RF Shielded PA-Antenna Switch Path for Harmonic Coupling Reduction
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Solution Overview
Problem
Mobile wireless communications devices face interference issues due to unwanted reception of conducted and near-field radiated energy from power amplifiers and antennas, particularly in GSM systems, which causes signal coupling through RF shields and bypasses filtering components.
Innovation Solution
A low pass filter, such as an RLC filter, is integrated within the transmission line between the power amplifier and antenna switch, reducing RF coupling of voltage standing waves at harmonic frequencies while maintaining signal transmission at the fundamental frequency, using capacitors and resistors configured to dominate impedance at harmonic frequencies and ensure effective filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If RF circuitry components are placed closer together to reduce device size, then device compactness is improved, but conducted energy interference between components increases
Solution Approach 1:
An RF shield is introduced as an intermediary component between the power amplifier and antenna switch to block conducted energy interference. The shield acts as a physical barrier that prevents harmful RF energy from coupling between closely spaced components while allowing the components to remain in compact proximity.
Solution Approach 2:
The RF circuitry is segmented into isolated compartments using RF shields. The power amplifier and antenna switch are separated by conductive shielding partitions that divide the RF circuit board into distinct zones, preventing interference while maintaining compact overall device structure.
2Object-affected harmful factors
If RF shield is used to isolate power amplifier and antenna switch, then conducted energy interference is reduced, but voltage standing waves of harmonic frequencies couple through the shield
Solution Approach 1:
A low-pass filter is introduced as an intermediary component within the transmission line between the power amplifier and antenna switch. This filter blocks voltage standing waves of harmonic frequencies from coupling through the RF shield while allowing fundamental frequency signals to pass through the shield and filter normally.
Solution Approach 2:
The harmful voltage standing waves of harmonic frequencies are extracted and removed from the transmission path using a low-pass filter. The filter extracts and attenuates these unwanted harmonic frequencies before they can couple through the RF shield to the antenna switch.
3Object-affected harmful factors
If low pass filter is added to reduce harmonic coupling, then RF interference is reduced, but device complexity increases
Solution Approach 1:
The low-pass filter is designed to perform multiple functions: it blocks voltage standing waves of harmonic frequencies, maintains impedance matching in the transmission line, and works in conjunction with the existing RF shield to provide comprehensive RF interference rejection without requiring additional separate components.
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 solution significantly reduces RF coupling of upper harmonic frequencies, minimizing interference and maintaining signal integrity through the RF shield, thereby enhancing the performance of mobile wireless communications devices.
Implementation Method 1
a low pass filter is formed within the transmission line and has an input connected to the power amplifier and an output connected to the antenna switch for reducing any RF coupling of voltage standing waves of upper harmonic frequencies from the power amplifier into the antenna switch between the input and output of the low pass filter through the RF shield
Implementation Method 2
An RF shield surrounds the power amplifier and antenna switch for isolating the power amplifier and antenna switch from the antenna and RF circuitry
Implementation Method 3
using capacitors and resistors configured to dominate impedance at harmonic frequencies and ensure effective filtering
Data Source
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AI summary
A mobile wireless communications device includes a housing and antenna supported by the housing. At least one circuit board is carried by the housing and has radio frequency (RF) circuitry operative with the antenna for receiving and transmitting RF signals through the antenna. A power amplifier is connected within a transmission line for amplifying RF signals to be transmitted over the transmission line to the antenna. An antenna switch is carried by the circuit board and connected to the antenna and RF circuitry. An RF shield surrounds the power amplifier and antenna switch isolates the power amplifier and antenna switch from the antenna and RF circuitry. A low pass filter has an input connected to the power amplifier and an output connected to the antenna switch for reducing any RF coupling of voltage standing waves of upper harmonic frequencies from the power amplifier into the antenna switch between the input and output of the low pass filter through the RF shield while maintaining transmission of signals through the transmission line at a desired fundamental frequency.