Connectors for TCA

Autor: Markus Witte, Michael Seele

New Families of Connectors for standardized Telecom Architectures

The telecommunications industry offers a steady stream of new services, such as high-speed DSL, WiMAX, UMTS and digital mobile television DVB-H, for the consumer market. There is a need for operators to provide new, efficient, reliable but also economical hardware in shorter time intervals because of the increasing amount of data.

With today‘s generally company-specific systems, it will become more difficult to realize new, economical systems. As a result of globalization and great competitive and cost pressures, manufacturers of such hardware are forced to use an increasing amount of external capacity rather than in-house developments. Standardized systems with a short development time enabling proprietary integration can reduce time to market and thus generate profits for the company more quickly.

PICMG standardizations

The PCI Industrial Computer Manufacturing Group (PICMG) is a consortium of customers and manufacturers with the common objective of specifying systems that meet the technical requirements and demands of the market. These specifications define not only the architecture but also the interfaces between the modules, i. e. connectors with PCB footprint and form factor.

Fig. 1: Trend from proprietary to standardized systems
Fig. 2: AdvancedTCA carrier module
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The range of PICMG specifications includes the groups

• Series 1.x passive backplanes

• Series 2.x CompactPCI

• Series 3.x AdvancedTCA® (Advanced Telecom Computing Architecture)

The AdvancedTCA standard was adopted to meet these requirements. The standard specifies a uniform design for racks, backplanes and blades and establishes protocols and system management functions. The uniform architecture should guarantee the interoperability of the components of various manufacturers. The result is a flexible and economical hardware system.

The AdvancedMC™ (Advanced Mezzanine Card) module specification was ratified in order to increase modularity and functionality. This describes the use of modules that are connected in parallel to the carrier module via a special direct connector. Unlike two-piece connectors, direct connectors contact directly with the PCB. This connection principle can be found in every PC. A further advantage of AdvancedMC is that cards are hot pluggable. The direct connection between connector and PCB reduces additional interference in terms of signal transmission in comparison with a two-piece connector.

Figure 2 shows an AdvancedTCA carrier module. The AdvancedMC module is available in four sizes:

• Single width, half height;

dimensions in mm: 73.8 x 13.88 x 181.5

• Single width, full height;

dimensions in mm: 73.8 x 28.95 x 181.5

• Double width, half height;

dimensions in mm: 148.8 x 13.88 x 181.5

• Double width, full height;

dimensions in mm: 148.8 x 28.95 x 181.5

Depending on the module sizes, it is possible to connect up to 8 AdvancedMC modules (single width, half height) to one carrier module.

The latest system alternative based on the AdvancedMC principle should reduce the costs of system hardware. Instead of placing modules as mezzanine cards on the ATCA blades, MicroTCA™ describes a concept where the module is connected directly to a backplane. This makes the system much more compact and economical.

Fig. 5: Network architecture [source: Lucent]
Fig. 4: MicroTCA shelf

Whereas ATCA is optimized for applications with very high capacities and performance, MicroTCA addresses applications that are physically smaller and less expensive. These applications have a smaller capacity, lower performance and perhaps also less stringent usage requirements.

On the strength of these advantages in terms of the cost and size of the system, MicroTCA has succeeded in expanding the application range to include medical technology and industrial markets, as well as the consumer market.

A MicroTCA system can have various designs. Unlike ­AdvancedTCA systems, in the MicroTCA system, a ­MicroTCA Carrier Hub (MCH) controls and addresses the modules. With AdvancedTCA, these functions are implemented on the carrier module.

ATCA and MicroTCA applications

AdvancedTCA supports wireline, wireless and broadband network components. The standard is focused on telecommunication applications and products that can be found in elements at transport, core and access level.

AdvancedTCA is mainly used for switch fabric applications. The AdvancedMC standard has sub-specifications describing the following applications:

AMC.1: PCI Express

AMC.2: 10 Gigabit Ethernet (10 GE), XAUI

AMC.3: Storage

AMC.4: Rapid I/O

For future applications, the target is to achieve serial data transmission rates of up to 12.5 Gbit/s. These data rates require high demands on the signal integrity of the connectors. They can no longer be characterized as individual components, rather they have to be considered in conjunction with the complete transmission channel between transmitter and receiver.

Fig. 6: Transmission path between transmitter and receiver module

Product groups for AdvancedMC

There are various AdvancedMC connector types for an AdvancedTCA carrier module that, depending on type allowing a different number of module slots:

• Type B (one-sided module connection with 85 contacts)

• Type B+ (two-sided module connection with 170 contacts)

• Type AB (one-sided module connection with 85 contacts for each of two slots)

• Type A+B+ (one-sided module connection with 170 contacts for each of two slots)

A carrier module supports up to eight AMC modules with four A+B+ connectors. Today, AMC B+ is the most common type since, with up to four AdvancedMC modules per carrier board, it does require less particular demands on module cooling. Furthermore, the modules are packed very densely so that, due to the installation height, it is still difficult to stack two modules.

HARTING developed the AdvancedMC connector in conventional press-fit technology. The manufacturing costs are lower than for compression-mount technology since a flexible PCB is not required for signal transmission within the connector. The high data transmission rates required by the standard can also be achieved. The PICMG AdvancedMC standard has now been extended with alternate footprints to the compression mount technology to include further termination technologies, such as press-fit or SMT. In response to market requirements, the AdvancedMC B+ type was manufactured first.

Furthermore, a press-fit signal connector was developed for MicroTCA as well. The connector shows excellent transmission properties and has a footprint with wide routing channels. The connector footprint was adopted in the MicroTCA standard and is impressive since it offers the backplane developer great routing flexibilities.

In the MicroTCA system, up to four AdvancedMC connectors have to be placed wall to wall for the MicroTCA carrier hub in order to realize the number of contacts necessary to control and manage the AdvancedMC modules. Power is supplied to the modules via a special power connector.

Figure 9 shows part of the MicroTCA system that harting offered for the PICMG interoperability workshop in Chicago in November 2005. harting is the first company that developed the MicroTCA connector and the first who demonstrated a functional MicroTCA system with a customer at the Supercomm in June 2005.

Until May 2006, the MicroTCA standard will have a status that allows systems to be developed according to this specification.

Fig. 7: AdvancedMC B+ connector in press-fit technology
Fig. 8: Signal connector for MicroTCA in press-fit technology
Fig. 9: VCM and power connector in a MicroTCA shelf


HARTING was involved with the standardization activities in an early stage. Thanks to the proactive participation with pertinent proposals on the relevant committees, it has succeeded in developing and manufacturing new products within a short period of time. Furthermore harting has developed functioning MicroTCA systems with partners.

Both connectors are now manufactured in series production and many customer enquiries have been received with regard to specific projects.

HARTING is the first manufacturer to offer press-fit AdvancedMC connectors.

In addition, the HARTING Technology Group provides comprehensive design-in support that includes signal integrity analysis with simulations and measurements. Customers are also supported with an extensive range of press-fit tools. Market launch of the power connectors for AdvancedTCA and MicroTCA is in preparation. The first specimens will be available in summer and series production is set to commence in fall 2006.

Markus Witte

Markus Witte

Senior Design Engineer Signal Integrity & CAE HARTING Electronics GmbH & Co. KG

Michael Seele

Michael Seele

Global Product Manager Metric Connectors HARTING Electronics GmbH & Co. KG