Single-Bit IQ Transmitter Using Sigma-Delta Modulation
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Solution Overview
Problem
There is a need for simplified and lower power wireless data transmission circuits to support the growing demands of mobile wireless and low power devices, particularly in applications like mesh sensor networks and implantable medical devices, where existing modulation schemes like BPSK and QPSK require efficient signal processing to maintain link quality and reduce bit error rates.
Innovation Solution
A single-bit transmitter architecture is developed, incorporating a signal generator, digital pulse shaping filter, upsampling, and sigma-delta modulation, along with configurable low-order analog filters to generate inphase and quadrature modulated carriers, which are optimized for power spectra compliance with standards like 802.11.b, enabling flexible transmit power masks and efficient data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional BPSK or QPSK modulation schemes are used, then link quality and noise resistance are improved, but power consumption and device complexity increase
Solution Approach 1:
The patent changes the fundamental parameter of signal representation from multi-bit words to single-bit sequences. By using sigma-delta modulation to convert multi-bit digital signals into 1-bit streams, the system achieves BPSK modulation with dramatically reduced power consumption while maintaining link quality through the noise-shaping properties of sigma-delta modulation.
Solution Approach 2:
The patent extracts only the essential modulation function needed for wireless transmission, eliminating complex signal processing stages. By using direct 1-bit modulation without requiring full BPSK/QPSK constellation management, the system reduces device complexity and power consumption while maintaining robustness through the inherent noise resistance of phase-shift keying.
2Reliability
If complex signal processing is used to maintain link quality, then bit error rate performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces complex mechanical signal processing hardware with a simplified digital-to-1-bit-analog conversion system. By using sigma-delta modulators and simple analog filters instead of complex modulators and multiple signal processing stages, the system achieves comparable bit error rate performance with dramatically reduced device complexity.
3Productivity
If high data rates are achieved through advanced modulation, then productivity is improved, but power consumption and complexity increase
Solution Approach 1:
The patent employs periodic pulse shaping and upsampling in the sigma-delta modulation process to achieve high data rates. By using periodic filtering and systematic upsampling of the 1-bit stream, the system can transmit data at high rates while maintaining low power consumption through the efficiency of single-bit processing.
Data Source
AI summary
Single-bit transmitter modulator having a digital pulse shaping filter configured to shape data pulses of an inphase signal and quadrature signal; an upsampling filter configured to increase the sample rate of the inphase signal and quadrature signal; a sigma-delta modulator providing a one-bit inphase output signal and a one-bit quadrature output signal; an inphase low-order analog low pass filter coupling the one-bit inphase output signal to an inphase channel input of a quadrature modulator, and a quadrature low-order analog low pass filter coupling the one-bit quadrature output signal to a quadrature channel input of a quadrature modulator; and, wherein the quadrature modulator is connected to a carrier signal generator and is configured to generate an inphase and quadrature modulated carrier.