Patents by Inventor John Tsitsiklis

John Tsitsiklis 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: 7280626
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Grant
    Filed: September 6, 2006
    Date of Patent: October 9, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis
  • Publication number: 20070105502
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Application
    Filed: January 2, 2007
    Publication date: May 10, 2007
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Patent number: 7177614
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Grant
    Filed: December 31, 2002
    Date of Patent: February 13, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Patent number: 7164736
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: January 16, 2007
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis
  • Patent number: 7027534
    Abstract: Techniques are provided for fine-tuning estimates of a delay value for a sampled signal. One aspect of the invention is to perform, for the sampled signal, coarse-grained calculations of the In Phase and Quadrature (I and Q) correlation integrals at a limited number of points, wherein the calculations are performed over a range of hypothesized delay values. A range of delay values of interest are then determined from the coarse-grained calculations of the I and Q correlation integrals. A subset of I and Q values based on the coarse granularity calculations of the I and Q correlation functions is used to perform a time-domain interpolation to obtain fine-grained values of the I and Q integrals in the range of the delay values of interest. Magnitude calculations are performed based on the fine-grained values of the I and Q integrals. Fine-tuned estimates of delay value are based on the magnitude calculations. Alternatively, fine-tuned estimates of delay value are based on the template-matching approach.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: April 11, 2006
    Assignee: SiRF Technology, Inc.
    Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
  • Publication number: 20040174943
    Abstract: System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
    Type: Application
    Filed: December 31, 2002
    Publication date: September 9, 2004
    Applicant: SiRF Technology, Inc.
    Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
  • Publication number: 20030156665
    Abstract: Techniques are provided for fine-tuning estimates of a delay value for a sampled signal. One aspect of the invention is to perform, for the sampled signal, coarse-grained calculations of the In Phase and Quadrature (I and Q) correlation integrals at a limited number of points, wherein the calculations are performed over a range of hypothesized delay values. A range of delay values of interest are then determined from the coarse-grained calculations of the I and Q correlation integrals. A subset of I and Q values based on the coarse granularity calculations of the I and Q correlation functions is used to perform a time-domain interpolation to obtain fine-grained values of the I and Q integrals in the range of the delay values of interest. Magnitude calculations are performed based on the fine-grained values of the I and Q integrals. Fine-tuned estimates of delay value are based on the magnitude calculations. Alternatively, fine-tuned estimates of delay value are based on the template-matching approach.
    Type: Application
    Filed: June 22, 2001
    Publication date: August 21, 2003
    Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
  • Publication number: 20030156664
    Abstract: Techniques are provided for synthesizing a long coherent I and Q correlation integral at a particular frequency by synthetically combining a sequence of shorter correlation integrals at the same or different frequency. Techniques are also provided for acquiring a carrier-modulated signal with an unknown shift of the carrier frequency, and possibly some additional unknown signal parameters. These techniques involve synthesizing coherent correlation sums at a fine frequency resolution, using coherent correlation sums that are calculated at a coarse frequency resolution. This approach allows for coherent processing of the received signal over an arbitrarily long time interval, while avoiding the excessive computational requirements of traditional methods.
    Type: Application
    Filed: June 22, 2001
    Publication date: August 21, 2003
    Inventors: Anant Sahai, John Tsitsiklis
  • Patent number: 6535163
    Abstract: To determine the location of a signal receiver, sampled data received from a receiver is divided into data segments of increasing length. Current ranges for a delay value and for a modulation frequency value are calculated relative to each satellite signal source that is overhead the signal receiver. Using the data segments of increasing length, the current ranges, estimates for the delay value and for the modulation frequency value are then iteratively calculated and updated. For each signal source, I and Q correlation integrals and their magnitude values are calculated using the modulation frequency value estimate and each of a range of delay values centered around the delay value estimate. The resulting magnitude-curve is interpolated using the calculated magnitude values. The location of the receiver is calculated using the shape of the magnitude-curve to represent the I and Q correlation integrals for each signal source.
    Type: Grant
    Filed: June 22, 2001
    Date of Patent: March 18, 2003
    Assignee: Enuvis, Inc.
    Inventors: Anant Sahai, John Tsitsiklis, Benjamin Van Roy, Andrew Chou, Wallace Mann, Jesse Robert Stone, Wungkum Fong
  • Patent number: 6525688
    Abstract: Some embodiments of the invention provide a location-determination system that includes several transmitters and at least one receiver. Each transmitter transmits a signal that includes a unique periodically-repeating component, and the receiver receives a reference signal. Based on the received reference signal, the location-determination system identifies an estimated location of the receiver as follows. For each transmitter in a set of transmitters, the system computes a phase offset between the received reference signal and a replica of the transmitter's periodically-repeating component. The system also identifies an approximate location of the receiver and an approximate receive time for the received signal. The system then uses the identified approximate location and time, and the computed phase offsets, to compute pseudoranges for the set of transmitters. Finally, the system identifies the estimated location of the receiver by using the computed pseudoranges.
    Type: Grant
    Filed: June 20, 2001
    Date of Patent: February 25, 2003
    Assignee: Enuvis, Inc.
    Inventors: Andrew Chou, Benjamin Van Roy, John Tsitsiklis
  • Patent number: 6525687
    Abstract: Some embodiments of the invention provide a location-determination system that includes a number of transmitters and at least one receiver. Based on a reference signal received by the receiver, this location-determination system identifies an estimated location of the receiver within a region. In some embodiments, the system selects one or more locations within the region. For each particular selected location, the system calculates a metric value that quantifies the similarity between the received signal and the signal that the receiver could expect to receive at the particular location, in the absence or presence of interference. Based on the calculated metric value or values, the system identifies the estimated location of the receiver.
    Type: Grant
    Filed: February 12, 2001
    Date of Patent: February 25, 2003
    Assignee: Enuvis, Inc.
    Inventors: Benjamin Van Roy, John Tsitsiklis, Andrew Chou
  • Publication number: 20020145557
    Abstract: Some embodiments of the invention provide a location-determination system that includes a number of transmitters and at least one receiver. Based on a reference signal received by the receiver, this location-determination system identifies an estimated location of the receiver within a region. In some embodiments, the system selects one or more locations within the region. For each particular selected location, the system calculates a metric value that quantifies the similarity between the received signal and the signal that the receiver could expect to receive at the particular location, in the absence or presence of interference. Based on the calculated metric value or values, the system identifies the estimated location of the receiver.
    Type: Application
    Filed: February 12, 2001
    Publication date: October 10, 2002
    Inventors: Benjamin Van Roy, John Tsitsiklis, Andrew Chou
  • Publication number: 20020097181
    Abstract: Some embodiments of the invention provide a location-determination system that includes several transmitters and at least one receiver. Each transmitter transmits a signal that includes a unique periodically-repeating component, and the receiver receives a reference signal. Based on the received reference signal, the location-determination system identifies an estimated location of the receiver as follows. For each transmitter in a set of transmitters, the system computes a phase offset between the received reference signal and a replica of the transmitter's periodically-repeating component. The system also identifies an approximate location of the receiver and an approximate receive time for the received signal. The system then uses the identified approximate location and time, and the computed phase offsets, to compute pseudoranges for the set of transmitters. Finally, the system identifies the estimated location of the receiver by using the computed pseudoranges.
    Type: Application
    Filed: June 20, 2001
    Publication date: July 25, 2002
    Inventors: Andrew Chou, Benjamin Van Roy, John Tsitsiklis