Signal Processing
Digital signal processing theory: FIR/IIR filters, FFT, sampling theory, adaptive DSP, and hardware implementation.
320 topics · 0 with articles
Intern Engineer· 40
- Aliasing: Overlapping Spectra When fs < 2·fmax
- All-Pass System: |H(e^(jω))| = 1 for all ω
- BIBO Stability: Σ|h[n]| < ∞
- CTFT Properties: Linearity, Shift, Scaling, Duality
- Complex Exponential: e^(jωt) = cos(ωt) + j·sin(ωt)
- Continuous-Time Fourier Transform (CTFT): X(jω) = ∫x(t)e^(-jωt)dt
- Continuous-Time vs. Discrete-Time Signals
- Convolution Theorem: Multiplication ↔ Convolution
- Correlation: Auto-Correlation and Cross-Correlation
- DTFT Periodicity: X(e^(j(ω+2π))) = X(e^(jω))
- Deterministic vs. Random Signals
- Discrete-Time Fourier Transform (DTFT): X(e^(jω))
- Energy Signal: E = ∫|x(t)|² dt < ∞
- Fourier Series Coefficients: Cn and Harmonic Power
- Fourier Series: Trigonometric and Exponential Form
- Frequency Response H(e^(jω)): Magnitude and Phase
- Gibbs Phenomenon at Discontinuities
- Group Delay: τg(ω) = -dφ/dω
- Ideal Sampling: Impulse Train Multiplication
- Impulse Response and Step Response Relationship
- LTI System: Characterization by Impulse Response h[n]
- Laplace Transform: X(s) = ∫x(t)e^(-st)dt, ROC
- Minimum-Phase System: Causality and Stability of Inverse
- Parseval's Theorem: Energy in Time = Energy in Frequency
- Periodic and Aperiodic Signals: Period T, Frequency f0
- Phase Delay vs. Group Delay: Linear Phase Condition
- Power Signal: P = lim(1/T)∫|x(t)|² dt < ∞
- Power Spectral Density (PSD): Wiener-Khinchin Theorem
- Practical Sampling: Sample-and-Hold (ZOH) Effect
- Quantization Noise: SNR = 6.02·N + 1.76 dB (N bits)
- Quantization: Uniform, Non-Uniform, Companding
- Sampling Theorem: fs ≥ 2·fmax (Nyquist Criterion)
- Sinusoidal Signal: Amplitude, Frequency, Phase
- Stochastic Signals: Stationarity, Ergodicity, Autocorrelation
- System Properties: Linear, Time-Invariant, Causal, Stable
- Transfer Function H(s) = Y(s)/X(s): Poles and Zeros
- Unit Impulse δ(t): Sifting Property
- Unit Step u(t) and Unit Ramp r(t)
- Z-Transform Properties: Shift, Convolution, Differentiation
- Z-Transform: X(z) = Σx[n]z^(-n), ROC
Junior Engineer· 80
- 2D FFT: Row-Column Algorithm for Image Processing
- AR / ARMA Model-Based Spectral Estimation
- Adaptive IIR Filter: Stability Challenges
- All-Pass Filter: Phase Equalization Application
- Analog Prototype Design: Normalized LP Butterworth
- Bartlett's Method: Non-Overlapping Periodogram Average
- Bessel Filter: Maximally Flat Group Delay (Linear Phase)
- Bilinear Transform (BLT): Pre-Warping, Frequency Mapping
- Blackman Window: -74 dB Side Lobe, Wide Transition Band
- Blackman-Tukey Method: Windowed Autocorrelation
- Burg Algorithm: Maximum Entropy Spectral Estimation
- Butterworth Filter: Maximally Flat Magnitude in Passband
- CIC (Cascaded Integrator-Comb) Filter: Integer Decimation
- Cascade (SOS) Biquad Form: Numerical Stability
- Chebyshev Type I: Equiripple Passband, Monotone Stopband
- Chebyshev Type II: Monotone Passband, Equiripple Stopband
- Chirp Z-Transform (CZT): Zoom FFT for High Resolution
- Cohen's Class of Time-Frequency Distributions
- Comb Filter: Delay-Based Periodic Frequency Response
- Continuous Wavelet Transform (CWT): Scale and Translation
- Cosine-Modulated Filter Bank (CMFB): PR Conditions
- DFT Circular Convolution and Linear Convolution Relation
- DFT Orthogonality: Twiddle Factor WN = e^(-j2π/N)
- DFT Properties: Linearity, Circular Shift, Symmetry
- Digital Differentiator and Hilbert Transformer Design
- Direct Form I and II: Signal Flow Graph Comparison
- Discrete Fourier Transform (DFT): Definition and Matrix Form
- Discrete Wavelet Transform (DWT): Mallat Algorithm
- ESPRIT: Estimation of Signal Parameters via Rotational Invariance
- Elliptic (Cauer) Filter: Equiripple in Both Passband and Stopband
- Empirical Mode Decomposition (EMD): Adaptive Sifting
- FIR Filter Order Estimation: Kaiser and Harris Formulas
- FIR Filter: Finite Impulse Response Definition
- FIR Linear Phase: Type I, II, III, IV Symmetry Conditions
- FIR Windowing Method: Rectangular Window Basics
- FIR vs. IIR: Linear Phase, Stability, Computational Cost
- Filter Design with MATLAB: fir1, fir2, firpm, butter, cheby1
- Fixed-Point Filter Design: Coefficient Quantization Effect
- Fractional Fourier Transform (FrFT): Rotation in TF Plane
- Fractional Sample Rate Conversion: L/M Polyphase
- Frequency Sampling FIR Design Method
- Frequency Transformation: LP→HP, LP→BP, LP→BS
- Goertzel Algorithm: Single Frequency DFT (DTMF Detect)
- Half-Band Filter: Efficient 2:1 Decimation
- Hamming Window: -43 dB Side Lobe, Optimized for Sidelobe
- Hann Window: -44 dB Side Lobe, 8 dB/oct Roll-Off
- Hilbert-Huang Transform (HHT): IMF and Instantaneous Freq
- IIR Filter: Infinite Impulse Response, Recursive Structure
- Impulse Invariance Method: Analog-to-Digital Conversion
- In-Place FFT: Bit-Reversal Permutation
- Kaiser Window: Adjustable β Parameter for Sidelobe Control
- Lattice Filter: All-Pole and All-Zero Structures
- MUSIC (MUltiple SIgnal Classification): Subspace Method
- Multirate Processing: Downsampling by M, Upsampling by L
- Multitaper (Thomson) Method: Reduces Variance in PSD
- Notch Filter: Twin-T and 2nd-Order IIR at f0
- Parks-McClellan (Remez) Algorithm: Equiripple FIR Design
- Pisarenko Harmonic Decomposition
- Polyphase Decomposition of FIR Filter
- Prime-Factor Algorithm (PFA) and Winograd FFT
- Python Filter Design: scipy.signal Design Functions
- Radix-2 DIF FFT: Decimation-in-Frequency Structure
- Radix-2 DIT FFT: Butterfly Operation, Bit-Reversal
- Radix-4 FFT: 25% Fewer Multiplications vs. Radix-2
- Real-Valued FFT: Exploit Conjugate Symmetry
- STFT Time-Frequency Resolution Trade-Off (Heisenberg)
- Spectral Leakage: Cause (Finite Observation) and Remedy
- Spectral Resolution: Δf = fs/N
- Spectrogram: STFT Magnitude² as Time-Frequency Map
- Split-Radix FFT: Mixed Radix-2 and Radix-4
- Synchrosqueezing Wavelet Transform: Sharpened TFR
- Transposed Direct Form II: Recommended for Fixed-Point
- Wavelet Filter Bank: QMF and Perfect Reconstruction
- Wavelet Packet Decomposition: Full Binary Tree
- Welch's Method: Averaged Periodogram for PSD Estimation
- Wigner-Ville Distribution (WVD): Time-Frequency Analysis
- Window Functions: Trade-Off (Main Lobe Width vs. Side Lobe)
- Windowed FFT: STFT (Short-Time Fourier Transform)
- Yule-Walker Equations: AR Parameter Estimation
- Zero-Padding: Interpolation in Frequency Domain
Middle Engineer· 80
- 16-QAM, 64-QAM, 256-QAM: Spectral Efficiency vs. SNR
- 5G NR PDSCH Processing Chain: LDPC, HARQ, OFDM
- Acoustic Echo Cancellation (AEC): Double-Talk Detection
- Adaptive Filter Structure: Transversal FIR with Adjustable Coefficients
- Adaptive Noise Cancellation (ANC): Reference Signal Method
- Affine Projection Algorithm (APA): Between LMS and RLS
- BCH Codes: Error-Correcting Capability t
- BPSK Bit Error Rate: BER = Q(√(2Eb/N0))
- Basis Pursuit (BP): L1 Minimization via Convex Opt.
- Bayesian Signal Processing: Prior, Likelihood, Posterior
- Beamforming: Analog Phase Shift, Digital Precoding
- Blind Source Separation (BSS): ICA, SOBI Algorithms
- CDMA: Walsh Code, Rake Receiver, Finger Assignment
- CFAR Detection: CA-CFAR, OS-CFAR, GOCA-CFAR
- CRC: Generator Polynomial, LFSR Implementation
- Carrier Recovery: Costas Loop, PLL-Based Methods
- Channel Coding: Convolutional Codes, Trellis, Viterbi
- Channel Equalization: MMSE-DFE, Turbo Equalization
- Compressed Sensing (CS): Sparsity, RIP, Mutual Coherence
- Cramér-Rao Lower Bound (CRLB) for Estimation
- Energy Detection: Radiometry for Spectrum Sensing
- Expectation-Maximization (EM) Algorithm in Signal Processing
- Extended Kalman Filter (EKF): Linearization via Jacobian
- Factor Graphs and Belief Propagation (Sum-Product)
- Hybrid Beamforming: Analog + Digital for mmWave
- Hypothesis Testing: NP Lemma, LRT, GLRT
- Independent Component Analysis (ICA): FastICA Algorithm
- Kalman Filter: State Equation, Measurement Equation
- Kalman Predict: x̂(k|k-1) = F·x̂(k-1|k-1) + B·u
- Kalman Update: Kalman Gain K, Covariance P Update
- LASSO Regression: L1-Regularized Least Squares
- LDPC Codes: Tanner Graph, Belief Propagation Decoding
- LMS Algorithm: w[n+1] = w[n] + 2µe[n]x[n]
- LMS Convergence: Step Size µ, Misadjustment, Excess MSE
- Leaky LMS: Preventing Coefficient Drift
- Link Adaptation: AMC (Adaptive Modulation and Coding)
- MAP (Maximum A Posteriori) Estimation
- MIMO Detection: ZF, MMSE, Sphere Decoder
- MIMO OFDM: Per-Subcarrier Precoding and Detection
- MIMO Spatial Multiplexing: V-BLAST, D-BLAST
- MIMO: Alamouti Space-Time Block Code (STBC)
- Massive MIMO: ZF Precoding, MRT, RZF Beamforming
- Matching Pursuit (MP) and OMP: Greedy Sparse Recovery
- Maximum Likelihood Estimation (MLE) for Signal Parameters
- Modulation: ASK, FSK, PSK, QAM Signal Constellation
- Normalized LMS (NLMS): Step Size Normalization by Power
- OFDM CFO Estimation: Moose, Schmidl-Cox Algorithms
- OFDM Channel Estimation: LS, MMSE with Pilot Symbols
- OFDM Cyclic Prefix (CP): ISI Elimination, Guard Interval
- OFDM PAPR: Definition, CCDF Curve, Reduction Methods
- OFDM Pilot Insertion: Comb-Type, Block-Type
- OFDM Principles: Subcarrier Orthogonality, DFT-Based
- OFDM Timing Synchronization: Schmidl-Cox Method
- OFDMA: Subcarrier Allocation for Multiple Users
- OTFS (Orthogonal Time-Frequency Space): Delay-Doppler Domain
- OTFS Input-Output Relation in Delay-Doppler Domain
- Online / Sequential Estimation: Sliding Window Adaptation
- Optimum FIR Wiener Filter: Direct and Levinson Solution
- PAPR Reduction: Clipping, SLM, PTS, Tone Reservation
- Particle Filter (Sequential Monte Carlo): Non-Gaussian/Nonlinear
- Polar Codes: Successive Cancellation (SC) Decoder
- QPSK: Gray Coding, BER = Q(√(2Eb/N0)) Same as BPSK
- RLS Algorithm: Recursive Least Squares, Exponential Forgetting
- RLS Initialization and Numerical Stability Issues
- Raised-Cosine Filter: Roll-Off Factor, ISI-Free Nyquist
- Reed-Solomon Codes: Symbol-Based, BCH Subfield Subcode
- Robust Statistics: M-Estimators for Outlier Rejection
- Root Raised-Cosine (RRC): Matched Filter in TX/RX
- SC-FDMA: DFT-Precoded OFDM for LTE Uplink
- SCL (Successive Cancellation List) Decoder for Polar
- Sign-LMS, Sign-Error LMS: Simplified Adaptation
- Sparse Bayesian Learning (SBL): Relevance Vector Machine
- Spread Spectrum: DSSS, FHSS, THSS Techniques
- System Identification: ARMA Model, Prediction Error Method
- Tensor Decomposition: Tucker, CP for Multi-Way Signals
- Timing Recovery: Early-Late Gate, Gardner TED
- Turbo Codes: Parallel Concatenated, BCJR Decoder
- Unscented Kalman Filter (UKF): Sigma Points, No Jacobian
- Variational Bayes (VB) Approximation
- Wiener Filter: MMSE Estimation, Wiener-Hopf Equation
Senior Engineer· 80
- AAC: Temporal Noise Shaping (TNS), Prediction, Huffman
- ARM Cortex-A NEON: Advanced SIMD for Audio/Video
- ARM Cortex-M DSP Extensions: SIMD, MAC, Saturating Arith.
- ARM Cortex-M55 Helium (MVE): 128-bit SIMD for DSP
- Acoustic Echo Cancellation (AEC): NLMS-Based
- Audio Bit Depth: 8, 16, 24 bit and Dynamic Range
- Audio Sampling Rates: 8, 16, 22.05, 44.1, 48, 96, 192 kHz
- Audio Source Separation: NMF, Deep Clustering, Conv-TasNet
- Blind Reverberation Estimation: Schroeder's Method
- CELP (Code-Excited Linear Prediction): G.729, AMR-NB
- CMSIS-DSP Library: arm_fir_f32, arm_rfft_fast_f32
- CMSIS-NN: arm_nn_fc_s8, arm_depthwise_conv_s8
- CORDIC on FPGA: Angle Rotation, Magnitude Calculation
- DDS (Direct Digital Synthesis): Spurious Performance
- DSP Co-Design: Algorithm → Architecture → VLSI Flow
- DSP Processor Architecture: Harvard, VLIW, SIMD
- Data Flow Graph: Task Graph for Parallel DSP
- Dereverberation: WPE (Weighted Prediction Error) Algorithm
- Digital Down-Converter (DDC): Mixer, CIC, FIR Chain
- Digital Up-Converter (DUC): FIR, CIC, Mixer Chain
- Double-Talk Detection in AEC: Geigel Detector
- EVS (Enhanced Voice Services): 3GPP 4G LTE Codec
- Edge AI Inference: TFLite Micro on Cortex-M (CMSIS-NN)
- FFT Benchmark: Precision, Speed, Power on CPU/GPU/FPGA
- FFT on FPGA: SDF (Single-Path Delay Feedback) Pipeline
- FPGA DSP48 Slice: Pre-Adder, Multiplier, Post-Adder
- FPGA FIR Filter: Direct-Form, Transposed-Form on DSP48
- FPGA Systolic Array FIR: Throughput = 1 Sample/Clock
- Fixed-Point Arithmetic: Q-Format, Overflow, Saturation, Rounding
- Fixed-Point Quantization Noise: SNR = 6.02·B + 1.76 dB
- Floating-Point DSP: IEEE 754 Single/Double Precision
- GNU Radio: Signal Processing Flowgraph for SDR
- GPU-Accelerated DSP: CUDA cuFFT, cuBLAS
- HiFi-GAN: GAN-Based Neural Vocoder for High Quality TTS
- High-Level Synthesis (HLS): C++ → RTL for DSP Blocks
- Human Auditory System: Basilar Membrane, Critical Bands
- Intel Agilex: High-Performance FPGA for DSP
- LC3 (LE Audio) Codec: Time-Frequency Transform, 24–48 kHz
- LPC Parameters: Reflection Coefficients, LSF (LSP)
- Language Identification: Acoustic and Phonotactic Models
- LibROSA: Python for Audio and Music Analysis
- Linear Predictive Coding (LPC): AR Model for Speech
- Loudness and Sound Pressure Level: dB SPL, A-Weighting
- MATLAB HDL Coder: Fixed-Point Verification and RTL
- MFCC (Mel-Frequency Cepstral Coefficients): 13–40 Features
- MMSE-STSA (Minimum Mean Square Error Spectral Amplitude)
- MP3 Filterbank: Polyphase Analysis, MDCT Transform
- MPEG Audio Coding: Layer I, II, III (MP3) Architecture
- Mel Scale: Logarithmic Frequency Perception Model
- Memory Architecture for FFT: In-Place, Butterfly Access
- Microphone Array Beamforming: Delay-and-Sum, MVDR
- Music Information Retrieval (MIR): Beat, Chord, Key Detection
- NCO (Numerically Controlled Oscillator): Phase Accumulator
- NPU Integration: EThos-U55 for Edge DSP and AI
- Noise Estimation: Minimum Statistics, IMCRA, MCRA
- OpenCL for Heterogeneous DSP (CPU + GPU + FPGA)
- Opus Codec: SILK + CELT Architecture, 6–510 kbps
- Perceptual Weighting Filter in CELP Speech Coding
- Pipeline Latency and Throughput Analysis
- Pitch Detection: ACF, AMDF, YIN, CREPE Algorithm
- Polyphase FIR on FPGA: Efficient Multi-Rate Implementation
- Power Profiling for DSP: J-Link Energy, Performance Counters
- Psychoacoustic Masking: Simultaneous and Temporal Masking
- PySDR / Numpy / Scipy: Python-Based DSP Prototyping
- Room Acoustics: RT60, Early Reflections, Reverberation
- Spatial Audio: Binaural Rendering, HRTF, Ambisonic
- Speaker Diarization: Who Spoke When in Meeting Recording
- Speaker Recognition: GMM-UBM, i-Vector, x-Vector
- Spectral Subtraction for Noise Reduction
- Speech Analysis: Short-Time Energy, ZCR, Pitch
- Stream Processing: Zero-Copy Buffer Management in DSP
- Superdirective Beamformer: High Directivity, Noise Sensitive
- TMS320C28x Fixed-Point DSP: Control Applications
- Texas Instruments C6748 / C6678: Multi-Core DSP
- Text-to-Speech (TTS): Concatenative, Statistical, Neural
- USRP / RTL-SDR: Hardware for SDR Prototyping
- Voice Activity Detection (VAD): Energy, ZCR, ML-Based
- WaveNet: Autoregressive Neural Vocoder Architecture
- Wiener Filter for Speech Enhancement
- Xilinx RFSoC: ADC/DAC + FPGA + ARM for Radio
Distinguished Engineer· 40
- AI-Assisted Radar: Target Classification with CNN
- Attention Mechanism in Signal Processing Applications
- Continual Learning for Non-Stationary Signal Streams
- Contrastive Learning for Audio: SimCLR on Spectrograms
- Convolutional Neural Network for 1D Signal Classification
- DNN Channel Estimation for OFDM: Pilot-Aided + NN
- DNN-Based Speech Enhancement: SEGAN, MetricGAN, FullSubNet
- Diffusion Models for Audio: AudioLDM, DiffWave
- ECG Arrhythmia Detection: 1D CNN on 12-Lead ECG
- EEG Artifact Removal: ICA + Deep Learning Hybrid
- End-to-End ASR: CTC, Attention-Based, RNN-T Models
- Explainable AI (XAI) for Signal Processing: Grad-CAM, SHAP
- Federated Learning for Distributed Signal Processing
- Foundation Models for Time-Series: Moirai, Chronos, TimesFM
- Graph Neural Network for Sensor Network Processing
- Gravitational Wave Detection: Matched Filter + CNN
- HuBERT: Hidden Unit BERT for Speech Pre-Training
- LSTM / GRU: Gated Recurrent Units for Time-Series
- ML for MIMO Detection: DetNet, OAMPNet
- ML-Based OFDM Receiver: DeepReceiver, TimNet
- Machine Learning for Condition Monitoring: Vibration, Acoustic
- Modulation Classification: CNN on Constellation Diagram
- MusicGen: Language Model for Conditional Music Generation
- Neural Beamforming: Filter-and-Sum with Learned Weights
- Neural TTS: FastSpeech 2, VITS, NaturalSpeech
- Neuromorphic Auditory Processing: SNN for Ultra-Low-Power
- PPG Signal Quality Assessment and SpO2 Estimation with ML
- Physics-Informed Neural Network (PINN) for Wave Equation
- RF Fingerprinting: Transmitter ID from Signal Imperfections
- Radar Micro-Doppler Signature Recognition
- Seismic Signal Processing with Deep Learning
- Self-Supervised Learning for Signal: BYOL, SimCLR Adaptation
- SoundStream and EnCodec: Neural Audio Codec Architecture
- Source Separation: Conv-TasNet, Dual-Path RNN (DPRNN)
- Temporal Convolutional Network (TCN): Causal Dilated Conv
- Transformer for Time-Series: Temporal Fusion Transformer (TFT)
- Uncertainty Quantification in Signal Processing ML Models
- Wav2Vec 2.0: Self-Supervised Speech Representation
- WaveNet: Dilated Causal CNN for Raw Waveform Generation
- Whisper: Large-Scale Supervised ASR (Encoder-Decoder)