Antennas with Non-Foster Matching Networks phần 4

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Antennas with Non-Foster Matching Networks phần 4P1: RVMMOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 26 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS -193 uV 2.09 nA 2.09 VR + -2.09 nA R1 P ort R =1 GOhm P1 -2.05 mV -5 V Num=1 13.8 uA V- 0 A -3.57 uA P ort C -456 uV -3.33 uA -1.53 mA P3 - C9 Num=3 C=0.1 uF opa 6901.56 mA P ort OP A1 5V P2 V+ Num=2 5V -5 V 0A 1.53 mA 0A V+ V- -1.56 mA C V_DC C V_DC C8 S RC3 C7 S RC4 C=0.1 uF Vdc=-5 V C=0.1 uF Vdc=5 V FIGURE 26: Schematic of OPA690 for simulation in Agilent ADS obtained by using the SPICE model and the data sheet for the device provided by TI performance of several of these NIC circuits. Unfortunately, successful simulation of an NIC circuit has not always led us to a successful physical implementation. One reason for this is that all NIC circuits are only conditionally stable—that is certain auxiliary conditions must be met for the circuit to be stable. In this section we will review our progress in physically realizing NIC circuits for use in active non-Foster matching networks. The reader should be aware that this topic is one for which a great deal of work remains to be done. It is this author’s opinion that the major advances in this area will be made by analog circuit designers who have been convinced by antenna engineers of the rewards to be reaped in pursuing the development of high frequency NICs. Rin Rg Vin Vneg NIC ZL Vg Iin Signal Generator Zin -ZL FIGURE 27: Circuit for evaluating the performance of a grounded negative impedanceP1: RVMMOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 27 The first NIC circuit that we consider is a grounded ne ...