1. What is H-MTD?
H-MTD is Rosenberger's answer to a simple question: what connector does Multi-Gigabit automotive Ethernet need?
Legacy connectors — FAKRA (coaxial, 6 GHz cap) and HSD (star quad, repurposed from LVDS) — were never designed for differential Ethernet at 10+ Gbps. H-MTD was designed from scratch with one goal: clean differential signal integrity at microwave frequencies. It is, for all practical purposes, the "RJ45 for automotive Ethernet" — but with the temperature, EMC, and vibration ratings that vehicles demand.
The connector uses a modular insert system: a single standardized outer housing accepts different inner inserts for 1-pair Ethernet, 2-pair Ethernet, USB 3.0, or LVDS. This modularity lets an OEM use one connector platform across multiple applications, simplifying sourcing, tooling, and harness assembly.
Key physical characteristics:
- Connector size: ~10 × 10 mm (single-pair version)
- Mating mechanism: Secondary locking latch (similar to FAKRA/HSD), with audible click confirmation
- Temperature rating: -40°C to +125°C (engine bay compatible)
- Mating cycles: ≥ 25 (USCAR-2)
- IP rating: IP67/IP69K with sealed variant (in development)
2. H-MTD Specifications: 10 Gbps and Beyond
| Parameter | Value | Notes |
|---|---|---|
| Differential impedance | 100 Ω ± 5% | Tighter than HSD (±10%), critical for Multi-Gig |
| Frequency range | DC – 20 GHz (connector) | Actual usable frequency depends on cable, shielding, length, and channel validation |
| Insertion loss (connector) | < 0.5 dB @ 10 GHz | Industry-leading; HSD is ~1.5 dB @ 600 MHz |
| Return loss | < -20 dB @ 10 GHz | Meets IEEE 802.3ch channel requirements |
| Crosstalk (pair-to-pair, 2-pair) | < -40 dB @ 10 GHz | 2-pair configuration only |
| Max data rate (current) | 10 Gbps (10GBASE-T1) | IEEE 802.3ch certified |
| Max data rate | Multi-Gigabit (exact rate depends on connector variant, cable, and OEM validation) | Confirm exact series and customer specification for high-speed links |
| Current rating | 3 A per contact | Sufficient for PoDL (up to 50W per IEEE 802.3bu) |
| Temperature range | -40°C to +125°C | Full automotive range |
3. H-MTD Pinout for Single and Dual Pair Configurations
Single-Pair H-MTD (1×2)
| Pin | Signal | Typical Use |
|---|---|---|
| Pin 1 | Ethernet + (non-inverting) | 100BASE-T1 to 10GBASE-T1 data line |
| Pin 2 | Ethernet − (inverting) | Differential pair, 100 Ω |
Dual-Pair H-MTD (2×2)
| Pair | Pin A (+) | Pin B (−) | Typical Use |
|---|---|---|---|
| Pair 1 | Pin 1A | Pin 1B | Primary Ethernet link (1-10 Gbps) |
| Pair 2 | Pin 2A | Pin 2B | Redundant Ethernet (fail-safe) or PoDL power (IEEE 802.3bu) |
4. H-MTD Standards: IEEE 802.3ch Compliance
H-MTD is validated against the IEEE 802.3ch standard for 2.5GBASE-T1, 5GBASE-T1, and 10GBASE-T1. The compliance requirements for Multi-Gigabit are significantly stricter than for 100/1000BASE-T1:
- Channel insertion loss: Tighter limits at higher frequencies (Nyquist at 2.8125 GHz for 5GBASE-T1, 5.625 GHz for 10GBASE-T1) demand precision connector design with consistent impedance through the transition zone.
- Return loss: Must stay below -20 dB across the entire operating frequency range. Any impedance discontinuity (from connector transition, PCB via, or cable joint) causes reflections that violate this limit.
- Mode conversion (differential to common): Critical for EMC. H-MTD's symmetrical design minimizes mode conversion, keeping radiated emissions within CISPR 25 Class 5 limits without external ferrites.
- OPEN Alliance TC9: H-MTD + cable assemblies are tested as complete channels per TC9 Class D (10GBASE-T1). This is the highest TC9 class currently defined.
5. Why ADAS L4/L5 Requires H-MTD
Level 4 and Level 5 autonomous vehicles are essentially data centers on wheels. The central compute platform ingests raw or lightly processed data from 8-14 cameras, 5+ radars, and 1-3 LiDAR units — then fuses it into a world model and generates driving decisions within 50-100 ms.
The bandwidth math is unforgiving:
- 8× 8MP cameras at 30 fps: ~10 Gbps (raw) or ~500 Mbps (compressed)
- 3× 4D imaging radars: ~3 Gbps total
- 2× solid-state LiDARs: ~2-5 Gbps each (depending on point cloud density)
- Total sensor ingest: 15-20 Gbps
This data must travel from zonal gateways to the central compute platform. 10GBASE-T1 is the minimum viable backbone for L4 — and H-MTD is the only connector validated end-to-end for this throughput in an automotive environment.
For L5 (no steering wheel, no driver), redundancy doubles the requirement: two independent high-speed links per critical path, each on a separate physical harness. The exact data rate and connector family must follow the OEM architecture and customer specification.
6. H-MTD vs HSD vs MATEnet: Performance Comparison
| Parameter | H-MTD | HSD | MATEnet |
|---|---|---|---|
| Max data rate (today) | 10 Gbps | 1 Gbps | 10 Gbps |
| Max data rate | Multi-Gigabit (confirm exact variant) | — (end of life for Ethernet) | Multi-Gigabit (confirm exact variant) |
| Frequency range | DC – 20 GHz | DC – 3 GHz | DC – 20 GHz |
| Pairs per connector | 1 or 2 | 2 (fixed star quad) | 2 or 4 |
| Modular inserts | Yes (ETH, USB, LVDS) | No (fixed pinout) | Yes (modular architecture) |
| Shielding | 360° metal (2-piece) | 360° metal (1-piece) | 360° metal (2-piece) |
| Supplier | Rosenberger (+ TE, Amphenol) | Rosenberger, TE | TE Connectivity |
| Primary OEM context | Commonly seen in European and Chinese EV platforms | Legacy platforms (all OEMs) | Per OEM platform and Tier-1 ecosystem |
| Cost per mated pair (est.) | $3-5 | $2-4 | $3-6 |
7. H-MTD Cable Construction and Shielding
H-MTD requires shielded twisted pair (STP) cable. UTP (unshielded) is not supported for any H-MTD application, unlike 100BASE-T1 and 1000BASE-T1 which can operate on UTP in low-EMI environments.
Recommended Cable Specifications
- Conductor: 26-22 AWG stranded copper (7-strand for flexibility, 19-strand for high-flex applications)
- Insulation: XLPE or PP foam (low dielectric constant for high-frequency performance)
- Twist rate: 15-25 mm lay length, tightly controlled to maintain 100 Ω differential impedance
- Shield: Aluminum-laminated polyester foil (100% coverage) + tinned copper braid (≥ 85% coverage)
- Jacket: XLPE or ETFE, depending on temperature zone
- Overall OD: 2.8-3.6 mm (single pair), 4.5-5.5 mm (dual pair)
The 2-Piece Shield Design
H-MTD uses a unique 2-piece shield ferrule system: an inner ferrule crimps the foil shield directly to the connector body (electrical contact), and an outer ferrule crimps the braid + jacket for mechanical strain relief. This separation of electrical and mechanical functions is one reason H-MTD achieves such low insertion loss — the foil is terminated with a consistent 360° contact, independent of the braid crimp force.
Frequently Asked Questions
Q: What does H-MTD stand for?
A: H-MTD stands for High-Speed Modular Twisted-Pair Data. It is Rosenberger's automotive Ethernet connector system for single-pair Ethernet (SPE), supporting 100BASE-T1 through Multi-Gigabit speeds.
Q: Is H-MTD only made by Rosenberger?
A: H-MTD was developed by Rosenberger. H-MTD-compatible products are also available from TE Connectivity, Amphenol, and others. Always confirm second-source availability with your supplier and approved vendor list.
Q: What data rate does H-MTD support?
A: H-MTD supports 100 Mbps (100BASE-T1), 1 Gbps (1000BASE-T1), and Multi-Gigabit Ethernet up to 10 Gbps (2.5GBASE-T1, 5GBASE-T1, 10GBASE-T1). A 25 Gbps variant is on the product roadmap. Actual channel performance depends on cable type, shielding, length, and PCB transition quality.
Q: Is H-MTD shielded?
A: Yes. H-MTD features a full 360° metal shield with a 2-piece ferrule system (inner for foil, outer for braid). This shielding is mandatory for Multi-Gigabit operation, which requires STP to meet CISPR 25 EMC requirements.
Q: When will H-MTD replace HSD?
A: H-MTD is the preferred connector for new 1000BASE-T1 and Multi-Gigabit Ethernet designs (BMW, Mercedes, and others). HSD remains active for legacy LVDS camera and display links where power-over-cable is needed. For new platforms, H-MTD is the forward-looking choice; HSD is a legacy maintenance choice.
Specifying H-MTD for Your Next Platform?
Send the mating connector part number, PHY speed (100M / 1G / Multi-Gig), cable type (UTP or STP), and length. We will confirm the correct H-MTD variant, shielding, and cable construction for your channel requirements.
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