CXA3038N Ver la hoja de datos (PDF) - Sony Semiconductor

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Fabricante

CXA3038N

IQ Detection IC for Digital Satellite Broadcast Tuner

Sony Semiconductor 

CXA3038N

Description of Operation

(See the Electrical Characteristics Measurement Circuit.)

Oscillator circuit

• This is a differential amplification-type oscillator circuit, and it is oscillated by connecting an LC parallel

resonance circuit via a coupling capacitance between Pin 15 and Pin 16.

A varicap diode is used as a capacitor for the LC parallel resonance circuit to configure the VCO. Set the L

value so that the OSC oscillation frequency is approximately 480 MHz when a voltage of 2.5 V is applied to

the varicap diode.

• The oscillator signal is injected into the phase shifter circuit.

Phase shifter circuit

• This is a phase shifter having CR configuration.

This circuit produces two local signals having a 90° phase difference at 479.5 MHz and injects these signals

to the IQ mixer circuit.

AGC amplifier circuit

• An IF signal (480 MHz band) from the tuner stage is input to Pins 9 and 10.

This IF signal which is input to Pins 9 and 10 is amplified by the AGC amplifier and injected into the IQ mixer

circuit.

• The gain can be adjusted by applying the AGC voltage to Pin 8.

The applied AGC voltage ranges from 0 to 4 V, with the minimum gain at 0 V and the maximum gain at 4 V.

IQ mixer circuit

• This is a double-balance mixer-type circuit consisting of two mixer circuits.

• The IF signal amplified by the AGC amplifier is converted into a base band signal by the local signal.

Low-pass filter circuit

• This is a low-pass filter with a CR configuration.

• The cut-off frequency is set at 25 MHz (–3 dB point).

Output amplifier circuit

• The signal is converted to a base band signal by the I and Q mixer circuits, and the high-frequency

component is removed by the low-pass filter. This signal is then amplified by the output amplifier circuit and

output to Pin 2 as a Q signal. In the same way, the I signal is output to Pin 4.

• The output is low impedance.

—10—

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