Читать книгу Antenna and EM Modeling with MATLAB Antenna Toolbox - Sergey N. Makarov - Страница 30

1 1. A small AM radio antenna operating at 1 MHz uses a thin copper wire with the diameter D of 0.2 mm and with the total wire length of 3 m.Calculate parasitic antenna's resistance (loss resistance) RL.What is the antenna efficiency percentage if the radiation resistance is 1 Ω?

2 2. In Example 1.4, we replace the 62 mil FR4 substrate by a Rogers substrate material RO4003 with the same thickness and with εr=3.55 and tan δ=0.0027. Is the efficiency of the patch antenna improved? What is the new efficiency value?

3 3. The generator's voltage source creates a sine wave with the amplitude of 10 V. The generator resistance is Rg = 50 Ω. The antenna impedance at a frequency of interest measuresΖa = 50 Ω + j0 Ω;Ζa = 75 Ω + j0 Ω;Ζa = 25 Ω + j0 Ω;Ζa = 50 Ω + j50 Ω;Ζa = 50 Ω − j50 Ω;Ζa = 50 Ω + j100 Ω.In every case, determineAverage power delivered to the antenna (show units).Average power radiated by the antenna assuming loss resistance of 10 Ω in every case.

4 4. The following antenna impedances are tested:Ζa = 75 Ω + j10 Ω;Ζa = 25 Ω + j0 Ω;Ζa = 50 Ω + j25 Ω.Which antenna is best matched to the generator resistance of 50 Ω (is characterized by the highest accepted power)?

5 5*. Approximately determine the resonant frequency of a strip dipole with the total length of 100 mm and the width of 2 mm. Prove your answer using MATLAB Antenna Toolbox and find the error. Present the text of the corresponding MATLAB script.

6 6*. Generate Figure 1.6 in MATLAB. Present the text of the corresponding MATLAB script.

7 7*.Draw the equivalent circuit for a generic transmitting antenna in frequency domain including the generator and the antenna. Label all circuit parameters.How do we define the “resonant” antenna condition?Create a strip dipole in MATLAB Antenna Toolbox with the length of 30 cm and the width of 2 mm. Use the impedance function over the frequency band 300–600 MHz and identify the frequency at which the antenna is resonant.What is the antenna radiation resistance at the resonance (assuming the lossless antenna)?Attach your MATLAB script to the homework report.

8 8*.Does the resonant frequency of a strip dipole increase or decrease with increasing its width? Prove your answer using MATLAB Antenna Toolbox.Does the resonant frequency of a cylindrical dipole increase or decrease with increasing its radius? Justify your answer.

9 9*. Use the dipole modeled in problem 7 C and analyze the impedance over the frequency band 300 MHz–1.5 GHz. Find all the series resonances in the impedance plot and annotate them. Report your results on the relationship between the resonant frequencies relative to the first resonance.

10 10*. In MATLAB Antenna Toolbox, the amplitude of the port excitation voltage of the strip dipole antenna changes from 1 to 2 V. How will the antenna impedance change?