Prevent Signal Distortion with Data Bus and Stub Terminators

In rock’n’roll, distortion is a good thing. It is what gives guitars that powerful, crunchy sound. But in data communications, distortion is bad.

When a digital signal hits the open end of a power bus, or individual stubs, it can bounce back and cause the signal to distort and impedance to change. What is the cure? Installing data bus and stub terminators minimizes the effects of signal reflections that can cause waveform distortion. Without them the communications signal can be compromised, causing disruption or intermittent communications failures.

This blog post details how data bus and stub terminators can improve your data signals. We conclude with some information about the MilesTek line of coaxial, twinaxial, and triaxial terminators for MIL-STD-1553 applications.

What Terminators Prevent

Data bus and stub terminators are components used in digital communication systems to prevent signal reflections and ensure proper signal integrity. They are particularly important in high-speed communication systems to avoid issues like signal degradation and data corruption. Here is what they prevent:

  • Signal Reflections: When a signal travels along a transmission line (such as a data bus), it encounters impedance mismatches at various points like connectors, branch points, or the end of the line. These mismatches can cause a portion of the signal to be reflected towards the source. These reflections can interfere with the original signal, leading to signal distortion, timing errors, and data corruption.
  • Signal Degradation: High-frequency signals can experience attenuation (loss of signal strength) as they propagate along a transmission line due to factors like resistance, capacitance, and inductance. Without proper termination, these signal losses can lead to degraded signal quality at the receiving end, resulting in difficulties in distinguishing between high and low signal levels.
  • Data Corruption: In digital communication systems, data is represented by different voltage levels (e.g., high and low). If reflections occur due to impedance mismatches, the reflected signals can overlap with the original signals, causing confusion at the receiving end about the intended data values. This can lead to errors in data interpretation and ultimately result in data corruption.

How Terminators Work

Data bus and stub terminators work to mitigate these issues by providing the following functions:

  • Termination: Termination resistors are used to match the impedance of the transmission line (data bus) to the characteristic impedance of the connected devices. This minimizes signal reflections by preventing the signal from being reflected when it reaches the end of the line. Proper termination helps maintain signal integrity and reduces the likelihood of data corruption.
  • Stub Termination: Stub terminators are used at the connection points of branches or stubs from the main transmission line. These stubs can act as additional paths for signal reflections. By properly terminating the stubs, reflections from these branches are minimized, preventing interference with the main signal.
  • Impedance Matching: Data bus and stub terminators ensure that the impedance of the transmission line is matched with the impedance of the connected devices. Impedance mismatch can lead to signal reflections and degradation, so matching impedances helps reduce these issues.

MilesTek’s Data Bus and Stub Terminators

MilesTek carries a complete line of in-stock data bus and stub terminators for coaxial, twinaxial, and triaxial cable. Some of the models include a steel or brass chain for anchoring the terminator to the device.

Our coaxial terminators close open connections for a cleaner, more robust signal through coax cable. Applications include RF and microwave designs, DS3 central office, analog and digital video, and thin-net Ethernet. You can choose between 50-ohm or 75-ohm resistance. Locking, bayonet-style BNC connectors are used for quick and secure joints, low signal loss, and consistent impedance.

Our twinaxial and triaxial stub terminators are used to simulate future loads from an unspecified device on the data bus. They come in 1000-, 2000-, and 3000-ohm versions and mate with the MilesTek 10-06593 three-slot jack, which is found on almost every standard MilesTek bus coupler and relay device.

MilesTek’s twinaxial and triaxial bus terminators are used to terminate an open bus line on a MIL-STD-1553 data bus. These 78-ohm devices mate to any TRB three-lug jack, which are found on almost every standard 1553 data bus coupler and relay device.

Most of our coax, twinax, and triax data bus and stub terminators are in stock and available for same-day shipping. For help on choosing what product is best for you, contact the U.S.-based MilesTek sales team at 1-877-924-1134 or via email at sales@milestek.com.

August 15, 2023