RF Transmitter Correction Signal for Receive-Band Intermodulation
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Solution Overview
Problem
Repeater systems face challenges in reducing unwanted spectral products in receive bands due to the non-linear characteristics of power amplifiers, which can interfere with weak uplink signals and violate spurious emission limits, especially in co-existence and co-location scenarios.
Innovation Solution
A method and device that utilize a memoryless power amplifier model to generate a correction signal by subtracting the transmit signal from the output signal, processing it through filters to isolate intermodulation products within receive bands, and then combining it with the amplified transmit signal to cancel out these products, using a digital repeater system with distributed antenna architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power amplifiers are used to amplify RF signals in the linear regime, then the RF power linearly relates to the input power, but non-linear characteristics of components generate unwanted spectral products including intermodulation products in receive bands
Solution Approach 1:
The patent generates a correction signal that contains the intermodulation products (harmful elements) and subtracts it from the amplified transmit signal. By converting the harmful intermodulation products into a usable correction signal, the system cancels out these unwanted spectral products in the receive bands, thereby improving signal quality without sacrificing amplification performance
Solution Approach 2:
The patent extracts the intermodulation products from the amplified transmit signal by generating a correction signal through a power amplifier model. This correction signal is then subtracted to remove the unwanted spectral products, effectively separating and eliminating the harmful components while preserving the desired signal
2Manufacturing precision
If linearization techniques such as digital pre-distortion are applied to meet spurious emission limits, then baseline spurious emission limits are achieved, but more stringent co-existence and co-location limits cannot be satisfied
Solution Approach 1:
The patent applies local quality by specifically targeting and canceling intermodulation products only in the receive bands where they cause harmful interference to uplink signals. The correction signal is processed through filters that isolate intermodulation products within receive bands, allowing precise cancellation of harmful spectral products in specific frequency regions while leaving other parts of the signal unaffected
3Productivity
If conventional amplifier designs are used, then basic amplification function is provided, but unwanted spectral products violate co-existence and co-location limits for radio transmitters
Solution Approach 1:
The patent introduces a correction signal as an intermediary element that mediates between the amplified transmit signal and the unwanted intermodulation products. This correction signal acts as a mediator that, when subtracted from the amplified signal, cancels out the harmful spectral products and allows the system to meet stringent co-existence and co-location limits while maintaining full amplification capability
Data Source
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AI summary
A radio frequency transmitter device, constituted for transmitting a radio frequency signal in a frequency band comprising at least one transmit subband and at least one receive subband, comprises: a transmit chain for processing a transmit signal associated with the at least one transmit subband; a power amplifier for amplifying the transmit signal; an output port for transmitting the amplified transmit signal; a processing unit for calculating, from the transmit signal associated with the at least one transmit subband, a correction signal in the at least one receive subband making use of a power amplifier model modelling the behavior of the power amplifier; and a coupler for adding the correction signal to the amplified transmit signal for cancelling intermodulation products in the amplified transmit signal produced by the power amplifier.