(10)
For proving the validity of the above equivalent circuit model, the
simulated reflection coefficient of the proposed PIUWA for TE
polarization under HFSS and ADS (Advanced Design System) are depicted
simultaneously in Fig.3(b). As
shown in the picture, the circuit model agrees well with the calculated
results of HFSS. The value of RL andRH is optimized in HFSS for achieving desire
absorbing performance. And the final value of the equivalent circuit
parameters is obtained by tuning and optimizing in circuit simulation,
here we use C1 =0.073pF,L1 =5.9nH, C2 =0.036pF,L2 =2.5nH, Z1 =94Ω,β1h1 =90@17.5GHz,Z2 =285Ω,β2h2 =110@14.1GHz. Different from
the three resonances in most wideband absorbers, the proposed PIUWA
generates four resonances in the absorption band which across 4.0 to
23.4GHz with a fractional bandwidth of 142%. The four resonance peaks
are represented by f(i) (i =1,2,3,4). To
prove that the added resonance is owing to the presence of the cascaded
transmission line between the two dipoles, here we simulated the model
without the vertical substrate in the middle of the two dipoles for
comparison, as shown in Fig.3(b). We can see that the comparative model
only creates three resonance points within the absorption band from 4.5
to 21GHz with FBW of 129.4%. From the results above, we know that the
existence of the cascaded transmission line between the two dipoles
generates another resonant peak, at the same time the absorption
bandwidth increased.
To get insight understand of the four resonant peaks, we give the
susceptance curves for the different constituent parts of the proposed
PIUWA, as depicted in Fig.3(c). From (2) we know that the admittance of
the PIUWA can be calculated as follows: