802.3bt and PoE

October 19, 2017 at 8:00 AM

 

In 2003 the first Power over Ethernet (PoE) standard was ratified and today there are more than 100 million devices that use PoE. It is an easy to install solution that provides an integrated and safe power standard for worldwide use. PoE has been deployed in high-volume applications such a wireless access points (APs) and Internet protocol (IP) phones to allow communications equipment to be installed in locations where no AC power source is available or where adding an AC outlet would be too costly.

 

The main limitation of PoE is the amount of power it’s able to supply. Even the most recent standardized version of PoE, 802.3at, is only able to provide a maximum of 25.5 Watts of power to a device. This modest amount of power has limited PoE use in many applications that require more power. Plus, with an increasing number of devices simultaneously connecting to Ethernet networks, the need for more PoE power continues to grow.

 

To address the demand for higher power PoE, the IEEE has been working on a new standard, 802.3bt. This newest standard is slated to debut this year and aims to double or triple the power output of the current PoE standard, 802.3at. IEEE 802.3bt increases the maximum PoE power available by employing all four pairs of the structured wiring of an Ethernet cable. It delivers extended power management capabilities and enables multiple PoE classes while also being backward compatible. Additionally, the 802.3bt standard may also standardize PoE with 10Gbase-T.

 

The ability to provide higher power to end devices will drastically expand the number of applications able to use PoE. This will include high-volume applications such as point-of-sale, building management and industrial control systems. Delivering power and data on the same link with PoE will make life easier, and cheaper for design engineers who will be able to save time and money on installation when compared to running separate data and power lines. It also makes relocation of devices simple and as easy as moving a cable, rather than having to hire an electrician to move or add AC power outlets. 

 

Posted in: Wired

Tags: , , ,

Case Study: Biometric ID

October 12, 2017 at 8:00 AM

 

Once a fictional storyline in a sci-fi movie, biometric identification is now very much a reality and a growing industry. Biometric identification allows people to be uniquely identified by the evaluation of one or more distinguishing biological traits. This can include fingerprints, hand geometry, retina and iris patterns, voice waves and DNA.

 

One of our customers is a manufacturer of core technology, products and solutions for the biometric identification industry. They make security and identity products such as fingerprint scanners, readers, access controls and locks. These products are used by companies in the finance, transportation, telecommunications and government sectors.

 

This customer had a unique request for a custom, dual-band, PCB-style, Omni-directional antenna for an application involving a wireless, handheld, point-of-sale (POS) payment system. The antenna also needed to meet their cost requirements, be compact in size and provide reliable wireless coverage for their OEM application.

 

To meet our customer’s needs, L-com designed a Omni-directional 2.4/5.8 GHz, 3/5 dBi PCB antenna with a 3-inch micro-coaxial lead terminated with a U.FL-style RF connector. This antenna featured double-coated tissue tape so it could be easily secured in place.

 

Our custom antenna not only met the customer’s requirements, but we were able to manufacture it faster than and our competitor could, meeting the customer’s critical delivery time frame.

 

To read the full case study, click here.

 

HDMI & DVI - Your Questions Answered

October 5, 2017 at 8:00 AM

 

HDMI and DVI cables are the two most popular video cables used today. Both HDMI and DVI far outperform traditional VGA cables cables that only transmit analog video signals. These digital interconnects are used to link everything from desktop computers and LCD monitors to HDTV’s and entertainment sysyems.

 

DVI is commonly used to connect computers to monitors. They are the most similar to traditional VGA with 24 pins that support analog and digital video. DVI can stream up to 1920x1200 HD video pixels, or up to 2560x1600 pixels using dual-link DVI technology. If the DVI cable or port does not have all 24 pins, it is designed for lower resolution devices, but as long as all the pins are accounted for, it should be able to support the maximum resolution. One downfall of DVI is that it doesn’t support HDCP encryption by default, which means you may not be able to play full HD Blu-rays or other HD content if your harware only includes DVI ports.

 

HDMI is the standard cable used on newer HDTVs, Blu-ray players, Apple TVs, computers and many other video devices. HDMI cables and ports are easy to use and connect with no pins to align, it’s a simple plug and play connection similar to USB. These cables can stream both digital video and audio at the same time. They support up to 1920x1200 HD video and 8 channel audio, as well as HDCP for the newest HD content. HDMI is the first industry supported, uncompressed, all digital audio/video interface and is backwards compatible with DVI-D.

 

 

Still have questions? Here are some of the most frequently asked questions our support team gets asked about HDMI and DVI:

 

 -  What is the maximum length for a DVI cable?

  •    A DVI-D signal can travel 5 meters over a single cable. For distances longer than 5 meters, a DVI extender/repeater is needed.

 

 -  What is the maximum length for an HDMI cable?

  •    A HDMI signal can travel 5 meters over a single 28 AWG cable. A HDMI extender/repeater is needed for distances longer than 5    meters.

 

 -  When using a long HDMI cable, the monitor display is blank or the resolution looks bad. Why?

  •   Currently, HDMI cables up to 5 meters in length will operate properly. If the cable is longer than 5 meters, the signal begins to       degrade and a signal extender is needed.

 

 -  Can I get a HDMI to DVI adaptor?

  •   HDMI is only compatible with single-link DVI-D and single-link DVI-I. It is not compatible with DVI-A, dual-link DVI-D or dual-link      DVI-I, the adaptors will plug-in but will not work for these formats.

 

 -  Can I get a HDMI to VGA adaptor?

  •   No, HDMI is not compatible with VGA.

 

Posted in: Wired

Tags: , , , , , ,

411 on DAS

September 28, 2017 at 8:00 AM

 

If you’ve ever lost your cellular signal in a building that you thought would be covered by your cellular network, you probably would have appreciated the help of a distributed antenna system (DAS). Today’s construction techniques and materials block or weaken internal and external wireless communication signals inside buildings. Blocked radio and cellular reception isn’t only a nuisance for consumers, it can be detrimental to public safety and hinder first responders in an emergency situation. Thus, distributed antenna systems were designed to counteract those effects and extend wireless coverage within structures to allow radios and cell phones to work everywhere within the building.

 

A distributed antenna system uses several small antennas, as opposed to one antenna, to provide wireless coverage and eliminate spots of poor coverage inside a large building. These antennas serve as repeaters and provide reliable coverage within the structure, without requiring much additional power. They provide voice and data services, just like a cellular tower would, without any noticeable difference to mobile device reception. Any densely populated indoor space is a good candidate for DAS deployment, such as shopping malls, medical centers and high-rise buildings. Distributed antenna networks also provide wireless coverage to hotels, subways, airports, hospitals, businesses, roadway tunnels and more. In addition to indoor use, a DAS can be designed to extend wireless coverage for outdoor use. Distributed antenna systems typically provide wireless services that include PCS, cellular, Wi-Fi, police, fire and emergency services.

 

A DAS often uses RF directional couplers and/or wireless amplifiers to split and amplify the wireless signal from the source to the distributed antennas. In many cases, a DAS will use a combination of low-loss coaxial cabling as well as fiber optic cabling to support radio-over-fiber (RoF) technology and distribute the wireless signals to the antennas. The antennas are physically connected to a central controller, which is then connected to the wireless carrier network’s base station. At least one carrier network must be involved with a DAS deployment because the systems operate on the RF spectrum, which is licensed to wireless carriers.

 

Distributed antenna systems can be passive or active. A passive DAS grabs cellular signals from roof antennas and runs them through leaky feeder cables that distribute the signal throughout the building. An active DAS passes the signal from the roof antennas through fiber cables, boosting and amplifying the signals as needed.

 

Deploying DAS is the most expensive aspect of the project, as it can be very labor intensive to install the antennas and run cables between antenna modules and the controller. Usually, the carrier network manages the cost and maintenance of the DAS system, as long as it aligns with their network plan and fills a significant gap in service. Responsibility for a distributed antenna system may be shared by multiple carriers to keep costs down.

 

75 Ohm vs. 50 Ohm - Coaxial Comparison

September 21, 2017 at 8:00 AM

 

Ohm may look like something you’d say while meditating, but when it comes to coaxial cables, it is actually a unit of resistance. Ohms measure the impedance within the cable. Impedance is resistance to the flow of electrical current through a circuit.

 

A smaller Ohm measurement equals less impedance. This means that a 50 Ohm cable has less resistance to the electrical current than a 75 Ohm cable. Though there really isn’t a "good" or "bad" level of impedance, it just depends on what is right for your application.

 

75 Ohm cables are the standard coaxial cables used throughout the home, they are often pre-wired into many homes and businesses. The primary application for 75 Ohm cables is transmitting video and audio signals. They are used to connect televisions to cable and satellite receivers and internet routers. These cables are ideal for smaller applications where a signal is transmitted up to 50 feet before the signal is repeated by an active device.

 

50 Ohm coaxial cables are mainly utilized in wired and wireless networks to relay data signals. Low-loss 50 Ohm cables are used for transferring RF signals in wireless networks. For commercial installations, 50 Ohm cables typically have the advantage over 75 Ohm because they perform better (less attenuation than 75 Ohm) over longer distances of more than 100 feet and over larger areas. The disadvantage of 50 Ohm cables is that they are much thicker and use larger connectors. Typical applications for 50 Ohm cables include GPS, cellular and test and measurement applications.

 

To recap, for the lowest impedance of electrical current, 50 Ohm is the best bet. 75 Ohm cables lose almost two times the amount of dB gain every 10 feet when compared to 50 Ohm cables.

 

Also, keep in mind that the 50 Ohm and 75 Ohm ratings only refer to the cables themselves and they can be mixed and matched with cables and connectors in any other system.

 

Posted in: Wired

Tags: , ,

© L-com, Inc. All Rights Reserved. L-com, Inc., 50 High Street, West Mill, Third Floor, Suite 30, North Andover, MA 01845