Cody Miller

Electrical Engineer and Web Developer


Focused on EMC, RF, and component level characterization. I enjoy spending time in the lab with a focus on test and measurement.

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900 MHz Dipole Antenna

Project Summary

After moving and installing an anechoic chamber, we needed to test the shielding effectiveness. We decided to build a matched set of 900 MHz Dipole antennas.

Project Description

We started by designing a half wave dipole antenna.
Figure:1 Half Wave Dipole Antenna

Figure 1  Half Wave Dipole Antenna

There is some good material on this topic at:

Dipole Antenna.

We found that we needed to design three things.

  • Antenna elements
  • Balun
  • Impedance Transformation Circuit

Antenna Elements

We used copper tubing from a hobby shop for our antenna elements.

Figure:2 Copper Tubing

Figure 2  Copper Tubing

Balun Design

This paper covers the Balun design we used:

Coaxial Balun

Impedance Transformation Circuit

The impedance of the Dipole Antenna is 75 ohms and we were designing this for a 50 ohm system so we needed to design an impedance transformation circuit.

This is a great tool for calculating values for this circuit.

Impedance Matching Circuit Tool

The antenna worked out great. Here is a picture of the final antenna with the enclosure cover removed.

Figure:3 Dipole Antenna

Figure 3  Dipole Antenna

Tags: dipole, antenna, RF design, balun, enclosure,

Comments on this Project:

Edward Henderson

4 years ago:  That is very nice. The Aero club at BSU uses 900Mhz Zigbee for telemetry data. It might be worthwhile to design a custom antenna rather than use the normal off-the-shell antenna. Something to look into later.

Sthitapragyan Pattanayak

1 year ago:  sir can you please suggest me how to design a 10watt directive antenna,in order to receive at least 5watt in a mobile platform situated 3meter away from transmitter.(radio licence in not a matter of issue)

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