4.2.2 Fabrication and measurements

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,

that is shown in Figure 21. The equivalent lumped circuit model results are

4.2.1 The equivalent lumped circuit model analysis of the proposed design

wave simulator.

Figure 22.

118

Figure 21.

The structure of the proposed filter [50].

UWB Technology - Circuits and Systems

g2 = 0.2 mm, and g3 = 0.3 mm. The simulated S11 and S21 are shown in Figure 24.

Figure 22 shows the equivalent lumped circuit model of the proposed UWB BPF

obtained using circuit model tool of the Advanced Design System (ADS) 2017. The lumped element values are manually optimized by changing each element value, so that it can have good agreement with the simulated results obtained from the full

The whole equivalent circuit of the proposed filter can be divided into the following subsections: DGS part at input and output ports, interdigital coupled lines

and stepped impedance open stub. As shown in the lumped element model (Figure 22), Rd1, Cd1, Ld1, Rd2, Cd2, and Ld2 represent the equivalent resistance,

Equivalent lumped circuit model of the proposed UWB BPF shown in Figure 21 [50].

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

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

Figure 23. A photo for the fabricated filter [50].

#### Figure 24.

The simulated and measured S11 and S21 without O.C stub. (a) D1 and D2 ON state (with frequency range from 1 to 20 GHz) and (b) D1 and D2 OFF state [50].

Figure 25. A photo for the fabricated filter of Figure 10.

5.1 Modified CMRC LPF using novel fractal patches

The proposed multiband filtenna (a) front view and (b) back view [53].

Passive Components for Ultra-Wide Band (UWB) Applications

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

Figure 27.

Figure 28.

121

The design of proposed low-pass filter [53].

A modified compact microstrip resonance cell (CMRC) low-pass filter (LPF) using novel fractal patches was proposed in [54], see Figure 28. The fractal patches produce additional transmission zeros to the stop-band, while the open-ended stubs

cause an extension in the stopband achieving a compact ultrawide and deep stopband filter with good selectivity and low insertion loss in the passband. The results show 10 dB bandwidth from 3.3 to 67 GHz with 181.5% relative stopband bandwidth. The 3-dB cutoff frequency is 2.85 GHz and less than 1.5 dB insertion loss in the passband and 0.55 GHz transaction from 3 to 20 dB and 20 dB suppression from 3.5 to 67 GHz, so that the filter can be expected to suppress the unwanted harmonics and prevent inter-modulation with the new systems with high frequency operating bands. The filter has been designed on a Rogers 5880 substrate with a relative dielectric constant of 2.2, substrate thickness of 0.508 mm, and 0.0009 loss tangent. Figure 28 shows the proposed filter design, and it consists of

two traditional triangle taper resonance cells in one side of the transverse

connecting narrow width transmission line which has almost the same performance of the complete CMRC structure, while two different sizes circular fractal patches are present on the other half. Each fractal consists of main circular patch and additional small circular patches at edges. The two fractals act as a dual behavior resonator to have additional transmission zeros in the stopband. Each fractal is resonating at certain frequency in addition with enhancing the low suppression bands of the entire stop-band. Also, four open ended stubs are used to extend the

Figure 26. The simulated and measured S11 and S21 with O.C stub. (a) D1, D2 ON, and D3 OFF, (b) D1, D2 OFF and D3 ON [50].

Photos for the fabricated filter with open stub are shown in Figure 25. Figure 26 (a) shows the measured and simulated results of the proposed filter with open stub at D1, D2 ON state, and D3 OFF with frequency range from 1 to 20 GHz. It should be noted 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 with open stub at D1, D2 OFF state and D3 ON, and the dual bands with 3 dB passbands extend from 3.8 to 5 GHz and from 9.5 to 10.8 GHz [50].
