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5347 results about "Intermediate frequency" patented technology

In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency. Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an IF for amplification before final detection is done.

Calibrated DC compensation system for a wireless communication device configured in a zero intermediate frequency architecture

A calibrated DC compensation system for a wireless communication device configured in a zero intermediate frequency (ZIF) architecture. The device includes a ZIF transceiver and a baseband processor, which further includes a calibrator that periodically performs a calibration procedure. The baseband processor includes gain control logic, DC control logic, a gain converter and the calibrator. The gain converter converts gain between the gain control logic and the DC control logic. The calibrator programs the gain converter with values determined during the calibration procedure. The gain converter may be a lookup table that stores gain conversion values based on measured gain of a baseband gain amplifier of the ZIF transceiver. The gain control logic may further include a gain adjust limiter that limits change of a gain adjust signal during operation based on a maximum limit or on one or more gain change limits. A second lookup table stores a plurality of DC adjust values, which are added during operation to further reduce DC offset. The calibration procedure includes sampling an output signal for each gain step of the baseband amplifier at two predetermined range values and corresponding DC offsets using successive approximation. The data is used to calculate gain, DC offset and DC differential values, which are used to determine the conversion values programmed into the lookup tables or the gain adjust limiter.

Satellite digital audio radio service tuner architecture for reception of satellite and terrestrial signals

A satellite digital audio radio receiver system and method. The inventive receiver includes a circuit for down-converting a first ensemble in a received combined signal in a first mode of operation and for down-converting a second ensemble from the received combined signal in a second mode of operation. The first ensemble includes a first signal received from a first transmitter, a second signal received from a second transmitter, and a third signal received from a third transmitter. The second ensemble includes a second signal from the first transmitter, a second signal from the second transmitter, and a second signal from the third transmitter. A controller is included to selectively switch the circuit from the first mode to the second mode. The first ensemble comprises first, second and third frequency slots and the second ensemble comprises fourth, fifth, and sixth frequency slots. In the illustrative embodiment, the first and second transmitters are mounted on first and second satellites and the third transmitter is a terrestrial repeater. Both ensembles are transmitted in accordance with the XM frequency plan. The first ensemble is down-converted using low side injection and the second ensemble down-converted using high side injection. The inventive circuit includes a synthesized frequency source. The circuit further includes a first intermediate frequency down-conversion stage with a first mixer for mixing the received combined signals with the output of synthesized frequency source. The circuit further includes first and second surface acoustic wave filters for separating the first and second signals received from the third signals. The inventive circuit further includes a second intermediate frequency down-conversion stage having second and third mixers for mixing the outputs of the first and second filters, respectively, with the output of a local oscillator.

Automotive anti-collision radar multi-target detecting method and system

The invention provides an automotive anti-collision radar multi-target detecting method and system. The method comprises the steps of emitting two types of triangular waves with different modulation periods in an alternating mode and acquiring echo data, carrying out windowing processing, carrying out distance dimension FFT and speed dimension FFT, carrying out modulo processing to obtain frequency spectrum of two types of echo waves, carrying out target paring to obtain a spectral line of the same target of the two echo waves, calculating distance and speed of each target, and judging target distance and speed obtained by the two echo waves through a tolerance function to obtain a final target. A radio frequency emitting and receiving part of the system comprises a radar sensor and an intermediate frequency processing module, and a data processing part comprises a modulus, a modulus converting module and a central control processing module FPGA. The FPGA comprises a modulation signal producing sub-module, an echo wave signal acquisition sub-module, an algorithm sub-module and a control sub-module. The modulation waves and corresponding algorithms effectively remove false targets and improve accuracy that multiple moving targets are detected under strong noise. A hardware system is simplified in structure and easy to achieve.

Amplitude-scaling resilient audio watermarking method and apparatus based on quantization

Disclosed is an amplitude-scaling resilient audio watermarking apparatus and method. An encoding apparatus includes: a polyphase filterbank for dividing an audio signal into a plurality of subbands; a psychoacoustic module for applying a psychoacoustic model to the audio signal to provide a signal-to-mask ratio; a watermark encoder for evaluating an encoding parameter from the subbands according to the signal-to-mask ratio and embedding the encoding parameter and a watermark into subbands corresponding to the middle frequency; and a synthesis filterbank for synthesizing the subband signals to output a watermarked audio signal. A decoding apparatus includes: a polyphase filterbank for dividing a received audio signal into the predetermined number of subbands; an EM estimator for estimating an scale factor from an encoding parameter contained in the audio signal and a watermarked subband according to an EM algorithm, and generating the quantizer step size Δd of a decoder according to the amplitude-scaling; a watermark decoder for extracting a watermark from a subband corresponding to the middle frequency considering the quantizer step size; and an integrated determiner for integrating outputs of the watermark decoder to determine a watermark.
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