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 人参与 | 时间:2021-06-20 02:49:00

The supercapacitor C and ESR should also allow for aging. Supercapacitors will slowly lose C and increase ESR over time. The aging rate will depend on cell voltage and temperature. The designer should select initial C and ESR so the end-of-life C and ESR can support the applications.

Multiple speakers, as seen in Figure 3, are placed in an array where the array size and shape also make certain directional patterns possible. The array is usually physically linear, but may also be built as two dimensional arrays such as curvilinear, planar, circular, or combinations thereof.

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As a general rule, spatial effects are more easily accomplished and discerned at higher frequencies. However, a large array along with speakers with very good low frequency response will allow better directional control over low frequencies.

The size and shape of the array partially determines the technique(s) to use to achieve the desired spatial effect. The other factor is the purpose for which the array is being built. For example, if the array is constructed for the picture-in-picture feature, allowing two viewers to watch two different TV channels (low use case), another technique would be needed if the purpose was to simulate a 5.1-channel surround sound environment (high use case) for several people seated in front of the TV. As a practical matter, the spatial audio system may have to support both methods (and possibly several others) in order for the consumer to have pleasurable listening experiences regardless of the TV program-mode.

Go to Part 2 of this article.

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About the author: Kenneth Boyce is Audio Technologist for Texas Instruments Silicon Valley Labs. He previously served as Technology Director for National Semiconductor's Audio Products Group, and before joining National, Boyce served as director of the Audio and Communications Division at Oak Technology, which developed initial implementations of AC-97 Codecs and Digital Audio Controllers. He holds a bachelor of science degree in electronics from West Virginia University.

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10093084-4060LF

The process of designing traditional fixed supply power amplifiers (PAs) has been well established for many years. Well defined metrics for performance assessment exist, and the PA designer’s job is ‘simply’ to design a PA with the best set of performance metrics. In reality of course this is far from a ‘simple’ task, but at least the assessment criteria are well established and well understood. For envelope-tracking (ET) PAs, the situation is more complex and requires the use of more sophisticated characterization techniques.ET Basics The objective of envelope tracking is to improve the efficiency of PAs carrying high peak to average power (PAPR) signals. The drive to achieve high data throughput within limited spectrum resources requires the use of linear modulation with high PAPR. Unfortunately, the efficiency of traditional fixed supply PAs when operated under these conditions is very poor.  The efficiency of an ET PA is improved by varying the PA supply voltage in synchronism with the envelope of the RF signal. The PA’s fundamental output characteristics (power, efficiency, gain, phase…) now depends on two ‘control’ inputs (RF input power and supply voltage) and may be represented as 3D surfaces.In a typical envelope tracking system, the supply voltage is dynamically adjusted to track the RF envelope at high instantaneous power. Here, the PA operates with high efficiency in compression. Its output characteristics are primarily determined by the instantaneous supply voltage.  Conversely, when the instantaneous RF power is low, the supply voltage is held substantially constant and the PA output characteristics are primarily determined by the instantaneous input power (linear region). A transition region in which both supply voltage and input power influence the output characteristics exists between these two extremes (see Figure 1)

10.Modified IBM 8B10B DC-balanced encoding allows easy Galvanic Isolation and many different physical cables including:

a) Shielded Twisted Pair up to 10m@4Gbps available

b) Co-ax cable with EqcoLogic4 Modulators up to 40m@1Gbps

c) UTP5 up to 70m@500Mbps with EqcoLogic4 Equalization

d) Glass Optical Fiber, as fast and as far as is possible

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