Passive Quadrature Upconverter for Harmonic Spur Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transmitter designs face challenges in minimizing spurious up-conversion products like 4fmod and counter-IM3 emissions, which are undesirable and must be kept below certain thresholds to meet stringent emission requirements, especially as transceiver designs become more miniaturized and power-efficient.
Innovation Solution
The use of multiple direct quadrature voltage modulators with scaled switch resistances and multiphase LO signals in passive mixers to generate upconverted signals with rejected spurious harmonic mixing products, allowing for harmonic reject upconversion without the need for additional filters, thereby reducing power consumption and circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If passive voltage switching mixers are used for upconversion, then power consumption is reduced, but spurious harmonic mixing products cannot be effectively suppressed
Solution Approach 1:
The upconversion process is divided into multiple parallel passive mixer paths (e.g., three mixers with different LO phases), each contributing to the final output. By segmenting the function across multiple passive mixers with scaled switch resistances, the patent achieves harmonic rejection while maintaining the power efficiency of passive mixing, as each segment operates passively but collectively they suppress spurious products through constructive and destructive interference patterns
Solution Approach 2:
The patent changes the resistance parameter of switch elements in different mixer paths by applying scaling factors (e.g., sqrt(2), 0.5). This parameter modification allows the passive mixers to achieve differential weighting of mixing products, enabling suppression of spurious harmonics through controlled interference while maintaining passive operation and low power consumption across all mixer segments
2Object-generated harmful factors
If active mixers are used to suppress spurious products, then emission requirements are met, but power consumption increases and device complexity increases
Solution Approach 1:
The patent converts the inherently non-linear behavior of passive mixers, which normally generates spurious products, into a beneficial mechanism for harmonic rejection. By carefully controlling the phase and amplitude relationships among multiple passive mixer outputs, the spurious products from each mixer interfere destructively at specific harmonic frequencies, transforming what would be harmful emissions into a mechanism for their suppression while maintaining passive, low-power operation
3Object-generated harmful factors
If filters are added to remove spurious products, then emission requirements are met, but device complexity and physical area increase
Solution Approach 1:
The patent replaces the mechanical/filter-based approach to harmonic rejection with an electrical/circuit-based approach. Instead of adding physical filters to remove spurious products, the invention uses scaled switch resistances and multi-phase LO signaling in parallel passive mixers to electrically suppress harmonics through controlled interference, thereby achieving emission compliance without adding filter components or increasing physical circuit area
4Object-generated harmful factors
If filters are added to remove spurious products, then emission requirements are met, but power consumption and physical area increase
Solution Approach 1:
The patent merges the functions of multiple passive mixers with different LO phases and scaled resistances into a unified upconversion structure. By combining these mixer paths directly without intermediate filtering stages, the invention achieves harmonic rejection through the merged output signal itself, eliminating the need for additional filter components and reducing the overall transmitter circuit area while meeting emission requirements
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Methods and apparatuses are presented for harmonic reject upconverting a baseband signal using at least one quadrature passive upconversion mixer. In some embodiments, an apparatus may include a first quadrature passive mixer configured to receive a first baseband input and a first LO input, and a second quadrature passive mixer configured to receive a second baseband input and a second LO input. A first output of said first passive mixer may be directly connected to a first output of said second passive mixer and together coupled to a first amplifier input. A second output of said first passive mixer may be directly connected to a second output of said second passive mixer and together coupled to a second amplifier input. The transmitter may be configured to output an upconverted signal with at least one rejected harmonic spurious mixing product based on the first and second amplifier inputs.