The Paper
Research
Experimental characterization of eigenmode-spectral encoding in a fused-silica plate resonator — classification performance, spatial non-separability, signal integrity, and stability.
Version 19r — June 2026
Spectral Fingerprinting in Piezo-Driven Fused-Silica Plate Resonators
Mike Tierce · June 2026
Experimental characterization of eigenmode-spectral encoding in a $38 fused-silica plate: 4 modes at 42–55 dB SNR, 100% pattern discrimination (80/80 trials), 4,096-state multi-level capacity, non-separable frequency×space structure (concurrence > 0.99), and 16.5M-cycle endurance. Honest about limitations: digital decoder dependency, pending cross-session validation, reservoir computing failure.
100%
Binary discrimination (80/80)
4,096
Multi-level states, zero error
C > 0.99
Spatial non-separability
16.5M
Endurance cycles (0.22% drift)
Prior Versions (Archive)
Validation Summary
Macro-Scale Prototype
A $38 fused silica plate with PZT transducers, Pico NCO drive, dual-channel PicoScope readout. 42–55 dB SNR at 4 modes.
Signal Integrity
PZT-lifted null test confirms 0% electrical feedthrough. Spatial contrast ratios (49:1) prove acoustic origin of spectral structure.
Spectral Classification
100% binary discrimination (80/80 trials, 9σ+ separation), 4,096-state multi-level encoding via digital nearest-centroid decoder.
Honest Failures
Temporal reservoir computing fails (rate/Q mismatch). Q-factor fits have R²<0.1. All limitations reported openly.
Spatial Non-Separability
Frequency×space concurrence > 0.99 across 5 mode pairs. Each eigenmode couples differently to spatially separated receivers.
Stability & Endurance
16.5M cycle endurance (0.22% drift). Non-separable state stable to 0.65% over 3.5 hours and 4.6°C temperature range.
Architecture at a Glance
CWM operates through three physical mechanisms — all exploiting the same vibrational eigenmode spectrum of a glass resonator.
Write (Encode)
Mass perturbations shift eigenmode frequencies via the Rayleigh perturbation formula. Each perturbation creates a unique spectral fingerprint.
Read (Detect)
Continuous-wave lock-in detection measures frequency shifts with sub-Hz precision. 3.8 µs readout latency per rod.
Compute (Recall)
Drive all rods with a query signal — the matching rod resonates most strongly. Nearest-neighbor search by wave physics, no algorithm needed.