A software-defined magnet-free isolator.

Every transmitter needs an isolator between the amplifier and antenna. For seventy years isolators have been made with a ferrite disc and a magnet.

ONUSKA Industries creates the same function from a printed transmission line: a switching pattern that travels along the line lets signals through one way and blocks them in the other direction. The switching pattern and function of the transmission line are set by firmware.

ONE-WAY PROPAGATION conceptual animation

■ traveling modulation ■ forward wave — passes ■ reverse wave — rejected

The striped box is the switching pattern sweeping along the line. A signal travelling with the stripes rides them and passes; a signal travelling against them is thrown out of the band and blocked.

01 · The product

Magnet-free non-reciprocity.

Isolators and circulators have required magnetized ferrite for seventy years. A time-modulated line breaks reciprocity with a traveling switching pattern instead, removing ferrite, magnets, and single-function components. Our first module targets VHF/UHF, where ferrite is at its worst.

Status · 4 September 2026

The first module is the 433 Alpha: a 96-cell printed line on a two-layer board, pumped by an on-board microcontroller: no ferrite, no magnet, no rings or resonators.

Design review of the fabrication-ready board is complete (v0.9d); first articles are pending order. Predicted performance is below, labeled as a prediction until board measurements are complete. The next design iteration targets under 6 dB of loss.

433 ALPHA — EVALUATION UNIT predicted · not yet measured

Rendered top view of the 433 Alpha board: four rows of 24 cells, on-board pump filters and controller, SMA ports
25–36 dBpredicted isolation after the firmware tunes pump frequency and varactor bias (independent SPICE model of the whole board; the tolerance Monte-Carlo is more optimistic)
10–16 dBpredicted insertion loss in the pass direction; the range spans the coil-Q uncertainty that the first measurement resolves
> 13 dBpredicted return loss, both ports, pump on
3 modelsa time-domain solver, an independent frequency-domain solver and a SPICE transient of the whole board; the first two agree to 0.3 dB, SPICE sets the isolation range; every number here is a prediction, replaced by VNA data when it exists
166 × 118 mmtwo-layer FR4, 96 varactor cells in four rows (selectable to 48 for scaling measurements), ~580 placed parts
USBpower and control through the on-board Raspberry Pi Pico; pump frequency, bias and on/off over serial, no external source
5 × SMAIN, OUT, a line tap, and ANT / RX OUT for circulator mode with a second board and the on-board hybrid
≈ −37 dBmpredicted pump residue at the RF ports near 55 MHz, behind on-board port filters — stated so an evaluator knows what the analyzer will show

Mechanism: a varactor-loaded transmission line with a traveling-wave pump; the direction the pump travels is the direction that passes. What gets measured first: pump-off transmission (which pins the coil quality), then pump-on transmission both ways, return loss, isolation against frequency, and spur levels.

Evaluation partners. First units go to small-satellite and UHF radio teams who want a flat, magnet-free isolator for testing and will share measurements with us. Contact us if interested.

Ask about an evaluation unit →

Why low band?

wavelength limit

A junction circulator's size is set by the wavelength itself. At VHF/UHF that means components are fist-sized and weigh hundreds of grams.

The lumped-ferrite workaround trades away loss, power handling, and bandwidth and still uses a magnet.

We are subwavelength by construction: no gyromagnetic volume, no magnet.

asymmetry

Time-modulation gets harder as frequency rises. The pump must run at a fraction of the carrier frequency so our mechanism functions easiest where ferrite is at its worst.

The funded efforts we have found targeted the GHz/integrated tier; the low-band module tier remains unaddressed.

"…a new category of subwavelength non-reciprocal circulators… operating at microwave frequencies without the need of magnetic materials… based on suitably tailored time-varying networks."
— DoD OSD STTR solicitation OSD21C-002 (2021). That is the component class we build.
status
433 Alpha v0.9d · design review complete, first articles pending
first target
VHF/UHF module
why it matters
SWaP + magnetically clean

02 · The physics

Boundaries in time, not just space.

Every conventional RF component is a structure in space: waves hit an interface, and the interface reflects, filters, or guides them. Frequency is fixed and geometry provides the effect. That is the physics of every filter, antenna, and ferrite isolator made in the last century.

A time-modulated medium adds the time axis. Switch the line's properties at a chosen moment, and the roles invert: wavelength holds, frequency shifts, and a portion of the wave returns as a time-reversed echo.

Sweep the switching pattern through space and time together, and the medium behaves as if it were moving producing Doppler shifts, one-way propagation, and effects no static circuit can produce. All without a magnet.

A WAVE CROSSING A BOUNDARY IN TIME computed in your browser

■ line voltage V(x) ■ probe trace V(t) @ marker ■ boundary instant fin 1.00 · predicted fout = β·fin 2.00 · measured —

Simulation shown: a discrete LC transmission line integrated live. Fire a burst. As it is mid-flight, every capacitor in the line switches at once: a boundary in time is produced. The wave keeps its wavelength, jumps in frequency (f → β·f, β=√r), and splits into a transmitted wave and a backward echo. This effect was first measured in an electrical lattice in 2023 (Moussa et al., 2023); it is the physics our components are built on.

THE SWITCHING PATTERN CONTROLS TRANSMISSION LINE interactive

regime SUBLUMINAL βmod = vfront/vwave 0.50

The shaded cone shows how fast waves travel in the line; the violet line is how fast the switching pattern sweeps along it.

If slower than the waves, then the pattern Doppler-shifts them differently by direction: this is the non-reciprocal method our isolator uses. If faster than the waves, then it acts as a boundary in time.

One hardware platform can perform every transmission line effect; only the program changes.

03 · The experiment

Bubble One: temporal-boundary physics on accessible equipment.

Time-modulated media are usually studied on microwave metamaterial rigs. Bubble One is our validation platform: a 96-section switched transmission line, microsecond-scheduled by a microcontroller, instrumented with a standard oscilloscope. This platform demonstrates that a programmable medium can be built from catalog parts for a few hundred dollars.

Measure specific predictions of temporal-boundary physics on accessible hardware, reproducibly. Results, hardware documentation, and the full build will be published here as they are validated.

MEASURED DATA Stage E campaign · 1 September 2026

Measured: a 25 kHz packet caught inside an opened segment exits at twice its frequency; measured spectrum peak against the 51.8 kHz prediction
×2.00frequency conversion at a temporal boundary, measured, against 2.07 ideal (sim 0–3 %)
6 / 6modulated segments certified by an automated phase-step ladder, 0.8–9 % from the time-domain model
87 mV vs 3 mVtemporal reflection at node 8 against the noise floor, confirmed by a no-packet control

Every test scripted by firmware: the oscilloscope, signal generator, and firmware were driven from code, predictions written before measurement, model parameters measured independently without fitting. Full bench log and hardware documentation publish with open-source release.

04 · The company

Building empirically.

ONUSKA Industries LLC is an independent hardware company founded by Ian Onuska, based in Pittsburgh, Pennsylvania, with a lab in South Amboy, New Jersey.

→ ian@onuskabrown.com