Electrical impedance is the measure of the opposition a circuit presents to a current when a sinusoidal AC voltage is applied. This cable is a coaxial cable. Instead of a coaxial cable, an antenna can be connected to the device by a cable formed of two round wires spaced apart from a flat plastic strip. As with the coaxial cable, the dimensions and materials of this wire are carefully controlled to give it the correct electrical impedance.
A TV antenna has a “natural” impedance. For Radio Frequencies (FR), the transfer of the maximum signal power from the antenna to the cables requires that the impedance of the cable matches the impedance of the antenna. In addition, the impedance of the TV must match the impedance of the cable.
Although we have to focus on wire interconnections, the same considerations apply to signal transfer through traces on a PCB. As recently as 1997, only the then high-speed exotic devices required PCBs with controlled impedance. These amounted to perhaps 20% of the manufactured PCBs.
In 2000, about 80% of all multilayer PCBs were manufactured with traces of controlled impedance. These included boards for all types of technologies including :
– Video signal processing
– High-speed digital processing
– Real graphic processing
– Process control
Most homes today have a great number of low-cost applications of these technologies, for example:
– Modem, phones, satellite TV
– Video games
– Low-cost PC
– Auto engine control modules
What kind of impedance design can we meet on PCB?
How to Control Impedance?
What is a test coupon?
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