@tscircuit/length-matching-solver

Standalone differential-pair length matching for routed PCB traces.

import { LengthMatchingSolver } from "@tscircuit/length-matching-solver"

const solver = new LengthMatchingSolver({
  hdRoutes,
  originalConnections,
  differentialPairs,
})

solver.solve()
const { matchedHdRoutes } = solver.getOutput()

The solver adds obstacle-aware, tapered multi-lobe meanders until each differential pair is within its configured length tolerance. It normally tunes only the shorter connection. When realizing the correction would require a tooth shallower than minMeanderHeight, it can add a jointly validated meander to each pair member instead of weakening the geometry constraint. For a multi-segment match, every selected segment uses the same tooth count, placement, and tapered profile. Invalid or impossible solver states throw with a specific error instead of returning partially matched routes.

HD-route post-processing

PostProcessingSolver accepts and returns native high-density routes, so an autorouting pipeline does not need to serialize routes before post-processing:

import { PostProcessingSolver } from "@tscircuit/length-matching-solver"

const solver = new PostProcessingSolver({
  hdRoutes,
  differentialPairs,
  obstacles,
  bounds,
  layerCount,
  // routingGrid: { innerGridStep: 0.25 },
})
solver.solve()
const { hdRoutes: postProcessedHdRoutes } = solver.getOutput()

Pair members resolve by connectionName or rootConnectionName and must each identify exactly one route. Unsupported or ambiguous geometry throws. Input, immutable non-pair routes, and returned outputs are independently cloned.

Meander geometry quality

In open routing space, the solver prefers broad, shallow tuning distributed over the available baseline instead of a narrow, deep hairpin. It evaluates a maximally relaxed pitch, an intermediate pitch, and the minimum-clearance pitch for each tooth count. Keeping the compact option allows the same search to work in constrained regions.

The quality score uses geometry-only electrical-risk proxies: depth-to-pitch aspect ratio, added-length density, deviation from the intended depth profile, bend count, and detour severity. It does not calculate impedance, inductance, or propagation delay; those require a PCB stackup and signal information that are not solver inputs. See Meander electrical-quality heuristic for the rationale, exact scoring model, limitations, owning files, and tests.

Input	Default and meaning
maximumMeanderDepth	5 mm maximum normal excursion.
maxToothCount	12 teeth per candidate.
minimumToothPitch	Optional lower bound, not a fixed requested pitch.
minMeanderGap	Greater of 0.3 mm and twice the trace width.
minMeanderHeight	Trace width plus the resolved meander gap.

The actual minimum pitch is the greater of minimumToothPitch and twice the resolved centerline spacing. Public input types are documented in lib/length-matching/types.ts.

Code map

Algorithm ownership and data flow are indexed in lib/length-matching/README.md. Visualization has a separate code map.

Development

bun install
bun run start
bun test
bun run build

bun run start opens the interactive React Cosmos fixture playground at http://localhost:5000.