The STV4100 terrestrial tuner is a direct- conversion (zero-IF) receiver with quadrature outputs intended for digital TV broadcasting.
On each VHF and UHF input is a low noise amplifier with both switchable and variable gain to ensure an optimal signal level for the two mixers. Each mixer, which down-converts the signal to baseband, is followed by a low-pass filter and amplifier. The baseband gain is programmable via a dedicated pin.
The LO signals are provided by an integrated PLL which contains an on-chip voltage controlled oscillator meeting stringent phase noise requirements. The LO frequencies are programmable. The comparison frequency for the phase/frequency detector is generated by dividing the crystal oscillator reference frequency. The crystal frequency can be from 16 MHz to 31 MHz depending on application.
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