Yun Zhang

6590962, Jul 8, 2003

Jun 21, 2000

09/598595

David J. Groessl - Vernon Hills IL
Kurt E. Schmidt - Burlington WI
Yun Zhang - Wheeling IL

Teradyne, Inc. - Boston MA

H04M 124

379 1401, 379 101, 379 1505, 379 2203, 379 2903, 324512, 324522, 324525

A method and apparatus to non-interactively test telephone networks and more specifically to localize faults such as resistive faults in the subscriber loop of the telephone network is presented. The method and apparatus determine whether the fault is in the tip line or ring line of a phone line. The existence of a fault voltage, if any, is also determined. The resistance of the tip line to ground and the resistance of the ring line to ground is measured. A fault resistance is calculated from this information, from which the location of the fault is determined.

8363853, Jan 29, 2013

Feb 23, 2007

11/710019

Sunil Bharitkar - Los Angeles CA, US
Yun Zhang - Santa Ana CA, US
Chris Kyriakakis - Altadena CA, US

Audyssey Laboratories, Inc. - Los Angeles CA

H03G 5/00

381103, 381 7112, 381 941, 381 943, 381 98, 37940612, 37940613, 37940614

A method for determining coefficients of a family of cascaded second order Infinite Impulse Response (IIR) parametric filters used for equalizing a room response. The method includes determining parameters of each IIR parametric filter from poles or roots of a reasonably high-order Linear Predictive Coding (LPC) model. The LPC model is able to accurately model the low-frequency room response modes providing better equalization of loudspeaker and room acoustics, particularly at the low frequencies. Advantages of the method include fast and efficient computation of the LPC model using a Levinson-Durbin recursion to solve the normal equations that arise from the least squares formulation. Due to possible band interactions between the cascaded IIR parametric filters, the method further includes optimizing the Q value of each filter to better equalize the room response.

58811303, Mar 9, 1999

Sep 15, 1997

8/929842

Yun Zhang - Wheeling IL

Teradyne, Inc. - Boston MA

H04M 124
G01R 2708
G01R 3108

379 6

Method and apparatus for detecting whether load coils are attached to a telephone line. A stimulus waveform having multiple frequency components is applied to the line. The current and voltage at the near end of the line are coherently sampled and transformed to the frequency domain. The frequency spectra are used to compute auto and cross power spectra of the current and voltage. These power spectra are then used to compute the impedance on the line as well as a coherence function that indicates the extent to which the computed impedance was influenced by noise. If the coherence values indicate that the computed impedance is sufficiently reliable, load coils are detected by finding peaks in the magnitude of the impedance function or sign changes in the phase of the impedance function. Calibration, offset adjustments and ensemble smoothing are used to increase the accuracy of the results. The computation is fast because computing the spectra avoids the need for individual measurements at multiple frequencies.