Abstract
This chapter provides a comprehensive review of analytical analysis for microwave planar passive devices, including directional couplers, hybrid branch-line couplers, phase shifters, filters, and power dividers/combiners. The passive devices were fundamental building components for developing 5G wireless and IoT systems. The performance and specifications of the devices were mainly determined by the physical dimension, size, and structure of the microstrip line on the PCB. Despite that, the physical dimensions and structure of the circuit can be predicted through analytical analysis. Hence, in this chapter, the analytical analysis for the planar passive devices was mainly focused on, and this method provides an explicit solution in the design of the devices. The passive devices can be accurately modeled by the ABCD matrix, transmission line theory, stepped impedance matching, cascaded network approach, and even-odd mode decomposition. In addition, this chapter attempts to provide a quick guide for the reader to quickly and easily understand the principles of passive components.
TopIntroduction
Microwave passive devices and components are increasingly important and commonly used in telecommunication and wireless technology, such as fifth-generation wireless technology (5G), the internet of things (IoT), and the fourth industrial revolution (IR 4.0). In addition, recently, the operating frequency for these devices is higher up to the millimeter-wave band, indirectly the size for these devices will also be smaller and more sensitive. Thus, in higher education or universities, the study of microwave passive devices is increasingly popular, in terms of operation principle, mathematical analysis, and the structure of the designed circuits.
In this book chapter, several planar microwave passive devices, such as directional couplers, branch-line couplers, power dividers, phase shifters, and filters are used in this analytical analysis. An ABCD matrix, transmission line principle, stepped impedance matching, cascaded network approach, and even-odd mode decomposition are applied to the analytical analysis. The final interpretation of the analytical analysis is converted into S-parameters versus operating frequency. The performance, specifications, and bandwidth of a designed circuit can be characterized based on calculated S-parameters over a specific frequency range. In addition, based on the analytical calculation, the dimensions of the device’s circuits are estimated.
This chapter intends to analyze microwave passive devices from a different perspective that is more practical and more suitable for the latest higher education curriculum. Although, the microwave passive devices analysis can be searched in most textbooks related to the microwave field. However, in this chapter, the analytical analysis of the device focuses more on broadband vector S-parameter analysis, which is widely used in device test measurements (using vector network analyzer) and the latest commercial electronic design automation (EDA) simulators. The reason is S-parameters have directly represented the performance of the designed device.
The relationship between S-parameters can be analyzed by using a signal-flow network which are containing multiple ports. For instance, the antenna can be represented by a single-port network and usually only return loss, S11 is observed. On the other hand, microwave filter is a circuit that can be considered as a two-port network circuit, in which both return loss, S11 and insertion loss, S21 for the filter will be studied. In addition, two-way power divider and directional coupler can be analyzed using 3-port and 4-port network circuits, respectively. Often, such explanations are rarely emphasized in general textbooks. Therefore, this chapter attempts to demonstrate and guide how to practice the learned microwave analytical techniques (such as ABCD matrix, transmission line principle, cascaded network approach, and even-odd mode decomposition, stepped transmission line/impedance matching, and equivalent lumped-element circuit theory) for full use in the design of microwave and millimetre-wave passive devices.
Over the past 30 years, developments in microwave engineering have gradually shifted towards designs based on printed circuit boards (PCBs) rather than metal waveguides (You, 2020). Clearly, many microwave components, such as couplers, filters, amplifiers, and mixers, are in the form of monolithic planar circuits (using microstrip transmission lines and integrated circuit chips) to reduce manufacturing costs and shrink the designed microwave system. Hence, in this chapter, only PCB-based RF/microwave circuit has been focused.
Figure 1.
RF & Microwave PCB ruler manufactured by SV1AFN
Figure 2.
RFkit-Model A experimental module manufactured by HAROGIC Technologies
Key Terms in this Chapter
ABCD Parameters: A parameter (similar to S -parameters) that is more convenient than S-parameters for analyzing the performance of multi-cascade networks.
Internet of Things (IoT): A system of interrelated computing devices, mechanical, and digital machines provided with unique identifiers (UIDs) and the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.
Power Divider/Combiner: A multi-port passive device is used to split or combine RF/microwave power which split a single transmission line into more than one line and divide the power, and vice versa, it is able to combine power from multiple feeders into one.
Scattering Parameters (S-Parameters): A parameter that describes the electrical behaviour of linear electrical networks when subjected to various steady-state stimuli by electrical signals.
Phase Shifter: A passive device used to fix or change the relative phase angle of a traveling signal.
Directional Coupler (DC): A four-port passive device includes an input incident signal port, a port isolated from the input port, a pass-through port, and a coupling port that couples a specified level of electromagnetic power in the transmission line.
Millimeter Wave (mmWave): A form of electromagnetic radiation with wavelengths ranging from 10 mm to 1 mm, which is corresponding to operating frequencies ranging from 30 GHz to 300 GHz (within UHF and EHF bands of microwave).
Passive Filter: A passive device consisting of a combination of capacitors and inductors tuned to resonate at a desired single frequency or certain frequency band.
Fourth Industrial Revolution (Industry 4.0): A major shift in industrial development tends to enable automation and data exchange in manufacturing technologies and processes, including cyber physical systems (CPS), industrial Internet of things (IIOT), cloud computing, cognitive computing, and artificial intelligence.
Analytical Solutions: A mathematical analysis using closed-form mathematical expressions that can be solved analytically.
Microwave Passive Components: A component that operates in the 300 MHz to 300 GHz frequency range without external sources, such as directional couplers, isolators, filters, power dividers/combiners, and phase shifters.
Branch-Line Hybrid Coupler: A four-port passive microwave device consists of four ?/4 transmission lines, namely two horizontal and two vertical transmission lines with characteristic impedance Z 1 and Z 2 , respectively and 90 o phase difference between the two output ports (port-2 and port-3).
Fifth Generation Wireless Technology (5G): Digital cellular mobile communication networks that began wide deployment in 2019.
Microwave (MW): A form of electromagnetic radiation with wavelengths ranging from 1 m to 1 mm, which is corresponding to operating frequencies ranging from 300 MHz to 300 GHz.