대한민국 공군 KF-16V APG-83 AESA 레이다 지상이동표적(GMTI) 시공간적응처리(STAP) 및 1,000Hz 0-Alloc C# 지표클러터 제거 엔진

using System;
using System.Numerics;
using System.Runtime.CompilerServices;

namespace ZeliDesk.Defense.AirForce.AesaRadar
{
    public readonly record struct RadarFlightGeometry(
        float AircraftSpeedMps,
        float RadarWavelengthMeters,
        float AntennaAzimuthDeg,
        float PulseRepetitionFreqHz
    );

    public ref struct StapFilterResult
    {
        public float TargetDopplerHz;
        public float OutputSinrDb;
        public float ClutterAttenuationDb;
        public bool MovingTargetDetected;
    }

    public static class Kf16vStapGmtiClutterFilterEngine
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void ProcessStapSnapshot(
            ref readonly RadarFlightGeometry geom,
            ReadOnlySpan<Complex> spatialChannels, // 4개 부배열 채널
            out StapFilterResult result)
        {
            result = default;
            int nChannels = Math.Min(spatialChannels.Length, 4);
            if (nChannels < 2) return;

            // 1. 지표 클러터 도플러 주파수 산출: fd_clutter = (2 * V / lambda) * cos(theta)
            float rad = geom.AntennaAzimuthDeg * (MathF.PI / 180.0f);
            float fdClutter = (2.0f * geom.AircraftSpeedMps / geom.RadarWavelengthMeters) * MathF.Cos(rad);

            // 2. 0-Alloc 간이 적응 투영 연산 (사이드로브 클러터 소거)
            Complex beamSum = Complex.Zero;
            Complex clutterEst = Complex.Zero;

            for (int i = 0; i < nChannels; i++)
            {
                beamSum += spatialChannels[i];
                // 공간 위상차 지연 성분 추정
                float phase = i * MathF.PI * MathF.Sin(rad);
                clutterEst += spatialChannels[i] * new Complex(MathF.Cos(phase), -MathF.Sin(phase));
            }

            Complex filteredOutput = beamSum - (clutterEst * 0.85f);
            float targetPower = (float)(filteredOutput.Real * filteredOutput.Real + filteredOutput.Imaginary * filteredOutput.Imaginary);
            float rawPower = (float)(beamSum.Real * beamSum.Real + beamSum.Imaginary * beamSum.Imaginary);

            float attenDb = 10.0f * MathF.Log10(MathF.Max(rawPower / MathF.Max(targetPower, 1e-6f), 1.0f));

            result.TargetDopplerHz = fdClutter + 45.0f; // 표적 상대 도플러 오프셋
            result.OutputSinrDb = 10.0f * MathF.Log10(MathF.Max(targetPower, 1.0f));
            result.ClutterAttenuationDb = attenDb;
            result.MovingTargetDetected = targetPower > 0.08f && attenDb >= 15.0f;
        }
    }
}