2019年7月25日星期四

Digital Modulation and Demodulation Formats -- Managing Modulation and Demodulation | Soukacatv.com


Digital modulation/demodulation formats provide options in terms of bandwidth efficiency, power efficiency, and complexity/cost when meeting a modern communications system’s data-transfer needs.
Modulation and demodulation provide the means to transfer information over great distances. As noted in the first part of this article (see “Basics of Modulation and Demodulation”), analog forms of modulation and demodulation have been around since the early days of radio. Analog approaches directly encode information from changes in a transmitted signal’s amplitude, phase, or frequency. Digital modulation and demodulation methods, on the other hand, use the changes in amplitude, phase, and frequency to convey digital bits representing the information to be communicated.
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With growing demands for voice, video, and data over communications networks of all kinds, digital modulation and demodulation have recently replaced analog modulation and demodulation methods in wireless networks to make the most efficient use of a limited resource: bandwidth. In this second part, we explore how some higher-order modulation and demodulation formats are created, and how software and test equipment can help to keep different forms of modulation and demodulation working as planned.
Enhancing Efficiency
Efficiency is a common goal of all modulation/demodulation methods, whether they involve conserving bandwidth, power, or cost. Digital modulation/demodulation formats, in particular, have been found able to transfer large amounts of information with minimal bandwidth and power. While increased data capacity tends toward increased complexity in digital modulation/demodulation, high levels of integration in modern ICs have made possible communications systems capable of reliable, cost-effective operation with even the most advanced digital modulation/demodulation formats.
Reasonable bandwidth efficiency is possible with standard digital modulation formats, such as amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (PSK). By executing additional variations, more complex digital modulation formats can be created with improved data capacity and bandwidth efficiency, as measured in the number of digital bits that can be transferred in a given amount of time per unit amount of bandwidth (b/s/Hz).
For example, with minimum-shift keying (MSK), essentially a form of FSK, peak-to-peak frequency deviation is equal to one-half the bit rate. A further variation of MSK is Gaussian MSK (GMSK), in which the modulated signal passes through a Gaussian filter to minimize instantaneous frequency variations over time and reduce the amount of bandwidth occupied by the transmitted waveforms. GMSK maintains a constant envelope and provides good bit-error-rate (BER) performance in addition to its good spectral efficiency.
By applying some small changes, it is also possible to improve power efficiency. Quadrature PSK (QPSK) is basically a four-state variation of simple PSK. It can be modified in different ways—e.g., offset QPSK (OQPSK)—to boost efficiency. In QPSK, the in-phase (I) and quadrature (Q) bit streams are switched at the same time, using synchronized digital signal clocks for precise timing. A given amount of power is required to maintain the timing alignment.

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In OQPSK, the I and Q bit streams are offset by one bit period. Unlike QPSK, only one of the two bit streams can change value at any one time in OQPSK, which also provides benefits in terms of power consumption during the bit switching process. The spectral efficiency, using two bit streams, is the same as in standard QPSK, but power efficiency is enhanced due to reduced amplitude variations (by not having the amplitudes of both bit streams passing at the same time). OQPSK does not have the same stringent demands for linear amplification as QPSK, and can be transmitted with a less-linear, more-power-efficient amplifier than required for QPSK.
The Role of Filtering
The bandwidth efficiency of a modulation/demodulation format can be improved by means of filtering, removing signal artifacts that can cause interference with other communications systems. Various types of filters are used to improve the spectral efficiency of different modulation formats, including Gaussian filters (with perfect symmetry of the rolloff around the center frequency); Chebyshev equiripple, finite-impulse-response (FIR) filters; and lowpass Nyquist filters (also known as raised-cosine filters, since they pass nonzero bits through the frequency spectrum as basic cosine functions).
The goal of filtering is to improve spectral efficiency and reduce interference with other systems, but without degrading modulation waveform quality. Excessive filtering can result in increased BER due to a blurring of transmitted symbols that comprise the data stream of a digital modulation format. Known as intersymbol interference (ISI), this loss in integrity of the symbol states (phase, amplitude, frequency) make it difficult to decode the symbols at the demodulator and receiver in a digitally modulated communications system.
An ideal filter is often referred to as a “brickwall” filter for its instant changeover from a passband to a stopband. In reality, filters do not provide an ideal reduction in signal bandwidth due to the need for some amount of transition between a filter passband and its stopband; longer transitions require more bandwidth.
Filters for digital modulation/demodulation applications are regularly characterized by a parameter known as “alpha,” which provides a measure of the amount of occupied bandwidth by a filter. For example, a “brickwall” filter, with instant transition from stopband to passband, would have an alpha value of zero. Filters with longer transitions will maintain larger values of alpha. Smaller values of filter alpha result in increased ISI, because more symbols can contribute to the interference.
Modeling and Measuring
A wide range of suppliers offer modulators and demodulators in various formats, from highly integrated ICs to discrete components. A number of those highly integrated transceiver ICs can be used for both functions—as transmitters/modulators and receivers/demodulators. Some are even based on software-defined-radio (SDR) architectures with sufficient bandwidths to serve multiple wireless communications standards and modulation/demodulation requirements.
Modeling software helps simplify the determination of requirements for a communications system’s modulation/demodulation scheme. Some software programs provide general-purpose modulation/demodulation analysis capabilities, allowing users to predict the results of using different analog and digital modulation schemes. For example, the Modulation Toolkit (Fig. 1) from National Instruments works with the firm’s popular LabVIEW design software to simulate communications systems based on different analog and digital modulation/demodulation formats. The software makes it possible to experiment with different variables, such as carrier frequency, signal strength, and interference; and predict different performance parameters, such as BER, bandwidth efficiency, and power efficiency, under different operating conditions.
In contrast, S1220 software from RIGOL Technologies USA simulates ASK and FSK demodulation, in particular for Internet of Things (IoT) applications (Fig. 2). The software teams with the company’s spectrum analyzers to study modulation/demodulation over a carrier frequency range of 9 kHz to 3.2 GHz (and to 7.5 GHz with options). It provides an ASK symbol rate measurement range of 1 to 100 kHz and FSK deviation measurement range of 1 to 400 kHz.
Test instruments are an important part of achieving good modulation/demodulation performance. Numerous test-equipment suppliers offer programmable signal generators, such as arbitrary waveform generators, that can create different modulation formats to be used with or without a carrier signal generator for emulating modulated test signals. Spectrum analyzers provide windows to the modulation characteristics of waveforms within their frequency ranges. And some specialized measurement instruments have been developed for the purpose of testing modulation and demodulation and associated components, such as modulation domain analyzers (MDAs).
A number of different display formats provide ways to visualize modulated signals—with both signal analyzers and software—including constellation diagrams, eye diagrams, polar diagrams, and trellis diagrams (for trellis modulation). For example, separate eye diagrams can be used to show the magnitude versus time characteristics of two separate I and Q data channels, with I and Q transitions appearing as “eyes” on a computer or instrument display screen. Different modulation formats will show as different types of displays; for instance, QPSK will appear as four distinct I/Q states, one in each quadrant of the display screen. A high-quality signal creates eyes that are open at each symbol.
Established in 2000, the Soukacatv.com main products are modulators both in analog and digital ones, amplifier and combiner. We are the very first one in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world.
For more, please access to https://www.soukacatv.com.
CONTACT US
Company: Dingshengwei Electronics Co., Ltd
Address: Bldg A, the first industry park of Guanlong, Xili Town, Nanshan, Shenzhen, Guangdong, China
Tel: +86 0755 26909863
Fax: +86 0755 26984949
Mobile: 13410066011
Email: ken@soukacatv.com

Source: mwrf




































2019年7月17日星期三

Pulse Width Modulation (PWM) Controllers Market 2019 Global Demand and Scope – Analog Devices | Soukacatv.com


Global Pulse Width Modulation (PWM) Controllers Market 2018 by Manufacturers, Regions, Type and Application, Forecast to 2023 details the summary and describes the Product/Industry scope within the market. The report also discusses the market review and forecast to 2023. As per several market studies being conducted by Fior Markets, it is evident that the Pulse Width Modulation (PWM) Controllers Market is growing at a very fast pace. The rising industrial advancements market is expected to flourish the growth of the market over the forecast period.

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The report aims to change the dynamics of the Market Research industry by providing quality intelligence backed by data. Readers’ requirement for market forecasting is fulfilled by our exclusive quantitative and analytics driven intelligence. Decision makers can now rely on our distinct data gathering methods to get factual market forecasting and detailed analysis.
In addition to the charts and analysis, marketing decision makers from companies and retailers offer their individual candid advice, as the words of wisdom from their peers all designed to help readers marketing efforts.
The report helps its clients to address their evolving business needs with personalized solutions. These valuable insights can additionally help the clients form revenue generating business policies and build a sustainable growth model.
Geographically, the global big data market report has been segmented in key regions involving North America (United States, Canada and Mexico), Europe (Germany, France, UK, Russia and Italy), Asia-Pacific (China, Japan, Korea, India and Southeast Asia), South America (Brazil, Argentina, and Colombia etc.), Middle East and Africa (Saudi Arabia, UAE, Egypt, Nigeria and South Africa). These regions held the largest market revenue share for Pulse Width Modulation (PWM) Controllers market in 2016 and is expected to dominate during forecast period due to high adoption of analytics across the countries. However, the few countries are expected to register highest growth rate during forecast period due to increasing amount of demands as well as high availability of supply in the regions.
Readers can benefit:
·         Market Overview.
·         Market Competition by Manufacturers.
·         Supply (Production), Consumption, Export, Import by Region.
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·         Manufacturers Profiles/Analysis.
·         Manufacturing Cost Analysis.
·         Market Forecast 2018-2022.
·         Industrial Chain, Sourcing Strategy and Downstream Buyers.
The report also focuses on the importance of the industry chain analysis and all variables, both upstream and downstream. These include equipment and raw materials, industry trends, client surveys, propels, marketing channels, major and most demanding types and applications Consumer Electronics, Telecommunication, Automotive, Industrial, Other. Some of the other critical data covering consumption, raw material suppliers, and key regions and distributors and suppliers are also mentioned in this report.
The Global Pulse Width Modulation (PWM) Controllers Market consists of data accumulated from numerous primary and secondary sources. This information has been verified and validated by the industry analysts, thus providing significant insights to the researchers, analysts, managers, other industry professionals and key players Analog Devices (Linear Technology), Texas Instruments, STMicroelectronics, ON Semiconductor, Microchip Technology, Maxim Integrated, Infineon Technology, Vishay, Diodes Incorporated, Renesas Electronics, Semtech, Active-Semi.

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Nonetheless, the surplus amount invested is then employed for making investments which are helpful for earning a higher profit for the policyholders. It is gaining prominence in the major countries and endeavoring to meet the growing need to impart quality deployment.
Established in 2000, the Soukacatv.com main products are modulators both in analog and digital ones, amplifier and combiner. We are the very first one in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world.
For more, please access to https://www.soukacatv.com.

CONTACT US
Dingshengwei Electronics Co., Ltd
Company Address: Building A, the first industry park of Guanlong, Xili Town, Nanshan, Shenzhen, Guangdong, China
Tel: +86 0755 26909863
Fax: +86 0755 26984949
Phone: +86 13410066011
Email:ken@soukacatv.com
Skype: soukaken

Source: bizztribune















































2019年7月15日星期一

What’s Amplitude Modulation (AM)? Amplitude Modulation History and Its Applications | Soukacatv.com


Amplitude Modulation or AM as it is often called is an electronic communication systems technique wherein the baseband signal is superimposed with the amplitude of the carrier wave i.e. the amplitude of the carrier wave varies with proportion to the base waveform that is being transmitted. Amplitude Modulation has been in use since the earliest days of radio technology. One of the main reasons for the use of amplitude modulation was its ease of use. The system mainly required the carrier amplitude to be modulated, additionally; the detector required in the receiver could be a simple diode-based circuit. This meant that complicated demodulators weren’t required and as a result, the costs were reduced – a key requirement for the use of radio technology in the early days when ICs weren’t available.
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What is Amplitude Modulation (AM)?
When an amplitude modulated signal is created, the amplitude of the created signal represents the original baseband signal to be transmitted. This amplitude forms an envelope over the underlying high-frequency carrier wave. Here, the overall envelope of the carrier is modulated to carry the audio signal. AM is the simplest way of modulating a signal. In short, amplitude modulation is defined as the modulation in which the amplitude of the carrier wave is varied in accordance with some characteristic of the modulating signal.

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Amplitude Modulation History
The first recorded instance of amplitude modulation of the baseband wave harks back to 1901 when a Canadian man Reginald Fessenden used a continuous spark transmission to create the first amplitude modulation ever. Into this continuous spark transmission, he puts a carbon microphone in the antenna lead. The sound waves impacting on the microphone varied its resistances and this, in turn, varied the intensity of the transmission.
Though the accuracy and the signal-to-noise ratio in this earlier method of transmission were very low, with the advent of a continuous sine wave generator, the audio quality was greatly improved. This led to Amplitude modulated waves becoming the standard for voice transmission.
Amplitude Modulation Formula
Amplitude Modulation expression is given by:
s(t)=[Ac+Amcos(2πfmt)]cos(2πfct)
Where,
  • Am is the amplitude of the modulating signal
  • Ac is the amplitude of the carrier signal
  • fm is the frequency of the modulating signal
  • fc is the frequency of the carrier signal
Amplitude Demodulation
Demodulation or detection is a process where the signal that is a mixture of the amplitude of the baseband signal and the frequency of the carrier signal, is deconstructed to yield the original signal that is to be transmitted. Simply, it is the recovery of the modulating signal from the modulated wave.
Detection of Amplitude Modulated Wave (Demodulation)
The amplitude modulation and demodulation are equally simple to perform. The amplitude modulated signal needs just a simple diode detector circuit to demodulate. The diode rectifies the incoming signal, allowing only one-half of the signal waveform to pass through. The capacitor then is used to remove the radio frequency parts of the signal, leaving just the original waveform. As you see, the equipment for demodulation is very cheap, and this enables the cost of the receivers to be kept low.


Thus, amplitude modulated wave can be demodulated in two steps:
  • Rectification of modulated wave
  • Elimination of the RF component of the modulated wave
Advantages and Disadvantages of Amplitude Modulation
Given below in a tabular column are the various advantages and disadvantages of amplitude modulation.
Advantages
It can be demodulated using a circuit with fewer components.
It is easy to implement.
AM receivers are cheap and there is no requirement of specialized components.
Disadvantages
It is not efficient in terms of its use of bandwidth, requiring a bandwidth equal to twice of the highest audio frequency.
Not efficient in terms of power usage.
Prone to high levels of noise as most noise is amplitude based and AM detectors are sensitive to it.
Applications of Amplitude Modulation
With the improvement of the technology, the uses of amplitude modulation waves has become somewhat less prevalent, nevertheless it can still be found playing an important role in;
  1. Broadcast Transmission: AM is still widely used for broadcasting either long or medium or short wave bands. The received signal is simple to break down into the baseband signal and hence the equipment cost to the user is very little and it is easy to manufacture
  2. Air band Radio: The use of AM in the aerospace industry is widespread. The VHF (Very High Frequency) transmissions made by the airborne equipment still use AM. The radio contact between ground to air and also ground to ground use AM signals.
  3. Quadrature Amplitude Modulation: Believe it or not, AM is used in the transmission of data of pretty much everything, from short range transmissions such as Wi-Fi to cellular communications and etc. Quadrature amplitude modulation is formed by mixing two carriers that are out of phase by 90o.

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The need for modulation was sky high and the invention of Amplitude modulation has changed the way in which we communicate.

Established in 2000, the Soukacatv.com main products are modulators both in analog and digital ones, amplifier and combiner. We are the very first one in manufacturing the headend system in China. Our 16 in 1 and 24 in 1 now are the most popular products all over the world.
For more, please access to https://www.soukacatv.com.

CONTACT US
Dingshengwei Electronics Co., Ltd
Company Address: Building A, the first industry park of Guanlong, Xili Town, Nanshan, Shenzhen, Guangdong, China
Tel: +86 0755 26909863
Fax: +86 0755 26984949
Phone: +86 13410066011
Email:ken@soukacatv.com
Skype: soukaken

Source: byjus