RF Transmission Device Parasitic Filtering via Series Coils
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Solution Overview
Problem
Radiofrequency transmission devices for motor vehicles generate parasitic radio waves at undesired frequencies, which can interfere with other on-board electronics and lead to non-compliance with national regulations, and existing filtering solutions are costly and inefficient.
Innovation Solution
The device employs a filtering mechanism comprising a series of coils with natural resonance frequencies matching the parasitic frequencies, connected in series to attenuate these frequencies without altering the total impedance, ensuring only the fundamental frequency is transmitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional band-pass filtering means are used to filter parasitic frequencies, then parasitic radio waves are attenuated, but the device complexity and cost increase due to requiring multiple capacitors and coils connected to ground
Solution Approach 1:
The invention extracts only the essential filtering function by using a simple series connection of inductors between the transmission unit and matching means, removing the need for complex band-pass filters with multiple capacitors and ground connections while maintaining parasitic frequency attenuation
Solution Approach 2:
The invention changes the filtering approach from impedance-based band-pass filtering to resonance-based frequency selection by carefully selecting inductor values whose natural resonance frequencies correspond to the parasitic frequencies to be filtered, thereby simplifying the circuit topology
2Manufacturing precision
If band-pass filters are used to filter parasitic frequencies, then frequency selection is improved, but the number of electronic components and manufacturing cost increase
Solution Approach 1:
The invention segments the filtering function across multiple inductors with specific resonance frequencies (e.g., L2 resonating at 2×fF, L3 at 3×fF, L4 at 4×fF), where each inductor targets a specific parasitic frequency, achieving comprehensive filtering with simpler individual components
Solution Approach 2:
The invention replaces expensive, complex band-pass filter assemblies with inexpensive inductors that can be easily manufactured and integrated, reducing bill of materials cost and simplifying the manufacturing process
3Object-generated harmful factors
If the filtering means are connected to ground as in traditional filters, then parasitic frequency filtering is achieved, but the total impedance of the circuit is altered affecting the fundamental frequency transmission
Solution Approach 1:
The invention introduces inductors as intermediary elements between the transmission unit and matching means that provide frequency-selective attenuation without creating direct ground paths, thereby maintaining the impedance relationship needed for fundamental frequency transmission while blocking parasitic frequencies
Solution Approach 2:
The invention uses the resonant vibration principle of inductors at specific frequencies to attenuate parasitic signals, where the inductors naturally resonate at frequencies corresponding to the parasitic harmonics, providing filtering without altering the fundamental frequency transmission path
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
This approach effectively filters out parasitic frequencies, preventing interference and ensuring compliance with regulatory standards while reducing the number of electronic components and costs.
Implementation Method 1
n-1 inductors, each having a natural resonance frequency corresponding to a harmonic of the predetermined fundamental frequency
Data Source
AI summary
A radiofrequency transmission device (D′) includes: a transmission unit (10) for transmitting a voltage signal (S) in pulsed form; a radiofrequency antenna (A); filtering elements (30′); and a voltage source (Vcc), wherein the filtering elements (30′) include:“n” coils (B1, B2. . . Bn), electrically connected in series, of which (n−1) coils each have a natural resonance frequency such that:fRLi=i×fF each having an inductance (Li) such that, at the predetermined fundamental frequency:LTOT=L1+L2+ . . . Li+ . . . Ln=ZTOT=Z1+Z2+ . . . Zi+ . . . Zn andLi=Zi wherefRLi Is the natural resonance frequency of the i-th coili is a number varying from 2 to n,LTOT is the total inductance of the n coils,Li is the inductance of the i-th coil,ZTOT is the total impedance of the n coils,Zi is the impedance of the i-th coil,n is an integer greater than zero.