Multi-Carrier Receiver Offset Shifting for Pilot SNR Stability
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Solution Overview
Problem
In multi-carrier communication systems, the challenge lies in achieving a broad and stable frequency characteristic while minimizing power consumption and cost, particularly in suppressing frequency distortion and 1/f noise, which degrades signal-to-noise ratio (SNR) and affects pilot sub-carriers.
Innovation Solution
A multi-carrier communication apparatus that generates a local carrier wave with a frequency offset, cyclically varying the offset to shift the signal band, thereby preventing SNR degradation caused by circuit frequency characteristics, and correcting sub-carrier indices to maintain signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If measures for suppressing frequency distortion in a filter are taken, then frequency characteristic stability is improved, but power consumption increases
Solution Approach 1:
The invention changes the frequency parameter of the local carrier wave by adding a cyclically varying offset. This parameter change shifts the signal spectrum away from the DC region where 1/f noise is prominent, thereby improving frequency characteristic stability without requiring additional filtering measures that would increase power consumption.
2Object-affected harmful factors
If an element is manufactured with a semiconductor process using SiGe to suppress 1/f noise, then noise performance is improved, but system cost increases
Solution Approach 1:
The invention converts the harmful effect of 1/f noise in the DC region into a beneficial situation by shifting the signal spectrum away from DC. The frequency offset technique transforms the noise problem into a solvable issue through spectral manipulation, avoiding the need for expensive SiGe semiconductor processes while effectively suppressing the impact of 1/f noise on pilot symbols.
3Productivity
If a broad effective band and narrow sub-carrier interval are used to implement high data throughput, then data throughput is improved, but frequency characteristic stability becomes more difficult to maintain
Solution Approach 1:
The invention dynamically changes the frequency parameter of the local carrier wave by adding a cyclic offset that is a constant multiple of the sub-carrier frequency interval. This parameter modulation allows the system to maintain stable frequency characteristics across a broad band by periodically shifting the signal spectrum, enabling high data throughput with narrow sub-carrier intervals without sacrificing frequency stability.
Data Source
AI summary
A local carrier wave output from a synthesizer to quadrature demodulators is multiplied by an offset that makes a frequency shift by an integer number of subcarriers in units of sub-carrier bands. The offset is set to a value obtained by multiplying the number sequentially counted up from 0 to the number of unused sub-carriers included in guard tones in a signal band by the bandwidth of a sub-carrier. By shifting the frequency of the local carrier wave at the time of quadrature demodulation with the offset, the SNR of a baseband signal is prevented from being constantly degraded by a frequency characteristic possessed by the circuit of a receiver in a particular sub-carrier signal. Especially, by preventing a pilot signal from being constantly degraded, the signal can be received with higher accuracy.