Li Dan Liu

US Patent:

7539458, May 26, 2009

Filed:

Oct 23, 2006

Appl. No.:

11/584831

Inventors:

Hamid Jafarkhani - Irvine CA, US
Li Liu - Aliso Viejo CA, US

Assignee:

The Regents of the University of California - Oakland CA

International Classification:

H04B 1/00
H04B 15/00

US Classification:

455 631, 455 6711, 455 6716, 455 69, 455 91, 343368, 343754, 343753

Abstract:

A multiple antenna wireless system including a transmitter and a receiver comprises a reconfigurable large antenna array having a plurality of antennas. A plurality of RF chains in the transmitter is coupled to the reconfigurable large antenna array. A pilot assisted round robin channel estimation means tracks the fading channel; and an adaptive round robin transmit beamforming means beam forms the reconfigurable large antenna array. A method for multiple antenna wireless communication comprising the steps of tracking a plurality of fading channels in a reconfigurable large antenna array having a plurality of antennas using pilot assisted round robin channel estimation to selectively couple a plurality of RF chains in the transmitter to the reconfigurable large antenna array, and adaptively, round-robin transmit beamforming the reconfigurable large antenna array.

US Patent:

7599419, Oct 6, 2009

Filed:

Jan 12, 2006

Appl. No.:

11/332019

Inventors:

Hamid Jafarkhani - Irvine CA, US
Li Liu - Aliso Viejo CA, US

Assignee:

The Regents of the University of California - Oakland CA

International Classification:

H04B 1/00

US Classification:

375137, 375135, 375229, 375261, 375265, 375267

Abstract:

A method for multiple-input-multiple-output (MIMO) wireless communication comprises the steps of generating inner and outer codes based on channel state information available at a transmitter and concatenating different inner codes with different outer codes; and using the generated concatenated inner and outer codes for wireless communication. The inner and outer codes are based on channel phase information at the transmitter or channel feedback. High-performance trellis codes or block codes for use in cellular networks are illustratively described. The space-time trellis codes are generated by set partitioning on a plurality of classes of signal designs to generate a series of inner codes, each of the series of inner codes being optimized by channel phase feedback, and concatenating each inner code with a multiple trellis coded modulated outer code to provide a complete space-time trellis code as a cophase space-time trellis code.

US Patent:

7656229, Feb 2, 2010

Filed:

Jan 28, 2008

Appl. No.:

12/021061

Inventors:

Junxiong Deng - San Diego CA, US
Li Liu - San Diego CA, US
Prasad S. Gudem - San Diego CA, US

Assignee:

QUALCOMM, Incorporated - San Diego CA

International Classification:

H03F 3/38

US Classification:

330149, 375296

Abstract:

An electronic device includes an amplifier circuit coupled to a linearizer. The amplifier circuit may receive a first input signal including first and second frequencies and generate a first output signal including a delta frequency signal at a delta frequency, which is the difference between the first frequency and the second frequency. The linearizer includes a signal detector circuit, a current-mirror circuit, a low pass filter, a phase shifter, and a bias circuit. The signal detector circuit may generate a second output signal. The current-mirror circuit may adjust an amplitude of a signal. The low pass filter may eliminate a portion of the second output signal having frequencies greater than the delta frequency. The phase shifter may generate a feedback signal corresponding to the delta frequency signal. An amplitude and/or a phase of the feedback signal is different from an amplitude and/or a phase of the delta frequency signal.

US Patent:

7692486, Apr 6, 2010

Filed:

Oct 5, 2007

Appl. No.:

11/868159

Inventors:

Mahim Ranjan - La Jolla CA, US
Li Liu - San Diego CA, US

Assignee:

QUALCOMM, Incorporated - San Diego CA

International Classification:

H03F 1/08

US Classification:

330 86, 330293, 330291

Abstract:

An amplifier is disclosed that includes configurable feedback based on the output of a received signal strength indicator. The feedback may be increased for high received signal levels, and decreased for low received signal levels. In an embodiment, the configurable impedance may comprise a plurality of discrete impedance settings. Amplitude and/or time hysteresis may be incorporated.

US Patent:

7912142, Mar 22, 2011

Filed:

Apr 4, 2008

Appl. No.:

12/062650

Inventors:

Jun Ma - Irvine CA, US
Nabil Yousef - Foothill Ranch CA, US
Li Liu - Aliso Viejo CA, US

Assignee:

Newport Media, Inc. - Lake Forest CA

International Classification:

H04B 15/00

US Classification:

375285, 375267, 375346, 375347

Abstract:

An apparatus, method, and system for reducing a C/N in an OFDM receiver using diversity combining techniques in the presence of ICI, wherein the apparatus comprises an encoded data estimator adapted to estimate data received in the OFDM receiver; a pair of ICI estimators operatively connected to the encoded data estimator and adapted to calculate an inter-carrier-interference term of the data; and a pair of diversity combining equalizers adapted to compensate multi-path interference of the data, wherein a first one of the diversity combining equalizers is operatively connected to the encoded data estimator, and a second one of the diversity combining equalizers is operatively connected to the pair of ICI estimators. The diversity combining equalizer may comprise a MRC diversity combining equalizer. Preferably, the encoded data estimator, the pair of ICI estimators, and the pair of diversity combining equalizers are implemented on a DVB-T/H diversity SoC.

US Patent:

8035447, Oct 11, 2011

Filed:

Aug 21, 2007

Appl. No.:

11/842712

Inventors:

Li Liu - San Diego CA, US
Prasad S. Gudem - San Diego CA, US

Assignee:

QUALCOMM, Incorporated - San Diego CA

International Classification:

H03F 1/26

US Classification:

330149, 330254

Abstract:

Active circuits with active loads linearized via distortion cancellation are described. In one design, an apparatus includes a first stage and a load stage. For an amplifier, the first stage amplifies an input signal and provides an output signal having a larger signal level. For a mixer, the first stage mixes an input signal with an LO signal and provides an output signal. The load stage provides an active load for the first stage and is linearized by canceling distortion generated by the active load. In one design, the load stage includes a first transistor that provides the active load and generates distortion due to its nonlinearity. The load stage further includes at least one transistor that generates a replica of the distortion from the first transistor. The distortion replica is used to cancel the distortion from the first transistor. The first stage may also be linearized with distortion cancellation.

US Patent:

8253506, Aug 28, 2012

Filed:

Oct 5, 2010

Appl. No.:

12/897918

Inventors:

Li Liu - San Diego CA, US
Chiewcharn Narathong - San Diego CA, US

Assignee:

QUALCOMM, Incorporated - San Diego CA

International Classification:

H03C 3/22
H03L 1/02

US Classification:

331177V, 331 36 C, 331117 R, 331176

Abstract:

A resonator of a VCO includes a fine tuning main varactor circuit, an auxiliary varactor circuit, and a coarse tuning capacitor bank circuit coupled in parallel with an inductance. The main varactor circuit includes a plurality of circuit portions that can be separately disabled. Within each circuit portion is a multiplexing circuit that supplies a selectable one of either a fine tuning control signal (FTAVCS) or a temperature compensation control signal (TCAVCS) onto a varactor control node within the circuit portion. If the circuit portion is enabled then the FTAVCS is supplied onto the control node so that the circuit portion is used for fine tuning. If the circuit portion is disabled then the TCAVCS is supplied onto the control node so that the circuit portion is used to combat VCO frequency drift as a function of temperature. How the voltage of the TCAVCS varies with temperature is digitally programmable.

US Patent:

8294528, Oct 23, 2012

Filed:

Dec 28, 2010

Appl. No.:

12/979659

Inventors:

Guansheng Li - San Diego CA, US
Li Liu - San Diego CA, US
Yiwu Tang - San Diego CA, US

Assignee:

Qualcomm Incorporated - San Diego CA

International Classification:

H03B 5/12
H03K 3/30
H03C 3/22

US Classification:

331117FE, 331 36 C, 331 36 L, 331 76, 331112, 331177 V

Abstract:

A VCO includes a transformer-based resonator that has a first LC tank and a second LC tank. The resonator has an even resonant mode and an odd resonant mode. The VCO further includes an active transconductance network that is coupled to a two-terminal port of the first tank and is also coupled to a two-terminal port of the second tank. A first terminal of the port of the first tank is capacitively coupled to a first terminal of the port of the second tank. A second terminal of the port of the first tank is capacitively coupled to a second terminal of the port of the second tank. The active transconductance network causes the resonator to resonate in a selectable one of the even and odd resonant modes depending on a digital control signal. The VCO is fine tuned by changing the capacitances of capacitors of the tanks.