IQ Mixer Feedback Circuit for Clock Subharmonic Cancelation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Clock generation circuitry in RF and mmWave transceivers faces challenges with subharmonic leakage, which causes distortion and out-of-band emissions due to unwanted subharmonic components in the clock signal, and existing solutions are either bulky, require manual calibration, or are sensitive to amplitude and phase mismatches.
Innovation Solution
The implementation of in-phase and quadrature mixers, filters, and a processing circuit to detect and automatically correct subharmonic components using direct current (DC) signals, enabling negative feedback for automatic subharmonic cancelation across process, voltage, and temperature changes, and using hard-limiters to facilitate 'large signal' processing, reducing sensitivity to amplitude and phase mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If frequency multiplier is used to generate clock signal, then desired frequency is achieved, but subharmonic components are introduced causing signal distortion
Solution Approach 1:
The patent detects subharmonic components using in-phase and quadrature mixers that convert the harmful subharmonic leakage into detectable DC components. These DC components are then used to generate correction signals that cancel the subharmonics, effectively converting the harmful effect into a useful detection and correction mechanism
Solution Approach 2:
The patent implements a feedback mechanism where the detected subharmonic components (converted to DC signals) are fed back through processing circuitry to generate correction signals. These correction signals are combined with the original clock signal to cancel the subharmonic leakage, creating a closed-loop system that continuously reduces harmful effects
2Object-generated harmful factors
If existing subharmonic cancelation mechanisms are used, then subharmonic effects are reduced, but device complexity increases or manual calibration is required
Solution Approach 1:
The patent implements an automatic detection and correction system that self-calibrates without manual intervention. The in-phase and quadrature mixers automatically detect subharmonic components and the processing circuitry automatically generates correction signals, enabling the system to self-adjust to process, voltage, and temperature variations without requiring manual calibration
Solution Approach 2:
The patent uses parameter changes in the mixing and filtering stages to enable automatic adaptation. By varying the mixing frequencies and filter characteristics based on detected DC components, the system dynamically adjusts its operation to maintain subharmonic rejection across different operating conditions without increasing fundamental circuit complexity
3Measurement precision
If conventional mixing approaches are used, then frequency conversion is achieved, but sensitivity to amplitude and phase mismatches increases
Solution Approach 1:
The patent employs asymmetric in-phase and quadrature mixing paths that are deliberately designed to be different in their processing characteristics. This asymmetry allows the system to detect and correct subharmonics while being less sensitive to typical amplitude and phase mismatches, as the detection mechanism specifically targets the asymmetric subharmonic components rather than relying on perfectly balanced mixing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces subharmonic components in the clock signal, improving signal quality and reducing die area requirements, while maintaining subharmonic rejection across varying conditions without the need for manual calibration.
Implementation Method 1
in-phase and quadrature mixers, first and second filters and a processing circuit. The in-phase mixer has a first mixer input and a first mixer output. The quadrature mixer has a second mixer input and a second mixer output
Implementation Method 2
The first filter circuit has a first filter input and a first filter output, the first filter input coupled to the first mixer output. The second filter circuit has a second filter input and a second filter output, the second filter input coupled to the second mixer output
Implementation Method 3
The processing circuit is configured to detect a subharmonic component of a wave at the first mixer input and the second mixer input using a first direct current (DC) component at the first input of the processing circuit and a second DC component at the second input of the processing circuit
Data Source
AI summary
A circuit for subharmonic detection includes in-phase and quadrature mixers, first and second filters, and a processing circuit. The in-phase mixer has a first mixer input and a first mixer output. The quadrature mixer has a second mixer input and a second mixer output, the first mixer input coupled to the second mixer input. The first filter circuit has a first filter input and a first filter output, the first filter input coupled to the first mixer output. The second filter circuit has a second filter input and a second filter output, the second filter input coupled to the second mixer output. The processing circuit has a first input and a second input, the first input of the processing circuit coupled to the first filter output, the second input of the processing circuit coupled to the second filter output. The processing circuit is configured to detect a subharmonic component of a wave at the first mixer input and the second mixer input using a first direct current (DC) component at the first input of the processing circuit and a second DC component at the second input of the processing circuit.