technology microelectronics
early days of television were wondrous for some, but for many the experience was marred by poor reception. Areas that were not in a line-of-sight path to the transmitting antenna had to make do with weak, snowy pictures. Viewers resorted to erecting tall towers and adding preamplifiers, which usually helped, but often not all that much.
TAT6254C: FTTH / RFoG low noise amplifier for CATV receivers / triplexers. AGC to maintain +19 dBmV/ch output (+23 dBmV / high output mode). Ensures video quality / ease of design
To address this weakness television pioneers, whose names have been lost to all but fervent followers of broadcast technology, created the first community antenna television (CATV) systems. The acronym CATV was apt as these systems allowed a community to achieve reliable reception of local stations on at least a few channels. Often these included major network channels and perhaps a public broadcast station.
CATV was enabled by finding the highest point in or around the community, erecting high-gain directional antennas, and pointing them at broadcast towers many miles away. Channels were aggregated at this “head- end”, and distributed via coaxial cable to the community’s residents. Although results varied, they were invariably better than those achieved by individual viewers. To maintain an adequate signal throughout the system, distribution amplifiers were periodically spaced along the path of the cable “plant”. They initially employed vacuum tubes that degraded the signal with high levels of second- order distortion, but this was remedied with the bipolar transistors introduced in the 1960s.
The tremendous benefits provided by CATV systems resulted in explosive growth, and the “community” antenna
television concept expanded to cover entire metropolitan areas, states, regions, and ultimately into today’s Multiple System Operators (MSOs) that provide standard- and high-definition television services throughout North America. Similar models were followed across the globe, although there was a notable difference. Residents of Europe and many other countries were initially restricted to broadcasts by state-operated monopolies that inaugurated television service, and these viewers had to wait to embrace the competitive service offerings that they enjoy today.
Growth of the cable TV service was achieved through exponential advances in every key technology, from RF devices through to the introduction of delivery via fiber optic cables, which now form the latest generation of hybrid fiber coax (HFC) networks. Significant additional contributions include signal-processing technology and improved devices, better software, advanced modulation schemes, and linearization techniques. Today, cable systems are flexible enough to provide over 80 channels of legacy analog television programming alongside digital and high-definition services, video-on-demand services, high-speed data service, and packetized telephony…and more is on the way.
Mixing old and new From a technical perspective, cable systems are incredibly diverse. The plant of a typical system contains decades- old semiconductor technology sitting alongside its leading-edge brethren. However, it is possible to combine analog, digital, RF, microwave, and lightwave technologies, and make them all work together more or less seamlessly to provide today’s high quality of service.
This approach is employed in cable hybrid amplifiers, the long-established staple of every cable distribution system. This device can be seen on utility poles everywhere, boosting signal levels throughout the system while maintaining high levels of linearity. While older silicon bipolar transistor amplifiers are still in service, the cable networks they support simultaneously employ fiber optic technology, advanced digital modulation schemes, and assorted other technologies that are at or near the state of the art. Not surprisingly, streamlining this technological alphabet soup is essential if the cable industry is to address three key objectives: meeting expectations set out by shareholders and investors; fending off competing network technologies; and wooing legions of consumers hankering after novelties such as 3-D TV.
Gallium Arsenide (GaAs) wafer processing in TriQuint’s Hillsboro, Oregon 150mm facility
16
www.compoundsemiconductor.net June 2010
In a larger context, the MSOs primary challenge is to deliver the greatest variety of entertainment choices with the highest performance, at the lowest cost, to the
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127