Microwave Systems Design Tech - Assignment
1. Introduction to Microwaves
Microwaves are a form of electromagnetic radiation. Describe:
1.1 The range of frequencies most often defined as "microwave"?
1.2 The associated wavelengths of these frequencies? (Assuming propogation in free space)
1.3 An equation which can be used to derive the wavelength from the frequency (in free space)? Explain all terms.
1.4 One thing to consider when working with microwave circuits is the physical length compared to the electrical length. Explain both of these terms [2] and give a brief explanation of what this means. [2] (HINT - how does a 1cm component vary at low and high frequencies?
2. Co-axial Transmission Lines
Three co-axial lines are to be fabricated using copper inner and outer conductors. In all cases the conductors are the same size. The outer conductor has an outer diameter of 15mm and a wall thickness of 2.5mm. The inner conductor is a solid copper rod and has outer diameter of 1mm.
2.1 If PTFE is used as the dielectric material then calculate the capacitance and inductance per unit length. Assume the dielectric constant of the PTFE is 2.1.
2.2 If a dielectric material which has a dielectric constant of 7.4 is used. How does this affect the capacitance and inductance? Calculate the values.
2.3 Although air is the best dielectric material it is difficult to have a transmission line made of air. For this reason small spacers are used which cause neglible disturbance to the EM fields. What would be the capacitance and inductance of an air filled line?
2.4 In order to calculate the wavelength of such structures, the equation given in 1.3 needs an additional term. Give this new equation and state the wavelengths of each of the above structures. The cables are used to deliver energy at 5.8GHz.
3. Multiple dielectric layer co-axial line
Sometimes multiple layers of dielectric material will be used within the same co-axial line. Calculate the capacitance per length of the following co-axial structure.
Inner conductor has an outer diameter of 2mm. Between 2mm and 7mm there is a dielectric material with a dielectric constant of 4. Between 7mm and 15mm the material has a dielectric constant of 7.
3.1 Draw the structure of the above co-axial line
3.2 Calculate the total capacitance per length of the above structure
4. Characteristic Impedance of Transmission Lines
4.1 Give a brief definition of the term characteristic impedance and what is it measured in?
4.2 Calculate the characteristic impedance using the following information.
4.2.1 The capacitance and inductance per unit length of a co-axial line is 107 pF/m and 300 nH/m
4.2.2 The inner conductor has an outer diameter of 1.5mm and the outer conductor has an inner diameter of 7mm. (Dielectric constant of 3.2)
4.2.3 The inner conductor has an outer diamter of 5mm and the outer conductor has an inner diameter of 20mm. (Dielectric constant of 2)
4.3 Given a capacitance of 160pF/m and a characteristic impedance of 54.3ohms. Calculate the inductance per length of the co-axial line.
Attachment:- Assignment File.rar