I/Q Transmitter Signal Processing for Harmonic Noise Suppression
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Solution Overview
Problem
Conventional digital RF transmitters face challenges with high power and hardware costs for Sigma-Delta Modulation (SDM) modules at high processing speeds, leading to increased out-of-band noise and ineffective suppression of modulation harmonics, which are difficult to attenuate even with external filters.
Innovation Solution
A signal processing arrangement that includes in-phase and quadrature modulators and demodulators configured for pulse code modulation or pulse width modulation, along with harmonic filters, to efficiently reduce modulation harmonics by cascading modulator blocks and using digital pre-distorters for noise shaping and filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Sigma-Delta Modulation (SDM) modules operate at high processing speeds, then processing speed is improved, but power consumption and hardware cost increase significantly
Solution Approach 1:
The patent changes the modulation parameter from Sigma-Delta Modulation to Pulse Width Modulation (PWM), which operates effectively at high processing speeds without the exponential power and hardware cost increase that characterizes high-speed SDM implementations
2Productivity
If Sigma-Delta Modulation (SDM) modules operate at high processing speeds, then processing speed is improved, but out-of-band noise increases
Solution Approach 1:
The patent changes the modulation parameter from Sigma-Delta Modulation to Pulse Width Modulation (PWM), which operates effectively at high processing speeds without the exponential power and hardware cost increase that characterizes high-speed SDM implementations
3Object-generated harmful factors
If external filters are used to attenuate modulation harmonics, then filtering is attempted, but the harmonics are difficult to attenuate effectively
Solution Approach 1:
The patent applies preliminary action by using digital pre-distorters before the power amplifier to pre-compensate for non-linearities and reduce the generation of modulation harmonics at their source, rather than attempting to filter them afterward
Solution Approach 2:
The patent extracts and removes the problematic SDM modules from the signal processing chain, replacing them with PWM-based modulation that inherently produces fewer harmonics, eliminating the need for complex harmonic filtering
4Device complexity
If Pulse Width Modulation is used instead of Sigma-Delta Modulation, then circuit design is simplified and processing speed increases, but noise shaping performance may be affected
Solution Approach 1:
The patent changes the modulation parameter from Sigma-Delta Modulation to Pulse Width Modulation (PWM), which operates effectively at high processing speeds without the exponential power and hardware cost increase that characterizes high-speed SDM implementations
Data Source
AI summary
A signal processing arrangement for a transmitter includes an in-phase modulator configured to receive an in-phase signal (I) and configured to modulate the in-phase signal (I); a quadrature modulator configured to receive a quadrature signal (Q) and configured to modulate the quadrature signal (Q); an in-phase demodulator configured to demodulate the modulated in-phase signal (I) and to output a demodulated in-phase signal (I); a quadrature demodulator configured to demodulate the modulated quadrature signal (Q) and to output a demodulated quadrature signal (Q); an in-phase harmonic filter configured to perform a filtering on harmonics in the demodulated in-phase signal (I) and to output an in-phase digital signal (I); and a quadrature harmonic filter configured to perform a filtering on harmonics in the demodulated quadrature signal (Q) and to output a quadrature digital signal (Q).