Asymmetric Filter Factorization for Wireless Selectivity
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Solution Overview
Problem
Current pulse shaping techniques, particularly using raised cosine filters, face challenges in achieving improved receiver selectivity while maintaining compatibility with industry-standard square root raised cosine filters at the transmitter, leading to suboptimal performance in wireless communications due to poor smoothness properties and noise tolerance.
Innovation Solution
Employing asymmetric factorization of higher order Nyquist structures, where the transmitter filter is a square root raised cosine filter and the receiver filter is a higher order Nyquist filter, effectively rolling over a cos(z/2) term from the transmit filter response to the receiver side, resulting in improved selectivity and frequency response equivalent to a higher order generalized raised cosine filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a square root raised cosine filter is used at the transmitter to maintain industry compatibility, then ease of operation is improved, but receiver selectivity performance deteriorates
Solution Approach 1:
The patent applies asymmetric filter design where the transmit filter uses a square root raised cosine (SRRC) filter for industry compatibility, while the receive filter uses a higher-order raised cosine (HORC) filter to achieve improved selectivity. This asymmetric configuration allows the system to maintain compatibility with existing transmit infrastructure while upgrading receiver performance through the HORC filter's enhanced frequency response characteristics and steeper roll-off.
2Measurement precision
If a higher order generalized raised cosine filter is used at both transmit and receive to improve selectivity, then receiver selectivity is improved, but device complexity increases
Solution Approach 1:
The patent segments the pulse shaping filter function between transmit and receive sides. The transmit side uses a simpler SRRC filter that is industry-standard, while the receive side implements the more complex HORC filter. This segmentation allows the system to achieve the benefits of higher-order filtering for improved selectivity without requiring complex higher-order filters at both ends, thereby reducing overall system complexity while maintaining performance improvements.
Data Source
AI summary
An apparatus to transmit and receive wireless communications is disclosed in which the transmit circuitry includes a square root raised cosine filter to pulse shape modulate signals and the receive circuitry includes a higher order Nyquist receive filter coupled to receive the input signals and remove the pulse shaping modulation. The cascaded combination of the transmit and receive filters has a frequency response equivalent to a higher order generalized raised cosine filter response.