Baseband High-Pass Filtering for WiGig Frequency Pulling Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high-frequency WiGig transceivers, particularly at 60 GHz, frequency pulling and locking issues arise due to parasitic capacitance and inductance, causing performance degradation in on-chip clock oscillators, and existing methods to separate oscillators are ineffective at reducing these effects.
Innovation Solution
Implementing a high pass filter in the baseband path with a cutoff frequency of 40 MHz to separate the oscillator frequency from the RF transmitter frequencies, reducing substrate coupling effects and allowing a closer physical distance between the oscillator and mixer, thereby minimizing parasitic inductance and capacitance impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oscillator and mixer are placed close together to reduce parasitic inductance and capacitance, then the performance of the transceiver is improved, but frequency pulling and locking issues occur due to substrate coupling
Solution Approach 1:
A high pass filter is introduced as an intermediary component between the oscillator and mixer. This filter blocks low frequency signals (including substrate coupling effects) while allowing high frequency signals to pass through, thereby eliminating frequency pulling and locking issues while maintaining close physical placement of components
2Object-affected harmful factors
If the oscillator is separated from the mixer by increasing distance to reduce substrate coupling, then frequency pulling is reduced, but parasitic inductance and capacitance increase degrading performance
Solution Approach 1:
The high pass filter serves as a mediator that allows the oscillator and mixer to remain physically close (minimizing parasitic inductance and capacitance) while simultaneously blocking substrate coupling effects through its frequency-selective properties
3Object-affected harmful factors
If a high pass filter is added to the baseband path, then frequency pulling and locking are reduced, but device complexity increases
Solution Approach 1:
The high pass filter is designed with a specific cutoff frequency parameter optimized for the 60 GHz application. By carefully selecting this parameter, the filter effectively blocks substrate coupling frequencies while passing the desired RF signals, achieving frequency pulling reduction with minimal added complexity
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
Significantly reduces frequency pulling and locking issues, maintaining the target frequency operation while enabling a reduction in physical distance between components, thus enhancing the performance of direct conversion transceivers.
Implementation Method 1
Implementing a high pass filter in the baseband path with a cutoff frequency of 40 MHz to separate the oscillator frequency from the RF transmitter frequencies
Implementation Method 2
parasitic capacitance plays an influential role in the performance of electrical circuits The drain/gate capacitance is about 10 fF per micron width
Implementation Method 3
the wire used to interconnect the drain to the inductor can have an inductance of 1 pH/μm
Implementation Method 4
In addition, the skin effect causes resistive losses as the length of the interconnect increases
Data Source
AI summary
In an up-converter path of a transmitter, wide-band signal system like direct conversion WiGig, a high pass filter (HPF) is placed in the baseband path after the low pass filter (LPF) but before the mixers. The baseband signal of WiGig can have a bandwidth of 800 MHz. The HPF removes the frequencies from 0-40 MHz from the baseband signal and degrades the overall signal of the baseband by a dB or so. However, the frequency pulling is significantly reduced since oscillator frequency and Radio frequency (RF) transmitter frequencies after conversion become further separated when compared a system using to the conventional approach. This causes the injected signal to fall outside the locking range of the oscillator. The concern of substrate coupling is reduced and allows for a reduction in the physical distance between the oscillator and the mixer and reduces a shift in the desired target frequency of operation.