AIDT 온디바이스 STEM 방사광 X선 극저온 테라헤르츠(0.1~10THz) 차주파수 생성(DFG) 듀얼 파장 서보 제어기

using System;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Stem.TerahertzDfg
{
    /// <summary>
    /// THz 차주파수 간섭 텔레메트리 상태
    /// </summary>
    public readonly ref struct TerahertzTelemetryState
    {
        public readonly double MeasuredBeatFrequencyThz; // 측정된 헤테로다인 비트 주파수 [THz]
        public readonly double TargetThzFrequency;       // 목표 테라헤르츠 주파수 [THz]
        public readonly double BolometerDetectedPowerUw; // 극저온 볼로미터 수신 THz 파워 [uW]
        public readonly double DastCrystalTemperatureK;  // DAST 유기 결정 온도 [K]

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public TerahertzTelemetryState(double beatThz, double tgtThz, double pwr, double temp)
        {
            MeasuredBeatFrequencyThz = beatThz;
            TargetThzFrequency = tgtThz;
            BolometerDetectedPowerUw = pwr;
            DastCrystalTemperatureK = temp;
        }
    }

    /// <summary>
    /// THz 듀얼 레이저 전류 및 온도 서보 명령
    /// </summary>
    public readonly ref struct TerahertzServoCommand
    {
        public readonly double SlaveLaserCurrentMilliAmps; // 슬레이브 DFB 레이저 전류 [mA]
        public readonly double CrystalTecVoltageVolts;      // 결정 온도 제어 TEC 전압 [V]
        public readonly double FrequencyOffsetMegahertz;    // THz 주파수 잔여 편차 [MHz]
        public readonly bool ThzPhaseLocked;               // THz 주파수 잠금 여부

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public TerahertzServoCommand(double current, double tecV, double offsetMhz, bool locked)
        {
            SlaveLaserCurrentMilliAmps = current;
            CrystalTecVoltageVolts = tecV;
            FrequencyOffsetMegahertz = offsetMhz;
            ThzPhaseLocked = locked;
        }
    }

    /// <summary>
    /// 10,000Hz 주기 테라헤르츠 DFG 듀얼 파장 서보 엔진
    /// </summary>
    public ref struct TerahertzDfgDualLaserServoEngine
    {
        private const double CurrentTuningGainMhzPerMa = 450.0; // 450 MHz/mA
        private double _accumulatedCurrentMa;
        private double _prevFreqErrorMhz;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public TerahertzServoCommand UpdateServo(
            in TerahertzTelemetryState state, double dtSeconds)
        {
            // 1. 주파수 오차 계산 [MHz 단위]
            double freqErrorMhz = (state.TargetThzFrequency - state.MeasuredBeatFrequencyThz) * 1e6;
            double errorDiff = (dtSeconds > 1e-9) ? (freqErrorMhz - _prevFreqErrorMhz) / dtSeconds : 0.0;
            _prevFreqErrorMhz = freqErrorMhz;

            // PI 폐루프 전류 제어
            _accumulatedCurrentMa += (0.65 * freqErrorMhz / CurrentTuningGainMhzPerMa) * dtSeconds;
            _accumulatedCurrentMa = Math.Clamp(_accumulatedCurrentMa, -25.0, 25.0);

            double commandCurrent = 120.0 + _accumulatedCurrentMa + (0.12 * freqErrorMhz / CurrentTuningGainMhzPerMa) + 0.001 * errorDiff;
            commandCurrent = Math.Clamp(commandCurrent, 50.0, 200.0);

            // 2. DAST 결정 위상정합 TEC 전압 (출력 파워 극대화)
            double commandTecV = 2.4 + 0.02 * (state.TargetThzFrequency - 2.5);
            commandTecV = Math.Clamp(commandTecV, 0.5, 5.0);

            // 잠금 상태 판정: 주파수 오차 1.5MHz 이내 & 볼로미터 파워 > 5uW
            bool isLocked = (Math.Abs(freqErrorMhz) < 1.5) && (state.BolometerDetectedPowerUw > 5.0);

            return new TerahertzServoCommand(commandCurrent, commandTecV, freqErrorMhz, isLocked);
        }
    }
}