Chunming Zhao

Author:

Chunming Zhao

ISBN #:

7508431782

US Patent:

8406113, Mar 26, 2013

Filed:

Oct 17, 2008

Appl. No.:

12/253635

Inventors:

Chunming Zhao - Chandler AZ, US
Ning Chen - Austin TX, US

Assignee:

Freescale Semiconductor, Inc. - Austin TX

International Classification:

H04J 5/04

US Classification:

370204, 370201, 370208, 375295, 375254, 375278, 375296, 375297

Abstract:

A wireless transmitter exhibits improved power de-rating reduction, which improves the power efficiency of non-constant envelop communication systems by mapping N first samples of a first discrete Fourier transform (DFT) of a group of coded symbols to M sub-carriers according to a first sub-carrier mapping rule (), performing a first inverse DFT (IDFT) on the M sub-carriers to provide M second samples (), clipping the M second samples according to a clipping rule to provide M third samples (), performing a second DFT on the M third samples (), and applying a frequency domain mask to generate M clipped samples () which may be mapped to O subcarriers according to a predetermined second subcarrier mapping rule. The transmitter may be advantageously implemented within a single carrier transmission scheme, such as a single carrier-frequency division multiple access (SC-FDMA) uplink transmission scheme.

US Patent:

20080019453, Jan 24, 2008

Filed:

Dec 11, 2006

Appl. No.:

11/588009

Inventors:

Chunming Zhao - Atlanta GA, US
Robert Baxley - Atlanta GA, US
Guotong Zhou - Atlanta GA, US

International Classification:

H04K 1/10

US Classification:

375260000

Abstract:

Disclosed is a constrained clipping technique for reducing the peak-to-average power ratio (PAR) or crest factor of a multicarrier communications signal. This is a transmitter-side processing technique that does not impose any modification at the receiver. Constrained clipping achieves PAR reduction while simultaneously satisfying spectral mask and error vector magnitude (EVM) constraints that are specified by most modern communications standards. The constrained clipping technique includes two independent processing units, one to satisfy an in-band EVM constraint and the other to satisfy an out-of-band spectral constraint. Achievable PAR reduction results vary depending on a particular standard's requirements, but by using constrained clipping on a QPSK WiMax signal with 256 subcarriers, for example, a 4.5 dB PAR reduction at the 10complementary cumulative distribution function (CCDF) level can be obtained.

US Patent:

20100113105, May 6, 2010

Filed:

Oct 31, 2008

Appl. No.:

12/262943

Inventors:

Bing Xu - Gilbert AZ, US
Mahibur Rahman - Chandler AZ, US
Chunming Zhao - Chandler AZ, US

Assignee:

FREESCALE SEMICONDUCTOR, INC. - Austin TX

International Classification:

H04B 1/38
H01Q 11/12
H04B 1/16

US Classification:

455572, 4551272, 4553431

Abstract:

Embodiments include methods and apparatus for performing transmit power control. A gain application element receives a sequence of digital input samples and a digital gain signal, and combines the digital gain signal with the digital input samples to generate a sequence of gain-compensated digital samples. A power amplifier receives and amplifies an analog version of the gain-compensated digital samples in order to generate an antenna output signal. A feedback path generates an analog feedback signal from the antenna output signal, produces a sequence of digital feedback samples from the analog feedback signal, and generates difference values based on the digital feedback samples. When a specified type of constant modulus symbol is represented in the antenna output symbol, the feedback path accumulates the difference values into an accumulated error value, and produces the digital gain signal from the accumulated error value.

US Patent:

20110299644, Dec 8, 2011

Filed:

Jun 8, 2010

Appl. No.:

12/796229

Inventors:

Bing Xu - Gilbert AZ, US
Chunming Zhao - Tempe AZ, US

International Classification:

H03D 3/24
H03L 7/00

US Classification:

375376, 331 15

Abstract:

A method may include synchronizing an output of a phase-locked loop to a signal received at its input. The method may further include suppressing emission at a potentially problematic channel by applying at least one of a first gain and a first resistance of the phase-locked loop for a communication at the potentially problematic channel, wherein at least one of the first gain and the first resistance are different from a second gain and a second resistance applied for communications at channels other than potentially problematic channels.