Wireless Transceiver LO Frequency Relocation for Leakage Suppression
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Solution Overview
Problem
Current wireless transceivers face challenges with LO leakage and third-order intermodulation distortion (IMD3) that affect the spectrum emission mask, particularly in wideband systems like 196MHz bandwidth, where existing solutions fail to consistently meet SEM requirements due to unstable LO leakage power levels and limited correction capabilities.
Innovation Solution
The solution involves shifting the LO frequency from the center of the operation bandwidth to a protection area of allocated carriers, allowing the LO leakage to be suppressed without affecting in-band data and ensuring that IMD3 falls within the digital pre-distortion (DPD) bandwidth for effective correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the LO frequency is positioned at the center of the operation bandwidth, then the LO signal can be generated for modulation, but the LO leakage interferes with useful radio signals and degrades output signal quality
Solution Approach 1:
The patent extracts the LO frequency from the center of the operation bandwidth and relocates it to a protection area. This separation removes the harmful LO leakage from the useful signal band while preserving the LO's essential modulation function. The LO frequency is specifically positioned in a protection area where it cannot interfere with allocated carriers, thus extracting the harmful interference component while retaining the useful modulation capability.
Solution Approach 2:
The patent introduces a protection area as an intermediary zone between the useful signal band and the LO frequency. This protection area acts as a buffer that isolates the LO leakage from the useful radio signals. By placing the LO frequency in this intermediary protection area, the system mediates between the need for LO signal generation and the need to prevent LO leakage interference.
2Object-affected harmful factors
If the LO frequency is shifted to a protection area, then the LO leakage is suppressed and does not interfere with in-band data, but the LO frequency positioning becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-defining protection areas within the operation bandwidth before signal transmission begins. These protection areas are predetermined zones where LO frequency can be placed without causing interference. By establishing these zones in advance, the system simplifies the LO frequency positioning process, as the LO can be directly placed in these pre-identified safe zones without requiring complex real-time calculations or adjustments.
3Reliability
If the LO frequency is positioned to suppress LO leakage, then SEM requirements can be met, but the IMD3 correction capability may be limited if IMD3 falls outside the DPD bandwidth
Solution Approach 1:
The patent applies dynamics by making the LO frequency position adjustable within the protection area based on system conditions. The LO frequency can be dynamically shifted to different locations within the protection area, and the DPD bandwidth can be dynamically adjusted to ensure IMD3 components remain within the correction range. This dynamic adjustment allows the system to maintain both SEM compliance and IMD3 correction capability under varying operating conditions.
Data Source
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AI summary
Embodiments of the present disclosure relate to a device, method and computer readable storage medium for wireless data transmission. In example embodiments, the device comprises a first NCO configured to shift a frequency of a pre-distorted downlink baseband signal by a first offset to generate a first signal. The baseband signal is associated with a plurality of allocated carriers. The device also comprises an RF processing unit including an LO configured to generate an LO signal at an LO frequency. The LO frequency is within a protection area of one of the plurality of allocated carriers or equal to a center frequency of the one of the plurality of allocated carriers. The device also comprises a power amplifier configured to generate, based on a modulated baseband signal, an amplified signal for transmission. The device also comprises a second NCO configured to shift a frequency of the amplified signal by a second offset to generate a second signal for generation of a pre-distortion coefficient.