Tunable SAW Resonators with DAC Biasing for Multi-Band RF Filters
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Solution Overview
Problem
Current RF filters in mobile devices require multiple fixed-frequency filters to cover various communication bands, leading to increased size and power consumption, as they cannot be tuned to accommodate multiple frequency ranges effectively.
Innovation Solution
Tunable Surface Acoustic Wave (SAW) interdigital transducers with embedded or elevated electrode doped regions, utilizing digital to analog converters (DACs) to apply DC bias voltages for adjusting the central frequency of acoustic waves, allowing for the creation of filters, oscillators, and switches that can operate across multiple frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple fixed-frequency filters are used to cover various communication bands, then frequency coverage is improved, but device size and power consumption increase
Solution Approach 1:
The patent applies dynamics by making the filter frequency tunable through voltage control. The interdigital transducer's resonant frequency can be dynamically adjusted by applying different DC bias voltages, allowing a single filter to cover multiple communication bands. This replaces the static multiple fixed-frequency filters with one dynamically adjustable filter, reducing device size while maintaining frequency coverage capability.
Solution Approach 2:
The patent implements universality by designing a single SAW filter that can perform multiple frequency selection functions. By embedding doped regions in the interdigital transducer, the filter can be electrically tuned to operate at different frequencies, making it a universal solution that replaces multiple band-specific filters with one multi-functional component.
2Adaptability or versatility
If multiple fixed-frequency filters are used to cover various communication bands, then frequency coverage is improved, but power consumption increases
Solution Approach 1:
The dynamic voltage-tunable frequency capability allows the system to activate only the specific filter frequency needed for current communication operations. Instead of powering multiple fixed-frequency filters simultaneously, the single tunable filter can be dynamically configured, reducing overall power consumption while maintaining the ability to cover various communication bands.
Solution Approach 2:
The universal tunable filter design consolidates multiple filter functions into one component, eliminating the need to power several separate filters. The single multi-functional filter reduces total power consumption while providing the same frequency coverage capability as multiple fixed-frequency filters would provide.
3Area of stationary object
If a single tunable filter is used to cover multiple frequency bands, then device size and power consumption are reduced, but frequency tuning capability must be precisely controlled
Solution Approach 1:
The patent employs parameter changes by utilizing the relationship between DC bias voltage and resonant frequency. By changing the electrical parameter (voltage) applied to the doped regions, the filter's operating frequency can be precisely tuned. This electrical control mechanism provides fine frequency adjustment capability, addressing the precision control requirement while maintaining the compact single-filter design.
Solution Approach 2:
The patent incorporates feedback mechanisms through voltage-controlled oscillators and phase-locked loops that monitor and adjust the filter's operating frequency. This feedback system ensures precise frequency tuning control, compensating for any drift and maintaining accurate frequency selection despite the simplified single-filter architecture.
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 the reduction of the number of RF filters needed, minimizing size and power consumption by allowing a single tunable filter to cover multiple frequency bands, thereby enhancing the versatility and efficiency of RF front ends in mobile devices.
Implementation Method 1
an input inter digital transducer IDT1 (120) with a center-to-center distance between adjacent electrodes controlled to a 'pitch' and connected to an electrical signal source (130) to excite acoustic waves (140) with a velocity v and at a frequency fo=v/(2×pitch)
Implementation Method 2
Surface Acoustic Wave (SAW) Filters
Implementation Method 3
an output inter digital transducer IDT2 (150) with a center-to-center distance between adjacent electrodes again also controlled to the 'pitch' to receive the acoustic waves (140) and to convert them into an output electrical signal (160)
Data Source
AI summary
Due to strong needs to reduce the dimensions and the cost of the RF filters and to reduce the number of filters required in an mobile handsets and wireless system covering numbers of operation bands, tunable RF filters which can cover as many bands or frequency ranges as possible are needed so that the number of filters can be reduced in the mobile handsets and wireless systems. The present invention provides tunable surface acoustic wave (SAW) IDT structures with the resonant frequency of the acoustic wave to be excited and to be transmitted tuned by digital to analog converters (DACs). The DAC converts an input digital signal to an output DC voltage and provide DC bias voltages to the SAW IDTs through integrated thin film biasing resistors. The polarity and the value of the output DC voltage are controlled by the input digital signal to achieve selection and tuning of the resonant frequency of the SAW IDTs.