Multi-Band RF Receiver Notch Filtering for Sub-Harmonic Blockers
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Solution Overview
Problem
Multi-band radio receivers face challenges due to bulky and expensive designs resulting from the need for multiple RF pre-selection filters and LNAs, which are not effective against sub-harmonic frequency blocking signals, leading to reduced signal-to-noise ratio (SNR) and increased complexity and power consumption.
Innovation Solution
A radio frequency receiver with a variable notch filter that attenuates sub-harmonics, comprising a serial arrangement of inductance and capacitance, allowing the same LNA to support multiple frequency bands without external filters, using a capacitor matrix to adjust the notch frequency and provide sufficient attenuation for sub-harmonic blockers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RF pre-selection filters and LNAs are used for multi-band support, then frequency band coverage is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a single LNA that can operate across multiple frequency bands by tuning its resonance frequency, eliminating the need for multiple dedicated LNAs for different bands. This universal approach allows one component to perform multiple functions that previously required separate components for each frequency band.
Solution Approach 2:
The patent employs variable resonance frequency filtering where the LNA's resonance frequency can be dynamically adjusted to match different frequency bands. This dynamic tuning capability allows the same hardware to adapt to multiple bands without requiring physical reconfiguration or multiple fixed-frequency components.
2Area of stationary object
If RF pre-selection filters are omitted to improve integration, then area on silicon is reduced, but linearity requirements increase
Solution Approach 1:
The patent applies preliminary filtering action by implementing resonance frequency filtering within the LNA itself, which attenuates out-of-band blocking signals before they can drive the amplifier into compression. This preliminary suppression of harmful signals allows the system to maintain linearity without requiring external pre-selection filters.
Solution Approach 2:
The patent introduces an intermediate resonance frequency control mechanism that acts as a mediator between the input signal and the LNA amplification stage. By inserting this frequency-selective element, the system can tolerate stronger blocking signals while maintaining linearity, effectively bridging the gap between filter omission and linearity requirements.
3Measurement precision
If linearization techniques are applied to reduce harmonic distortion, then SNR is improved, but complexity and power consumption increase
Solution Approach 1:
The patent converts the potentially harmful effect of blocking signals at sub-harmonic frequencies into a beneficial outcome by using resonance frequency filtering to selectively attenuate these specific frequencies. Rather than applying complex linearization techniques to all harmonics, the system targets and eliminates the root cause (sub-harmonic blockers) before they can generate harmful intermodulation products.
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 configuration improves the SNR by effectively attenuating sub-harmonic signals, reducing the need for multiple filters and LNAs, resulting in a more compact, cost-effective, and efficient multi-band receiver design.
Implementation Method 1
a variable notch filter acting on signals passing from the antenna to the RF amplifier, said variable notch filter having a resonance frequency fr selected from a plurality of possible resonance frequencies such that fr=ft/n where n is a whole number between 2 and 10, the variable notch filter thereby acting to attenuate signals from the antenna at said resonance frequency
Data Source
AI summary
A radio frequency receiver is provided that comprises an antenna, an RF amplifier, at least one down conversion mixer stage and a variable notch filter. The at least one down-conversion mixer stage is arranged to act on signals provided by the RF amplifier and is tuned to a tuned frequency ft which is selected from a plurality of possible tuned frequencies corresponding to a frequency of the RF signal to be received at the antenna. The variable notch filter is arranged to act on signals passing from the antenna to the RF amplifier and has a resonance frequency fr which is selected from a plurality of possible resonance frequencies such that fr=ft in where n is a whole number between 2 and 10. The variable notch filter thereby acts to attenuate signals from the antenna at said resonance frequency.