DIPOL Weekly Review – TV and SAT TV, CCTV, WLAN

Energy from WiFI.

The development of digital data transmission has resulted in the exponential growth of Wi-Fi sources. The 2.4 GHz frequency is widely used which has prompted researchers to try to recover the emitted energy. The team of researchers at the National University of Singapore (NUS) and Tohoi University (TU) in Japan have developed a technology that uses small STOs (spin-torque oscillators) to collect and convert wireless radio signals into energy to power small electronic devices. In the experiment, the researchers managed to power an LED without using batteries.

The research breakthrough was achieved by a team led by Professor Yang Hyunsoo (left).
Dr. Raghav Sharma (right), the first author of the paper, holds an integrated circuit containing about 50 spin torque oscillators.

STOs are a new class of microwave-generating devices with applications in wireless communication systems. However, their use is hampered by low output power and high bandwidth. Although mutual synchronization of multiple STOs is a way to overcome this problem, some of their characteristics, such as short-range magnetic coupling between multiple STOs, are the reason for space limitations. On the other hand, long-range electrical synchronization using spin oscillators is limited in frequency responses to only a few hundred MHz. This solution also requires dedicated current sources for each STO, which can complicate the overall impedance on the chip. To overcome the space and low-frequency limitations, the research team developed an array in which eight STOs are connected in series. Using the array, the 2.4 GHz electromagnetic radio waves used by Wi-Fi were converted into a direct voltage signal, used to charge a capacitor and power a 1.6 V LED. After having been charged for 6 seconds, a capacitor was able to light up the same LED for one minute after the wireless power was turned off. In their study, the researchers also emphasized the importance of electrical topology in the design the of on-chip STO systems and compared the series design with the parallel one. They found that the parallel configuration to be more suitable for wireless transmission due to better time-domain stability, spectral noise conservation and control of the impedance mismatch. On the other hand, series connections have an advantage in terms of energy harvesting performance due to the additive effect of diode voltage with the STO.

In the future, to collect more energy, the researchers wish to increase the number of STOs in the circuit they designed. Moreover, they plan to test their energy harvesters for wireless charging of other useful electronic devices and sensors.

The research is a step toward turning readily available 2.4 GHz radio waves into a green energy source, reducing the need for batteries to power the electronics we regularly use. In this way, small electrical gadgets and sensors could be powered wirelessly via radio waves as part of the Internet of Things. With the advent of smart homes and cities, their work could lead to energy-efficient applications in communications, computers and systems.

Various multimedia interfaces in one video system.

Signal HD HDMI (VGA) to IP converters make it possible to connect high-definition (HD) signal to a receiver (TV set, monitor) equipped with HDMI(VGA) connector through a dedicated computer network. The devices also enable the user to extend IR (remote control) and/or USB (mouse, keyboard) signals, e.g. for controlling an NVR or STB player.

In systems where the source of the signal has different multimedia interface than the TV set, one can use Signal IP converters to run the system.

Diagram of a system for connecting a computer (VGA connector) to a TV set (HDMI connector)

In the example above, the computer has been connected via VGA cable to VGA Signal H3618 IP converter. With the HDbitT protocol, it is possible to receive the signal from another converter (in the above case the HDMI to IP converter H3614R) and convert it to another interface. Such systems are often made when the source of the signal is an older DVR or computer.

Advantages of fiber optic cabling in SMATV systems.

Originally located on the roofs of buildings, the SMATV systems are particularly prone to surges caused by lightning. In spite of proper grounding of all system components, some devices suffer irreparable damage. It has to be stressed that not only the system devices alone are exposed to surges, but, in extreme cases, the subscriber equipment, such as satellite receivers or TV sets, are also affected. Fiber optic cable provides excellent surge insulation. This means that any electric charges induced near the antennas will stop at the very downstream optical transmitter, so the remaining components of the system are 100% protected.

Optical fiber cables are safe to be placed together with copper cabling for transmission of other signals, power (100% resistance to electromagnetic interference). The diagram below shows an example of an optical-copper cabling that enables the transmission of TV/SAT signals.

Automatic start of live monitoring when connecting to Hikvision DVR via Internet browser.

When connected to Hikvision DVR via web browser, automatic live preview playback is disabled by default. The preview can be activated for all cameras each time from the main window and the type of stream played can be specified. In the local configuration, after logging in to the DVR, it is possible to enable automatic live playback. It is also possible to specify the type of stream from which the cameras are to be displayed during automatic playback (main or auxiliary stream). This configuration applies to the specific browser running on the computer. The settings can be changed after logging in to the DVR in the Configuration -> Local tab.

View of the configuration window for automatic playback of live images after logging in to the Hikvision DVR via a web browser

OTDR vs. distance measurement.

Measurements of an optical path with an OTDR carry a lot of information. In fact, the time (the OTDR measures the return time of the generated pulse) and the power of the reflected signal are measured. Other information, such as distance and attenuation, is, against a common opinion, calculated, not measured.

Installers care about precise determination of a specific point of action (splice, macroswitch, connector) or precise determination of cable length. One of the key issues here is correct setting of group index of refraction value for measured fibers (IOR parameter). This parameter is set manually, and its value should be provided by the manufacturer of a given cable (specifically, by the fiber manufacturer). It provides information on the speed of pulse propagation in a given fiber. Each differently doped fiber will vary slightly in this regard. Since the information on the action distance comes directly from the pulse return time measured by the OTDR, which in turn depends on the speed, incorrect setting of this parameter will cause erroneous distance readings.

With measurement parameters set correctly, the GRANDWAY FHO3000-D26 L5828 reflectometer
can determine the location of an event with accuracy close to 1 m

Typically, the value assumed for single-mode cables is 1.471 (the actual value should be read from the catalog card). The longer the distance, the greater the negative impact of the wrongly set refractive index. The table below shows the dependence of the error of determining the distance on longer connections from the difference between the set and actual values of this parameter (it has been assumed that 1.471 is the correct, actual value).

The value of 1.481 is typical for multimode fibers. So, it can be seen that neglecting the change of this parameter for single-mode fibers may cause significant distance errors, and thus eliminating the ability to determine the precise locations of events.

Note also that, in practice, the distance displayed by the OTDR screen will never correspond to the real cable length. This is due to the fact, that fibers inside the cable are always longer than its outer sheath (in order to avoid stress). Furthermore, if the fibers are placed in several tubes wrapped around a core the difference between the fiber length and the cable length will increase even more (there are loose fibers inside the twisted tube, longer than the cable). In extreme cases the difference in length of the fibers in relation to the length of the cable can reach even several percent.

Since the IOR values are given for the fibers, not for the cable, super precise measurement is possible when so called effective value of IOR parameter is determined for the given cable. To calculate it, measure several dozen meters of the cable using standard refractive index, noting down the measured and the actual length resulting from markers on the cable. Compare the two values, and then adjust the IOR at the same ratio to obtain the rms value.

How to solve the problem of voltage drop on a long power line? PSCU04344SEP M1833 power supply is designed to power devices over long cable sections. In order to eliminate voltage drops on a device caused by current flowing through a conductor with significant resistance, the power supply delivers DC voltage increased to 30-35 V to the power line. The cameras are equipped with DCDC10H M1834 converters providing stable 12 VDC voltage with a maximum current of 0.8 A. The PSU features 4 independent, galvanically separated outputs protected by fuses...>>>more

Application diagram of the PSCU04344SEP M1833 power supply

Overview of Hikvision video intercom systems