AIDT 온디바이스 STEM 방사광 X선 극저온 광주파수 콤(Optical Frequency Comb) 캐리어-엔벨로프 오프셋(f_ceo) 및 반복률(f_rep) 듀얼 서보 제어기

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.OpticalFrequencyComb
{
    /// <summary>
    /// 광주파수 빗 위상 주파수 텔레메트리 계측 상태
    /// </summary>
    public readonly ref struct FrequencyCombTelemetryState
    {
        public readonly double RepetitionRateErrorHz;    // f_rep 주파수 오차 [Hz]
        public readonly double CeoOffsetPhaseErrorRad;   // f_ceo 비트 위상 오차 [rad]
        public readonly double CavityTemperatureCelsius; // 공진기 기준 온도 [degC]
        public readonly double BeatSignalToNoiseDbm;     // f-to-2f 비트 SNR [dBm]
        public readonly double IntracavityPowerWatts;    // 공진기 내부 광파워 [W]

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public FrequencyCombTelemetryState(
            double repErr, double ceoErr, double temp, double snr, double pwr)
        {
            RepetitionRateErrorHz = repErr;
            CeoOffsetPhaseErrorRad = ceoErr;
            CavityTemperatureCelsius = temp;
            BeatSignalToNoiseDbm = snr;
            IntracavityPowerWatts = pwr;
        }
    }

    /// <summary>
    /// 광주파수 빗 듀얼 서보 출력 명령
    /// </summary>
    public readonly ref struct CombDualServoCommand
    {
        public readonly double PztVoltageVolts;         // 공진기 PZT 피에조 전압 [V]
        public readonly double PumpCurrentMilliAmps;    // 펌프 LD 전류 보정값 [mA]
        public readonly double SynthesizedClockAllanDev;// 추정 알란 분산(Allan Dev)
        public readonly bool IsPhaseLocked;             // 위상 고정 잠금 성공 여부

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public CombDualServoCommand(double vPzt, double iPump, double adev, bool locked)
        {
            PztVoltageVolts = vPzt;
            PumpCurrentMilliAmps = iPump;
            SynthesizedClockAllanDev = adev;
            IsPhaseLocked = locked;
        }
    }

    /// <summary>
    /// 10,000Hz 주기 광주파수 빗 초정밀 듀얼 록킹 서보 엔진
    /// </summary>
    public ref struct OpticalFrequencyCombDualServoEngine
    {
        private double _accumulatedPztVolts;
        private double _accumulatedPumpCurrentMa;
        private double _prevRepErrorHz;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public CombDualServoCommand CalculateServoControl(
            in FrequencyCombTelemetryState state, double dtSeconds)
        {
            // 1. 반복률 f_rep 미세 주파수 오차 제어 (PZT 루프)
            double repDiff = (dtSeconds > 1e-9) ? (state.RepetitionRateErrorHz - _prevRepErrorHz) / dtSeconds : 0.0;
            _prevRepErrorHz = state.RepetitionRateErrorHz;

            _accumulatedPztVolts += 0.025 * state.RepetitionRateErrorHz * dtSeconds;
            _accumulatedPztVolts = Math.Clamp(_accumulatedPztVolts, -10.0, 10.0);

            double commandPzt = 50.0 + _accumulatedPztVolts + 0.008 * state.RepetitionRateErrorHz + 0.0001 * repDiff;
            commandPzt = Math.Clamp(commandPzt, 0.0, 100.0);

            // 2. 캐리어-엔벨로프 오프셋 f_ceo 위상 오차 제어 (펌프 레이저 전류 EOM/LD 루프)
            _accumulatedPumpCurrentMa += 1.2 * state.CeoOffsetPhaseErrorRad * dtSeconds;
            _accumulatedPumpCurrentMa = Math.Clamp(_accumulatedPumpCurrentMa, -5.0, 5.0);

            // 상호 간섭 감쇄 (PZT 전압 변화가 f_ceo에 미치는 기여 제거)
            double crosstalkCorrectionMa = -0.05 * (commandPzt - 50.0);
            double commandPumpCurrent = 250.0 + _accumulatedPumpCurrentMa + 0.85 * state.CeoOffsetPhaseErrorRad + crosstalkCorrectionMa;
            commandPumpCurrent = Math.Clamp(commandPumpCurrent, 100.0, 400.0);

            // 위상 잠금 판정: 위상 오차 < 0.1 rad, SNR > 25 dB
            bool isLocked = (Math.Abs(state.CeoOffsetPhaseErrorRad) < 0.10) && (state.BeatSignalToNoiseDbm > 25.0);

            // 1초 기준 알란 분산 근사 추정치
            double allanDev = isLocked ? 1.2e-18 : 5.8e-16;

            return new CombDualServoCommand(commandPzt, commandPumpCurrent, allanDev, isLocked);
        }
    }
}