Frequency-Translated Notch Filter for SAW-Less Wideband RF Receivers
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Solution Overview
Problem
Current RF receiver designs face challenges in attenuating large out-of-band interferers on semiconductor substrates, leading to increased noise factor and reduced sensitivity, particularly due to the limitations of silicon-based inductors and the need for high-Q filters that are not amenable to monolithic integration.
Innovation Solution
The implementation of a frequency translated notch filter (FTNF) on a semiconductor substrate, which uses a passive mixer and baseband impedance to create a high-Q notch filter, effectively attenuating out-of-band interferers while allowing desired signals to pass through, thereby reducing noise factor and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SAW filters are used to provide high-Q filtering, then out-of-band interferers are attenuated effectively, but the filters cannot be monolithically integrated on semiconductor substrate and add cost and circuit board area
Solution Approach 1:
The patent replaces mechanical SAW filters with an electronic frequency translated notch filter (FTNF) implementation using passive mixers and baseband impedance networks. This substitution enables high-Q filtering to be achieved through electronic means that can be monolithically integrated on semiconductor substrates, eliminating the need for separate mechanical filter components
Solution Approach 2:
The patent introduces frequency translation as an intermediary mechanism to achieve high-Q filtering. By translating the notch filter operation to RF frequencies through mixing operations, the system achieves SAW-filter-level performance using integrated circuit elements, bridging the gap between mechanical filter performance and electronic integrability
2Ease of manufacture
If silicon-based inductors are used for integration, then monolithic integration is achieved, but the Q-factor is limited and insufficient for wideband applications
Solution Approach 1:
The patent replaces traditional silicon-based inductor-based filtering approaches with frequency translation using passive mixers. This substitution bypasses the fundamental Q-factor limitations of silicon inductors by achieving high-Q filtering through the mixing process itself, which can preserve the Q characteristics of low-Q baseband filters when translated to RF frequencies
Solution Approach 2:
The patent changes the operating parameters of the filtering function by translating it from baseband to RF frequencies through mixing. This parameter change allows low-Q filters at baseband to effectively function as high-Q filters at RF frequencies, overcoming the Q-factor limitations inherent in silicon-based passive components
3Reliability
If band-pass filters are placed before LNA to attenuate blockers, then LNA gain compression is prevented, but the filters add insertion loss and increase noise factor
Solution Approach 1:
The patent introduces frequency translation as an intermediary approach to achieve blocker attenuation. By using passive mixers to translate and reject out-of-band interferers, the system achieves the linearity protection function without the insertion loss penalty of conventional band-pass filters, as the mixing process can be performed with minimal loss active elements
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 FTNF provides effective attenuation of out-of-band interferers, reducing the noise factor and increasing the sensitivity of RF receivers by integrating high-Q filtering capabilities on a semiconductor substrate, thus overcoming the limitations of silicon-based inductors and SAW filters.
Implementation Method 1
passive mixers and associated impedance networks to translate baseband notches to RF frequencies
Data Source
AI summary
Embodiments of a SAW-less RF receiver front-end that includes a frequency translated notch filter (FTNF) are presented. An FTNF includes a passive mixer and a baseband impedance. The baseband impedance includes capacitors that form a low-Q band-stop filter. The passive mixer is configured to translate the baseband impedance to a higher frequency. The translated baseband impedance forms a high-Q notch filter and is presented at the input of the FTNF. The FTNF can be fully integrated in CMOS IC technology (or others, e.g., Bipolar, BiCMOS, and SiGe) and applied in wireless receiver systems including EDGE/GSM, Wideband Code Division Multiple Access (WCDMA), Bluetooth, and wireless LANs (e.g., IEEE 802.11). In addition, embodiments of a generalized FTNF for wideband applications are presented.