2019年4月30日星期二

LG’s C9 4K OLED TV-- for the TV lovers who want premium picture quality | Soukacatv.com

If you’re looking for a TV with a picture so good that when watching David Attenborough’s latest documentary you feel like you’re actually in nature, then you need to check out LG’s latest OLED range.

LG is the king of OLED — considered the gold standard in TV display technology — and the company has imbued its latest range of high-end TVs with improved intelligence and features that make them a true standout.

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LG has been working with audio engineering company Meridian in recent years to improve its sound equipment, and along for the ride with the review unit was LG’s SL10YG soundbar ($1699) that pumped out a rich and well calibrated sound. The soundbar is designed to bounce parts of the audio off its surroundings to provide an immersive surround-sound audio experience.

DESIGN

It looks similar to its popular C8 predecessor, which was considered one of the best TV options out there for enjoying high-quality picture.

The C9 looks much the same with a super thin screen that can blend into any room. It has a stand on the back that LG has reduced in depth compared to last year’s model. Or there is the option of wall mounting if you purchase a special bracket from the manufacturer.

FEATURES

The C9 TV supports HDMI 2.1, which provides a better experience and picture quality when watching content from external sources thanks to the improved throughput provided by the upgrade in HDMI technology. It supports a faster refresh rate and more frames per second.

If you’re buying this TV, you’re doing so for the exceptional picture quality. As we have come to expect with LG’s top TVs, Dolby Vision and Dolby Atmos are back.

Dolby’s stellar high-dynamic range video format provides a hyper-rich colour gamut and deeper black. While Dolby Atmos is a multidimensional surround-sound technique that is object-based, rather than channel-based, and treats sound elements as virtual objects that can be placed anywhere. Coupled with support for HDR10, essentially the twin technologies ensure that given you have the right equipment, your movie watching experience is about as good as a TV can look and sound.

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The most significant upgrade to the C9 is the Alpha 9 second generation intelligent processor, which can be found on board LG’s top range of 2019 TVs.

The AI processor is responsible for handling tasks like upscaling picture quality from non 4K sources and finetuning the settings to deliver the optimal picture quality.

It has a handy ability to apply real-time colour correction and adjust the brightness and contrast of the display depending on the ambient lighting in your living room. To test this out, you can hold your smartphone camera to the bottom of the screen and watch as the sensors pick up the change in light and adjust the picture to allow for greater detail to be viewed. It brightens the shadows to reveal more detail without washing out the picture and works quite well.

An improved Dynamic Tone Mapping feature also delivers a significantly higher baseline brightness level with high dynamic range (HDR) sources.

The C9 is part of LG’s ThinQ series of gadgets, which is the company’s branding for its smart internet-enabled devices. The company’s voice recognition — allowing users to deliver voice commands to a microphone in the remote control — is very impressive.

Depending on the command, it will be sent to either LG’s servers (for things like volume adjustment) or Google’s servers (for things like restaurant recommendations) to be handled. Rather amazingly, it even spelt my surname correctly when dictated to once.

UPDATES TO WEBOS

The TV is powered by LG’s WebOS platform, which comes with some new updates for its 2019 range.

Along the menu bar, which appears along the bottom of the TV, if you hover over an icon, a second layer of menu pops up with additional information. For instance, if you hover the remote control pointer over Netflix, a row of icons pop up linking directly to shows you’ve been watching on the streaming service.

The launcher bar also has a new Intelligent Edit feature, which when turned on will automatically and continuously arrange the menu bar in order of the most-used apps. Given the fact you can add specific YouTube channels to the menu bar, this is a handy feature because it has the potential to get pretty long.

SOUNDBAR WORTH CONSIDERING

The SL10YG soundbar also has AI smarts and Google Assistant integration. The soundbar is able to decode most surround audio formats and provides a dynamic, and you shouldn’t have to tinker with the settings to get the right level of dialogue and ambient sound.

The 5.1.2 channel soundbar (five channels and a subwoofer, plus two additional speakers adding height information in stereo) is a worthwhile addition if you are already spending big on a TV.

The 570W speaker system pumps out a level of volume that will suffice for most users. In a large space it doesn’t exactly fill the room, but sitting in front of the TV where the speakers are directed, it ensures you have a high-quality sound experience in a sleek device that rests under your TV and comes with a wireless subwoofer.

WHY OLED IS KING

The deep inky black, rich colour and sharp resolution of OLED displays are what all TV lovers should consider.

Brands differ slightly in how they aim to boost brightness, achieve perfect blacks and produce a wide colour gamut and offer different options at different price points.

An important distinction in TV screen technology is between LCD/LED and OLED screens and the different ways the TVs illuminate the pixels on the display.

LCD (liquid crystal display) and LED TVs can offer much higher screen luminance whereas OLED (organic light emitting diode) TVs offer precise control per pixel.

Instead of having a constant light source at the back and a panel to either allow the light or block it out like LCD and LED TVs, an OLED display will only light up each pixel that needs to be on.

As a result OLED is capable of a perfect black picture with no light leakage, providing better contrast. This “perfect black” is referred to as zero nits and is really only truly possible on OLED displays.

LG is the only maker of OLED panels, and many other brands buy them before applying their own technology to the end product.

However, Samsung — a bitter rival of fellow Korean-based LG — has backed a different horse. It has QLED displays (the Q stands for Quantum-dot) that use a film of tiny crystal semiconductor particles that can be precisely controlled for their colour output.

You can certainly find cheaper OLED TVs on the market (for instance HiSense is selling a 55 inch OLED TV for less than $1500), but if you’re looking for the real McCoy, it’s definitely worth checking out LG’s C9 range.

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2019年4月29日星期一

The Many Types of Radio Frequency Modulation | Soukacatv.com

RF communication is built upon a simple concept: by continually altering the characteristics of a sinusoid, we can use it to transfer information.

At this point, we have covered a variety of important concepts that serve as a foundation for the successful design and analysis of real-world RF circuits and systems. We are now ready to explore a fundamental aspect of RF engineering: modulation.

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What Is Modulation?

The general meaning of the verb “to modulate” is “to modify, to regulate, to vary,” and this captures the essence of modulation even in the specialized context of wireless communication. To modulate a signal is simply to intentionally modify it, but of course, this modification is done in a very specific way because the goal of modulation is data transfer.

We want to transfer information—ones, and zeros if we’re dealing with digital data, or a sequence of continuously varying values if we are working in the analog realm. But the restrictions imposed by wireless communication do not allow us to express this information in the typical way; instead, we have to devise a new “language,” or you might think of it as a code, that allows us to convey the same information but within the constraints of an electromagnetic-radiation-based system. More specifically, we need a language that is compatible with high-frequency sinusoidal signals, because such signals constitute the only practical means of “carrying” information in a typical RF system.

This high-frequency sinusoid that is used to carry information is called, appropriately, the carrier. It’s a helpful name because it reminds us that the purpose of an RF system is not to generate and transmit a high-frequency sinusoid. Rather, the purpose is to transfer (lower-frequency) information, and the carrier is simply the means that we must use to move this information from an RF transmitter to an RF receiver.

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Modulation Schemes

In verbal communication, the human body generates sound waves and modifies—or modulates—them so as to produce a wide variety of vowels and consonants. Intelligent use of these vowels and consonants results in the transfer of information from the speaker to the listener. The system according to which the sound waves are modulated is called a language.

In RF communication, the situation is very similar. A device modulates electrical waves according to a predefined system called a modulation scheme (or modulation technique). Just as there are many human languages, there are many ways in which a carrier can be modulated.

It is possible that certain human languages are especially effective in conveying certain types of information; to take an example from the ancient world, perhaps Greek was better for philosophy and Latin was better for codifying laws. There is no doubt, however, that reliable communication is possible with any properly developed language, as long as the speaker and the listener both know it. The same is true for RF systems. Each modulation scheme has its advantages and disadvantages, but all can provide excellent wireless communication if the fundamental requirement is fulfilled—i.e., the receiver must be able to understand what the transmitter is saying.

Amplitude, Frequency, Phase

A basic sinusoid is a simple thing. If we ignore DC offset, it can be completely characterized with only two parameters: amplitude and frequency. We also have phase, which comes into play when we consider the initial state of the sinusoid, or when changes in wave behavior allow us to contrast one portion of the sinusoid with a preceding portion. Phase is also relevant when comparing two sinusoids; this aspect of sinusoidal phase has become very important because of the widespread use of quadrature (or “IQ”) signals in RF systems. We’ll look at IQ concepts later in the textbook.

As discussed above, modulation is modification, and we can modify only what is already present. Sinusoids have amplitude, frequency, and phase, and thus it should come as no surprise that modulation schemes are categorized as amplitude modulation, frequency modulation, or phase modulation. (Actually, it is possible to bridge these categories by combining amplitude modulation with frequency or phase modulation.) Within each category we have two subcategories: analog modulation and digital modulation.

Amplitude Modulation (AM)

Analog AM consists of multiplying a continuously varying sinusoidal carrier by an offset version of a continuously varying information (aka baseband) signal. By “offset version” I mean that the amplitude of the baseband signal is always greater than or equal to zero.

Let’s assume that we have a 10 MHz carrier and a 1 MHz baseband waveform:

If we multiply these two signals, we get the following (incorrect) waveform:

You can clearly see the relationship between the baseband signal (red) and the amplitude of the carrier (blue).

But we have a problem: If you look only at the amplitude of the carrier, how can you determine if the baseband value is positive or negative? You can’t—and, consequently, amplitude demodulation will not extract the baseband signal from the modulated carrier.

The solution is to shift the baseband signal so that it varies from 0 to 2 instead of -1 to 1:

If we multiply the shifted baseband signal by the carrier, we have the following:

Now the amplitude of the carrier can be mapped directly to the behavior of the baseband signal.

The most straightforward form of digital AM applies the same mathematical relationship to a baseband signal whose amplitude is either 0 or 1. The result is referred to as “on-off keying” (OOK): when the information signal is logic zero, the carrier’s amplitude is zero (= “off”); when the information signal is logic one, the carrier is at full amplitude (= “on”).

Frequency Modulation (FM) and Phase Modulation (PM)

FM and PM are closely related because frequency and phase are closely related. This is not so obvious if you think of frequency as the number of full cycles per second—what does cycles per second have to do with the position of the sinusoid at a given moment during its cycle? But it makes more sense if you consider the instantaneous frequency, i.e., the frequency of a signal at a given moment. (It is undoubtedly paradoxical to describe a frequency as instantaneous—but, in the context of practical signal processing, we can safely ignore the complicated theoretical details associated with this concept.)

In a basic sinusoid, the value of the instantaneous frequency is the same as that of the “normal” frequency. The analytical value of instantaneous frequency arises when we are dealing with signals that have a time-varying frequency, i.e., the frequency is not a constant value but rather a function of time, written as ω(t). In any event, the important point for our current discussion regarding the close relationship between frequency and phase is the following: instantaneous angular frequency is the derivative, with respect to time, of phase. So if you have an expression φ(t) that describes the time-varying behavior of the signal’s phase, the rate of change (with respect to time) of φ(t) gives you the expression for instantaneous angular frequency:

ω(t)=dϕ(t)dtω(t)=dϕ(t)dt

We’ll take a closer look at frequency and phase modulation later in this chapter. For now let’s conclude with the following plot, which applies the mathematical relationship for frequency modulation to the baseband and carrier signals used above:

Summary

Modulation refers to the process of carefully modifying an existing signal so that it can transfer information.
In the context of RF, the existing signal is called the carrier, and the information is contained in the baseband signal.
There are many different modulation schemes, meaning that there are different ways of incorporating baseband information into a sinusoidal carrier wave.
Modulation involves modification of a carrier’s amplitude, frequency, or phase, and it can be used to transfer analog signals or digital data.