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

0 500 50 100 150 200 250 300 350 400 450

-30

-20

-10

-40

0

freq, MHz

m3

m3

freq = 104.0MHz

dB(S(1,1)) = -20.022

0 500 50 100 150 200 250 300 350 400 450

0.2

0.4

0.6

0.8

1.0

0.0

1.2

freq, MHz

(a)

(b)

dB(S(1,1)) MuPrime1

FIGURE 42: 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 R3 = 50 is depicted in Fig. 44

where the FNR is placed inside a two-port data item box. To minimize noise and maximize

gain, R1 and R2 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 Xin is negative and

so might be compensated over a limited frequency range using a series inductor. By trial and