In addition, to expand upper rejection band
and improve selectivity, a transmission zero is placed at 2.6 GHz using short ended stubs coupled with gaps to the wide sections of the transmission line as shown in Figure 5(a).
An SIR microstrip filter with tapped-line excitation at the input and output is developed to further extend the upper rejection band
. By properly allocating the two transmission zeros, the first and/or second spurious resonances in this filter are effectively cancelled.
5 that a decrease in the slot width, [W.sub.s], increases the capacitance of the slit and hence causes the rejection band
of the filter to shift to lower frequencies.
The thickness and the split gap of the edges of the CSRR rings exhibit band-rejection UWB characteristic creating 5.5 GHz rejection band
. By virtue of significant selection of slotted CSRRs parameters, it is observed that the reported antenna can obtain ultrawide band with rejected 5.5 GHz WLAN band.
Denidni, "Experimental investigations of a novel ultrawideband dielectric resonator antenna with rejection band
using hybrid techniques," IEEE Antenna Wirel.
Lai, "New dual-band bandpass filter with wide upper rejection band
," Progress In Electromagnetics Research, Vol.
We can find that the proposed antenna operates from 3 to 16 GHz covering the entire UWB band with a sharp rejection band
around 3.3-3.8 GHz.
The numeric and experimental studies have demonstrated efficient rejection (-19 dB) in the rejection band
, low insertion losses (< 1.30 dB) in the pass band, and very sharp cutoff.
But impedance result of the equivalent circuit is not close to simulation result or they show about 30% rejection band
difference between equivalent circuit and simulation result [25, 26].
The simulation results are shown in Figure 3, in which a rejection band
in the vicinity of 2.9 GHz can be observed, clearly given by the quasistatic resonance frequency of the SRR elements.
For other frequencies outside rejection band
, gain remains well satisfied.
Measured results from the fabricated device agree well with the simulated ones, and they exhibit a continually tuned rejection band
with a centre frequency that can be adjusted between 4.434 and 4.814 GHz.