An open, from-scratch vector signal analyser for Windows — a behavioural reimplementation of the Keysight/Agilent 89600 VSA software line (89601A/B, now PathWave VSA).
Status: Phase 0. The first measurement runs end to end: pick the simulated source under Hardware, then Acquisition → Start, and a live calibrated spectrum is displayed. Most of the product is still absent — no markers, no demodulation, no real front end, one fixed measurement setup. Work is tracked as GitHub issues, one per requirement, grouped into milestones by delivery phase.
A behavioural clone, not a source clone. Someone familiar with the 89600 VSA should find the same measurement model, the same trace/format separation, the same demodulation setup vocabulary and numerically comparable results.
The full requirements specification lives in requirements/ and is the authoritative source for everything below.
- Reproducing Keysight source, proprietary file-format internals, or undocumented DSP.
- Feature gating of any kind. OpenVSA is one edition, free, with everything in it — no
licence files, no entitlements, no activation, no paid tier (
REQ-LIC-010). The reference product's option SKUs appear in the specification only to explain its documentation. - Metrological traceability. OpenVSA reports what the front end delivers; absolute amplitude accuracy is a property of the instrument.
- Real-time streaming with hard latency guarantees. Like the reference product, OpenVSA is a block-based, non-real-time analyser — an architectural decision, not a shortcoming.
Acquisition and analysis are strictly separated. The analysis engine consumes nothing but a
stream of complex samples plus acquisition metadata (IqBlock), so it runs identically against
live hardware, a recorded file, or the simulator — and cannot tell which it is talking to.
This is REQ-ARC-001, and it is enforced by automated tests in
tests/OpenVSA.Architecture.Tests, not by convention.
L6 Automation OpenVSA.Api COM + .NET + SCPI
L5 Presentation OpenVSA.Ui WPF, MVVM
L4 Orchestration OpenVSA.Measurement contexts, trace graph, markers, limits
L3 Analysis OpenVSA.Dsp OpenVSA.Demod
L2 Capture session OpenVSA.Capture block assembly, recording, playback
L1 Front-end HAL OpenVSA.Hal IFrontEnd and friends
L0 Transport OpenVSA.Hal.Visa OpenVSA.Hal.File OpenVSA.Hal.Sim
Signal synthesis OpenVSA.Synthesis modulation, impairments, bursts
OpenVSA.Synthesis sits outside the stack rather than in it. It generates signals and measures
impairments back out of samples, and it references OpenVSA.Core alone — so the simulated transport
can transmit a modulated signal without an analysis assembly appearing beneath it, and the analysis
stack's own tests can use it without a transport appearing inside them.
Four data sources are first-class: the Agilent E4406A over NI-VISA/GPIB, a pluggable instrument abstraction for further VISA instruments, file playback and recording, and a simulated source with controllable impairments.
These are fixed, and are recorded here because they look like free choices and are not:
| Constraint | Why |
|---|---|
| .NET Framework 4.7.2, C# 7.3 | Required to consume the IVI/NI-VISA .NET assemblies. Consequences: portable-only Span<T>, no System.Runtime.Intrinsics, no MathF, no async streams — hence the pull-based AcquireNextAsync HAL contract. |
x64 only, gcAllowVeryLargeObjects |
A 30 s capture at 25.6 MS/s of Complex32 is 6.1 GB. Even so, a single float[] tops out near 8.6 GB, so long captures must be chunked. |
| WPF | Mandated. The plot surface is the main technical risk; see RISK-03. |
Requires Visual Studio 2022+ (or Build Tools) with the .NET Framework 4.7.2 targeting pack.
Full MSBuild is needed rather than dotnet build, because the WPF targets for .NET Framework
ship only with MSBuild.
msbuild OpenVSA.slnx /restore /p:Configuration=Debug /p:Platform=x64The application runs with no hardware and no VISA installed (REQ-NFR-032), against the
simulated source and file playback. That is an architectural constraint, not a convenience —
it is what makes the DSP developable, testable in CI and demonstrable.
The shell uses Syncfusion WPF controls for its generic furniture — docking, grids, editors, ribbon. They require a licence key registered at start-up, or they display an unlicensed banner.
A key is not needed to build or run. Without one the application launches in trial mode and says so. Nothing is gated: OpenVSA ships as one free edition with everything included, and the key is a build-time step for contributors, never a gate on anything a user receives.
To remove the banner, get your own key — a free Community licence is available from Syncfusion for qualifying individuals and organisations — and supply it either way.
The licence is yours, not the project's: OpenVSA cannot supply one, and a key committed here would be a leaked credential (see the warning below).
- Check you qualify. At the time of writing Syncfusion's Community License is free for individuals, and for organisations with under $1M USD annual gross revenue, 5 or fewer developers, and 10 or fewer total employees, that have never taken more than $3M USD from an outside source such as private equity or venture capital. Non-profits under a $1M USD annual budget also qualify. These terms are Syncfusion's and they change — read the linked page rather than this paragraph, which is a signpost and not the licence.
- Register. Create a Syncfusion account from that page. Registering through the Community License link routes you to the request form automatically. Syncfusion raises a ticket to verify eligibility; a LinkedIn or Xing profile speeds that up.
- Generate the key once approved, from License & Downloads in your Syncfusion account (Trial & Downloads if you are on a trial). Pick the edition and generate against it.
- Match the version. Keys are version- and edition-specific. This repository pins Syncfusion at the version recorded in DEPENDENCIES.md — generate the key for that major version, or registration succeeds and the banner appears anyway. From v31.1.17 Syncfusion moved from per-platform to per-edition keys, so a key generated for an older release under the previous scheme will not do.
Then supply it either way:
Environment variable (takes precedence):
[Environment]::SetEnvironmentVariable('SYNCFUSION_LICENSE_KEY', '<your key>', 'User')Or a local config file:
copy src\OpenVSA.Ui\local.secrets.config.example src\OpenVSA.Ui\local.secrets.config
# then edit it and replace the placeholder with your keyThe key must never be committed. This repository is public, so a key in the tree is a leaked credential regardless of what it costs.
local.secrets.configand*.secrets.configare git-ignored; only the.exampletemplate is tracked. Do not put the key inApp.config, which is tracked.
.\tools\build_installer.ps1 -Version 0.1.0 -EmbedLicenseKeyProduces installer\OpenVSA.Installer\bin\x64\Release\OpenVSA.msi: a per-machine MSI with a
Start Menu entry, a proper uninstall, and upgrade handling that replaces rather than accumulates.
-EmbedLicenseKeyreadsSYNCFUSION_LICENSE_KEYfrom the build environment and embeds it, so the installed application shows no Syncfusion banner and an end user needs no Syncfusion account. The key is written only intoobj\, which is git-ignored; it is never committed and never placed in the MSI as a file. Omit the switch and the build warns and produces an installer that runs in evaluation mode.- NI-VISA is not bundled. It is a pre-installed dependency: its implementation is placed in the
GAC by NI's own installer, and only a reference assembly exists in the package feed. The
installer detects it and, if it is absent, says so on the final page and installs anyway —
REQ-NFR-032requires OpenVSA to run with no VISA at all, against the simulated source and file playback, so refusing to install would contradict the software being installed. - The script checks the MSI's own file table before it finishes, and fails if a
local.secrets.config, anIvi.Visaor aNationalInstrumentsfile got in. A developer machine may have a real secrets file sitting in the payload directory, and a leaked key is not something to discover after publishing.
The installer project is not a member of OpenVSA.slnx, for the same reason the C++ FFT
project is not: the dotnet CLI cannot evaluate every project type, and dotnet test OpenVSA.slnx
has to keep working. The script builds both.
Every release is a prerelease until the final phase of the requirements is complete; only then does OpenVSA take a major version number. A release is cut at each phase boundary, when that phase's milestone reaches zero open issues, CI is green and the full bench verification has run.
Newest first.
The first release. There is no previous version to compare against, so what follows is what the release contains rather than what changed.
An installable, runnable vector signal analyser with the foundations proved: 49 requirements closed, 1 952 unit tests, 94 of 94 bench features exercised against real hardware, 6 of 6 cross-validation scenarios.
Architecture — strict acquisition/analysis separation with the analysis stack buildable with
every transport absent (REQ-ARC-001); front ends interchangeable at run time and discovered
rather than referenced (REQ-ARC-002, REQ-HAL-003); measurement personalities as plug-ins
dropped into Personalities\ with no rebuild of the host (REQ-ARC-003).
DSP — block-based analysis, double-precision accumulation, the window set with periodic definitions and gain correction, a managed FFT and a native one behind one interface, min/max pixel-column decimation, and bit-for-bit reproducible results.
Signal generation — a synthetic modulated source with deterministic seeding, twelve controllable impairments, and burst/pulse scenarios.
Shell — docking layout, trace windows, the three-zone plot surface with in-place hot-spot editing, a software rasteriser for trace geometry, per-monitor DPI awareness and a content scale factor.
Non-functional — x64 with large-object support, bounded steady-state allocation with zero gen-2 collections over a ten-minute run at 2²⁰ points, immutable snapshot hand-off to the UI, back-pressure rather than unbounded buffering, a defined thread topology, structured logging with support-bundle export, no telemetry or network egress, and a performance regression gate in CI.
Known limitations, stated rather than omitted:
- Demodulation is not in this release.
Phase 2is where it arrives. The constellation, eye and symbol-table displays exist and are verified against generated signals, but nothing yet produces a live demodulated result from a hardware acquisition. REQ-NFR-007a(window scale factor) is deferred, not done: its acceptance criterion needs two monitors at different DPI scalings. The feature is implemented and unit-tested; the verification is not. Closed underdeferred:revisit.- Two requirements were amended on measurement rather than implemented as written —
REQ-NFR-005withdrew theD3DImagerendering path (decimation makes the cost it defended against unreachable, and it degrades to software under RDP), andREQ-NFR-003replaced a fixed SIMD throughput ratio with a measured working-set sweep. Both retain the original text and the reasoning in the specification. - NI-VISA is a prerequisite for hardware, not bundled. Without it OpenVSA still runs against the simulated source and file playback.
DSP defects are quiet: the software produces a plausible number that is wrong, and nobody notices for months. The test strategy is built around making wrongness loud.
- Analytic unit tests — every DSP primitive checked against a closed-form result, never against a previous run of itself.
- The impairment round-trip matrix — for every modulation format and every impairment, inject a known magnitude and assert the corresponding metric recovers it. This closes the loop generator → channel → demodulator → metric and is the primary correctness proof.
- Hardware cross-validation — OpenVSA's flexible demod compared against the E4406A's own W-CDMA, EDGE and cdmaOne personality measurements. The only truly independent reference available on the bench.
MIT. See LICENSE.
Note on intellectual property: this project clones documented behaviour and interfaces only. It does not decompile the reference product, and does not reproduce proprietary file-format internals or trade dress.