What shunt inductance is required to move the impedance from point 2 to point 3, assuming a frequency of 915 MHz?Īssume the inductance of a straight conductive line is Should this be Bob’s raise at his next performance review? 3.Ĭonsider the matching problem shown below. Being Bob, he doesn’t want to design a matched antenna and instead simply attaches the IC to the 915-MHz resonant dipole antenna he took from Amy’s desk (see Figure 7.9). What is the voltage multiplication factor at the band edge at 902 MHz?Īfter sitting through three hours of PowerPointless slides and a lunch whose fat content is measured in ounces rather than grams, Bob the lazy RF designer snags a prototype IC from Fundless’ VP of Sales, Sal E.
What is the bandwidth of the overall antenna-IC circuit?
#Parallel resistance series#
What is the voltage amplification factor for a conjugate-matched antenna?Īssume the input capacitance was matched using a simple series inductor, and that the antenna looks like a voltage source and radiation resistance matched to the load series resistance. What are the series equivalent input circuit values at 915 MHz?
Treat the IC load as a simple parallel resistor and find the resistance value: The current automatically transfers to the reactor when the superconductor quenches.Ī new tag IC from the Silicon Valley startup company Fundless Networks is reported to consume a DC power of 0.3 microwatts at an input voltage of 0.5 V.
#Parallel resistance install#
Other possibilities are to install a reactor in parallel with the FCL. This switch quickly isolates the superconductor after most of the current has transitioned to the shunt element, thereby allowing the superconducting element to begin the recovery cycle while the limiting action is sustained by the shunt. Termed hybrid resistive FCLs, they may include a separate, fast switch in series with the superconducting element. Several groups have developed variations on the theme shown in Fig. 9.3. The action protects the power grid and decreases the maximum current that is seen by the circuit breakers. The ratio of the prospective fault current to the resulting fault current can be as much as ten, and depends on the design of the FCL. The value of the limited fault current depends on R p and the impedance of the load. The passive transition of the superconductor and the high normal resistance causes the actual current to be considerably less than the prospective fault current. If the FCL requires some time to recover, then switch S2 can be closed and switch S1 opened until the FCL is ready to operate again. If the FCL can recover under load, then S1 will remain closed after the fault. Its operation will depend on the overall capabilities of the FCL. The normally closed switch, S1, may be included as part of the FCL or it may already be a part of the grid. Even though the overall current is greater than the normal operating current, the superconductor current i SC( t) decreases sufficiently so that the superconductor is not damaged:
Once the superconductor quenches, its resistance increases by several orders of magnitude and the normal material begins to carry the majority of the current. Completely quenching the superconductor avoids hot spots and assures sharing, particularly if multiple parallel superconducting elements are used. In the event of a fault in which the current increases over some threshold, the superconductor must rapidly transition to the normal state over its entire volume in a fraction of a cycle. During normal operation, the resistance of the superconductor is zero, it carries the entire operating current and the voltage drop is zero. A parallel resistor R P may be in the form of a sheet of normal material in contact with the superconductor, or may be a separate element that has no physical contact with the superconductor. The current limiting element consists of a superconductor, which can be wire, tape, or bulk material that provides a path R SC for the current. Figure 9.5 shows the principle of the resistive SFCL.
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