CXA3018R 查看數據表（PDF） - Sony Semiconductor

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CXA3018R

Demodulator for Satellite Receivers

Sony Semiconductor 

CXA3018R

Description of Operation

This IC consists of the following six function blocks. First, the signal flow is explained briefly, followed by the

functions of each block.

(1) AGC block

(2) FM demodulation block

(3) SWAMP block of video signal processor

(4) CLAMP & VAMP blocks of video signal processor

(5) AFT block

(6) C/N detection block

The 2nd IF differential signal input to Pins 38 and 39 passes through the AGC block to stabilize the signal

level and is then input to the FM demodulation block. The FM demodulated signal is then input to the

SWAMP and AFT blocks of video signal processor.

The SWAMP block outputs the detective signal from DETOUT after adjusting the gain to support worldwide

video systems. The detective signal output becomes the final video signal by being input to the CLAMP &

VAMP blocks through an external de-emphasis time constant block and an LPF. Also, part of the detective

signal output is input to the C/N detection block through an external BPF.

The AFT block detects the frequency lag of the 2nd IF signal by the voltage value of the detective signal

output, and outputs a command signal to the external frequency conversion block in order to correct the local

frequency.

The C/N detection block detects noise outside the video band and has a voltage output to indicate the C/N

noise level that is input (1st IF signal) to the receiver.

(1) AGC block

The 2nd IF differential signal is input to Pins 38 and 39 to fix the signal level with the AGC block. Connect a

capacitor which fixes the AGC loop time constant to Pin 30, and apply an adjustment voltage at the output

setting level of this AGC (2nd AGC) to Pin 31. The 2nd AGC control voltage is output from Pin 35. Apply the

starting level adjustment voltage of the 1st AGC for the 1st IF to Pin 32. Input the Pin 35 output to Pin 33

through a 10 kΩ resistor and the Pin 36 output through a 0.1 µF capacitor. Output the 1st AGC control

voltage from Pin 34, and output the voltage obtained by adding the 1st AGC control voltage of the Pin 34

output to the 2nd AGC control voltage of the Pin 35 output from Pin 36.

(2) FM demodulation block

The FM demodulation block is a PLL demodulator which consists of an oscillator (OSC), phase discriminator

and DCAMP. Connect the oscillator resonance circuit to Pins 21 to 24 and the loop filter to Pins 28 and 29.

The DCAMP differential output comes from Pins 18 and 19, and this output is used as the drive voltage for

the varicap that comprises the oscillator.

(3) SWAMP block of video signal processor

The SWAMP block of video signal processor amplifies only gains selected by LOGIC and outputs detective

signal output from Pin 42. The output from Pin 42 is output externally as the DETOUT (detective output)

signal. This signal enters an internal buffer from Pin 43 through the de-emphasis time constant block, and is

then output again from Pin 44. The Pin 44 BUFOUT output is input to VAMPIN after the high frequency

component outside of the video band is removed by an external LPF.

LOGIC controls SWAMP according to corresponding satellite switching commands (3 bits) input from Pins 25

to 27. In addition, the SWAMP gain is finely adjusted by applying the DETOUT level adjustment voltage from

Pin 41.

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