Dual-Mode Notch Filter for Multi-Band mmWave LO Spur Rejection
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Solution Overview
Problem
Millimeter-wave (mmW) communication systems face challenges in minimizing spurious emissions from local oscillator (LO) frequencies, which can degrade communication signals, especially in multi-band operations, as existing solutions like narrow band amplifier stages require separate paths and increase chip area.
Innovation Solution
A dual mode notch filter is implemented to reject spurious LO and 2LO signal energy, capable of operating in specific bands with minimal impact on other bands, using a switched shunt trap configuration with MOS transistors to selectively couple capacitances across transformers, allowing for state-dependent filter responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If narrow band amplifier stages are used to reject spurious LO signals, then spurious signal rejection is improved, but chip area increases due to requiring separate paths for each band
Solution Approach 1:
The notch filter is designed to provide spurious signal rejection for multiple communication bands (e.g., 3.7-43.5 GHz and 47.2-48.2 GHz) using a single shared filter structure rather than separate filters for each band, thereby reducing chip area while maintaining effective rejection of LO and 2LO spurious signals across all bands
Solution Approach 2:
The patent combines the spurious signal rejection function for multiple bands into a single notch filter that is shared across different communication bands, merging what would traditionally require separate narrow band amplifier stages into one unified structure that reduces overall chip area
2Adaptability or versatility
If communication systems operate at millimeter-wave frequencies with multiple bands, then communication capability is improved, but spurious emissions from LO frequencies degrade signal quality
Solution Approach 1:
The notch filter acts as an intermediary element placed in the signal path between the mixer and subsequent stages, specifically designed to remove spurious LO and 2LO emissions that would otherwise degrade communication signals in multi-band mmW operations, enabling clean signal transmission across multiple bands
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 dual mode notch filter effectively rejects spurious signals at LO and 2LO frequencies, maintaining signal integrity across multiple communication bands with minimal chip area overhead, enhancing communication system performance and compliance with emission standards.
Implementation Method 1
The notch filter is tuned such that its resonant frequency is a harmonic of the LO frequency signal
Implementation Method 2
a notch filter comprising an inductor and a capacitor connected in parallel
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A dual mode notch filter for use in a multi-band millimeter wave (mmW) transmitter includes a transmit filter circuit disposed between two amplifiers in a mmW transmit signal path, the transmit filter circuit formed by at least one switch, at least one capacitor, and a double-tuned transformer, the transmit filter circuit having at least two modes configured to selectively filter a spurious signal in at least a first communication band.