Symbol Timing Recovery Circuit for Multipath Interference Cancellation
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Solution Overview
Problem
Existing symbol timing recovery circuits face challenges in accurately recovering symbol timing in multipath environments due to interference waves, which can degrade the accuracy of timing recovery and reduce interference wave immunity.
Innovation Solution
A symbol timing recovery circuit is designed with a combination of finite impulse response (FIR) and infinite impulse response (IIR) filters, along with tap coefficient calculation units, to eliminate forward and backward interference waves, and a timing recovery unit that adjusts tap coefficients based on identification and error signals to improve timing recovery accuracy and immunity to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional symbol timing recovery circuits are used, then the circuit structure is simple, but timing recovery accuracy degrades in multipath environments due to interference waves
Solution Approach 1:
The equalizer is segmented into forward equalizer (FIR filter) and backward equalizer (IIR filter), each handling different types of interference waves. The forward equalizer processes forward interference waves while the backward equalizer processes backward interference waves, allowing specialized optimization for each direction and improving overall timing recovery accuracy in multipath environments.
Solution Approach 2:
The circuit uses a composite filter structure combining FIR and IIR filters. The FIR filter provides linear phase response and stability for forward equalization, while the IIR filter provides efficient backward equalization with fewer coefficients. This composite approach leverages the strengths of both filter types to achieve better interference wave immunity and timing recovery accuracy.
2Measurement precision
If forward and backward equalizers are introduced to eliminate interference waves, then timing recovery accuracy improves, but device complexity increases
Solution Approach 1:
The forward equalizer and backward equalizer are merged into a unified timing recovery circuit architecture that shares common components such as the interpolator, tap coefficient calculating units, and error signal processing paths. This integration reduces overall circuit complexity while maintaining the benefits of both forward and backward equalization for improved timing recovery accuracy.
Solution Approach 2:
The tap coefficient calculating units serve multiple functions: they calculate coefficients for both the forward FIR filter and backward IIR filter, process error signals from both equalizers, and adapt to varying channel conditions. This multi-functionality reduces the need for separate dedicated circuits, thereby managing device complexity while achieving superior timing recovery performance.
Data Source
AI summary
Disclosed is a symbol timing recovery circuit which includes an interpolator to generate, using a first filter, interpolation data of an input signal; a forward equalizer to eliminate, using a second filter, a forward interference wave from the input signal based on the interpolation data, and to output the resultant signal after the elimination, a first identification signal, and a first error signal; a backward equalizer to eliminate, using a third filter, a backward interference wave from the input signal based on the interpolation data, and to output the resultant signal after the elimination, a second identification signal, and a second error signal; and a timing recovery unit to generate a tap coefficient of the first filter, based on a tap coefficient of the second filter, a tap coefficient of the third filter, the first identification signal, the first error signal, the second identification signal, and the second error signal.