Dan Q Tu

US Patent:

6518802, Feb 11, 2003

Filed:

Jun 27, 2001

Appl. No.:

09/893054

Inventors:

Dan Q. Tu - San Diego CA

Assignee:

Webtv Networks, Inc. - Mountain View CA

International Classification:

H03B 2100

US Classification:

327106, 327119, 327129, 708275, 331 57

Abstract:

A numerically controlled oscillator that generates an accurate digital representation of a repeating waveform such as a sinusoidal wave. Based on the desired output frequency, multiple samples are calculated from multiple cycles of the repeating waveform. As samples are taken, they are stored in a memory location until a sufficient number of samples are accumulated. After the samples are accumulated, they are output in a specified order, which generates an accurate digital representation of a sinusoidal wave at the desired output frequency.

US Patent:

6888888, May 3, 2005

Filed:

Jun 26, 2001

Appl. No.:

09/892124

Inventors:

Dan Q. Tu - San Diego CA, US

Assignee:

Microsoft Corporation - Redmond WA

International Classification:

H03D003/02
H03D003/06

US Classification:

37524001, 3785322

Abstract:

Methods and systems for processing a single sub-channel that includes two or more combined channels. Using intermediate frequency sub-sampling, two or more channels from a broad band signal are combined into a single sub-channel for further analog and digital processing. Each of the two or more channels is down converted to an intermediate frequency, filtered to remove certain undesired channels, and combined such that the two or more channels are adjacent to each other. A digital representation of the sub-channel is produced from the combined intermediate frequency channels. Each channel within the digital representation is down converted to baseband, and the in-phase and quadrature components are separated from each other. Compared to one direct down conversion technique, intermediate frequency sub-sampling as described in the application may reduce the number of analog to digital converters and control amplifiers used in analog processing by a factor of four.

US Patent:

7664203, Feb 16, 2010

Filed:

Feb 14, 2005

Appl. No.:

11/058076

Inventors:

Dan Q. Tu - San Diego CA, US

Assignee:

Microsoft Corporation - Redmond WA

International Classification:

H03K 9/00

US Classification:

375316, 375243, 375254, 375261, 375268, 375270, 375271, 375277, 375278, 375284, 375285

Abstract:

Methods and systems for processing a single sub-channel that includes two or more combined channels. Using intermediate frequency sub-sampling, two or more channels from a broad band signal are combined into a single sub-channel for further analog and digital processing. Each of the two or more channels is down converted to an intermediate frequency, filtered to remove certain undesired channels, and combined such that the two or more channels are adjacent to each other. A digital representation of the sub-channel is produced from the combined intermediate frequency channels. Each channel within the digital representation is down converted to baseband, and the in-phase and quadrature components are separated from each other. Compared to one direct down conversion technique, intermediate frequency sub-sampling as described in the application may reduce the number of analog to digital converters and control amplifiers used in analog processing by a factor of four.

US Patent:

56404247, Jun 17, 1997

Filed:

May 16, 1995

Appl. No.:

8/442510

Inventors:

Noi N. Banavong - Corona CA
George Gomez - Montebello CA
Long Quoc Nguyen - Laguna Hills CA
Dan Q. Tu - San Diego CA

Assignee:

Interstate Electronics Corporation - Anaheim CA

International Classification:

H04L 2706

US Classification:

375316

Abstract:

A digital downconverter circuit for a digital data transmission system is provided, comprising (i) a bandpass filter circuit for filtering a received analog intermediate frequency (IF) carrier signal onto which baseband information has been modulated, and outputting a bandpass analog IF signal; (ii) an analog-to-digital converter for converting the bandpass analog IF signal into a bandpass digital IF signal; (iii) a phase shifter device for outputting a complex pair of phase shifted baseband signals operating at a local baseband frequency; (iv) a mixer device for mixing the bandpass digital IF signal separately with each of the complex pair of phase shifted baseband signals and outputting a complex combined baseband/bandpass signal comprising inphase and quadrature components; (v) filtering circuitry for recovering the baseband information onto the phase shifted baseband signals; and (vi) sampling circuitry for sampling the information-bearing recovered baseband signals and outputting a sampled complex baseband output signal. The phase shifter device, the mixer device, the filtering circuitry, and the sampling circuitry are all implemented on a gallium arsenide (GaAs) application specific integrated circuit (ASIC). The filtering circuitry includes a single half-band pre-filter and a multi-pole low pass filter.