Shigeo Matsuura

Frequency Synthesizing Tuning System with Saw Device

Recently many kinds of TV digital tuning systems have been developed. Especially in the United States the PLL frequency synthesizing method has been widely used. This system has advantages such as 10-key direct addressing, digital channel indication, high stability and accuracy of the local oscillator frequency, and so on. However it has also disadvantages such as harmonic interferences caused by a 1000 MHz ECL prescaler, and radiation from the prescaler which needs a large input level of 0.3 ~ 1 Vp-p.

Automatic Chennel Indicating System with Saw Device

Today television receivers have reached a stage where electronic tuners are widely used in the place of mechanical ones. Basically two types of the digital tuning system are existing. One is voltage synthesizing utilizing a digital to analogue converter (D-A converter) and a semiconductor memory device. The other is frequency synthesizing utilizing a 1 GHz prescaler. We have already successfully developed a tuner addressing system based on the former type.(1) This tuning system is featured with one touch tuning and one touch automatic search preset and contributed to the improvement of easy operation and reliability. However, this tuning system can not indicate channel numbers automatically because it indirectly controls the local oscillator frequency by means of the tuning voltage control.

Low-Cost Digital Tunung System with Full-Function Automatic Search Preset

One of the most widely used tuning system in the USA at present is a one-knob rotary channel selector, which presets TV channels with potentiometers, and selects them with a mechanical rotary switch. But in this system we need the experienced adjustment labor and devoted time in order to preset the exact tuning point with potentiometers.