Wireless Receiver Common-Mode Trap Circuit for Mixer Interference
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Solution Overview
Problem
Existing mobile wireless receivers face challenges in suppressing undesired common mode components due to non-ideal behavior of mixer and balun circuits, leading to interference and increased power consumption, which complicates the design and increases costs.
Innovation Solution
Incorporating first and second common mode traps, configured as Y circuits with coils and capacitors, to selectively short-circuit undesired common mode signals at specific frequencies, thereby simplifying the receiver structure and reducing power consumption while maintaining differential signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common mode traps are added to suppress undesired common mode components, then interference is reduced and receiver robustness is improved, but device complexity increases
Solution Approach 1:
The receiver circuit is segmented into differential and common mode pathways. The common mode traps are selectively placed only where needed (between mixer outputs and balun circuits) rather than throughout the entire circuit, allowing suppression of common mode interference while maintaining simplicity in other circuit sections.
Solution Approach 2:
Common mode traps serve as intermediary components inserted between the mixer outputs and balun circuits. These traps act as frequency-selective mediators that allow desired differential signals to pass while blocking undesired common mode components, resolving the contradiction by providing targeted interference suppression without requiring complete circuit redesign.
2Object-generated harmful factors
If linear mixer behavior is maintained to reduce intermodulation, then interference is reduced, but power consumption increases
Solution Approach 1:
The invention converts the potentially harmful non-linear mixer behavior into a benefit by using common mode traps to capture and redirect the resulting common mode intermodulation products. This allows mixers to operate in their more efficient non-linear region while the traps convert the harmful intermodulation into a manageable common mode signal that can be easily filtered.
Solution Approach 2:
Undesired common mode components and intermodulation products are extracted from the differential signal pathway using common mode traps. By separating and removing these harmful components, the system can tolerate greater mixer non-linearity without degrading performance, thus reducing power consumption while maintaining low interference.
3Object-generated harmful factors
If more components are added to suppress common mode signals, then interference suppression is improved, but manufacturing cost increases
Solution Approach 1:
Common mode traps with specific impedance characteristics are placed only at critical locations where common mode interference generation is most problematic (between mixers and baluns). This localized approach provides effective interference suppression only where needed, avoiding the cost of adding components throughout the entire receiver circuit.
Solution Approach 2:
The common mode traps are designed with specific impedance parameters (typically 50-100 ohms) that are optimized for the operating frequency range. By carefully selecting these parameters, a single trap design can suppress a broad range of common mode frequencies, reducing the need for multiple different components and simplifying manufacturing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The common mode traps significantly reduce interference by over 20-30 dB at specific frequencies, enhancing mixer performance, suppressing unwanted emissions, and allowing for lower power consumption and cost-effective design with fewer components.
Implementation Method 1
The common mode trap comprises a Y-shaped circuit of two coils and a capacitor which form a common mode high pass which can short circuit high-frequency common mode signals
Implementation Method 2
The common mode trap comprises a Y-shaped circuit of two coils and a capacitor
Implementation Method 3
A balun circuit forms a passive circuit which is configured to convert between symmetrical (differential/balanced) and asymmetrical (unbalanced) signals
Implementation Method 4
The output signals of the two mixers form the two poles of a second differential signal which is fed to the second balun circuit
Data Source
AI summary
A mobile wireless receiver is provided comprising an HF input, an intermediate-frequency output, a first and second mixer, which are each operated in common mode with a frequency of a local oscillator, a first balun circuit, which is coupled to the HF input and a second balun circuit, which is coupled to the intermediate-frequency output, a first common mode trap, which is coupled to the first balun circuit and the first and second mixer and a second common mode trap, which is coupled to the second balun circuit and the first and second mixer.