We have proposed a 5 GHz microstrip-line-based bandpass filter in the applications of future wireless communication, which locates at 4.9 to 5.85 GHz of IEEE 802.11ac regulated by Federal Communications Commission (FCC). The proposed filter is composed of a folded half guided-wavelength coupled-line resonator and a pair of folded T-shaped open-end stubs, which are slightly longer and shorter than the quarter guided-wavelength. The bandpass filter possesses the sizes of 0.330  0.150, which is compact compared to a traditional hairpin-line bandpass filer, an interdigital bandpass filter, and an open-loop bandpass filter, etc., which are on the level of 0.520  0.300, 0.500  0.330 and 0.870  0.290, respectively. Note that, 0 represents the guided wavelength of the substrate at the central frequency. Next, we manipulate the lengths of the coupled line and the two open-end stubs to obtain the three transmission poles in the passband that a three-order bandpass filter can be achieved. This proposed bandpass filter can be further analyzed by the electrical circuit. The certain part of the entire structure can be corresponding to the electrical components, such as an inductance, a capacitance and an inverter. The selectivity of our bandpass filter is great because the two transmission zeroes locate outside the frequency range of the passband with the band-edge transitions equal to 113 and 48.6 dB/GHz on the lower and higher frequencies, respectively. Moreover the stopband is suppressed below -20 dB down to DC and up to 12 GHz. In addition, the performance of the insertion loss and return loss are further improved by designing an impendence-matching line, which are to 0.6 and -22 dB, respectively. Finally, the proposed filter is fabricated on the Roger board 5880 by the printed-circuit-board (PCB) fabrication process and measured by the high-frequency measurement system, a vector network analyzer Agilent N5245A. The measurement results agree with the simulated results well.

Abstract i
Contents iii
List of Figures v
List of Tables ix
Chapter 1 Introduction 1
1.1 Introduction to Wireless Communication and Its Devices 1
1.1.1 IEEE 802.11ac 1
1.1.2 RF front end 4
1.1.3 A Microstrip Line 5
1.2 Thesis Organization 6
Chapter 2 Literature review 8
2.1 Microstrip transmission line 8
2.1.1 Transmission line theory 8
2.1.2 Microstrip transmission line 10
2.1.3 Microstrip discontinuities 13
2.1.4 Impedance matching 15
2.2 Background of the bandpass filter components 17
2.2.1 Equivalent circuit of the bandpass filter 17
2.2.2 Immittance inverters 20
2.2.3 Parallel-coupled line 24
2.2.4 Transmission line resonators 27
2.3 Microstrip bandpass filters 29
2.3.1 A parallel coupled microstrip bandpass filter 29
2.3.2 A interdigital microstrip bandpass filter 32
2.3.3 A pseudo-interdigital microstrip bandpass filter 34
2.3.4 A triple-mode microstrip bandpass filter 36
2.4 De-embedding method 39
Chapter 3 Design and Simulations 44
3.1 Motivation 44
3.2 CST Microwave Studio transient solver setup 44
3.3 Simulation results and discussion 46
3.3.1 Design the compact layout 46
3.3.2 Addition of Impedance-matching Line 49
3.3.3 Influence from each parameter 58
Chapter 4 Fabrication, Measurement and Calibration 66
4.1 Fabrication process 66
4.2 Measurement 67
4.2.1 High-frequency circuit measurement system 67
4.2.2 Design of De-embedding pads 69
4.2.3 Measurement results and Discussion 72
Chapter 5 Conclusions 81
Appendix 83
References 86

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