Wideband Baseband LOL Estimation Under Carrier Frequency Offset
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Solution Overview
Problem
Existing methods for estimating local oscillator leakage (LOL) in Zero-IF systems are inefficient, require redundant calibration processes, and fail to account for Carrier Frequency Offset (CFO), leading to inaccurate and time-consuming LOL estimation.
Innovation Solution
A method using a wideband baseband signal to directly estimate LOL by removing or blocking the DC element, setting the average to zero, and processing the signal to determine the magnitude and phase of the DC offset, thereby simplifying the calibration process and reducing hardware dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration processes are used to estimate LOL, then LOL estimation can be performed, but the process is time-consuming and requires redundant calibration steps
Solution Approach 1:
The patent extracts only the necessary calibration operations by directly using the wideband baseband signal for LOL estimation without performing redundant calibration steps. The method isolates the essential measurement process from unnecessary procedural overhead, achieving accurate LOL estimation while eliminating time-consuming redundant operations.
Solution Approach 2:
The patent performs preliminary processing of the wideband baseband signal to prepare it for direct LOL estimation. By pre-processing the signal to extract relevant characteristics before estimation, the method enables accurate measurement without requiring subsequent redundant calibration steps, thereby reducing overall calibration time.
2Measurement precision
If traditional LOL estimation methods are used, then LOL can be estimated, but the accuracy is compromised when Carrier Frequency Offset (CFO) is present
Solution Approach 1:
The patent changes the approach by using the wideband baseband signal directly for LOL estimation rather than relying on traditional methods that assume no CFO. This parameter change in the estimation methodology makes the process robust to CFO conditions while maintaining measurement accuracy.
Solution Approach 2:
The patent incorporates feedback mechanisms that allow the system to adapt to CFO conditions during the estimation process. By using feedback from the wideband baseband signal characteristics, the method maintains accurate LOL estimation even when CFO is present, enhancing adaptability without sacrificing precision.
3Object-generated harmful factors
If filtering is applied to remove LOL signal, then unwanted emissions can be reduced, but portions of the wanted transmission signal are also filtered out
Solution Approach 1:
The patent converts the harmful LOL signal into a beneficial estimation target by using it to calculate and compensate for DC offset. Instead of attempting to filter out the LOL signal (which would also remove wanted signal portions), the method utilizes the LOL characteristics to improve overall signal quality through DC offset correction, thereby eliminating harmful effects without sacrificing transmission integrity.
4Measurement precision
If redundant calibration processes are performed, then LOL estimation can be achieved, but hardware complexity and dependency increase
Solution Approach 1:
The patent makes the wideband baseband signal serve multiple functions: it is used both for normal communication operations and for LOL estimation. This multi-functionality eliminates the need for separate dedicated calibration hardware or signals, reducing hardware complexity and dependency while maintaining accurate LOL estimation capability.
Solution Approach 2:
The system performs self-calibration by using its own wideband baseband signal for LOL estimation without requiring external calibration equipment or additional hardware components. This self-service approach reduces hardware dependency while achieving accurate measurement through intelligent signal processing.
Data Source
AI summary
A method of estimating local oscillator leakage (LOL) for a radio frequency (RF) signal transmitter. The method comprises generating a transmitter wideband baseband signal (s(t)) with a direct current (DC) voltage element of the transmitter wideband baseband signal (s(t)) removed or blocked and an average of the transmitter wideband baseband signal (s(t)) set to zero. The method includes processing said transmitter wideband baseband signal (s(t)) to form a RF signal; processing the RF signal to obtain a receiver baseband signal (y(t)); and determining a magnitude of an average of the receiver baseband signal (y(t)) as comprising a magnitude of the transmitter DC offset.