Frequency translation and applications of same are described herein, including wireless local area network (WLAN) applications such as IEEE Standard 802.11 WLANs. Such applications include, but are not limited to, frequency down-conversion, frequency up-conversion, enhanced signal reception, unified down-conversion and filtering, and combinations and applications of same.

Wireless local area network (WLAN) technology and applications including techniques of universal frequency translation

A sigma-delta digital-to-analog converter (DAC) (40) receives oversampled input data representative of an analog signal. The data may be optionally interpolated to a higher rate in a interpolator (41). A noise-shaping sigma-delta modulator (42) is connected to the output of the interpolator (41). The output of the modulator (42) is provided to a finite impulse response (FIR) filter (43). The FIR filter (43) has a frequency response characteristic which reduces the shaped noise and aliased components. This noise has a tendency to intermodulate back into the DAC's passband. The FIR filter (43) uses a series of flip-flops (81, 82, 83) functioning as delay elements with well-controlled timing edges. The outputs of the flip-flops (81, 82, 83) control current sources (91, 92, 93) weighted according to corresponding filter coefficients. The outputs of the current sources (91, 92, 93) are then summed in a summing device such as an amplifier (101).

Sigma-delta digital-to-analog converter with reduced noise

Methods, systems, and apparatuses, and combinations and sub-combinations thereof, for down-converting and up-converting an electromagnetic (EM) signal are described herein. Briefly stated, in embodiments the invention operates by receiving an EM signal and recursively operating on approximate half cycles (½, 1½, 2½, etc.) of the carrier signal. The recursive operations can be performed at a sub-harmonic rate of the carrier signal. The invention accumulates the results of the recursive operations and uses the accumulated results to form a down-converted signal. In an embodiment, the EM signal is down-converted to an intermediate frequency (IF) signal. In another embodiment, the EM signal is down-converted to a baseband information signal. In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal. Up-conversion is accomplished by controlling a switch with an oscillating signal, the frequency of the oscillating signal being selected as a sub-harmonic of the desired output frequency.

Method and system for down-converting and up-converting an electromagnetic signal, and transforms for same

Methods and apparatuses for reducing DC offsets in a communication system are described. In a first aspect, a feedback loop circuit reduces DC offset in a wireless local area network (WLAN) receiver channel. The frequency response of the feedback loop circuit can be variable. In a second aspect, a circuit provides gain control in a WLAN receiver channel. First and second automatic gain control (AGC) amplifiers are coupled in respective portions of the receiver channel. Circuits for monitoring DC offset, and for providing control signals for controlling the frequency response of the DC offset reducing circuits are also provided.

Method and apparatus for reducing DC offsets in a communication system

A communication system comprising a multi-protocol, multi-bearer sub-system is described herein. The sub-system is a universal platform module that can transmit and receive one or more information signals in one or more protocols using one or more bearer services. In one embodiment, the sub-system may form a portion of a transceiver that is composed of a transmitter and a receiver, and which is a gateway server between a personal area network (PAN) and the global wireless network.

Universal platform module and methods and apparatuses relating thereto enabled by universal frequency translation technology

A combined finite impulse response filter and digital-to-analog converter for converting sigma-delta over-sampled data into analog form. The filter removes out-­of-band noise energy from the reconstructed analog signal resuting from the sigma-­delta encoding process. The filter/converter is implemented in switched-capacitor technology. Further, a method of designing the optimum number of taps and the tap weight coefficients of the filter is given.

Integral switched capacitor for filter/digital to analog converter for sigma-delta encoded digital audio

A technique for compensating for variations in a resistor set overall gain switched-capacitor circuits, such as high accuracy digital-to-analog converters. The variation in overall gain from the desired gain is due to the variation in the total capacitance of the capacitors, compared to the variation in the resistance of the resistor, in the circuit during manufacture. A bias circuit, with two reference voltage outputs, is adapted to have a capacitor and a fixed resistor vary one of the voltage references depending on the capacitance thereof. The voltage difference between the two voltage references varies the overall gain of the switched capacitor circuit to compensate for variations in the overall gain. Also, a switched-capacitor digital-to-analog converter utilizing the above technique is presented.

Jeffrey William Scott

Papers

Integral switched capacitor for filter/digital to analog converter for sigma-delta encoded digital audio

Technique for compensating switched capacitor circuits having gain-setting resistors

Integraler FIR Filter/Digital-Analog-Wandler mit geschalteten Kapazitäten für sigma-delta-kodierte digitale Audiosignale