Harmonic Impedance Circuit for Transmitter Image Signal Suppression
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Solution Overview
Problem
Conventional transmitters with quadrature modulation architecture face challenges in completely eliminating image signals due to non-ideal factors, and as wireless transmission rates increase, stringent signal quality requirements necessitate further suppression of these image signals.
Innovation Solution
Incorporating a harmonic impedance adjustment circuit between the mixer and amplifier nodes to reduce specific harmonic components of the mixed signals, thereby minimizing the strength of image signals generated by harmonic mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional quadrature modulation architecture is used, then the transmitter structure is simple, but image signals cannot be completely eliminated due to non-ideal factors
Solution Approach 1:
A harmonic impedance adjustment circuit is introduced as an intermediary component between the mixer and amplifier. This circuit includes impedance adjustment units connected to harmonic components of the mixer output, which adjust the impedance at harmonic frequencies to reduce the strength of image signals generated by harmonic mixing, without significantly complicating the overall transmitter structure
Solution Approach 2:
The impedance adjustment units dynamically adjust impedance parameters at specific harmonic frequencies (e.g., 2nd, 3rd, 4th harmonics) to optimize image signal suppression. By changing impedance parameters selectively at different frequency points, the system reduces image signal strength while maintaining the simplicity of the conventional quadrature modulation architecture
2Productivity
If wireless transmission rate is increased, then transmission performance is improved, but signal quality requirements become more stringent
Solution Approach 1:
The harmonic impedance adjustment circuit performs preliminary suppression of image signals before they are amplified and transmitted. By adjusting impedance at harmonic frequencies in advance, the system reduces image signal strength proactively, ensuring signal quality requirements are met even at higher transmission rates where image signals would otherwise become more problematic
3Object-generated harmful factors
If image signal suppression is enhanced, then signal quality is improved, but device complexity increases
Solution Approach 1:
The impedance adjustment units are designed to handle multiple harmonic frequencies (2nd, 3rd, 4th harmonics) simultaneously using a unified circuit topology. This multi-functional approach allows effective image signal suppression across broad frequency ranges without proportionally increasing device complexity, as a single impedance adjustment unit can address multiple harmonic components
Data Source
AI summary
The present invention provides a transmitter including a mixer, a harmonic impedance adjustment circuit and an amplifier. The mixer is configured to mix a first baseband signal with a first oscillation signal to generate a first mixed signal to a first node, and to mix a second baseband signal with a second oscillation signal to generate a second mixed signal to a second node. The harmonic impedance adjustment circuit is coupled between the first node and the second node, and is configured to reduce harmonic components of the first mixed signal and the second mixed signal to generate an adjusted first mixed signal and an adjusted second mixed signal. The amplifier is coupled to the harmonic impedance adjustment circuit, and is configured to generate an amplified signal according to the adjusted first mixed signal and the adjusted second mixed signal.