TV Tuners Using Low Loss and Low Distortion GaAs Varactor Diodes

The noise figure of conventional TV varactor tuners is fairly high, when typical Si diodes, whose average resistance is 0.65¿at 470 MHz, are used. Low noise tuners which comply with FCC noise requirements can be realized if low loss varactor diodes are developed. However, Si diodes with still lower losses can not be manufactured by conventional Si process technology with high production yield. Low noise Si rf transistors with a noise figure of 1.3 dB at 470 MHz is commercially available. However, noise figure improvement using these transistors at 470 MHz is only 1.0 ~ 1.2 dB when compared with conventional tuners. These low noise Si transistors are high in cost and low in production yield because the specification uniformities are insufficient.