of the first signal and a second signal, transforming the first correlation values into a plurality of second correlation values related to a frequency content of the first correlation values, and searching for the embedded signal by evaluating the second correlation values. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.
    Type: Application
    Filed: January 24, 2002
    Publication date: July 24, 2003
    Inventors: Mark Roh, Raghu Challa, Serguei A. Glazko
  • Patent number: 6594501
    Abstract: Systems and techniques for controlling transmission power involve receiving a first to second channel power ratio, receiving a first to second channel power ratio, adjusting the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and computing gain of the first channel as a function of the power ratio. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.
    Type: Grant
    Filed: March 20, 2002
    Date of Patent: July 15, 2003
    Assignee: Qualcomm Incorporated
    Inventors: Peter J. Black, Nagabhushana Sindhushayana, Raghu Challa, Rashid Attar
  • Publication number: 20030112856
    Abstract: Systems and techniques are disclosed wherein a gated pilot signal can be acquired by producing a plurality of product values for each of a first and second signal and a generated signal, coherently combining portions of the product values produced from the first signal and noncoherently combining those coherently combined portions to produce a first value, coherently combining portions of the product values produced from the second signal and noncoherently combining those coherently combined portions to produce a second value, and noncoherently combining the first and second values. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.
    Type: Application
    Filed: March 28, 2002
    Publication date: June 19, 2003
    Inventors: Raghu Challa, Rao Yallapragada
  • Publication number: 20030114180
    Abstract: Systems and techniques for controlling transmission power involve receiving a first to second channel power ratio, receiving a first to second channel power ratio, adjusting the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and computing gain of the first channel as a function of the power ratio. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.
    Type: Application
    Filed: March 20, 2002
    Publication date: June 19, 2003
    Inventors: Peter J. Black, Nagabhushana Sindhushayana, Raghu Challa, Rashid Attar
  • Patent number: 6580746
    Abstract: A spread spectrum wireless device (100) may include a receiver (110), a searcher (128), a search controller (130) and other features. The search controller (130) selectively generates control signals to control the searcher (128), which searches for a spread-spectrum signal. In one embodiment, the architecture of the searcher (128) is dynamically configurable by the search controller (130) to selectively search multiple channels using multiple frequency bins for the signal.
    Type: Grant
    Filed: August 28, 2001
    Date of Patent: June 17, 2003
    Assignee: Qualcomm Incorporated
    Inventors: Raghu Challa, Farrokh Abrishamkar, Ian Fevrier, Serguei Glazko, Way-Shing Lee, Christopher Patrick, Gil Sih