Electronically Tunable Harmonic Filter for Multiband RF Transmitters
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Solution Overview
Problem
Conventional radio transmitters face challenges in efficiently filtering harmonics across multiple frequency bands due to the limited bandwidth of harmonic filters, leading to increased form factor and manufacturing costs, as well as performance limitations in high-power output paths.
Innovation Solution
The implementation of an electronically tunable harmonic filter (ETHF) using CMOS-SOI and/or MEMS switches to dynamically control filter characteristics such as bandwidth, center frequency, input impedance, and output impedance, allowing the radio transmitter to operate on multiple frequency bands with reduced harmonic interference and optimized power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional harmonic filters are used in a multiband transmitter, then harmonic filtering can be provided for each frequency band, but the number of filters required increases leading to increased device complexity and form factor
Solution Approach 1:
The patent implements a single harmonic filter that can be electronically tuned to provide filtering for multiple frequency bands. The filter is designed with adjustable parameters (center frequency, bandwidth, impedance) that allow it to adapt to different operating bands, replacing what would traditionally require multiple fixed-frequency filters. This multi-functional approach reduces the total number of filter components while maintaining comprehensive harmonic filtering coverage across all bands.
Solution Approach 2:
The patent employs electronic tuning mechanisms that dynamically adjust the filter's characteristics during operation. By using electronic control to modify the filter's center frequency and bandwidth based on the current operating band, the system transitions from static fixed-frequency filtering to dynamic adaptive filtering. This enables a single filter to effectively cover multiple bands that would otherwise require separate fixed filters.
2Reliability
If multiple harmonic filters are used to cover multiple frequency bands, then comprehensive harmonic filtering is achieved, but the form factor and manufacturing costs increase
Solution Approach 1:
The patent designs a universal harmonic filter capable of operating across multiple frequency bands through electronic tuning. This single multi-functional filter replaces multiple band-specific filters, reducing the bill of materials and assembly complexity. The filter incorporates adjustable parameters that allow it to be configured for different bands, eliminating the need to manufacture and stock multiple different filter types.
Solution Approach 2:
The patent combines the functionality of multiple separate harmonic filters into a single integrated filter unit. By merging the filtering capabilities for multiple bands into one component with electronic reconfiguration ability, the system reduces component count, simplifies assembly, and lowers manufacturing costs while maintaining comprehensive harmonic filtering coverage across all operating bands.
3Device complexity
If a single harmonic filter is used for multiple frequency bands, then device complexity is reduced, but the filter must handle high power output which challenges filter performance
Solution Approach 1:
The patent implements dynamic impedance matching and electronic tuning capabilities that adapt the filter's characteristics to match the high-power output conditions of the power amplifier. The filter can dynamically adjust its parameters to optimize performance under varying power levels and frequency conditions, ensuring reliable operation across all bands without requiring multiple filters. This dynamic adaptation allows the single filter to maintain stability and performance despite high power handling requirements.
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 solution enables efficient harmonic filtering across multiple frequency bands, reducing the need for multiple filters, minimizing form factor and manufacturing costs, and ensuring high-power handling capabilities while maintaining low insertion loss and linearity.
Implementation Method 1
The method includes selectively controlling at least one filter characteristic of the ETHF using at least one RF switch
Implementation Method 2
such unwanted interaction can be reduced by interposing or connecting at least one capacitor component between the at least one RF switch and an RF transmit signal path
Implementation Method 3
Similarly, parasitic effects of at least one inductor component can be reduced
Data Source
AI summary
Reducing harmonics in a radio transmitter can involve using an electronically tunable harmonic filter (ETHF) in a transmit path at the output of an RF power amplifier stage to reduce harmonic signal components in the RF transmit signal. At least one filter characteristic of the ETHF is selectively controlled using one or more RF switch. The one or more RF switches that are used to control the ETHF can include a CMOS-SOI and/or a MEMs type of switch. Various filter characteristics of the ETHF can be controlled including a bandwidth and/or a center frequency of the ETHF.