Differential Mode And Common Mode Radiation

Common Mode Choke Symbol

Unintentional radiation can be described as either differential mode or common mode. The two terms relate to the currents that create the radiation. Differential mode currents are equal but travel in opposite directions. Common mode currents travel in the same direction. On any transmission line, the signal current and the return current travel in opposite directions. As long as the two currents are close together the radiation is very small, albeit non-zero. The two currents Figure 12.18 Here...

Static Electricity And Lightning

Static Electricity Free Energy

Let's go back to the charged sphere of Figure 2.5. If the second metal ball is placed closer to the charged ball so that they actually touch, the Figure 2.11 A Water molecule. B Water molecules in random orientation with no field applied. C Water molecules line up when an electric field is applied. Figure 2.11 A Water molecule. B Water molecules in random orientation with no field applied. C Water molecules line up when an electric field is applied. negative charge will now redistribute itself...

Power Supply Decoupling Problems And Techniques

Parallel Decoupling Capacitors

Power supply decoupling is the term given to the technique of making sure the DC power line variations do not affect the loads amplifier, ICs, logic gates, etc. and vice versa. Since most ICs have AC signals as inputs and outputs, the current drawn from the power supply will vary in an AC manner. For example, an RF circuit that amplifies a 900 MHz signal will draw a supply current that varies at 900 MHz. A digital CMOS circuit that buffers a 100 MHz digital signal will also draw a supply...

Antenna Pattern Versus Electrical Length

Magnetic Loop Antenna Radiation Pattern

Antennas do not radiate equally to all directions. The directional dependence of antenna radiation is aptly called the antenna pattern. An electric dipole that is 1 2 1 in length or smaller exhibits a fairly simple antenna pattern. The most power is radiated in the direction broadside to the antenna that is, perpendicular to the antenna's length. The power decreases with decreasing angle such that at zero degrees, no power is radiated. In other words, no power is radiated in the direction of...