Attenuators

An attenuator is an electronic device which reduces the amplitude or power of a signal without distorting its waveform. It is opposite of amplifier .while amplifier provides gain but attenuator provides loss or gain less than 1. The attenuators are made from voltage divider networks and are passive devices With the help of potentiometers adjustable attenuators are made and stepped attenuators are made from switching between resistances. To reduce voltage, dissipate power and to improve matching fixed attenuators are used. Attenuators are also used to 'match' impedances by lowering apparent Standing Wave Ratio. The coupling portions are available in all types of plug and jack combinations of attenuators and stainless steel is used for the external cladding to form a small and durable structure. Although some attenuators are of the surface mount type, but they offer superior high frequencycharacteristics from DC to 8 Ghz.

There are different types of attenuators like RF Attenuators and Audio Attenuators

RF attenuators

Radio frequency attenuators are typically coaxial in structure with precision connectors as ports and coaxial, micro strip or thin-film internal structure.

Important characteristics are:

• accuracy,
• low Standing Wave Ratio,
• flat frequency-response and repeatability

The size and shape of the attenuator depends on its ability to dissipate power. RF attenuators are used as loads for and as known attenuations and protective dissipations of power in measuring RF signals.

Features

1.Variations of Attenuators

Attenuators are available in wide variety of variations from 0 to 30 dB in 0.5 dB to 1 db steps, so that levels can be finely adjusted.

2.High Degree of Matching and High Reliability

Attenuators use a distributed constant circuit and metal film resistors. A high degree of matching is also achieved. Furthermore,these attenuators show stable characteristics for environments of varying temperature, humidity, and gases.

3.Small Size and Economical

The attenuators are in abundance of small size less weight and very economical. Small size and light weight allows side-by-side panel mounting of several attenuators. Small, lightweight and low V.S.W.R makes it ideally suited for the widely used high frequency transmission applications. Frequency bandwidth and high reliability is achieved by the use of resistance substrate on the extremely thin board, to form a suspended line. HRS unique resistance substrate design and center conductor connection assures consistent and stable performance in changing temperature environments

4.Easy connection

Because of output / input connectors face back,connection and disconnection is quietly possible. Attenuators even can be modified to fit specific requirements

Applications

• Wide variety of measuring instruments and other devices requiring control of high frequency
• transmission lines.
• Optical transmission devices
• Network analyzers
• BERTS (Bit Error Ratio Testing Systems)
• FWA (Fixed Wireless Access)
• Measurement applications requiring transmission frequencies of up to 65 Ghz.
• W-CDMA base stations and a wide variety of high frequency devices.
• DWDM applications
• Aerospace industries
• Telecoms industries
• Security connections
• Testing

Read more: NAS Knowelge Base http://www.beganto.com/

Ultracapacitors

Ultracapacitors are also known as Super capacitors or Electrochemical Double Layer Capacitors (EDLC) which stores the energy in an electric field rather electrochemically. Today, automotive industries have gone under a drastic change from internal combustion engine to electric and hybrid engines.

Ultracapacitors are electronic devices that store energy electrostatically by polarizing an electrolytic solution but there is no chemical reactions occur to store the energy. They are charged and discharged number of times and are highly reversible.

The cars have become a sophisticated vehicle with electronic subsystems and accessories and due to the increasing demand of electric power in such vehicles, so there is a need of a component which can overcome the problem of battery, energy storage, cost effective delivery, charging rate and high maintenance. For this purpose, Ultracapacitors have been designed to fill the automotive power gaps. High energy lead acid batteries and Ultracapacitors together can achieve high energy, charging, cycle stability and efficiency.

The power of ultracapacitors can be used to save energy because when the vehicle stops, it allows the engine to stop as well and then instantly restarts it. Ultracapacitors also captures the regenerated braking energy thus increases the efficiency and lower down the level of pollution. Ultracapacitors play a major role in improving the power management in hybrid electric vehicles and extend battery life. If we compare the performance of engines using Ultracapacitors with conventional diesel engines, it can be seen that fuel consumption has been reduced by more than 50% and emission is lowered by 90%.

Ultracapacitors are also utilized by the fuel cell based engines. These types of engines are very big in size and expensive. But hybrid engines having fuel cell with the Ultracapacitors not only brings down the cost but also achieves the maximum load condition.

Advantages of Ultracapacitors:

• Long Lifetime
• More Efficient
• Environmentally Friendly
• Extremely Safe
• Offer 10 times more power.
• Function even in cold weather at -40⁰C

Switched Mode Power Supply (SMPS)

SMPS stands for Switched Mode Power Supply or switching-mode power supply. SMPS is a power supply unit (PSU) for electronic use that contains a switching regulator. While a linear regulator maintains the desired output voltage by dissipating excess power in a "pass" power transistor, the SMPS switches a power transistor at the faster rate between saturation (full on) and cutoff (completely off) with a variable duty cycle whose average is the desired output voltage. This process gives rectangular waveform as a result which is filtered by a low-pass filter with using inductor and capacitor.

The supreme benefit of using this process In SMPS is that it gives a better efficiency. It is because of the small dissipation of the power by the switching transistor in the saturated state and the off state compared to the semiconducting state (active region). Other advantages of Switch Mode Power Supply (SMPS) include smaller size and lighter weight which is greater in low frequency transformers which have a high weight. Moreover it generates lower heat from the higher efficiency.

Disadvantages of SMPS are:

• Greater complexity

• The generation of high amplitude

• High frequency energy that the low-pass filter must block to avoid electromagnetic interference (EMI)

• Ripple voltage at the switching frequency and the harmonic frequencies

SMPS can be categorized into four different types on the basis of its input and output waveforms, as follows.

• AC in, DC out: rectifier, off-line converter input stage.

• DC in, DC out: voltage converter, or current converter, or DC to DC converter

• AC in, AC out: frequency changer, cycloconverter

• DC in, AC out: inverter

For more: NAS Knowledge Base

Fiber Optic Communicaiton

Communication system has three main phases:-

• Transmitter
• Transmission Media (Fiber Optic)
• Receiver

Suppose two persons are sanding at short distance. One person says something to another person by shouting. Voice travels via a medium air. When the distance is longer than, we can not transmit the voice by air only. At this time it is very necessary that we have to use some medium which could carry the sound wave along with. When transmission takes place between two devices transmitting medium is required. These transmission media are the transmission lines or communication channels.
Here we are going to introduce fiber optic Communication Fiber Optic Communication:-

Fiber Optic Communication is a technique of transmitting information from one place to another by sending light through an optical fiber. The light forms an electromagnetic carrier wave which is modulated to carry information. Fiber Optic developed in the 1970’s. Fiber optic has revolutionized the telecommunication industry and offers the advent of the information technology. In Fiber Optics, semiconductors lasers transmit information in the form of light passing through the hair thin glass fibers, with no significant loss of intensity over very long distance. Electrical signals are converted into light wave and feed to the optical fiber medium which carries the light signals to the another end and than again the light signals are converted to the electrical signals with the help of photoelectric diode. These signals are amplified and sent to the receiver.

Advantages of the optical fiber:-
Optical fiber provides high quality of transmission of signals at very high speed. Whereas in copper wire transmission it takes about one hour but in optical fiber it just took one second.
Optical fiber may be used to communicate either analog or digital signals. In analog transmission, the light intensity varied continuously but, in digital transmission the light source is tuned on and off.
Optical fiber transmission is not affected by the electromagnetic interference, by which noise and distortion are also reduced which provides the better communication.
Fiber Optic provide the security to our information which we used to transmit over the medium.
Due to all above mentioned points optical fiber is popular and growing very rapidly in the market.

Read more:

NAS Knowledge Base

www.beganto.com

Importance of PWM in SMPS Design

Different power-supply specifications drive the need for different power-supply topologies. These different power-supply topologies require various types of PWM modes. Each PWM mode play an important role in wide variety of SMPS designs including standard, push-pull, complementary, multi-phase, current-reset, variable-phase and current-limit PWM modes.

The most common PWM mode is the standard edge-aligned PWM. In this mode flow of power controls by the ratio of the on time verses the off time. Only one of the PWM outputs per output pair is used in these Asynchronous Buck, Boost and Flyback converter circuits.

Push-pull converters are mostly used in AC/DC power supplies and DC/DC converters. The term "multiphase PWM" means multiple PWM outputs that are not edge-aligned. Multiphase converter circuits are mostly used in DC/DC converters that must supply high current in applications where the load may change very rapidly.

Our Synchronous Buck Converter uses a complementary PWM mode, where the complementary output controls a "synchronous switching" rectifier that is implemented with a MOSFET, instead of the typical rectifier. The complementary PWM mode can also be used in other circuits that use synchronous rectification to improve system efficiency.

Phase-shifted PWM mode is widely used in personal computer power supplies so that it is becoming more common mode. SMPS family supports all of the known PWM modes currently in wide use by the power-supply industry.

A pulse width modulation (PWM) generator featuring very high speed and high resolution capability and the ability to generate standard complementary PWM, push-pull PWM, variable offset PWM, multiphase PWM, current limit PWM, current reset PWM, and independent time base PWM while further providing automatic triggering for an analog-to-digital conversion (ADC) module that is precisely timed relative to the PWM signals. Applications include control of a switching power supply that requires very high speed operation to obtain high resolution at high switching frequencies, and the ability to vary the phase relationships among the PWM output signals driving the power supply power components. A single PWM duty cycle register may be used for updating all PWM generators at once to reduce the workload of a digital processor as compared to updating multiple duty cycle registers.

For more:

• NAS Knowledge Base
• Torex Knowledge Base