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: 7280626Abstract: 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: GrantFiled: September 6, 2006Date of Patent: October 9, 2007Assignee: SiRF Technology, Inc.Inventors: Anant Sahai, John Tsitsiklis
-
Publication number: 20070105502Abstract: 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: ApplicationFiled: January 2, 2007Publication date: May 10, 2007Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
-
Patent number: 7177614Abstract: 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: GrantFiled: December 31, 2002Date of Patent: February 13, 2007Assignee: SiRF Technology, Inc.Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
-
Patent number: 7164736Abstract: 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: GrantFiled: June 22, 2001Date of Patent: January 16, 2007Assignee: SiRF Technology, Inc.Inventors: Anant Sahai, John Tsitsiklis
-
Patent number: 7027534Abstract: 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: GrantFiled: June 22, 2001Date of Patent: April 11, 2006Assignee: SiRF Technology, Inc.Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
-
Publication number: 20040174943Abstract: 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: ApplicationFiled: December 31, 2002Publication date: September 9, 2004Applicant: SiRF Technology, Inc.Inventors: Nainesh Agarwal, Anant Sahai, John Tsitsiklis
-
Publication number: 20030156664Abstract: 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: ApplicationFiled: June 22, 2001Publication date: August 21, 2003Inventors: Anant Sahai, John Tsitsiklis
-
Publication number: 20030156665Abstract: 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: ApplicationFiled: June 22, 2001Publication date: August 21, 2003Inventors: Anant Sahai, John Tsitsiklis, Stefano Casadei, Andrew Chou, Benjamin Van Roy, Jesse Robert Stone
-
Patent number: 6535163Abstract: 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: GrantFiled: June 22, 2001Date of Patent: March 18, 2003Assignee: Enuvis, Inc.Inventors: Anant Sahai, John Tsitsiklis, Benjamin Van Roy, Andrew Chou, Wallace Mann, Jesse Robert Stone, Wungkum Fong
-
Patent number: 6525687Abstract: 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: GrantFiled: February 12, 2001Date of Patent: February 25, 2003Assignee: Enuvis, Inc.Inventors: Benjamin Van Roy, John Tsitsiklis, Andrew Chou
-
Patent number: 6525688Abstract: 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: GrantFiled: June 20, 2001Date of Patent: February 25, 2003Assignee: Enuvis, Inc.Inventors: Andrew Chou, Benjamin Van Roy, John Tsitsiklis
-
Publication number: 20020145557Abstract: 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: ApplicationFiled: February 12, 2001Publication date: October 10, 2002Inventors: Benjamin Van Roy, John Tsitsiklis, Andrew Chou
-
Publication number: 20020097181Abstract: 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: ApplicationFiled: June 20, 2001Publication date: July 25, 2002Inventors: Andrew Chou, Benjamin Van Roy, John Tsitsiklis