By James T. Aberle, Robert Loepsinger-Romak, Constantine A. Balanis
So much antenna engineers tend to think that antennas are one know-how that's kind of impervious to the speedily advancing semiconductor undefined. although, as tested during this lecture, there's a technique to contain lively elements into an antenna and remodel it right into a new type of radiating constitution that may benefit from the most recent advances in analog circuit layout. The technique for making this alteration is to use non-Foster circuit components within the matching community of the antenna. by means of doing so, we're now not restricted through the legislation of physics that practice to passive antennas. in spite of the fact that, we needs to now layout and build very sensitive lively circuits. This new antenna know-how is now in its infancy. The contributions of this lecture are (1) to summarize the present state of the art during this topic, and (2) to introduce a few new theoretical and sensible instruments for supporting us to proceed the development of this know-how.
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Additional resources for Active Antennas with Non-Foster Matching Networks (Synthesis Lectures on Antennas)
9 0 0 50 100 150 200 freq, MHz (b) FIGURE 48: Simulated (a) return loss and (b) stability of the all-pass test circuit for the NE85630 FNR neglected here, but do affect the circuit performance especially stability. The simulated results for the NE85630 are the best FNR results that we obtained. Thus, the NE85630 FNIC is used in the next section for the floating non-Foster reactance used in the active matching network for our ESA monopole. In addition to the NIC circuits discussed in detail in this section, we also made considerable effort trying to realize NIC circuits that utilized CCII- blocks implemented as cascades of GaAs PHEMT devices.
One clever way, proposed in , to both ensure stability and evaluate the performance of the grounded negative impedance is to set the condition that Rin − ZL = 50 . This choice allows us to evaluate performance in terms of return loss in a 50 vector network analyzer (VNA). cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 29 FIGURE 30: Photograph of fabricated OPA690 NIC evaluation board If the GNR in the circuit of Fig. 27 is functioning properly, then ideally we should have Vneg = −Vin .
Using this gain model for the op amp, the overall transfer function T (s )of the OPA690 evaluation circuit (without the generator) can be computed (employing the golden rules of op-amps) as T (s ) = 1 ZL −Rin ZL +R − s A0 ωb 1+ Rin R . (39) It is well known that it is necessary for the poles of T (s ) to lie in the left-half of the s -plane in order for the system to be stable. Consequently, the input resistor Rin must be greater than the load impedance ZL . One clever way, proposed in , to both ensure stability and evaluate the performance of the grounded negative impedance is to set the condition that Rin − ZL = 50 .
Active Antennas with Non-Foster Matching Networks (Synthesis Lectures on Antennas) by James T. Aberle, Robert Loepsinger-Romak, Constantine A. Balanis