On-Chip Two-Tone Signal Generation for RF Linearity Calibration
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Solution Overview
Problem
Current RF circuit calibration methods face challenges in generating high-quality two-tone signals with minimal harmonics for linearity calibration, often requiring additional hardware, increased cost, area, and power consumption, and are not easily implemented on-chip with existing components.
Innovation Solution
A method and apparatus that generate a two-tone calibration signal from distortion-rich sources within the RFIC, using a tone generating circuit to create a first single-tone signal and mixing it with a second single-tone signal, incorporating harmonic rejection and filtering to minimize harmonics, allowing for on-chip linearity calibration with reduced overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional two-tone signal generation methods are used, then calibration quality is improved, but hardware complexity and cost increase
Solution Approach 1:
The RFIC uses its own internal distortion-rich sources (such as phase-locked loops or voltage-controlled oscillators) to generate the two-tone calibration signals, eliminating the need for external signal generators. The system serves itself by utilizing internally available resources that would otherwise be wasted or unused.
Solution Approach 2:
The patent extracts and utilizes the distortion products (harmonics) that are naturally generated by internal RFIC components. Instead of treating these distortion products as unwanted artifacts, the invention extracts them and repurposes them as the two-tone calibration signals, thereby eliminating the need for additional hardware signal generators.
2Ease of manufacture
If distortion-rich sources are used for signal generation, then on-chip integration is improved, but signal quality deteriorates due to excessive harmonics
Solution Approach 1:
The patent converts the harmful distortion products and harmonics generated by internal RFIC sources into beneficial two-tone calibration signals. By intentionally utilizing these distortion-rich sources and processing them through mixing and filtering stages, the invention transforms what was previously considered waste or interference into the desired calibration signal.
Solution Approach 2:
The patent changes the frequency parameters of the internally generated signals by mixing them at specific frequency ratios (e.g., 1:2, 1:3). This frequency transformation, combined with selective filtering, converts the distortion-rich single-tone signals into clean two-tone calibration signals with controlled harmonic content.
3Manufacturing precision
If additional filtering stages are added to reduce harmonics, then signal purity is improved, but power consumption and area increase
Solution Approach 1:
Instead of attempting to eliminate all harmonics through extensive filtering, the patent applies partial filtering that removes only the most problematic harmonics while leaving less significant ones. This approach achieves sufficient signal purity for calibration purposes while minimizing the number of filtering stages and associated power consumption.
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 enables efficient on-chip generation of a high-quality two-tone signal for RF circuit calibration, minimizing harmonics and reducing design complexity, cost, and power consumption, while ensuring proper calibration without the need for external components.
Implementation Method 1
mixing the first single-tone signal with a second single-tone signal to provide a two-tone signal having frequencies at a sum and a difference of frequencies of the first and second single-tone signals
Implementation Method 2
the tone generating circuit includes a harmonic rejection circuit configured to perform harmonic rejection on the digital clock signal to remove the 3rd and the 5th harmonics from the digital clock signal
Implementation Method 3
the tone generating circuit also includes a low-pass filter configured to filter out at least the 9th and higher harmonics of the digital clock signal
Implementation Method 4
the tone generating circuit further includes a notch filter configured to reject the 7th harmonic of the digital clock signal
Data Source
AI summary
Certain aspects of the present disclosure provide methods and apparatus for generating a two-tone signal for performing linearity calibration of a radio frequency (RF) circuit. One example apparatus generally includes a tone generating circuit configured to generate a first single-tone signal from a digital clock signal and a mixer connected with the tone generating circuit and configured to mix the first single-tone signal with a second single-tone signal to provide a two-tone signal having frequencies at a sum and a difference of frequencies of the first and second single-tone signals.