TX Driver Amplifier Gain Asymmetry for Spurious Harmonic Control
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Solution Overview
Problem
Non-linearity in transmitter circuit blocks generates undesired harmonics, particularly third and fifth harmonics, which can desensitize aggregated receivers in LTE systems, posing a challenge for controlling these harmonics effectively.
Innovation Solution
The use of multiple upconverters and amplifiers with specific gain settings and phase configurations for the local oscillator signals, combined to suppress undesired upconverted signal components at frequencies corresponding to multiples of the local oscillator and baseband signal frequencies, effectively reducing harmonic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If non-linear amplification is used in transmitter circuit blocks, then signal amplification is achieved, but undesired harmonics are generated
Solution Approach 1:
The transmitter output is divided into multiple parallel signal paths (at least two paths), with each path containing separate amplifiers. By segmenting the amplification function across multiple paths with different gain settings, the system achieves overall signal amplification while the differential combination suppresses harmonics generated by individual non-linear amplifiers.
Solution Approach 2:
The patent applies asymmetric gain configuration where amplifiers in different signal paths have deliberately different gain values. This asymmetry in gain settings creates differential harmonic cancellation when the paths are combined, allowing the system to suppress unwanted harmonics while maintaining effective overall amplification.
2Object-generated harmful factors
If multiple amplifiers with different gains are used, then harmonic suppression is achieved, but device complexity increases
Solution Approach 1:
Multiple amplifiers are configured to perform dual functions: each amplifier provides signal amplification for its respective path while simultaneously contributing to harmonic suppression through differential combination. This multi-functionality reduces the need for separate harmonic cancellation circuits, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent combines multiple signal paths with different gain characteristics into a single differential output. By merging the amplified signals from multiple paths in a differential configuration, the system achieves harmonic suppression through constructive and destructive interference, eliminating the need for additional dedicated harmonic filtering components.
Data Source
AI summary
The transmission path of a communication device includes, in part, N upconverters each of which receives M phases of a signal to be transmitted. Each upconverter further receives one of N sets of phases of a LO signal. Each of the N sets includes M phases of the LO signal. The communication device further includes at least one combiner, and N amplifiers each responsive to a different one of the N upconverters to generate N amplified signals. The combiner combines the N amplified signals to generate an output signal. By selecting the gain of one of the amplifiers to be different than the gain of the remaining amplifiers, the undesired harmonics of the signal to be transmitted, caused by non-linearity of the amplifiers, is reduced. Each upconverter optionally includes a multitude of upconverters whose outputs are combined to further reduce the spurious harmonic upconversion products and the counter-intermodulation distortion (IM3).