CE-BPSK Modulation for Mode S Radar Amplitude Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional BPSK modulation experiences amplitude dropouts during phase reversals, leading to undesirable effects like spectral regrowth, constellation distortion, and amplitude settling issues when used with saturated power amplifiers and filters, which are challenging to address in applications such as mode S radars and digital radios.
Innovation Solution
The implementation of constant envelope bi-phase shift keying (CE-BPSK) modulation using an I-Q quadrature modulator, which maintains a substantially-constant amplitude during phase reversals by controlling both in-phase and quadrature signals to achieve phase transitions without amplitude changes, allowing the use of saturated power amplifiers and filters with reduced amplitude and phase transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional BPSK modulation is used, then phase reversal is achieved, but amplitude dropouts occur during phase reversals causing spectral regrowth and constellation distortion
Solution Approach 1:
The patent changes the modulation parameters by using continuous phase transitions instead of abrupt phase reversals. The in-phase and quadrature components are continuously adjusted during phase transitions, maintaining constant envelope amplitude while achieving the required phase changes. This resolves the amplitude dropout issue by transforming the discontinuous phase reversal into a continuous parameter transition.
Solution Approach 2:
The patent introduces dynamic control of the I and Q signal components during phase transitions. Rather than static phase reversal, the system dynamically adjusts the amplitude and phase of the I and Q components over time, ensuring the envelope remains constant while the phase transitions smoothly. This dynamic approach eliminates the harmful amplitude dropouts associated with traditional BPSK.
2Use of energy by moving object
If saturated power amplifiers are used with traditional BPSK, then power efficiency is improved, but amplitude settling issues and spectral regrowth occur
Solution Approach 1:
The patent changes the signal envelope parameter from variable to constant. By maintaining a constant envelope amplitude during modulation, the signal becomes compatible with saturated power amplifiers without causing spectral regrowth. The continuous phase transition with constant envelope allows the amplifier to operate in saturation mode efficiently while avoiding the spectral distortion that would otherwise occur.
3Productivity
If traditional BPSK modulation is used, then data transmission is achieved, but phase reversal duration requirements are not met due to amplitude settling time
Solution Approach 1:
The patent uses dynamic continuous phase transitions instead of static abrupt reversals. By continuously adjusting the I and Q components, the phase transition occurs smoothly without amplitude settling time. This dynamic approach reduces the phase reversal duration, allowing faster data transmission rates while meeting the minimum phase reversal duration requirements specified in mode S protocols.
Data Source
AI summary
A method includes obtaining an in-phase (I) input signal and a quadrature (Q) input signal at a quadrature modulator. The method also includes performing constant envelope bi-phase shift keying (CE-BPSK) modulation using the quadrature modulator to generate a modulated output signal. The modulated output signal includes a CE-BPSK modulated waveform containing phase reversals, and the CE-BPSK modulated waveform has a substantially-constant amplitude during the phase reversals.