End of Class

Important Announcement

For the mid-term test on thursday, you can bring in a piece of "cheat sheet" size A4. You can only write on one side of the sheet. Write your name and matriculation number on the sheet. This sheet must be submitted along with your answer scripts. Notes and books are not allowed.

Bring along your own protractor, drawing tools, etc. No sharing is allowed.

Good luck.

Reflection coefficient of a terminated network

If the reflection coefficient of a network terminated with a matched load is S11, what would the reflection coefficient be when the load is generally ZL?

Maximum power transfer

For a network with a scattering parameter S11, what would be the condition for maximum power transfer from a source? Satisfy yourself that the condition is true.

Reference text

follow my twit for the name of the author who i referred to in class today

Review of microwave propagation and scattering parameters

I hope the quiz last week tested briefly your understanding of radio wave propagation. Microwave propagation is interesting because of the many ways the waves interact with objects and media along the path.

You should by now appreciate the mechanisms of microwave propagation. Lest one forgets, we are talking of not only terrestrial but also space communications using microwaves.

The next topic to be discussed would be microwave networks. Here, a network is meant to be a device (active or passive) that accepts signals at microwave frequencies. We would see that low frequency network representation fails at microwave frequencies. We need to introduce a new set of parameters to describe the networks.

At microwave frequencies, we do not use open-circuit and short-circuit tests as these would introduce oscillations and irradiations. To ensure the system is stable, we use matched load tests. The result would be the scattering parameters.

see you in class.

Quiz #1

There will be a quiz on Tuesday, 25 August. The topic will be on propagation covering:

1. Line-of-sight range and antenna heights,
2. Free space loss calculation
3. Fresnel zone clearance
4. Diffraction and shadow zone
5. Ducting, sub- and super-refraction propagation

Be Prepared

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Class on Tuesday 25 August

There will be a class on Tuesday, 25 August. Time as usual at 11:00am

We will continue our discussions on propagation of radiowaves with emphasis on microwaves.

Recitals for the class have been given in previous posts.

Microwave article and reference text

1. Primer on propagation

Books:

1. Radio Engineering by G. K. Mithal, Khanna Publishers.

2. Radio WAve Propagation and Antennas by John Griffith, Prentice Hall.