Ami Semiconductor, Inc.

Ga-tek, Inc.

Andrei R Petrov

Craig L Christensen

Kenneth L Reinhard

Jeremy J Rice

Shane A Blanchard

A direct conversion circuit that includes an in-phase and quadrature-phase feedback path that reduces Direct Current (DC) offset. Each feedback path includes a compensating mixer that generates an error correction voltage that is passed through a loop gain circuit and an integrator. The integrated signal is applied to the output of a low pass filter that operates on the down-converted baseband signal. The direction conversion circuit may not only down convert the received modulated signal using a down-converting mixer into a baseband signal, but also, after performing a passive low pass filtering to remove higher-order components, performs up-conversion of the baseband signal using an up-converting mixer. This allows active elements operating on the up-converted signal to introduce less 1/f noise.

Direct conversion receiver with direct current offset correction circuitry

A direct conversion circuit that not only down-converts the received modulated signal using a down-converting mixer into a baseband signal, but also, after performing a passive low pass filtering to remove higher-order components, performs up-conversion of the baseband signal using an up-converting mixer. Active elements such as highly sensitive amplifiers do not operate on the baseband signal itself, but on the up-converted version of that baseband signal, thereby reducing the 1/f noise introduced by those active elements. The downstream circuitry after the up-conversion may be coupled by intervening capacitors since the downstream circuitry is operating on a higher frequency signal. Accordingly, the DC offset introduced by the downstream active elements is reduced.

Up-conversion of a down-converted baseband signal in a direct conversion architecture without the baseband signal passing through active elements

A receiver circuit that includes a direct conversion receiver that receives a modulated signal, and generates an in-phase differential signal and a quadrature-phase differential signal. The receiver circuit includes an in-phase branch that processes the in-phase differential signal, and a quadrature-phase branch that processes the quadrature-phase differential signal. Each branch includes an amplifier and a summer. The amplifier is configured to receive and amplify the respective in-phase or quadrature-phase differential signal. The summer receives the resulting amplified differential signal and sums the signals to generate a single signal. A log amplifier receives the summed in-phase and quadrature-phase signal, and generates an RSSI signal that is proportional to the log of the difference between the two summed signals. The data may then be extracted based on the amplitude of the RSSI signal.

Direct conversion receiver for amplitude modulated signals using linear/log filtering

A diversity receiver circuit that adaptively selects a variable number of one or more antennas for use in improving signal quality. Each antenna is provided its own receiver that each generates a representation of a received signal. This adaptive selection offers high dynamic adaptability in using the appropriate antennas and receivers at the appropriate time to thereby improving signal-to-noise ratio. The receivers may be direct conversion receivers that implement up-conversion of the baseband signal to reduce DC offset and 1/f noise characteristic of direct conversion architectures.

Adaptive diversity receiver architecture

Amplitude detection of a baseband electrical signal. The detection may be performed by performing full wave rectification on both an in-phase portion of the electrical signal, as on a quadrature-phase portion of the electrical signal. The output signal may be generated by summing the rectified in-phases signal and the rectified quadrature-phase signal. The peak amplitude of the output signal may then be used to determine the amplitude of the original baseband signal.

Absolute value amplitude baseband detector

A direct conversion receiver is disclosed that converts RF signal into corresponding quadrature baseband signals without requiring conversion through an intermediate frequency. The direct conversion receiver abates local oscillator leakage, increases dynamic range and increases RF selectivity as compared to conventional direct conversion circuits. The circuit includes an in-phase branch and a quadrature-phase branch, each branch including two mixers instead of the conventional one. Each mixer is provided with balanced control signals that include a primary control signal and a complementary control signal. For each branch, the signals from the mixer pass through an operational amplifier and a low pass filter to extract the corresponding baseband signal component.

Structures and methods for direct conversion from radio frequency modulated signals to baseband signals

A phase shift keyed carrier recovery and demodulator circuit which includes a phase detector and subsequent feedback control loop circuitry which maintains an initial phase relationship. By comparing an incoming phase modulated carrier with the multiple phase outputs of a local oscillator, the circuit is able to generate a correcting signal which allows coherent phase tracking of the incoming phase modulated carrier. The phase detector produces a correction signal which allows the circuit to phase lock any two sequential phases of the locally generated phase outputs to phase positions on either side of the phase of the incoming phase modulated carrier. Once the circuit has obtained carrier phase lock, the multiple phases produced by the local oscillator will remain fixed (without phase change) relative to the initial detected phase of the incoming phase modulated carrier. Since the local oscillator is fixed (locked) to the phase of the incoming phase modulated carrier, demodulation can be accomplished simply by clocking one or more flip flops with respective phases of the local oscillator.

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Pocatello, ID, United States of America

Andrei R Petrov