Inter-Band CA Transmitter Noise Cancellation Without RF Output Filters
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Solution Overview
Problem
Current inter-band carrier aggregation (CA) digital transmitters face challenges in effectively reducing out-of-band noise, necessitating the use of high-order multi-band RF output filters, which increase design complexity and insertion loss.
Innovation Solution
The implementation of a multi-stage out-of-band noise canceller (MSOB-NC) using delta-sigma modulation and asymmetric power combiners to generate noise mitigation signals, reducing out-of-band emissions without the need for multi-band RF output filters, and utilizing a dual-band quadrature modulator and digital gain units to control and quantify noise cancellation signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delta-sigma modulation based CMB technique is used for IB-CA DTX, then excellent dynamic range without spurious tones is achieved, but large amount of out-of-band noise is generated
Solution Approach 1:
The patent generates a noise mitigation signal that mirrors the out-of-band noise characteristics and subtracts it from the encoded multi-band signal. This converts the harmful noise into a beneficial cancellation mechanism, reducing out-of-band emissions while preserving the excellent dynamic range properties of delta-sigma modulation
Solution Approach 2:
The noise mitigation signal is generated in advance by processing the encoded multi-band signal through a noise canceller circuit before transmission. This preliminary anti-action prevents the out-of-band noise from being transmitted, rather than attempting to filter it after transmission
2Object-generated harmful factors
If conventional noise cancellation technique is used in IB-CA DTX, then some noise suppression is achieved, but high-order multi-band RF output filter is still required
Solution Approach 1:
The patent replaces the mechanical/electrical filtering system (high-order multi-band RF output filter) with an electronic signal processing system (noise canceller circuit that generates and subtracts noise mitigation signals). This substitution achieves superior noise suppression without the complexity and insertion loss of high-order RF filters
Solution Approach 2:
The invention changes the approach from passive filtering (fixed frequency response) to active noise cancellation (dynamic signal generation and subtraction). By changing the fundamental parameter of noise control from frequency-based filtering to time-domain signal subtraction, the system achieves better performance with lower complexity
3Object-generated harmful factors
If high-order multi-band RF output filter is used to reduce out-of-band noise, then noise reduction is achieved, but insertion loss increases and design complexity increases
Solution Approach 1:
Instead of passively filtering noise with energy-lossy RF filters, the patent actively generates a noise mitigation signal that cancels the out-of-band noise through subtraction. This converts the energy loss problem into an active cancellation solution that preserves signal energy while removing noise
Solution Approach 2:
The patent extracts and separates the out-of-band noise component from the encoded multi-band signal by generating a dedicated noise mitigation signal. This extracted noise cancellation approach removes only the harmful out-of-band components without affecting the in-band signal quality, avoiding the energy loss inherent in broad-spectrum RF filtering
Data Source
AI summary
A radio frequency transmitter for wireless communication includes a plurality of input ports to receive a plurality of sequences of baseband symbols to be transmitted on a plurality of disjoint frequency bands, a power encoder to modulate and encode the plurality of sequences of baseband symbols to produce an encoded multi-band signal including the plurality of disjoint frequency bands carrying the plurality of sequences of baseband symbols, a first power amplifier for amplifying the encoded multi-band signal to produce an amplified encoded multi-band signal, a first noise canceller to generate a first noise mitigation signal from the encoded multi-band signal and the plurality of sequences of baseband symbols, a first power combiner to combine the amplified encoded multi-band signal and the first noise mitigation signal to produce an RF multi-band signal, and an antenna for transmitting the RF multi-band signal.