Frequency-Translated Notch Filter for SAW-Less Receiver Area Reduction

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Solution Overview

Problem

Conventional RF receiver designs face challenges in attenuating large out-of-band interferers on semiconductor substrates while minimizing area requirements, especially in multi-band applications, due to the limitations of silicon-based inductors and the need for external SAW filters which increase noise factor and cost.

Innovation Solution

The implementation of frequency translated notch filters (FTNFs) on a semiconductor substrate, which use a passive mixer and baseband impedance to create a high-Q notch filter, effectively attenuating out-of-band interferers and reducing noise factor, thereby replacing the need for external SAW filters and minimizing area requirements in multi-band devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If SAW filters are used to attenuate out-of-band interferers, then attenuation performance is improved, but area requirement and noise factor increase

Engineering Contradiction:

Improveout-of-band interferer attenuationVSAvoidfilter area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The patent replaces mechanical SAW filters with an electronic solution using a notch filter implemented on the semiconductor substrate. This electronic filter uses a resonant circuit with inductor and capacitor to achieve the same attenuation function without requiring external mechanical filter components, thereby reducing area while maintaining interferer rejection capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent integrates the filter function directly into the receiver front-end circuitry on the semiconductor substrate, merging what were previously separate external SAW filter and receiver components into a single integrated unit. This eliminates the need for external filter components and reduces overall device area

Inventive Principle:

Principle #5Merging (Combining)

2Object-affected harmful factors

If SAW filters are used to attenuate out-of-band interferers, then attenuation performance is improved, but noise factor increases

Engineering Contradiction:

Improveout-of-band interferer attenuationVSAvoidnoise factor

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent substitutes the mechanical SAW filter with an electronic notch filter implemented on-chip, eliminating the insertion loss inherent in mechanical filters. The electronic filter maintains signal integrity while providing the necessary attenuation, thereby reducing the noise factor compared to external SAW filter solutions

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If multiple SAW filters are used for multi-band applications, then frequency band coverage is improved, but area requirement and cost increase

Engineering Contradiction:

Improvemulti-band frequency coverageVSAvoidtotal filter area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The patent implements a universal filter architecture on the semiconductor substrate that can be configured to support multiple frequency bands through electronic tuning or switching of the resonant circuit parameters. This single multi-functional filter replaces what would traditionally require multiple separate SAW filters, significantly reducing area while maintaining multi-band capability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines multiple filter functions for different frequency bands into a single integrated filter structure on the semiconductor substrate. By merging the functionality of multiple external filters into one on-chip component, the design achieves multi-band support with reduced area and lower cost

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8224275B2Area reduction techniques for saw-less receivers

Publication Date: 2012.07.17 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

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 multi-band SAW-less RF receiver front-end and techniques to share components of FTNFs included within the multi-band SAW-less RF receiver front-end are presented.