Antenna Theory - DESIGN

[thandana]

Hi,

I haven't done antenna theory since high and need some help here. I'm trying to answer these questions below in preparation for an exam. Can someone please help me out.

A system has these parameters:
- Frequency of operation = 42MHZ
- Transmitter power output = 160 watts
- Receive antenna gain = Transmit antenna gain
- Transmission path loss = 187dB
- Receiver threshold = -108dBm
- Minimum S/N margin required = 15dB

QUESTIONS:
- By completing the link budget, determine the required antenna gain.
- Design a single boom, horizontally polarized Yagi-Uda antenna to meet the above calculated antenna gain.

Can someone please guide me on how to answer the above questions.

 

[hagster]

1. Required signal strength = -108dB + 15dB

2. Convert the Tx power to dBm and subtract the path loss.

The difference between 1 and 2 is your link budget margin. This is probably negative, and is the gap you need to reclaim with the antenna gain.

As each antenna is the same the required gain for each is just the gap that you just calculated. If this is not a sensible figure then you have done something wrong.

Then design your antenna.

 

[thandana]

Hi Hagster,

Thank for the help.

When designing this antenna, what are parameters that i need to focus on?

 

[hagster]

Hi Hagster,

Thank for the help.

When designing this antenna, what are parameters that i need to focus on?

First have you calculated the required gain for the antenna?

A yagi-uda is defined by the number of elements and the length and spacing of those elements. These parameters are normally obtained from experimentally derived tables. Antenna-theory is a good place to look for guidance https://www.antenna-theory.com/antennas/travelling/yagi.php