This article provides a derivation of the Rayleigh criterion for surface roughness. As a once-flat surface roughens, the specular reflected wave begins to degrade in power as some of it is scattered in different directions. The result is a predictable degradation that is a function of the rough surface statistics. The end result — the Rayleigh criterion — is used throughout science and engineering to describe everything from propagation off of building sides to the specifications for a satellite dish antenna. Download the article here here.
Tianchong “Michael” Jiang’s MS thesis entitled “Tri-band Object-Resistant Antenna Design“, is now available on SmartTech. From the thesis:
A new tri-band monopole antenna is proposed in this thesis. The antenna is made up of two simple L-shaped structures making it easy to fabricate and low in cost. The three target ISM bands (915MHz, 2.4GHz and 5.8GHz) enable it to be used for for low-power and short range telecommunications, such as WiFi, Bluetooth, Zigbee, wireless telephones, RFID, and NFC links. The bandwidths are designed to be in excess of the allotted bands making the antenna resistant to the presence of nearby object variations. This allows the antenna design to be used across the broadest possible application space. The proposed antenna is fabricated on an 80mm * 80mm RO4730 board and achieves a bandwidth of 9.3%, 66.7% and 12.4% at 915MHz, 2.4GHz, and 5.8GHz respectively. For the antenna gain, it achieves 2.5dBi, 4dBi and 4.3dBi at 915MHz, 2.4GHz and 5.8GHz respectively.
Low-Observable Reflectors Using Perfect Pulses
Mohammad Alhassoun, Michael A. Varner, Gregory D. Durgin
2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting
Year: 2018, Page s: 915 – 916
This paper presents a new technique for suppressing specular reflection using binary reflective surfaces (such as those easily fabricated on a printed circuit board)that maximally suppress mean currents on the reflector using the theory of perfect pulses. We simulate multiple versions (or orders)of these structures to characterize the nulling depth and manufacturing tolerance of the designs. In addition, we run another set of simulations to characterize the specular reflection as a function of the direction of incidence. The simulation reveals that the specular reflection from the proposed structures is at least 9.3 dB less than that from a flat metal plate of the same dimensions.