Bi-Polar Quadrature Modulator Using Amplitude Paths and Phase Switching
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Solution Overview
Problem
Existing quadrature modulation techniques using mixers have suboptimal performance, and amplitude modulators face challenges in directly modulating signals with both positive and negative values due to phase restrictions.
Innovation Solution
A bi-polar modulator design utilizing two amplitude modulators and a summer to generate a quadrature modulated signal by amplitude modulating carrier signals based on the absolute values and signs of inphase (I) and quadrature (Q) modulating signals, with phase switching of local oscillator signals to preserve signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If mixers are used for quadrature modulation, then the modulation can be performed, but the power performance is suboptimal and noise performance is poor
Solution Approach 1:
The patent changes the operating parameters of the modulation system by replacing mixers with amplitude modulators operated in saturation mode. This parameter change enables both I and Q signals to be amplitude modulated simultaneously, achieving superior power efficiency and noise performance while maintaining quadrature modulation functionality
Solution Approach 2:
The patent substitutes the traditional mixer-based modulation mechanism with an amplitude modulator-based mechanism. By using amplitude modulators that can handle both positive and negative signal values, the system achieves better power and noise performance without requiring the complex mixing operation
2Ease of operation
If amplitude modulators are used to directly modulate signals with positive and negative values, then amplitude modulation can be achieved, but phase restrictions prevent direct modulation
Solution Approach 1:
The patent segments the modulation process into two independent paths: one for amplitude modulation using absolute values, and another for phase control using sign information. This segmentation allows each amplitude modulator to operate independently without phase restrictions, while the overall quadrature modulation function is achieved through combining the two paths
Solution Approach 2:
The patent introduces an intermediary processing step where the input signals are separated into absolute value components (for amplitude modulation) and sign components (for phase control). This intermediary representation enables amplitude modulators to process the signals without encountering phase restrictions, while still preserving the original signal information
Data Source
AI summary
A bi-polar modulator that can perform quadrature modulation using amplitude modulators is described. In one design, the bi-polar modulator includes first and second amplitude modulators and a summer. The first amplitude modulator amplitude modulates a first carrier signal with a first input signal and provides a first amplitude modulated signal. The second amplitude modulator amplitude modulates a second carrier signal with a second input signal and provides a second amplitude modulated signal. The summer sums the first and second amplitude modulated signals and provides a quadrature modulated signal that is both amplitude and phase modulated. The first and second input signals may be obtained based on absolute values of first and second modulating signals, respectively. The first and second carrier signals have phases determined based on the sign of the first and second modulating signals, respectively. Each amplitude modulator may be implemented with a class-E amplifier.