[blackcat] L1 Dual Ehlers Bandpass Filter

OVERVIEW
The Dual Ehlers Bandpass Filter combines two bandpass filters tuned to the dominant and subdominant market cycles, creating a powerful signal extraction tool. This indicator uses John Ehlers' advanced digital signal processing techniques to isolate specific frequency components from price data. By mixing the outputs of two bandpass filters, it provides a smoother, more responsive signal that captures both primary and secondary market cycles. The indicator includes divergence detection capabilities and multiple mixing methods for customizable signal extraction.

FEATURES
- Dual bandpass filtering with dominant and subdominant cycle detection
- Multiple dominant cycle calculation methods (HoDyDC, PhAcDC, DuDiDC, CycPer, BPZC)
- Flexible mixing options: weighted, sum, difference, dominant-only, or subdominant-only
- Adjustable bandwidth parameters for both filters
- Built-in divergence detection with customizable lookback periods
- Optional display of individual filter components
- Color-coded signals and alerts for bullish/bearish divergences

HOW TO USE
1. Select your preferred price source (close, high, low, etc.)
2. Choose the dominant cycle calculation method from the available options
3. Set the subdominant cycle ratio (typically 0.1-0.9 of the dominant cycle)
4. Adjust bandwidth parameters for both filters (0.1-1.0 range)
5. Select your preferred mixing method:
- Weighted: Mix based on adjustable weights
- Sum: Add both filter outputs
- Difference: Subtract subdominant from dominant
- Dominant: Show only the dominant filter
- Subdominant: Show only the subdominant filter
6. Enable divergence detection to identify potential trend reversals
7. Optionally enable individual filter plots for analysis

LIMITATIONS
- The indicator requires sufficient historical data for accurate cycle detection
- Dominant cycle calculations may vary significantly during low volatility periods
- Divergence signals are lagging indicators and should be used with confirmation
- Bandpass filters may produce false signals during choppy market conditions
- The indicator is not suitable for all trading styles and timeframes

NOTES
- The indicator uses the blackcat1402/dc_ta library for advanced cycle calculations
- Zero line crossing can indicate potential trend changes
- Positive values typically suggest bullish momentum, negative values bearish momentum
- Divergence signals appear as colored dots and labels on the chart
- Alert conditions are available for both bullish and bearish divergences

THANKS
Special thanks to John Ehlers for his pioneering work in digital signal processing for financial markets.