4.2 Electronically switchable ultra-wide band/dual-band band-pass filter using defected ground structures

Ref. [50] proposed a suitable UWB to dual-band band-pass filter with defected ground structure DGS. This filter consists of four parts, namely, meandered inter digital coupled line sections, stepped impedance open stubs, coupled lines, and rectangular DGS. The filter is miniaturized and has a total area of 12.5 10 mm, Figure 21. This filter is fabricated on Duroid Teflon substrate with a dielectric constant of 2.2 and a dielectric height of 0.7874 mm. The UWB mode extends from 3.6 up to 10.6 GHz with attenuation greater than 20 dB up to 18 GHz (upper stopband). The dual passbands extended from 3.8 up to 18 GHz (upper stopband). The dual passbands extend from 3.8 up to 5 GHz and from 9.5 up to 10.8 GHz. The proposed filter suppresses WiMAX and X (military) band of satellite that extends from 7 up to 8 GHz. The filter is designed, fabricated, and measured. The mode of the filter is changed by using suitable matrix equipment [50].

DGS at input and output ports of the proposed filter produces two resonances at 7.5 and 9.6 GHz and improve the performance of proposed filter while an overall size reduction of 20% is obtained. The meander lines and stepped impedance open stub are also used to reduce the overall size. By adjusting the connection between

inductance, and capacitance of the defected ground structure (DGS) [51]. L5, C5, L6, and C6 represent the equivalent inductance and capacitance of the stepped impedance resonator (SIR). Interdigital coupled arm is represented by the series capacitance with parasitic inductance and resistance, and shunt capacitances [52] as shown in Figure 22. The S-parameters versus frequency response of EM simulation and circuit model are compared. There is a very good agreement between the

Photolithographic technique was used to fabricate this filter on Teflon substrate (Duroid RT 5880) with physical properties of ε<sup>r</sup> =2.2 and tan∂ = 0.0009, while the dielectric thickness is 0.7874 mm. Figure 23 shows a photograph for the fabricated filter for both sides (the front and back sides). The soldered wires shown in

Figure 23 are used to connect the filter with diode switch matrix tool. The filters are measured using the vector network analyzer (N9928A FieldFox Handheld Micro-

Figure 24(a) shows the measured and simulated results of the proposed filter at

ON state with frequency range from 1 to 20 GHz. It should be noted that the frequency range is extended up to 20 GHz in order to show that the out of band rejection is good, and the measured 3 dB passband of the proposed filter is between 3.6 and 10.6 GHz. Figure 24(b) shows the measured and simulated results of the proposed filter at OFF state, and the dual bands with 3 dB passbands extend from

The simulated and measured S11 and S21 without O.C stub. (a) D1 and D2 ON state (with frequency range

simulated and equivalent lumped circuit model results.

Passive Components for Ultra-Wide Band (UWB) Applications

DOI: http://dx.doi.org/10.5772/intechopen.88444

wave Vector Network Analyzer, 26.5 GHz) [50].

3.8 to 5 GHz and from 9 to 10.8 GHz [50].

Figure 23.

Figure 24.

119

A photo for the fabricated filter [50].

from 1 to 20 GHz) and (b) D1 and D2 OFF state [50].

4.2.2 Fabrication and measurements

Figure 21. The structure of the proposed filter [50].

the coupled lines in the center of the design, the center frequency and 3 dB frequency band can be easily adjusted. The proposed filter achieves UWB performance with good selectivity and low insertion loss in the passband from 3.6 to 10.5 GHz and good stopband from 10.6 to 18 GHz. Moreover, it achieves dual bands with good stopband from 5 to 9.5 GHz and from 10.8 to 18 GHz by using open circuit stub to suppress unwanted interference signals in the band of WLAN, WIMAX, and X (Military) band of satellite. All dimensions of the proposed filter are as follows: L1 = 3.75 mm, L2 = 1.95 mm, L3 = 1.8 mm, L4 = 7.5 mm, L5 = 2.1 mm, L6 = 1 mm, L7 = 5.65 mm, W1 = 0.2 mm, W2 = 0.5 mm, W3 = 0.15 mm, g1 = 0.2 mm, g2 = 0.2 mm, and g3 = 0.3 mm. The simulated S11 and S21 are shown in Figure 24.
