Tunable RF Filter for Subharmonic Blocking in Multiband Receivers
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Solution Overview
Problem
Multiband radio receivers face challenges in filtering out subharmonic frequency blocking signals, which cause harmonic distortion and degrade signal-to-noise ratio without conventional band-specific RF preselection filters, leading to increased complexity and power consumption.
Innovation Solution
A tunable radio frequency filter with a series resonant circuit comprising a tunable capacitor and inductor, configured to resonate at subharmonics of operating frequencies, providing impedance matching and filtering out first and second subharmonics while maintaining low complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional band-specific RF preselection filters are used, then subharmonic blocking signals are filtered effectively, but device complexity and power consumption increase
Solution Approach 1:
The patent implements a single tunable RF filter that can be configured to filter multiple different frequency bands by adjusting the resonant frequency of its LC circuit. This universal filter replaces what would traditionally require multiple band-specific filters, thereby reducing device complexity while maintaining effective subharmonic blocking signal attenuation across multiple operating bands
Solution Approach 2:
The filter employs a tunable LC circuit where the resonant frequency can be dynamically adjusted based on the operating band. By changing the inductance or capacitance values, the filter adapts to different frequency bands, enabling a single filter structure to perform the function of multiple static filters, thus reducing overall system complexity
2Object-affected harmful factors
If traditional band-specific RF preselection filters are used, then subharmonic blocking signals are filtered effectively, but power consumption increases
Solution Approach 1:
The single tunable filter serves multiple frequency bands, eliminating the need for multiple parallel filter circuits that would each consume power. By consolidating the filtering function into one reconfigurable circuit, the overall power consumption is reduced while maintaining effective attenuation of subharmonic blocking signals across all bands
3Device complexity
If a single tunable RF filter is used, then device complexity is reduced, but filtering effectiveness across multiple bands must be maintained
Solution Approach 1:
The filter uses a tunable LC circuit that can dynamically adjust its resonant frequency to match different operating bands. This dynamic tuning capability allows a single filter structure to adapt to multiple frequency bands, maintaining filtering effectiveness across all bands while reducing device complexity compared to having separate filters for each band
4Object-affected harmful factors
If heavy filtering is provided before LNA, then blocking signals are attenuated, but receiver linearity requirements can be relaxed
Solution Approach 1:
The single tunable filter provides heavy attenuation of blocking signals across multiple bands by being selectively tuned to each band's subharmonic frequencies. This universal approach achieves the same blocking signal attenuation as multiple band-specific filters would provide, but with reduced structural complexity
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 effectively filters out subharmonic frequency blocking signals, reducing harmonic distortion and improving signal-to-noise ratio without increasing power consumption or silicon area, while supporting multiple frequency bands.
Implementation Method 1
The series resonant circuit is configured to be resonant at a plurality of first subharmonics of frequencies of the operating frequency bands
Implementation Method 2
The series resonant circuit comprises a first inductor and a tunable capacitor connected in series with first inductor and having a plurality of tuning values corresponding to operating frequency bands
Data Source
AI summary
According to an aspect, there is provided a tunable radio frequency filter (209) for preselection in a multiband radio receiver or transceiver with a low-noise amplifier with a single-ended input. The tunable radio frequency filter comprises a first capacitor (C1, 1001) having a first terminal for connecting to at least one antenna of the multiband radio receiver or transceiver and a second terminal; and a series resonant circuit, connected between the second terminal of the first capacitor and the ground. The series resonant circuit comprises a first inductor (L1 1003) and a tunable capacitor (Ct, 1004) connected in series with first inductor and having a plurality of tuning values corresponding to operating frequency bands of the multiband radio receiver or transceiver. The tunable capacitor is implemented in an integrated circuit. The series resonant circuit is configured to be resonant at a plurality of first subharmonics of frequencies of the operating frequency bands. Optionally the filter comprises a second capacitor (C2, 1002) and a second inductor (L2, 1010) in series between the resonant circuit to ground and the input of the LNA. The second inductor adds to impedance matching and low pass filtering above the operating frequency bands.