Antennas with Non-Foster Matching Networks phần 5 doc

P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 38 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 50 100 150 200 250 300 350 400 4500 500 -30 -20 -10 -40 0 freq, MHz m3 m3 freq = 104.0MHz dB(S(1,1)) = -20.022 50 100 150 200 250 300 350 400 4500 500 0.2 0.4 0.6 0.8 1.0 0.0 1.2 freq, MHz (a) (b) dB(S(1,1)) MuPrime1 FIGURE42: Simulated (a) return loss and (b) stability of the all-pass test circuit for the THS3202 FNR An all-pass implementation simulation in Agilent ADS with R 3 = 50 is depicted in Fig. 44 where the FNR is placed inside a two-port data item box. To minimize noise and maximize gain, R 1 and R 2 are chosen to be as small as possible (200  and 400 , respectively) without affecting the performance of the FNR. The two 25  resistors on each side of the FNR complete the all-pass test circuit. The simulation results of Fig. 45 show that the −20 dB return loss bandwidth is only about 30 MHz, but the network is close to being unconditionally stable over almost the entire frequency range. We found that the input reactance X in is negative and so might be compensated over a limited frequency range using a series inductor. By trial and P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 39 Port P2 Num=2 Port P1 Num=1 ths3202_port X1 ths3202_port X2 R R5 R=R3 Ohm R R6 R=R3 Ohm R R2 R=R1 Ohm R R4 R=R2 Ohm R R3 R=R2 Ohm R R1 R=R1 Ohm FIGURE 43: Schematic captured from Agilent ADS of the THS3202 FNR circuit formed by two back-to-back GNRs S_Param SP 1 Step = 1000 kHz Stop = 300 MHz Start = 10 MHz S-PARAMETERS MuPrime MuPrime 1 MuPrime 1 = mu_prime (S) MuPrime R R9 R=25 Ohm R R10 R=25 Ohm Floating_NIC_Back_to_Back_port X1 Term Term1 Z=50 Ohm Num=1 Term Term2 Z=50 Ohm Num=2 0 FIGURE 44: Schematic captured from Agilent ADS of the THS3202 FNR of Fig. 42 installed in the all-pass evaluation circuit P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 40 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS m1 freq=33.00MHz Simulated_Return_Loss=-20.066 50 100 150 200 2500 300 -30 -25 -20 -15 -10 -35 -5 freq, MHz m1 50 100 150 200 2500 300 1.0 1.1 1.2 1.3 0.9 1.4 freq, MHz (a) (b) Simulated_Return_Loss MuPrime1 FIGURE45: Simulated (a) return loss and (b) stability of the all-pass test circuit for the THS3202 FNR formed by two back-to-back GNRs error, we found that placing an inductance of 45 nH in series with the FNR maximized the return loss bandwidth and stability of the all-pass test circuit as shown in Fig. 46. The simulated –15 dB return loss bandwidth is expanded to greater than 250 MHz. Unfortunately, the circuit is not unconditionally stable for frequencies less than 125 MHz, but may be relatively easy to stabilize since μ  is so close to unity. Another way to implement an FNIC is to use two BJTs to realize the circuit shown in Fig. 23. Following the work reported in [15] and [16], we use the NE85630 NPN silicon P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 41 (a) (b) 50 100 150 200 2500 -35 -30 -25 -20 -15 -40 -10 freq, MHz 50 100 150 200 2500 300 300 1.0 1.2 1.4 1.6 0.8 1.8 freq, MHz Simulated_Return_Loss MuPrime1 FIGURE46: Simulated (a) return loss and (b) stability of the all-pass test circuit for the THS3202 FNR formed by two back-to-back GNRs with a 45 nH series inductor RF transistor from NEC. The schematic of the FNR all-pass test circuit using these devices captured from Agilent ADS is shown in Fig. 47. The simulated performance of this FNR test circuit is shown in Fig. 48. As can be seen, the −20 dB return loss bandwidth approaches 200 MHz, and the circuit is unconditionally stable at all simulation frequencies. It should be noted that the simulation is performed using only the S-parameters of the NE85630 (rather than a SPICE model) valid under a specified bias condition. 2 The exact details of the biasing circuit are 2 S-parameters for the NE85630 device are provided from 50 MHz to 3.6 GHz. Since we are simulating our circuits below 50 MHz, we are also relying on an accurate extrapolation of the S-parameters. P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 42 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS FIGURE 47: Schematic captured from Agilent ADS of the all-pass test circuit for the NE85630 FNR P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 43 50 100 150 200 2500 (b) (a) 300 -28 -26 -24 -22 -20 -18 -30 -16 freq, MHz dB(S(1,1)) 50 100 150 200 2500 300 0.95 1.00 1.05 0.90 1.10 freq, MHz Mu P rime 1 FIGURE48: 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. Inadditiontothe NICcircuitsdiscussedindetail inthissection,wealso madeconsiderable effort trying to realize NIC circuits that utilized CCII- blocks implemented as cascades of GaAs PHEMT devices. We simulated these circuits extensively and were able to obtain excellent performance in simulation with bandwidths greater than 1 GHz. Unfortunately, our attempts to physically implement these designs have all ended in failure. Other researchers have also reported a lack of success using this approach [16], and so we have abandoned it for the present. P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 44 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS FIGURE 49: Schematic captured from Agilent ADS of VHF monopole with active matching network P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 45 40 50 60 70 8030 90 -25 -20 -15 -30 -10 freq, MHz dB(S(1,1)) Return Loss (dB) FIGURE 50: Return loss at input of optimized active matching network and antenna computed using Agilent ADS SIMULATED PERFORMANCE OF ESA WITH A PRACTICAL NON-FOSTER MATCHING NETWORK To illustrate the potential of non-Foster matching networks for ESAs, we designed and opti- mized in Agilent ADS a practical implementation of the active matching network shown in Fig. 12 for our ESA monopole antenna. We used a single FNIC of the form shown in Fig. 23 to implement the non-Foster series reactance consisting of − ( L a + L m ) in series with −C a . The 40 50 60 70 8030 90 75 80 85 90 70 95 freq, MHz mag(S(2,1))*100 Overall Efficiency (%) FIGURE 51: Overall efficiency (in percent) of optimized active matching network and antenna com- puted using Agilent ADS P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 46 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 40 50 60 70 8030 90 0.98 0.99 1.00 0.97 1.01 freq, MHz Mu1 MuPrime 1 FIGURE 52: Small-signal geometrically derived stability factor for the optimized active matching net- work and antenna computed using Agilent ADS active devices (NE85630 silicon bipolar NPN transistors) were modeled using the S-parameter library in Agilent ADS. Not surprisingly, we found that the simulated NIC performance was far from ideal. Nevertheless, using the gradient optimizer in Agilent ADS, we were able to adjust the values of the capacitor and inductors in the matching network to achieve remark- able broadband performance from the ESA monopole. The schematic of the two-port antenna model and active matching network captured from Agilent ADS is shown in Fig. 49. Note the presence of the measurement component for the small-signal geometrically derived stability factors μ and μ  . The computed return loss looking into the input of the matching network is shown in Fig. 50, and the total efficiency of the antenna together with the active matching network is shown in Fig. 51. Note that an extremely broadband and highly efficient match has been achieved. The geometrically derived stability factors as a function of frequency are shown in Fig. 52. These factors must be strictly greater than 1 for the circuit to be unconditionally stable. Note that below about 31 MHz, the overall circuit is not unconditionally stable. This situation should ultimately be remedied to avoid spurious radiation from the antenna. CONCLUSIONS In this lecture, we discussed an exciting new area of research in antenna technology, namely, the use of non-Foster circuit elements in the matching network of an electrically small antenna. The contributions of this lecture were to summarize the current state-of-the-art in this subject, and to introduce some new theoretical and practical tools for helping others to continue the advancement of this technology. The new contributions include a rigorous method for gener- ating a two-port model for an antenna, an all-pass test circuit for evaluating the performance of P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 47 floating negative impedances, and a new kind of floating negative impedance converter formed from two back-to-back grounded negative impedance converters. REFERENCES [1] C. A. Balanis, Antenna Theory: Analysis and Design. 3rd ed. New York: John Wiley and Sons, Inc., 2005. [2] D. M. 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Sussman-Fort, “Gyrator-based biquad filters and negative impedance converters for microwaves,” Int. J. RF Microwave CAE Vol. 8, pp. 86–101, 1998. [10] A. Sedra, G. Roberts, and F. Gohh, “The current conveyor: history, progress, and new results,” IEEE Proc. G, Vol. 137, No. 2, pp. 78–87, Apr. 1990. [11] Texas Instruments,OPA690WidebandVoltage-FeedbackOperationalAmplifierwithDisable, 2005. [12] A. Sedra and K. C. Smith, Microelectronic Circuits, 4th ed., New York: Oxford University Press, 1998. [13] Maxim, MAX435/MAX436 Wideband Transconductance Amplifiers, 1993. [14] Texas Instruments, THS3202 Low Distortion, 2 GHz, Current Feedback Amplifier, 2004. [15] S. E. Sussman-Fort, “Matching network design using non-Foster impedances,” IEEE Long Island Section, Circuits and Systems Society [Online]. Available: http://www.ieee.li/ cas/index.htm [Accessed: Dec. 6, 2005]. [16] S. E. Sussman-Fort and R. M. Rudish, “Progress in use of non-Foster impedances to match electrically-small antennas and arrays,” Antenna Applications Symposium, Allerton, 2005. . ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 50 100 150 200 250 300 350 400 450 0 50 0 -30 -20 -10 -40 0 freq, MHz m3 m3 freq = 104.0MHz dB(S(1,1)) = -20.022 50 100 150 200 250 300 350 400 450 0 50 0 0.2 0.4 0.6 0.8 1.0 0.0 1.2 freq,. 2007 17:23 40 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS m1 freq=33.00MHz Simulated_Return_Loss=-20.066 50 100 150 200 250 0 300 -30 - 25 -20 - 15 -10 - 35 -5 freq, MHz m1 50 100 150 200 250 0 300 1.0 1.1 1.2 1.3 0.9 1.4 freq,. [ 15] and [16], we use the NE 856 30 NPN silicon P1: RVM MOBK060-01 MOBK060-Aberle.cls January 19, 2007 17:23 ANTENNAS WITH NON-FOSTER MATCHING NETWORKS 41 (a) (b) 50 100 150 200 250 0 - 35 -30 - 25 -20 - 15 -40 -10 freq,