Mediatek Corporation

Hyperband Communication, Inc.

Koninklijke Philips Corporation N.v.

Uniband Electronic Corp.

Hyperband Communications, Inc.

Hongyu Li

Chieh-Yuan Chao

Yiping Fan

Kanyu Cao

Syang-Myau Hwang

Sifen Luo

Chen-Yi Chang

Abolfazl Khosrowbeygi

Tung-Shan Chen

A spread spectrum receiver whose de-spreading process based on transformed spreading codes is provided. Instead of de-spreading with original spreading codes, this approach de-spreads received signal with the spreading codes transformed from the original codes in order to eliminate the negative impact of system impairments such as frequency offset to a spread spectrum receiver. Before de-spreading with the transformed code, the received signal goes through the same transformation as the original codes do. After a transformation, the transformed codes may exist some undesirable property such as spreading code having DC content. An approach is given to cancel unwanted side effects relating the transformed spreading codes. The approaches are very effective for spread spectrum system based on frequency modulation scheme such as MSK. For this kind of system, the frequency offset translates to DC offset after the transformation and the DC offset can be cancel since the DC property of the transformed spreading code is known in advance.

Receiver based method for de-spreading of spread spectrum signal

Fast settling circuits and methods designed to align input signal amplitude level and to remove DC offset voltages with minimal loss of low frequency signal in receiving analog circuits are disclosed. With the key innovative circuits and methods for signal peak alignment, the disclosed circuits and methods achieve fast settling without significant attenuation of the input signal. Peak aligning circuits and methods can be implemented along with conventional RC AC coupling circuits. In applying the aligning circuits and methods to differential signal pair, DC offsets can be easily removed.

Circuits and methods for fast-settling signal alignment and DC offset removal

In a spread spectrum system, methods and despreader architectures for despreading the received spreaded codes with the use of a single correlator and a single correlation code is provided. Before despreading the incoming received spreaded codes, a single correlation code is generated using a symbol from a set of symbols that has been mapped into a set of differential encoded PN codes. Despreading output samples for each received spreaded code are obtained by correlating the received spreaded code with this single correlation code. Correlation is accomplished by multiplying each received sample of the received spreaded codes with the correlation code samples and accumulating the products of this multiplication. After correlation, the index for the maximum or minimum peak of the despreading output samples for each code is identified. This index can then be mapped into a symbol corresponding to the transmitted information. Corresponding despreader architectures comprise of a number of taps attached to a series of shift registers. Received samples of each received spreaded codes are inputted into the shift registers. The despreader architectures accumulates the products of multiplication of the value of the shift register with a predetermined value associated with each tap to produce the despreading output samples of a received spreaded code. It identifies the despreading output index producing the maximum of the absolute value of the despreading output and maps said index into a symbol corresponding to the transmitted information.

Chip-to-symbol receiver despreader architectures and methods for despreading spread spectrum signals

The present invention provides methods and apparatuses for an amplifier circuit for amplifying an input signal. An amplifier circuit for amplifying an input signal comprises an amplifying transistor circuit having a power transistor and a dc bias circuit having a plurality of current mirror circuits and a discharge transistor wherein the discharge transistor and the power transistor form a combined current mirror circuit to control quiescent current in the power transistor.

RF amplifier with a bias boosting scheme

The present invention provides methods and apparatuses for a polyphase filter, comprising: a first and second cascoded differential amplifiers configured to receive a first and second differential signals, the first cascoded differential amplifier having a first resistor coupled between current legs of the first cascoded differential amplifier and the second cascoded differential amplifier having a first capacitor coupled between current legs of the second cascoded differential amplifier; and a third and fourth cascoded differential amplifiers configured to receive said first and said second differential signals, the third cascoded differential amplifier having a second resistor coupled between current legs of the third cascoded differential amplifier and the fourth cascoded differential amplifier having a second capacitor coupled between current legs of the fourth cascoded differential amplifier; wherein the first and second cascoded differential amplifiers are configured to provide a first differential output in response to the first and second differential signals and the third and fourth cascoded differential amplifiers are configured to provide a second differential output in response to the first and second differential signals.

Active polyphase filter

A fast-setting DC offset removal circuit with continuous cutoff frequency switching is disclosed. In the preferred embodiment, the circuit is implemented using a pair of RC filters for receiving a differential signal pair and a continuous, variable resistance control circuit. The control circuit can be current-controlled or voltage controlled to provide fast settling of the received signal and the removal of the DC offset components. Additionally, by using a current-controlled control circuit, the cutoff frequency of the RC filter can be ramped from high to low in a continuous manner, thereby minimizing the generation of DC offsets.

Fast-settling DC offset removal circuits with continuous cutoff frequency switching

The present invention is directed to advantages discovered in connection with controlling DC current passing between and adversely affecting cascaded current-mode blocks. According to a particular example application, the present invention includes first and second cascaded current-mode circuit blocks, and a circuit-replication and comparison block adapted to replicate the operation and output impedance of the first current-mode circuit block and to replicate the operation and input impedance of the second current-mode circuit block. This replication-comparison block includes a differential comparator adapted to detect and correct for a voltage differential corresponding to current passing from the first current-mode circuit block and the second current-mode circuit block. This approach can result in a number advantages relating to improvements in terms of various operational aspects including, for example, reductions in power consumption.

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Cupertino, CA, United States of America

Hongyu Li