Part 1 of the Report: http://www.slideshare.net/CiscoSP360/report-what-is-signal-level-part-1
Read a blog post by the author covering his recent technical paper on signal leakage: http://cs.co/slsr
The following resources come from the 2009/10 BEng (Hons) in Digital Communications & Electronics (course number 2ELE0064) from the University of Hertfordshire. All the mini projects are designed as level two modules of the undergraduate programmes.
The objective of this module is to have built communication links using existing AM modulation, PSK modulation and demodulation blocks, constructed AM modulators and constructed PSK modulators using operational function blocks based on their mathematical expressions, and conducted simulations of the links and modulators, all in Simulink®.
The following resources come from the 2009/10 BEng (Hons) in Digital Communications & Electronics (course number 2ELE0064) from the University of Hertfordshire. All the mini projects are designed as level two modules of the undergraduate programmes.
The objective of this module is to have built communication links using existing AM modulation, PSK modulation and demodulation blocks, constructed AM modulators and constructed PSK modulators using operational function blocks based on their mathematical expressions, and conducted simulations of the links and modulators, all in Simulink®.
A parallel-plate capacitor implemented by a rectangular double-sided printed circuit board is characterized by means a stimulus signal injected at a corner. Both frequency-domain (VNA) and time-domain (TDR) techniques are utilized to determine the step response of the reflected wave (S11) to be compared to the theoretical behavior of the equivalent parallel plate capacitance. A commercial application is utilized to convert the frequency domain tabulated data of the frequency response into the corresponding TDR response. A very accurate and fast 2D TLM (Transmission Line Model) model can be easily extracted from these single time-domain experimental responses.
A parallel-plate capacitor implemented by a rectangular double-sided printed circuit board is characterized by means a stimulus signal injected at a corner. Both frequency-domain (VNA) and time-domain (TDR) techniques are utilized to determine the step response of the reflected wave (S11) to be compared to the theoretical behavior of the equivalent parallel plate capacitance. A commercial application is utilized to convert the frequency domain tabulated data of the frequency response into the corresponding TDR response. A very accurate and fast 2D TLM (Transmission Line Model) model can be easily extracted from these single time-domain experimental responses.
EEE 117L Network Analysis Laboratory Lab 1
1
EEE 117L Network Analysis Laboratory
Lab 1 – Voltage/Current Division and Filters
Lab Overview
The objective of Lab 1 is to familiarize students with a variety of basic applications of
passive R, C devices, and also how to measure the performance of these circuits using
both Spice simulations and the Digilent Analog Discovery 2 on the circuits constructed.
Prelab
Before coming to lab, students need to complete the following items for each of the
circuits studied in this lab :
• Any hand calculations needed to determine the values of components used in the
circuits such as resistors and capacitors, or specifications such as pole frequencies.
• A Spice simulation of each circuit to get familiar with how it works, and determine
what to expect when the circuit is built and its performance is measured.
Making connections on a Breadboard
Breadboards are used to easily construct circuits without the need to solder parts on a
printed circuit board. As seen in Figure 0 they have columns of pins that are connected
together internally, so that all the wires inserted in a column are shorted together. Note
that the columns on top and bottom are not connected together. There are also rows of
pins at the top and bottom that are connected together. These rows are intended for use
as the power supplies, and are typically labeled + and – and color coded red and blue for
the positive and negative power supplies. These rows are not connected in the middle.
Figure 0.
EEE 117L Network Analysis Laboratory Lab 1
2
Circuits to be studied
When choosing resistor and capacitor values use standard values available to you,
and keep all resistor values between 100 W and 100 kW.
1. Voltage and Current Dividers
One of the most commonly used circuits is a voltage divider
like the one shown in Figure 1.a. For example, if a signal is
too large to be input to a voltmeter or oscilloscope it can be
attenuated (reduced in size) using voltage division. The DC
voltage that an AC signal like a sine wave varies around can
also be reduced using this circuit.
For example, if all of the resistors in this circuit are the same
value, and the VS input source provides a DC voltage of 4V,
then the voltages in this circuit will be VA = 4V, VB = 3V,
VC = 2V, and VD = 1V. That is, voltage division will cause the voltage at node B to be
¾ of VS , the voltage at node C to be ½ of VS , and the voltage at node D to be ¼ of VS.
If a sine wave with an amplitude of 1V is then added so that VS = 4 + sin(wt) Volts, then
voltage division will cause the new values of VA , VB , VC and VD to be :
VA = 1.00*VS = 1.00*(4 + sin(wt)) = 4 + 1.00*sin(wt) Volts
VB = 0.75*VS = 0.75*(4 + sin(wt)) = 3 + 0.75*sin(wt) Volts
VC = 0.50*VS = 0.50*(4 + sin(wt)) = 2 + 0.50*sin(wt) Volts
VD = 0.25*VS = 0.25*(4 + sin(wt)) = 1 + 0.25*sin(wt) Volts
In this example both the amplitude of the ...
it is a indtoduction about the analog television, we learn in this slides how can analog television work and when it is use with fequancy band it is need also we will learn about the frame, PAL NTSC and SECAM these tech. are suit for analog television with two systems that 625 line and 525 lines. in this seminer we can learn about the flicking and the finite beam fly-back time , learn about odd and even fields and why we sued them
Digital communication viva questions.( 50+)
MCQ of digital communication (50+)
communication systems MCQ. (50+)
communication systems viva questions (50+)
covered topic list:
sampling,quantization,digital,discrete,AM,FM,PM,ASK,FSK,PSK,DM,DPCM,QPSK,ADM,differences,modulation,block diagram,applications,PAM,PWM,PPM,line encoding,polar encoding,bipolar encoding,unipolar encoding,RZ,NRZ,AMI,HDB3,B8ZS
Cisco will be at OFC, the world’s premier optical event again showcasing our industry leading Packet Optical Convergence innovations and solutions. We encourage you to be part of the experience by visiting our Exposition booth (#3109) where you can interact with Cisco demonstrations, technical experts and Cisco Service Provider executives.
[Infographic] Cisco Visual Networking Index (VNI): Mobile-Connected Devices p...Cisco Service Provider
This Cisco Visual Networking Index (VNI) Global Mobile Data Traffic Forecast infographic provides some of the global and regional highlights from the updated study that covers forecast for 2014 to 2019.
For more information, please tweet us @CiscoVNI and follow our hashtag #VNI, and visit: http://cs.co/vnilpss.
[Infographic] Cisco Visual Networking Index (VNI): Mobile Users GrowthCisco Service Provider
This Cisco Visual Networking Index (VNI) Global Mobile Data Traffic Forecast infographic provides some of the global and regional highlights from the updated study that covers forecast for 2014 to 2019.
For more information, please tweet us @CiscoVNI and follow our hashtag #VNI, and visit: http://cs.co/vnilpss.
Operating costs decrease and agility increases, allowing you to react quickly to new market opportunities.
http://www.cisco.com/web/offers/sp04/simplifying-operations/index.html?KeyCode=000947566
Service creation is simpler and delivery is faster, allowing you to react quickly to new market opportunities.
http://www.cisco.com/web/offers/sp04/entering-new-markets/index.html?KeyCode=000947734
What if the orchestrator could also automate the deployment and configuration of an accompanying service assurance solution, tailored to the specific services being delivered? This is now becoming a reality using a concept called Orchestrated Assurance.
Operator Drives Bandwidth Efficiency and Optimizes Satellite Link PerformanceCisco Service Provider
Providing network connectivity and services, such as data, voice, live TV, high- definition (HD) on-demand video, and mobile services, EMC caters to customers with operations in some of the most remote corners of the planet. Managing satellite bandwidth requires sophisticated monitoring tools to ensure consistent performance of voice, video and data during events, such as rain, that can affect the quality. This telecommunications leader prides itself on delivering carrier-class services through its global mobility platform, using its hybrid satellite and terrestrial broadband network.
The EMC network features fully meshed, Multiprotocol Label Switching (MPLS) enabled and interconnected teleports in the United States, Europe, South America, Africa, and Asia. With EMC’s proprietary tools, it can manage and optimize every megabyte delivered. Its customer-facing tools further maximize every bit delivered over each customer’s WAN and LAN.
Application Engineered Routing Segment Routing and the Cisco WAN Automation ...Cisco Service Provider
The Cisco® Application Engineered Routing solution provides end-to-end control over how the network infrastructure transports applications. In the past, dedicated clusters of servers would deliver specific applications, but the number and diversity of applications continue to increase as the infrastructure becomes more converged.
Traffic patterns are dynamically changing and new applications come with specific transport requirements. Combining Segment Routing (SR) with the Cisco WAN Automation Engine (WAE) provides the necessary intelligence to optimize network resources and make informed decisions dynamically, helping to ensure a consistent, high-quality customer experience.
This white paper describes SR and the Cisco WAE and highlights how they work together to deliver an intelligent, dynamic, highly optimized network.
Research Highlight: Independent Validation of Cisco Service Provider Virtuali...Cisco Service Provider
Service providers want to know how they can build and run programmable, intelligent, responsive, efficient, flexible, and highly secure yet open networks with a high degree of automation. They want to be able to configure and activate new services quickly, utilize emerging cloud capabilities, and meet customer needs. Nimble, smart innovators in the global communications and networking industry are working on the answers and coming up with solutions every day. But providers need to know if these next-generation technologies can already meet their requirements today
In the world of service providers and networks, the demand for new and better services continue to grow, while the networks must expand and quickly adapt to these demands. One way that operators are evolving their network is to adopt some of the latest technologies like NFV (network functions virtualization). Infonetics recently found that 35 percent of the worldwide telecom carriers they surveyed are planning to deploy NFV in 2015. They are doing this because they believe that NFV and its SDN (software-defined networking) architecture will deliver benefits in service agility and new revenue, operational efficiencies and capex savings. Finding new ways to build revenue paths out of the network is critical for operators today as they innovate to find new sources of revenues.
Operators have been looking to Policy to help them find new ways to find value in their network. Specifically, they need a policy platform which can help them quickly adapt to build new services and even new networks for other operators or enterprises. We are now announcing the availability of Cisco Policy Suite version 7.5 for download. With it, operators will benefit from NFV-based policy enforcement and new access selection technologies. These new capabilities are enabling service providers to not only use policy software to open new services and markets, but they are also providing policy to the handset to ensure the best access method for the end user.
Deploy New Technologies Quickly with Cisco Managed Services for Service Provi...Cisco Service Provider
Service providers’ businesses and operations are undergoing major changes. New initiatives, like IP convergence, cloud, software-defined networks and network virtualization, are driving new business models. These initiatives are also creating opportunities for new revenue streams and greater efficiencies. Speed, agility and flexibility are required for fast access to IT and new applications. Now is the time to invest effort and resources in figuring out how to make this opportunity work for you. You have a chance to disrupt rather than being disrupted.
Segment routing is a network technology focused on addressing the pain points of existing IP and Multiprotocol Label Switching (MPLS) networks in terms of simplicity, scale, and ease of operation. It’s a foundation for application engineered routing because it prepares the networks for new business models where applications can direct network behavior.
Segment routing seeks the right balance between distributed intelligence and centralized optimization and programming. It was built for the software-defined networking (SDN) era.
Segment routing enables enhanced packet forwarding behavior. It enables a network to transport unicast packets through a specific forwarding path, other than the normal shortest path that a packet usually takes. This capability benefits many use cases, and you can build those specific paths based on application requirements.
Segment routing uses the source routing paradigm. A node, usually a router but it can also be a switch, a trusted server, or a virtual forwarder running on a hypervisor, steers a packet through an ordered list of instructions, called segments. A segment can represent any instruction, topological or service-based. A segment can have a local semantic to a segment-routing node or global within a segment-routing network. Segment routing allows you to enforce a flow through any topological path and service chain while maintaining per-flow state only at the ingress node to the segment-routing network. To be aligned with modern IP networks, segment routing supports equal-cost multipath (ECMP) by design, and the forwarding within a segment-routing network uses all possible paths, when desired.
Cisco Virtual Managed Services: Transform Your Business with Cloud-based Inn...Cisco Service Provider
Service providers face big challenges along with tremendous opportunities. Maturing technologies such as software-defined networking (SDN), network function virtualization (NFV), cloud, and open-source software are enabling exciting business innovations and market disruptions. To keep up with the pace of change today, you need to rethink how to engage with your customers to meet their business needs. At Cisco, we have the right approach to harness the transformative power of the cloud, SDN, and NFV. The Cisco® Virtual Managed Services Solution portfolio provides a rich set of secure cloud-based network services with prepackaged software capabilities over any access technology. The Cisco Virtual Managed Services solution makes it easy for you to deploy, manage, and sell new premium cloud managed services while reducing current operating expenditures (OpEx) and accelerating time to revenue.
Imagine if you could deploy highly secure new services at web speed on demand to customers and partners - complete with personalized capabilities. With this environment you’re creating innovative new services in minutes, not months, accelerating your time-to-revenue while reducing operational costs on an open platform. You have pre-packaged software service solutions that help you transform your business and the businesses of your customers. And you’re letting your customers use their existing customer premises equipment (CPE), to connect to virtual services from the cloud, reducing capital costs and business risk associated with rolling out new services.
It’s all possible with the Cisco Virtual Managed Services Solution based on the combination of the complementary Cisco Evolved Programmable Network (EPN) and the Cisco Evolved Services Platform (ESP). This open infrastructure and software combined with industry leading service orchestration, software-defined networking (SDN), and network functions virtualization (NFV) technologies automate the delivery of business services tailored to your customers from the cloud.
Cisco cBR-8 Evolved CCAP: Deliver Scalable Network and Service Growth at a Lo...Cisco Service Provider
An explosion of new over-the-top (OTT) video services and consumer devices is placing huge demand on cable access networks. To compete for new customers and retain the loyalty of existing ones, multiple system operators (MSOs) will need to expand capacity substantially, rolling out new services and gigabit tiers.
As they strive to meet insatiable market demand and stay competitive, MSOs are looking at significant access network capital expenditures (CapEx) increases over the next 5 years - and steadily rising operating expenses (OpEx) due to higher power costs and a larger network footprint. But current integrated Cisco® Converged Cable Access Platform (CCAP) solutions are limited to supporting only 24 to 32 channels per service group, and they are not designed to support DOCSIS® 3.1 at scale. Using these platforms, MSOs would need to significantly increase CapEx spend in order to compete with gigabit billboard rates and keep pace with growth.
Alternatively, MSOs can use the Cisco cBR-8 Converged Broadband Router, a full-spectrum CCAP-compliant platform that is designed to support DOCSIS 3.1. The Cisco cBR-8 enables cable operators to offer multigigabit broadband and Internet of Everything (IoE) services, and provide a path to virtualization. It empowers MSOs to scale economically to deliver more capacity and best-in-class services with much lower total cost of ownership (TCO).
This white paper examines the consumer trends affecting cable access networks and the projections for how the network and services will evolve in the coming years. It provides a long-term economic analysis of an evolved access network using the Cisco cBR-8, compared with competitive Advanced Telecommunications Computing Architecture (ATCA) platforms. And it demonstrates how MSOs will be able to meet capacity and service demands over the next several years at a 40-percent savings in hardware, space, and power costs.
Le nuove frontiere dell'AI nell'RPA con UiPath Autopilot™UiPathCommunity
In questo evento online gratuito, organizzato dalla Community Italiana di UiPath, potrai esplorare le nuove funzionalità di Autopilot, il tool che integra l'Intelligenza Artificiale nei processi di sviluppo e utilizzo delle Automazioni.
📕 Vedremo insieme alcuni esempi dell'utilizzo di Autopilot in diversi tool della Suite UiPath:
Autopilot per Studio Web
Autopilot per Studio
Autopilot per Apps
Clipboard AI
GenAI applicata alla Document Understanding
👨🏫👨💻 Speakers:
Stefano Negro, UiPath MVPx3, RPA Tech Lead @ BSP Consultant
Flavio Martinelli, UiPath MVP 2023, Technical Account Manager @UiPath
Andrei Tasca, RPA Solutions Team Lead @NTT Data
A tale of scale & speed: How the US Navy is enabling software delivery from l...sonjaschweigert1
Rapid and secure feature delivery is a goal across every application team and every branch of the DoD. The Navy’s DevSecOps platform, Party Barge, has achieved:
- Reduction in onboarding time from 5 weeks to 1 day
- Improved developer experience and productivity through actionable findings and reduction of false positives
- Maintenance of superior security standards and inherent policy enforcement with Authorization to Operate (ATO)
Development teams can ship efficiently and ensure applications are cyber ready for Navy Authorizing Officials (AOs). In this webinar, Sigma Defense and Anchore will give attendees a look behind the scenes and demo secure pipeline automation and security artifacts that speed up application ATO and time to production.
We will cover:
- How to remove silos in DevSecOps
- How to build efficient development pipeline roles and component templates
- How to deliver security artifacts that matter for ATO’s (SBOMs, vulnerability reports, and policy evidence)
- How to streamline operations with automated policy checks on container images
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
The Metaverse and AI: how can decision-makers harness the Metaverse for their...Jen Stirrup
The Metaverse is popularized in science fiction, and now it is becoming closer to being a part of our daily lives through the use of social media and shopping companies. How can businesses survive in a world where Artificial Intelligence is becoming the present as well as the future of technology, and how does the Metaverse fit into business strategy when futurist ideas are developing into reality at accelerated rates? How do we do this when our data isn't up to scratch? How can we move towards success with our data so we are set up for the Metaverse when it arrives?
How can you help your company evolve, adapt, and succeed using Artificial Intelligence and the Metaverse to stay ahead of the competition? What are the potential issues, complications, and benefits that these technologies could bring to us and our organizations? In this session, Jen Stirrup will explain how to start thinking about these technologies as an organisation.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Enhancing Performance with Globus and the Science DMZGlobus
ESnet has led the way in helping national facilities—and many other institutions in the research community—configure Science DMZs and troubleshoot network issues to maximize data transfer performance. In this talk we will present a summary of approaches and tips for getting the most out of your network infrastructure using Globus Connect Server.
1. Special Report:
What Is Signal Level?
Part 2
By Ron Hranac
An Industry Expert Digs In
BTR SPECIAL REPORT: WHAT IS SIGNAL LEVEL?
Sponsored by
2. MSO To-Do List
¨ Installation/
Fulfillment
¨ Monitoring
Return/Forward
¨ Carrier Class
Ethernet
¨ Headend
¨ Maintenance/
OSP
¨ Workforce
Management
¨ FCC Proofs
¨ Sweep
¨ Business
Services
PCheck.
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3. Special Report:
What is Signal Level?
In the previous installment, we established a foundation for digging a little deeper into the concept of signal
level. As was stated at the end of Part 1, most RF carrier power measurements are expressed in average power.
Does that rule apply to signal level measurements in cable networks? Read on to find out.
Imagine a sine wave viewed in the time domain
– that is, amplitude versus time, as might be seen
on an oscilloscope. See Figure 4.
The AC waveform’s amplitude or level can be
characterized in a variety of ways. For instance,
we can measure the sine wave’s peak-to-peak,
peak, RMS or average values of current and voltage, as illustrated in Figure 5.
Figure 4. Time domain display of a sine wave.
The voltage or current of an AC waveform is usually expressed as an RMS value. For instance, the electricity from a North American household electrical outlet
is a low frequency (60 Hz) sine wave whose RMS voltage is about 117 VAC. See Figure 6.
Click here to learn about the VeEX VePAL CX 350
BTR SPECIAL REPORT: WHAT IS SIGNAL LEVEL?
Sponsored by
4. Figure 5. Relationships between RMS, average, peak, and peak-to-peak values of AC current and
v ltage (example courtesy of ARRL).
o
An unmodulated sinusoidal RF signal is a high frequency (typically several kilohertz, megahertz, or more) AC
waveform. The amplitude of an RF signal also can be expressed in a variety of ways: voltage (volts), current (amperes) or power (watts).
Let’s look at some example RF signal voltages at various locations in a cable network. As you might suspect, perchannel signal voltages in a 75-ohm impedance cable network can vary over a considerable range of values:
Line extender output: 100 mV RMS
Tap spigot output: 7.08 mV RMS
TV set input: 1 mV RMS
Line extender input: 10 mV RMS
Figure 6. North American household electrical waveform.
BTR SPECIAL REPORT: WHAT IS SIGNAL LEVEL?
Sponsored by
4
5. The decibel and dBmV
A convenient way to deal with this wide variety of signal levels is to use the decibel (dB). A signal level in millivolts may be expressed in decibels as a ratio of that signal level to a reference of 1 mV across 75 ohms, or 13.33
nanowatts. This relationship forms the basis for the decibel-millivolt (dBmV), which is technically a unit of
power expressed in terms of voltage. Mathematically, dBmV = 20log10(millivolts/1 mV).
For example, 10 mV RMS is +20 dBmV:
dBmV = 20log(10 mV/1 mV)
dBmV = 20 * log(10)
dBmV = 20 * 1
dBmV = 20
After converting to dBmV, the previous signal level examples become:
Line extender output: 100 mV RMS = +40 dBmV
Tap spigot output: 7.08 mV RMS = +17 dBmV
TV set input: 1 mV RMS = 0 dBmV
Line extender input: 10 mV RMS = +20 dBmV
Adding modulation to the mix
What happens when the RF carrier is, say, amplitude modulated? Where in the varying amplitude signal shown
in Figure 7 do we measure the signal level?
Figure 7. Varying amplitude sine wave.
One approach is to measure peak envelope power (PEP), where PEP is the average power (watts) during one cycle
at the crest of the modulation envelope.
BTR SPECIAL REPORT: WHAT IS SIGNAL LEVEL?
Sponsored by
5
6. Start with peak envelope voltage (PEV) – for this example let’s assume the PEV is 14.14 mV, as shown in Figure 8.
Figure 8. Modulation envelope and peak envelope voltage.
PEP = (PEV x 0.707)2/R
PEP = (0.01414 volt x 0.707)2/75 ohms
PEP = (0.01)2/75
PEP = 0.0001/75
PEP = 1.33x10-6 watt, (0.00000133 watt, or 1.33 µW), during each cycle at the crest of the modulation envelope.
It would be quite cumbersome to express cable network signal levels in PEP – as in “the line extender’s per-channel input signal level is 0.00000133 watt PEP.” As previously mentioned, PEP is the average power of one cycle
during the crest of the modulation envelope, which, in the case of an analog National Television System Committee (NTSC) TV signal’s visual carrier occurs during the sync pulses.
The sync pulses represent the carrier’s maximum power; the sync pulses have a constant amplitude even as picture content varies.
Assuming a 75-ohm impedance, 0.00000133 watt is 10 mV RMS, or +20 dBmV.
Here, +20 dBmV is the RMS value of the instantaneous sync peaks – a unit of power (0.00000133 watt PEP) expressed in terms of voltage (10 mV RMS).
The unmodulated analog TV signal’s visual carrier amplitude in the left screen shot in Figure 9 is 100 mV RMS,
or +40 dBmV. When video modulation is applied, the carrier’s amplitude is measured just during the sync peaks
(arrows in right screen shot). Here, too, the level is 100 mV RMS, or +40 dBmV.
BTR SPECIAL REPORT: WHAT IS SIGNAL LEVEL?
Sponsored by
6
7. Figure 9. Unmodulated and modulated analog TV signal’s visual carrier in the time domain.
The previous example is a measurement in the time domain; the screen shots were taken from an oscilloscope
display. The screen shots in Figure 10 show a frequency domain representation of an unmodulated carrier as
seen on a spectrum analyzer (left image), and the same signal as seen in the time domain on an oscilloscope
(right image). The smaller inset screen shot in the upper right also is from an oscilloscope display, but with the time-per-division control adjusted to spread out the signal
horizontally and show a close-up of the sine wave.
Figure 10. Unmodulated RF carrier in the frequency and time domains.
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8. What about QAM signals?
As just discussed, the level of an analog TV signal is the PEP of its visual carrier.
When measuring the level of a quadrature amplitude modulation (QAM) signal, we measure that signal’s average power (not its PEP), also called digital channel power or digital signal power.
Figure 11. 64-QAM signal in the frequency and time domains.
Most digital-capable signal level meters (SLMs), QAM analyzers, and similar test equipment measure the level
at several points across a QAM signal’s occupied bandwidth – say, 6 MHz – then integrate the results to provide
the average power of the entire “haystack.” Results are typically comparable to what a thermocouple power meter
would measure.
The screen shot on the left in Figure 11 shows a frequency domain representation of a 64-QAM signal as seen on
a spectrum analyzer, and the right screen shot is the same signal as seen in the time domain on an oscilloscope.
Wrapping up the basics
When we measure the level of an analog TV signal’s visual carrier, we are measuring its peak envelope power.
When we measure the level of a QAM signal, we are measuring the entire haystack’s average power. The measurement results can certainly be expressed in watts or even volts, but those values tend to be pretty cumbersome. Use of the decibel in the form of dBmV provides a handy way of stating signal level relative to a specified
reference, where 0 dBmV equals 1 mV or 13.33 nW across 75 ohms.
Is measuring signal level enough?
The answer definitely falls into the “it depends” category. Sometimes we just need to know the signal level, perhaps to ensure that an amplifier is adjusted correctly. But signal level alone doesn’t tell the whole story.
A classic example is the service technician who visits a subscriber’s home to troubleshoot an intermittent tiling
problem in some of the digital video pictures. The first thing checked usually is the signal level. Let’s assume the
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9. input levels to the set-top box are OK. “Ah, must be the set-top,” says the tech. So he swaps out the box. Maybe
that will fix the problem, maybe not. The signal level doesn’t tell what the quality of the signal is.
A little more detective work with a QAM analyzer might show bit errors and low modulation error ratio (MER)
on a couple adjacent downstream QAM signals, perhaps indicating in-channel ingress from an over-the-air
UHF TV station. Instead of a faulty set-top, the culprit in this example might be a loose connector at the ground
block outside, allowing the over-the-air interference to get into the drop. Signal levels are fine, but signal quality
is not.
Clearly, there is risk in relying upon just signal level. Yes, it’s an important metric, but sometimes one must dig a
little deeper to sort out a problem.
“What is signal
level? It’s the power
of a signal, stated in
dBmV, which is technically a unit of power
expressed in terms of
voltage.”
Calibration
When a signal level meter reads +10 dBmV, is the signal level really
+10 dBmV? This is another “it depends.” The good news is that most
modern test equipment capable of measuring signal level – when
properly calibrated and used in accordance with the manufacturer’s
instructions – has pretty decent accuracy, perhaps in the range of ±1.5
dB or so. But in the real world, instruments bounce around in the
back of service vehicles, are exposed to the elements, occasionally get
dropped, and may be used for months or years without being checked
for accuracy. Yes, some instruments have a built-in calibration feature,
but what if the internal calibrator is out of spec?
All test equipment requires occasional factory-level calibration. Check
with the manufacturer for recommended calibration service intervals, and cycle the test equipment as required
through the calibration process at the factory or an authorized service center.
Troubleshooting tips
A book could be written about specific troubleshooting tips using a signal level meter and similar instruments,
so the following is provided as general guidance.
√√ Become familiar with the instrument’s setup and operation – read the manual.
√√ As discussed previously, ensure that the equipment meets factory calibration requirements.
√√ When using a given piece of test equipment for troubleshooting, follow the manufacturer’s instructions for
warm-up (if applicable) and field calibration. Ensure that the battery is fully charged.
√√ The test lead should be made from suitable quality cable such as tri-shield or quad-shield coax.
√√ Keep the test lead as short as possible to minimize unnecessary signal attenuation. If the lead is much more
than about 3 or 4 feet in length, it may be necessary to account for coax attenuation at higher frequencies. For
example, 10 feet of 6-series drop cable has about 0.64 dB of loss at 1 GHz, and 25 feet of the same cable has
about 1.6 dB of loss at 1 GHz.
√√ Avoid the use of push-on fittings on test leads. As convenient as push-on fittings are, intermittent connections
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10. may result. The fittings themselves, depending on design, may allow ingress interference from over-the-air
signals, too.
√√ Depending on the specific problem, it may be necessary to measure signal levels on anywhere from one to
multiple channels. When looking at problems that may affect a wider frequency range, measure levels on several channels that are representative of the entire operating spectrum.
√√ One problem that may be overlooked is total downstream RF power exceeding the capability of a set-top,
modem, other CPE, or even the test equipment itself. Checking RF input levels at just the higher frequencies
may provide insufficient information. Significant reverse tilt can cause levels at low frequencies to be too high,
possibly overdriving the affected device despite more or less correct levels at higher frequencies.
√√ If signal level is OK but problems persist, it might be necessary to do a little digging into the quality of the
signal or signals in question with more sophisticated test equipment.
√√ Use the tried-and-true divide-and-conquer technique for troubleshooting. Identify a location where the
problem exists and one where it doesn’t exist, then go to the half-way point between those two locations. If the
problem is present at the half-way point, it is occurring somewhere between the half-way test point and the
point where the problem does not exist. Conversely, if there is no problem at the half-way point, the problem is
occurring somewhere between that half-way point and the point where the problem does exist. Keep dividing
the plant, drop, etc., into smaller half-segments until the source of the problem has been found.
What is signal level? It’s the power of a signal, stated in dBmV, which is technically a unit of power expressed in
terms of voltage. Measuring signal level in a cable network is relatively straightforward, and modern test equipment simplifies the task of accurate measurement of both analog TV signals and QAM signals. Understanding the limitations of signal level measurement is important, though: Sometimes signal level might be fine, but
signal quality might not.
Part One of this Special Report is available here.
Ron Hranac is the Technical Leader
for Cisco Systems.
Sponsored by VeEx Inc.
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