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>>>2024-06-02 Consumer Electronics Control (PDF)

by Lakeisha Clem (2025-01-22)


Tv manufacturers want to capture as much of your entertainment attention and funds as possible, so ideally they promote you a Tv and their matching soundbar system (which will be fairly inexpensive since it's carefully coupled to the Tv and needs very little of its own control logic). An unshielded twisted pair, until its terminations are balanced (see Section 4.1), offers very little protection against capacitive (electric field) pickup, but it is superb for protection in opposition to magnetic field pickup. As was mentioned in Section 2.5.2, a shield provides no magnetic field safety at low frequency. Using another problem in PCB design for example: In PCB design, there's a tough consensus that, if the PCB is already partitioned into digital and analog sections, the return current in every section is generally contained in their own area. Thus, unless very excessive isolation is required, splitting the analog and digital floor planes is commonly counterproductive.



Consequently, for a pure digital USB device, without analog or blended-sign circuits, and not using a steel chassis, connecting the shield directly to the circuit ground, whereas violating all of the foundations, in truly an acceptable compromise for many applications with justification. Thus, USB shield connection appears to be a rather "polarized" drawback: if you are doing it flawed, you'd better to do it unsuitable all the way. The inside shield can then be terminated at just one end, thus avoiding the bottom-loop coupling that might occur if grounded at each ends. However, at excessive frequency, the capacitor turns into a low impedance, which converts the circuit to 1 that's grounded at both ends. The actual implementation of an effective hybrid cable shield floor may, nevertheless, be difficult, shield control cable because any inductance in series with the capacitor will decrease its effectiveness. Therefore, the proper strategy to terminate the cable shield is to the equipment’s shielded enclosure, to not the circuit floor.



It is, subsequently, vital to determine a low-impedance connection between the chassis and the circuit ground in the I/O space of the board. Establishing a low-impedance connection between the circuit floor and the chassis within the I/O area can be advantageous with respect to radio frequency (rf) immunity. Proper circuit grounding will reduce the radiated emissions from the product in addition to improve the product’s immunity to exterior electromagnetic fields. The reference for the cable radiation is due to this fact the chassis and not some exterior ground such as the earth. Media companies that distribute STBs, principally cable and satellite tv for pc operators, tend to be in a little bit of a conflict to personal your tv watching expertise. Instead, they use a tv and maybe (hopefully!) a soundbar system, which regularly supports wireless satellites if there are satellites at all. Two causes to use a double- shielded cable are as follows: One is to increase the excessive-frequency shielding effectiveness; the other is when you could have both excessive-frequency and low- frequency indicators in the same cable.



For those who consider a cable shield as being an extension of the enclosure’s shield, then it becomes clear that the shield should be terminated to the enclosure not to the circuit floor. Chassis ground is any conductor that is connected to the equipment’s metallic enclosure. The key to minimizing noise and interference is to find out the place and how to attach the sign ground to the chassis. The potential difference throughout the 2 conductors create a noise present flow throughout all the cable's length, creating common-mode radiation. In addition, any shield present present is equally coupled (ideally), by mutual inductance, to each inner conductors and the two equal noise voltages cancel. The primary reason to shield cables at low frequency is to protect them in opposition to electric field coupling primarily from 50/60-Hz power conductors. This potential distinction, and therefore the shield present, is usually the results of 50/60-Hz currents in the ground. The outer shield is commonly additionally used to forestall radiation from the cable, which outcomes from excessive-frequency frequent-mode currents on the cable. If, nevertheless, the circuit floor is linked to the enclosure at the I/O connector, the voltage driving widespread-mode present out onto the cable will ideally be zero.





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