Wireless audio equipment using a quadrature modulation system

摘要

A communications system, e.g., a wireless microphone, incorporates a quadrature modulator system to reduce power consumption with respect to traditional approaches and is general in nature to support any two-dimensional digital technique. The quadrature modulator system comprises different subsystems, including a digital-analog transformation circuit, a baseband filter, and a quadrature modulator. The digital-analog transformation circuit converts discrete time samples to a continuous time signal, and further includes an oversampling noise-shaping modulator such as a sigma-delta modulator. The baseband filter then removes out-of-band energy including sampling images and quantization noise. Some of the circuit components may comprise discrete devices that may result in a reduction of power consumption for the quadrature modulator system. Alternatively, some or all of the circuit components may be incorporated in a single electronic device. For example, an in-phase/quadrature-phase (I/Q) converter and oversampling noise-shaping modulator may be implemented within one field-programmable gate array.

主权项

1. An apparatus comprising;
an in-phase/quadrature-phase (I/Q) converter receiving an input signal and converting the input signal to the digital in-phase (I) signal and the digital quadrature (Q) signal, wherein the input signal is received within a wireless audio equipment; at least one oversampling noise-shaping modulator converting (i) a digital in-phase (I) signal and a digital quadrature (Q) signal to a quantized I signal and (ii) the digital Q signal to a quantized Q signal, wherein the quantized I signal and the quantized Q signal are quantized with a desired number of quantized bits per sample, wherein the at least one oversampling noise-shaping modulator comprises a sigma-delta modulator and wherein the sigma-delta modulator comprises:
a modulator filter characterized by a transfer function;a first signal combiner summing the digital I signal and a filtered signal from the modulator filter to form a first summed signal;an N-bit quantizer quantizing the first summed signal to form the quantized I signal in accordance with N quantized bits;a second signal combiner subtracting the quantized I signal from the first summed signal to form a second summed signal; anda modulator filter filtering the second summed signal in accordance with the transfer function to reduce a noise level of the second summed signal to obtain the filtered signal; at least one digital-analog converter (DAC) converting the quantized I signal and the quantized Q signal to an analog I signal and an analog Q signal, respectively; at least one filter reducing noise components of the analog I and Q signals by a predetermined level to form filtered I and Q signals; and an analog quadrature modulator transforming the filtered I and Q signals and a local oscillator signal to a transmitted output signal, wherein the transmitted output signal is transmitted to a wireless receiver.