摘要:
Provided are, among other things, systems, apparatuses, methods and techniques for converting a discrete-time quantized signal into a continuous-time, continuously variable signal. An exemplary converter preferably includes: (1) multiple oversampling converters, each processing a different frequency band, operated in parallel; (2) multirate ( i.e. , polyphase) delta-sigma modulators (preferably second-order or higher); (3) multi-bit quantizers; (4) multi-bit-to-variable-level signal converters, such as resistor ladder networks or current source networks; (5) adaptive non-linear, bit-mapping to compensate for mismatches in the multi-bit-to-variable-level signal converters ( e.g ., by mimicking such mismatches and then shifting the resulting noise to a frequently range where it will be filtered out by a corresponding bandpass (reconstruction) filter); (6) multi-band ( e.g. , programmable noise-transfer-function response) bandpass delta-sigma modulators; and/or (7) a digital pre-distortion linearizer (DPL) for canceling noise and distortion introduced by an analog signal bandpass (reconstruction) filter bank.
摘要:
An RF transceiver apparatus comprises transmitter circuitry arranged to convert signals from a baseband frequency to RF transmission frequencies and receiver circuitry arranged to convert signals from RF reception frequencies to the baseband frequency. The transmitter and receiver circuitry each comprise three mixers arranged to convert a signals between the baseband frequency, a first intermediate frequency; a second intermediate frequency that is higher than the transmission frequencies; and a second intermediate frequency to the transmission frequency.
摘要:
A method of generating a quantized signal in a Sigma-Delta modulator (25) comprises the steps of feeding a modulator input signal to a quantizer (15) via at least one integrator (12, 13); generating in the quantizer (15) a quantized signal; feeding back the quantized signal to be subtracted from the modulator input signal; and generating a dither signal to be applied to a point in the Sigma-Delta modulator. The dither signal is applied to a selected one of a number of different points (11, 14) in the Sigma-Delta modulator (25) in dependence of a control signal. In this way a method of generating a quantized signal in a Sigma-Delta modulator is provided which provides optimal results for different modes of the application, such as phase modulation mode and frequency modulation mode in a Bluetooth receiver.
摘要:
A ΔΣ modulation digital-analogue converter of the present invention includes: a look-up table in which a correspondence relationship between each of a plurality of possible input values of an input signal externally supplied, and each of compensation values individually associated with the possible input values, are stored; and a nonlinear compensation circuit (6) for compensating the input signal externally supplied, based on a compensation value associated with the input signal among the compensation values, and supplying a ΔΣ modulation section (1) the input signal thus compensated. A sine wave is used as the input signal. The compensation value is set based on magnitudes of a spectrum of odd-order harmonics whose frequencies are A times more than a frequency of the sine wave (A is an odd number), the spectrum obtained in such a manner that an output of a D-Class amplifier (2) or an output of the ΔΣ modulation digital-analogue converter is subjected to a frequency analysis without a compensation with respect to the sine wave by the nonlinear compensation circuit (6). Therefore, it is possible to provide a ΔΣ modulation digital-analogue converter which (i) suppresses generation of odd-order harmonics with a simple circuit arrangement, and therefore (ii) is excellent in SNR and THD+N.
摘要:
A noise shaper includes a first feedback loop for noise shaping a first feedback signal under normal operating conditions and having a first filter (201) with a first signal transfer function and a second feedback loop that is stable under overload conditions and has a second filter (202) having a second signal transfer function differing from the first signal transfer function. The noise shaper also includes an output circuit block including a quantizer (203) and steering circuitry (204). The quantizer (203) includes an input simultaneously responsive to outputs of the first (201) and second filters (202). The steering circuitry (204) steers a feedback from an output of the quantizer (203) to input of the first and second feedback loops. The steering circuitry (204) steers feedback from output of the quantizer (203) to inputs of the first and second feedback loops, the steering circuitry (204) including a first output for providing the first feedback signal to the first feedback loop and a second output for providing a second feedback signal to the second feedback loop.
摘要:
A delta-sigma modulator includes a quantization bit rate detection unit that detects a quantization bit rate of a digital audio signal, a volume setting value detection unit that detects a volume setting value of the digital audio signal; a filter that includes plural sets of filter coefficients having different shaping properties and allows the quantization noise to pass, and a filter coefficient switcher that switches the filter coefficients of the filter in accordance with the detection results of the quantization bit rate detection unit and the volume setting value detection unit. The delta-sigma modulator detects the quantization bit rate of an input signal and switches the filter coefficients to the low-order filter coefficient set when a source has a low quantization bit rate.
摘要:
Un modulateur Sigma-Delta numérique-numérique (1) comprend une entrée (10) pour recevoir une valeur numérique d'entrée (X) codée sur N bits, où N est un nombre entier déterminé, une sortie (20) pour délivrer une valeur numérique de sortie (Y) codée sur n bits, où n est un nombre entier déterminé inférieur à N, et au moins une première cellule Sigma-Delta (100) qui inclut un quantificateur (Q1) ayant un échelon de quantification (q) qui est un nombre premier. Le choix d'un nombre premier diminue la puissance des cycles limites (raies de puissance plus élevée que la moyenne locale) pouvant apparaître en fonction du code d'entrée du modulateur et des conditions initiales. Application à un synthétiseur de fréquence numérique.