Ferrite RF Filter Reduces Inductance in Mobile Antenna Contacts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mobile wireless communications devices face interference issues due to conducted or near-field radiated energy from power amplifiers and antennae, leading to degradation of total radiated power and harmonic interference, especially in GSM systems, and linearity issues with power amplifiers and antenna matching.
Innovation Solution
The design incorporates a separate power amplifier circuit for each In-phase and Quadrature circuit, along with an RF filter near the battery charging contacts to minimize harmonic emission and improve antenna performance by using a ferrite-based RF filter to increase impedance and reduce digital noise, and an L-configured multi-frequency band antenna positioned at the lower edge of the device to enhance transmission and reception characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If components are placed closer together to reduce device size, then device compactness is improved, but conducted energy interference between components increases
Solution Approach 1:
The patent introduces ferrite beads as intermediary components placed on the antenna contact and charging contacts. These ferrite beads act as mediators that block conducted RF energy while allowing DC power and signal transmission, thereby preventing interference between closely spaced components without increasing device volume.
Solution Approach 2:
The patent employs composite material structures combining ferrite particles embedded in a polymer matrix to create RF-blocking contacts. This composite approach allows the contact structure to simultaneously provide electrical connectivity for power/signals while blocking harmful RF conducted energy, resolving the interference issue in compact designs.
2Reliability
If antenna contact length is reduced to minimize RF inductance, then RF performance is improved, but contact reliability may deteriorate
Solution Approach 1:
The antenna contact uses a composite structure of ferrite particles in a polymer matrix that provides both mechanical strength for reliable contact and RF-blocking properties. This composite material allows the contact to be short (improving RF performance by reducing inductance) while maintaining adequate mechanical strength and reliability.
Solution Approach 2:
The patent changes the material parameters of the antenna contact by using ferrite-loaded polymer instead of traditional conductive materials. This parameter change allows the contact to have low inductance due to short length while the ferrite particles provide the necessary mechanical strength and RF-blocking capability.
3Object-generated harmful factors
If power amplifier linearity is improved to reduce harmonic interference, then harmonic emission is reduced, but device complexity increases
Solution Approach 1:
The patent places ferrite beads on the power amplifier housing and circuit board as intermediary elements that filter harmonic emissions. This approach reduces harmonic interference without requiring complex power amplifier circuit designs, thereby reducing device complexity while achieving the desired reduction in harmonic emissions.
Solution Approach 2:
Instead of making the power amplifier itself more complex to reduce harmonics, the patent extracts the harmonic filtering function to separate ferrite bead components. This separation allows the power amplifier to remain simple while the ferrite beads handle the harmonic suppression function.
4Reliability
If ferrite-based RF filter is added to increase impedance and reduce digital noise, then antenna performance is improved, but device complexity increases
Solution Approach 1:
The ferrite beads serve multiple functions simultaneously: they block conducted RF energy, filter harmonic emissions, increase impedance to reduce digital noise, and provide mechanical support. This multi-functionality means that while components are added, the overall complexity increase is minimized because a single component type (ferrite beads) performs multiple protective and filtering functions.
Solution Approach 2:
The patent uses ferrite beads to change the impedance parameter of the antenna contact and surrounding circuitry. This parameter change naturally reduces digital noise and improves antenna performance without requiring additional complex filtering circuits, as the impedance transformation itself provides the noise reduction.
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 configuration reduces harmonic interference, improves antenna matching, and increases battery life by using more linear power amplifiers, while maintaining efficient digital modulation and meeting SAR requirements across multiple frequency bands.
Implementation Method 1
using a ferrite-based RF filter to increase impedance and reduce digital noise
Implementation Method 2
RF filter near the battery charging contacts to minimize harmonic emission and improve antenna performance
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A mobile wireless communications device includes a housing and at least one circuit board. Radio frequency (RF) circuitry is carried by the circuit board and includes a transceiver. A processor is carried by the at least one circuit board and operative with the RF circuitry. An antenna is mounted within the housing. An antenna contact is secured on the at least one circuit board and operatively connects the RF circuitry and engages the antenna at an antenna contact point. Electromagnetic interference (EMI) shielding is positioned at the antenna contact point and reduces RF inductance effects. In an alternative configuration, said antenna comprises a flex section at the contact point and forming an RF stub and the antenna contact comprises a lower key that is secured to the circuit board and an upper key having an inverted V-shaped upper contact member engaging the antenna at the antenna contact part such that the inverted V-shaped upper contact member provides parallel inductances and reduces RF inductance effects.