NEUTRIK BNC Connectors Professional Cable User Guide
- June 1, 2024
- NEUTRIK
Table of Contents
NEUTRIK BNC Connectors Professional Cable
White Paper – BNC
- Title: NWP06
- © NEUTRIK AG. All rights reserved.
This white paper is a publication of NEUTRIK AG. This white paper represents the technical status at the time of printing. The product information, specifications, and all technical data contained within this white paper are not contractually binding. NEUTRIK AG reserves the right to make changes at any time to the technology and/or configuration without announcement.
- NEUTRIK AG is not to be held liable for statements and declarations given in this white paper.
- NEUTRIK AG explicitly exonerates itself from all liability for mistakes in this white paper.
ABSTRACT
Currently, data transport of high-definition serial digital interface (HD-SDI) signals at 3 Gb/s is state-of-the-art and standardized by the Society of Motion Picture & Television Engineers (SMPTE). For return loss and voltage standing wave ratio (VSWR) measurements, suitable equipment is available. With upcoming ultra-high definition (UHD) signals and related high frequencies, the discrepancies between the available 50Ω measuring equipment and the defined 75Ω video standards increase. This paper explains the influence and importance of return loss in a video system and shows a suitable test method which Neutrik believes is the best for high frequencies. Further return loss measurements compare Neutrik`s new rearTWIST UHD BNC connector, which is specifically designed for high frequencies, UHD-optimised connectors from common manufacturers up to 18 GHz (ST 2082-1).
RETURN LOSS
What is return loss
Return loss is signal attenuation caused by impedance variations in the structure of a cable or associated connection parts like Bayonet Neill–Concelman (BNC) connectors. These variations cause some part of the signal to reflect (return) back to the source. At lower frequencies, return loss is a minor effect; at frequencies above 50 MHz, it can have a significant impact on the signal performance and the transmitted distance. For signals with high bandwidth (e.g. UHD) and resulting high frequencies, it can be a critical factor. In addition, also the VSWR is a function of the reflection coefficient, which describes the power reflected from the end of the system and is another representation of the return loss.
About return loss
With the transition to UHD signals, including 4K and 8K signals with their higher data rates up to 24 Gb/s (ST 2083-1 pending) and related increased clock frequencies, the impedance of BNC connectors becomes more important than ever. Every impedance deviation has a negative influence on the return loss and VSWR values. To maintain the square waveform of digital signals harmonics (table 1) up to the 5th order should be considered. Taking the 3rd harmonic as a limit represents a reasonable compromise between signal waveform and reliable test results.
table 1
DATA RATE
| 3rd HARMONICS|
APPLICATION
---|---|---
3.0 Gb/s| 4.5 GHz| HD acc. ST 424
6.0 Gb/s| 9.0 GHz| 4K acc. ST 2081-1
12.0 Gb/s| 18.0 GHz| 4K acc. ST 2082-1
HOW TO MEASURE RETURN LOSS UP TO 18 GHZ
Challenges
As mentioned, for high definition signals (HD) up to 3 GHz, there are suitable
return loss and VSWR measuring devices available. For 4K and 8K signals with
related high frequencies (table 1), there is only some dedicated 75 return
loss measure-ment equipment and related calibration kits available, but with a
limited frequency range (see references No 2.). 50-based test instrument
systems have to be used to carry out measurements in the required extended
frequency range. The Time Domain Gating (TDG) method can be used as an
alternative to the conventional S11 (ST2081-1 & ST2082-1) measurement
procedure on the frequency domain to avoid calibration uncertainties due to
components (e.g. adapters, matching pad, etc.) which are not specified for
higher frequencies. The major advantage of TDG is an easier visualization and
localisation of impedance deviations.
Principle – Time Domain Gating (TDG)
- The device under test (DUT) is connected to the network analyser via a short adapter cable. This increases the distance between the test port, any existing adapters and the DUT, which enhances the distinct identification from impedance deviations.
- The measured signal is transformed from frequency to time domain (Figures 1 & 2). Similar to a conventional Time Domain Reflectometer (TDR), all impedance deviations from DUT components (e.g. BNC connector, cable, etc.) can be identified.
- A gate (figure 2) with defined start and end points is positioned on the DUT component (e.g. BNC connector, cable, etc.) which has to be measured.
- Current return loss values inside the gate are transformed back from the time domain to the frequency domain (figure 3), representing the return loss from a defined position within the DUT.
MEASUREMENT–TDG METHOD
RETURN LOSS MEASUREMENT UP TO 18 GHZ
The following return loss measurement demonstrates the functionality of the TDG method by an example and compares the performance of Neutrik`s new rearTWIST UHD BNC with well-known connectors from US and French manufacturers, offering UHD-optimized BNC connectors, to provide a verifiable reference of com-monly used products in the professional broadcast industry.
Measurement setup & condition
Figure 4 and Table 2 show the measuring setup including the network analyzer,
adapter cable, DUT and a 75 load for the return loss measurement via the TDG
method.
table 2
ITEM
|
TYPE
---|---
Network Analyser| HP 8722D
Adapter cable| SMA terminated with Belden 1694A (0.8 m length)
and a BNC female jack on the other side
COAX cable DUT| Belden 1694A (8 m)
BNC connectors I
BNC connectors II
BNC connectors III
| Neutrik rearTWIST UHD BNC NBNC75BTU11X
Common French manufacturer
Common US manufacturer
Measurement results “non-gated” in frequency and time domain
The measured return loss values are transformed from the frequency domain
to the time domain. The gate (figure 5) is manually positioned (table 3 lists
used gate parameters) to measure the BNC connection and blend out the
impedance of the cable, analyser, etc.
table 3
PARAMETER
|
VALUE
---|---
Spam| 5 ns
Zero point| 5,5 ns
Endpoint| 8 ns
Conclusion & Results
- The goal was to receive verifiable return loss characteristics of BNC connectors, measured with a suitable test method for high frequencies up to 18 GHz (ST 2083-1). Due to limited calibration kits for 75 systems for high frequencies the
- TDG method (section 3.2) has been chosen to measure the return loss of the connector only, suppressing the impedance deviations of the cable and adapters.
- To compare the new rearTWIST UHD BNC, specifically UHD optimized connectors from common manufacturers were used as reference.
- All BNC connectors indicate low return loss values and sufficient headroom to the required UHD limit (figure 6) over the entire frequency range up to 18 GHz (ST8083-1). Therefore all 3 connector types are suitable for high-resolution video signal transmission.
- Figure 6 represents the optimum measuring setup with minimum connection points to avoid additional adulteration from the return loss values. In reality, real broadcast installations contain multiple BNC connection points which have a significant influence on the return loss performance. Therefore sufficient distance (headroom) to the UHD limit is essential to guarantee appropriate signal transmission.
- Neutrik’s new rearTWIST UHD BNC achieves increased headroom compared to the connectors from the US or French manufacturers and offers additional return loss reserve for potential impedance deviations resulting from cable bending, incorrect connector assembly or faulty connection interfaces without signal interruption.
References/Literature
- Neutrik BNC White Paper “Optimum Performance of Neutrik rearTWIST 75 BNC-Connectors in HD 1080p applications”
- Samtec “Characterizing Non-Standard Impedance Channels with 50 Ohm Instruments”
- Belden “High-Definition Cabling and Return Loss”
- Axon “Adventures In Return Loss”
Contact Information
Liechtenstein (Headquarters)
- NEUTRIK AG, Im alten Riet 143, 9494 Schaan
- T +423 237 24 24, F +423 232 53 93, [email protected]
Germany/Netherlands/Denmark/Austria
- Neutrik Vertriebs GmbH, Felix-Wankel-Strasse 1, 85221 Dachau, Germany
- T +49 8131 28 08 90, [email protected]
Great Britain
- Neutrik (UK) Ltd., Westridge Business Park, Cothey Way Ryde, Isle of Wight PO33 1 QT
- T +44 1983 811 441, [email protected]
France
- Neutrik France SARL, Rue du Parchamp 13, 92100 Boulogne-Billancourt
- T +33 1 41 31 67 50, [email protected]
USA
- Neutrik USA Inc., 4115 Taggart Creek Road, Charlotte, North Carolina, 28208
- T + 1 704 972 30 50, [email protected]
Japan
- Neutrik Limited, Yusen-Higashinihonbashi-Ekimae Bldg., 3-7-19 Higashinihonbashi, Chuo-ku, Tokyo 103
- T +81 3 3663 47 33, [email protected]
Hong Kong
- Neutrik Hong Kong LTD., Suite 18, 7th Floor Shatin Galleria Fotan, Shatin
- T +852 2687 6055, [email protected]
China
- Ningbo Neutrik Trading Co., Ltd., Shiqi Street, Yinxian Road West Fengjia Villiage, Yinzhou Area, Ningbo, Zhejiang, 315153
- T +86 574 88250488 800, [email protected]
India
- Neutrik India Pvt. Ltd., Level 3, Neo Vikram, New Link Road, Above Audi Show Room, Andheri West, Mumbai, 400058
- T +91 982 05 43 424, [email protected]
Associated companies
Contrik AG
- Steinackerstrasse 35, 8902 Urdorf, Switzerland
- T +41 44 736 50 10, [email protected]
H. Adam GmbH
- Felix-Wankel-Straße 1, 85221 Dachau, Germany
- T +49 08131 28 08-0, [email protected].
