Abstract
To accommodate the future growth in wireless internet traffic, more bandwidth using higher carrier frequencies will be essential. To achieve this, antennas operating in the terahertz frequency range have great potential for wireless connections, but also some challenges to overcome. For example, the great free space path loss and low penetration depth. It is essential to know how these antennas operate and to investigate the characteristics of these antennas to maximize their potential. The goal of this project is to design a setup and measure the output power for different frequencies, radiation patterns and potential leakages of a new prototype optoelectrical terahertz antenna.The antenna uses photomixing to emit terahertz waves, whereby two independent laser signals are combined in an optical fiber coupler to create an optical beat tone which has the frequency difference of the two original lasers signals. This optical tone is launched into the antenna consisting of a p-i-n photodiode that generates electromagnetic radiation with the same frequency as the optical beat tone. Keeping one laser fixed with the other laser tuning to a desired frequency, a frequency sweep from 50 GHz up to 1 THz can be realised.
To measure the output power of the antenna a measuring system based on a Golay cell is designed used. For every frequency the output power was measured to create a power spectrum with a range of 50 to 490 GHz. To measure the radiation pattern the frequency was kept at a constant while the antenna is turned with steps of 0.29° by a servo motor. For the radiation patterns the Half-power beam width is calculated. The measurements showed that the power spectrum has variance of around +-100% in the lower frequencies and after frequencies higher than 400 GHz the power was flatting out. The variance does not seem to be time dependent. The flatting out is suspected to be caused by the phenomena that one laser will give a small output. So when the frequency drops below 400 GHz the signal of both laser gets so low that the signal produced by one laser will act sort of as a second noise floor. The general shape of the spectrum measured is similar to the spectrum provided by the supplier. The setup has good reproducibility, determined by (partially) measuring again with similar results. The equipment designed, built, and programmed in this project to measure the antennas radiation pattern worked successfully to measure the radiation patterns of the antenna. However, more data about the specification is needed to make an accurate comparison between the measurement and the reference provided by the supplier. The radiation patterns of 50, 100, 130, 150, 200, 250, 300, 350 and 400 GHz were measured. The pattern of 100 GHz is measured three times to check the reproducibility. The measurements indicates that the setup is robust and gives reproducible results. For statistical conclusions, more measurements are needed.
In the future, it is recommended to measure the output of the antenna with a device capable of measuring the polarization and phase to research the data transmitting capabilities.
| Date of Award | Jan 2022 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Gleb Nazarikov (Supervisor 1), Simon Rommel (Supervisor 1) & Willem-Jan van Harskamp (Supervisor 1) |
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