HDTV Test Process Improvement (TOSHIBA RF) Sponsor: Aaron Foster TOSHIBA America Consumer Products, Inc. Manufacturing Division Project Team: Josue Caballero, Brett DiCio, Daniel Hooper, Efosa Ojomo, George Sewell TOSHIBA subjects each TV that comes off the line to a series of quality control tests. As each TV comes into the test station, a person sitting behind the TV connects a coaxial cable. A specially generated test pattern is displayed onscreen, which is then analyzed by a camera on the other side. The captured image is compared against a known good image, and if any flaws are detected, the TV is taken off the line. The problem with this system is that it requires a person behind each station who has the sole task of connecting and disconnecting the cable. This is inefficient and costly, so to work around this problem TOSHIBA created a wireless test system. A receiving antenna is attached to the TV before it enters the testing line, and as it enters each testing station, the receiver lines up with the transmitter. This system works, but it interferes with adjacent stations, and the inefficiency of the design is causing damaging feedback. Our goal is to find an antenna that can transmit consistent power over a large bandwidth. In order to characterize our antennas we implemented a simple testing method. We measured the power of the signal received at the antenna versus changes in frequency and distance. The antennas we used are all directional, which means they transmit in one axis better than any other; we called this the “On-Axis” direction. The ideal position for an antenna pair is with both of their On-Axis directions aligned. The first two graphs below are power versus distance graphs. The testing frequency remained constant while the distance in either On- Axis or Off-Axis values were changed. When a power value is zero, it means the signal was too low and was obscured by background noise. The third graph shows the most important character- istic. This is the power received versus frequency. The main goal of our project was to find an antenna that has a strong signal across a large bandwidth. The higher and flatter lines in this graph are the better performers. The antennas outperformed each other in different areas, so the best antennas were those that had the best overall average. Our final solution was the 16AWG Mag Spiral 3.75” design, which is in bold blue. Compare this to the TOSHIBA antenna design in bold red. We worked with Janice Rock from Redstone Arsenal in Huntsville, AL, who let us use more sophisticated equipment. We tested two antenna designs: TOSHIBA’s current antenna pair, and our spiral antenna. Plots on the left show return signal in dB, with complete return as reference (0 dB). Plots on the right show the standing wave ratio (SWR), or percent of signal return across the spectrum. Single Arm Spiral Antenna 15GHz bandwidth Limited directionality Low attenuation over bandwidth Adjustable by number and density of turns The best antennas were constructed with magnet wire. The thin insulation allows the wire to be wrapped tightly, creating a strong electromagnetic field. The connection between the coaxial cable and the antenna can be a point of high signal loss. N-Type connectors meet military quality specifications and have less than 0.1dB loss. The receiving antenna shows nearly complete signal return to the network analyzer. This is a very poor antenna. The transmitting antenna, though better, still shows massive amounts of signal return. Over time, this could burn out the output stage of an RF amplifier. Our spiral design is better than the previous two designs, however there are still significant signal return problems. More must be done to develop this design.