Tunable RF Front-End Circuit for In-Band Carrier Aggregation
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Solution Overview
Problem
Current front-end circuits for wireless communication devices face complexity in supporting multiple frequency bands and enabling carrier aggregation modes, particularly in in-band scenarios where frequency bands are within the same range or closely adjacent, lacking efficient solutions for simultaneous operation in multiple bands.
Innovation Solution
A front-end circuit design featuring tunable filters with independent signal paths and adjustable tuning ranges, allowing for simultaneous operation in multiple transmission and reception bands, including the use of high-quality LC resonant circuits and tunable capacitors, and optional antenna tuners or phase shifters for optimal frequency selection and interference reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple fixed filters are connected to support different frequency bands, then frequency band coverage is improved, but device complexity increases
Solution Approach 1:
The patent employs tunable filters with adjustable resonance frequencies that can be dynamically reconfigured to support multiple frequency bands. The filter circuit includes variable capacitors and inductors that allow the resonance frequency to be tuned across different bands (e.g., Band 1 at 700 MHz, Band 2 at 1800 MHz, Band 3 at 2600 MHz), replacing the need for multiple fixed filters with a single dynamically adjustable filter, thereby reducing circuit complexity while maintaining broad frequency band coverage
Solution Approach 2:
The front-end circuit is designed with a universal filter structure that can operate across multiple frequency bands by adjusting its resonance characteristics. The same filter circuit serves multiple functions by being reconfigurable to different frequency bands through controlled adjustment of its reactive components, enabling a single circuit to replace what would traditionally require multiple separate filters for different bands
2Adaptability or versatility
If tunable impedance elements are added to expand filter functionality, then frequency band adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements frequency band adaptation by changing the electrical parameters (capacitance and inductance values) of the filter components. Variable capacitors with different capacitance values are switched or tuned to adjust the resonance frequency of the LC circuits, enabling the filter to adapt to different frequency bands through controlled parameter changes rather than requiring precise manufacturing tolerances for fixed values
Solution Approach 2:
The filter uses dynamically adjustable impedance elements (variable capacitors and inductors) that can be tuned during operation to achieve the desired resonance frequency for different frequency bands. This dynamic adjustment capability reduces the stringency of manufacturing precision requirements by allowing post-manufacturing tuning and adaptation
3Adaptability or versatility
If switches are used to connect filter elements, then filter topology flexibility is improved, but device complexity increases
Solution Approach 1:
Instead of using switches to dynamically reconfigure filter topology, the patent employs fixed filter elements with adjustable reactive components (variable capacitors and inductors) that change the filter characteristics through parameter adjustment rather than topological reconfiguration. This approach maintains filter topology flexibility while avoiding the complexity of switch networks and associated control logic
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
Enables simplified carrier aggregation mode and efficient data rate doubling in both uplink and downlink operations by allowing flexible frequency band selection and interference-free parallel operation across multiple bands, with reduced complexity and loss.
Implementation Method 1
A filter whose frequency band can be tuned by means of a control circuit is arranged in each of the signal paths
Implementation Method 2
The article 'Tunable Filters Using Wideband Elastic Resonators', Kadota et al., IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol. 60, No. 10, October 2013, pages 2129-2136, discloses filter circuits in which tunable capacitors are added to RF filters having acoustic resonators
Data Source
AI summary
A front end circuit is disclosed. In an embodiment, the circuit includes a first antenna connection and first to third signal paths, each of which include a tunable filter and each of which is connected to the first antenna connection. The circuit further includes at least one phase shifter arranged in at least one of the signal paths between a respective filter and the first antenna connection and a control circuit configured to tune frequency bands of the filters, wherein the filters are operable in a FDD operating mode or a TDD operating mode, and wherein the front-end circuit is simultaneous operable in at least one transmission band and at least one reception band using all three filters and the associated signal paths.