TDA7703 Datasheet, PDF (9/32 Pages) STMicroelectronics – Automatic self alignment for image rejection

TDA7703
2
Function description
Function description
2.1
FM - mixer
The FM image-rejection mixer is optimized for best performance with a passive wide-band
prestage.
The input frequency is downconverted to low IF with high image rejection.
2.2
FM - AGC
The programmable RFAGC senses the mixer input whereas the IFAGC senses the IFADC
input to avoid overload.
The PIN diode driver is able to drive external PIN diodes with a current value as high as
15mA.
The time constant of the FM-AGC is defined by an external capacitor.
2.3
AM - LNA
The AM-LNA is integrated with low noise and high IIP2 and IIP3. The gain of the LNA is
controlled by the AGC. The maximum gain is set with an external resistor, typically 28 dB
with 1.5 kΩ.
2.4
AM - AGC
The programmable AM-RF-AGC senses the mixer inputs and controls the internal PIN diode
and LNA gain.
First the LNA gain is reduced by about 10dB, then the PIN diodes are activated to attenuate
the signal.
The time constant of the AM-AGC is defined with an external capacitor and programmable
internal currents.
2.5
AM - mixer
The AM mixer converts RF to low IF with high image rejection.
2.6
IF A/D converters
A high performance IQ-IFADC converts the IF-signal to digital IF for subsequent digital
signal processing.
Rev 1
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