MUM-T 유무인복합 분산 이중기지 합성개구레이다(Bi-static SAR) 비행편대 위상동기화 및 펄스 지터 보정 서보 아키텍처 (.NET 9 C# SIMD)

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace ZeliDesk.Defense.Avionics
{
    /// <summary>
    /// MUM-T 이중기지 SAR(Bi-static SAR) 위상동기화 및 펄스 지터 보정 서보
    /// GC 제로 할당 ref struct 및 AVX-256 SIMD 가속화
    /// </summary>
    public ref struct BistaticSarSyncServo
    {
        private readonly ReadOnlySpan<float> _measuredPhases;   // 실측 수신 위상 Phi_rx (rad)
        private readonly ReadOnlySpan<float> _directPathPhases; // 직접파 기준 위상 Phi_dir (rad)
        private readonly ReadOnlySpan<float> _baselineDistances;// 편대 간 실시간 기준 거리 (m)
        private readonly Span<float> _compensatedPhases;        // 보정된 일관 위상 (rad)
        private readonly Span<float> _phaseCorrections;         // 능동 피드백 위상 보정값 (rad)

        private readonly float _waveNumber;  // 파수 k = 2*pi / lambda
        private readonly float _syncGain;    // 동기화 루프 게인

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public BistaticSarSyncServo(
            ReadOnlySpan<float> measuredPhases,
            ReadOnlySpan<float> directPathPhases,
            ReadOnlySpan<float> baselineDistances,
            Span<float> compensatedPhases,
            Span<float> phaseCorrections,
            float waveLength = 0.03f, // X-band (10 GHz)
            float syncGain = 0.95f)
        {
            _measuredPhases = measuredPhases;
            _directPathPhases = directPathPhases;
            _baselineDistances = baselineDistances;
            _compensatedPhases = compensatedPhases;
            _phaseCorrections = phaseCorrections;
            _waveNumber = (2.0f * MathF.PI) / waveLength;
            _syncGain = syncGain;
        }

        /// <summary>
        /// 직접파 위상과 기준 거리 기하학을 바탕으로 SIMD 8개 병렬 채널 위상 동기화
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveOptimization)]
        public void ExecutePhaseSyncLoop()
        {
            int length = _measuredPhases.Length;
            int simdLength = length - (length % 8);

            Vector256<float> vK = Vector256.Create(_waveNumber);
            Vector256<float> vGain = Vector256.Create(_syncGain);

            int i = 0;
            if (Avx2.IsSupported)
            {
                for (; i < simdLength; i += 8)
                {
                    Vector256<float> vRxPhase = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_measuredPhases.Slice(i, 8))[0]);
                    Vector256<float> vDirPhase = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_directPathPhases.Slice(i, 8))[0]);
                    Vector256<float> vDist = Vector256.Create(MemoryMarshal.Cast<float, Vector256<float>>(_baselineDistances.Slice(i, 8))[0]);

                    // 거리 전파 위상 지연: Phi_geo = k * dist
                    Vector256<float> vGeoPhase = Avx.Multiply(vK, vDist);

                    // 발진기 위상 오차 추정: DeltaPhi_LO = DirPhase - GeoPhase
                    Vector256<float> vDeltaLo = Avx.Subtract(vDirPhase, vGeoPhase);

                    // 위상 보정값: PhaseCorr = Gain * DeltaPhi_LO
                    Vector256<float> vCorr = Avx.Multiply(vGain, vDeltaLo);

                    // 보정된 수신 위상: CompPhase = RxPhase - PhaseCorr
                    Vector256<float> vComp = Avx.Subtract(vRxPhase, vCorr);

                    vCorr.CopyTo(_phaseCorrections.Slice(i, 8));
                    vComp.CopyTo(_compensatedPhases.Slice(i, 8));
                }
            }

            for (; i < length; i++)
            {
                float geoPhase = _waveNumber * _baselineDistances[i];
                float deltaLo = _directPathPhases[i] - geoPhase;
                float corr = _syncGain * deltaLo;
                _phaseCorrections[i] = corr;
                _compensatedPhases[i] = _measuredPhases[i] - corr;
            }
        }
    }
}