Digital Outphasing Transmitter With Delta-Sigma PAPR Handling
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Solution Overview
Problem
High Peak to Average Power Ratio (PAPR) in wireless communication and radar systems degrades the efficiency of RF power amplifiers, requiring complex circuitry for linear power amplification, which compromises power efficiency and spectral efficiency.
Innovation Solution
An all-digital outphasing transmitter with a decomposition unit, delta sigma modulator, mixing units, amplifiers, combiner, and band pass filter is used to decompose and amplify signals efficiently, reducing combiner loss and achieving high efficiency by employing a Chireix combiner with Class D RF power amplifiers and delta sigma modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If complex modulation schemes are used to meet high data rate and spectral efficiency requirements, then signal quality and spectral efficiency are improved, but power consumption increases and efficiency deteriorates
Solution Approach 1:
The transmitter architecture segments the amplitude-modulated signal into two constant-envelope signals through outphasing modulation. Each signal path uses a simple on-off keying modulator instead of complex modulation schemes, while the combination of these paths reconstructs the desired amplitude-varying output signal, thereby achieving high data rates without complex modulation in individual paths.
Solution Approach 2:
The invention uses a composite transmitter structure combining outphasing modulation with delta-sigma modulation. The outphasing section handles amplitude variation while the delta-sigma modulator handles spectral shaping, creating a composite system that achieves both high data rates and power efficiency.
2Manufacturing precision
If linear power amplification is used to maintain signal quality, then spectral efficiency is improved, but power efficiency deteriorates
Solution Approach 1:
Instead of using linear amplification to achieve signal quality, the invention inverts the approach by using constant-envelope signals that can be amplified non-linearly (using efficient Class C or Class E amplifiers) and then combining them to produce the desired amplitude-varying output signal with high signal quality.
3Use of energy by moving object
If Envelope Elimination and Restoration (EER) transmitter is used, then power efficiency is improved, but circuit complexity increases
Solution Approach 1:
The invention extracts the amplitude information from the signal and processes it separately through delta-sigma modulation, while the phase information is handled through outphasing modulation. This separation allows each processing path to use simpler, more efficient components.
4Manufacturing precision
If high Peak to Average Power Ratio (PAPR) signals are transmitted, then signal quality is maintained, but amplifier efficiency deteriorates
Solution Approach 1:
The invention dynamically adjusts the amplitude of the combined signal through the outphasing mechanism, allowing the use of constant-envelope signals that can be efficiently amplified. The dynamic combination of two constant-envelope signals produces the desired amplitude-varying output with high PAPR characteristics while maintaining amplifier efficiency.
Data Source
AI summary
An all digital outphasing transmitter includes, at least one decomposition unit for decomposing an input signal to generate a first sub-signal and a second sub-signal; at least one outphasing signal generator to convert said first sub-signal to an outphasing signal; at least one delta sigma modulator to convert said second sub-signal to a delta sigma modulated signal; at least one mixing unit for mixing the outphasing signal and delta sigma modulated signal to generate a first and second mixed signal; at least one first amplifier for amplifying the first mixed signal; at least one second amplifier for amplifying the second mixed signal; at least one combiner for combining the first and second amplified mixed signals to generate a delta sigma modulated output signal and at least one band pass filter for filtering the delta sigma modulated output signal to recover the input signal envelope back on to the output signal.