cxa3038n Sony Electronics, cxa3038n Datasheet - Page 10

• Manufacturer Part Number: cxa3038n
• Description: Iq Detection Ic For Digital Satellite Broadcast Tuner
• Manufacturer: Sony Electronics

Description of Operation
Oscillator circuit
• This is a differential amplification-type oscillator circuit, and it is oscillated by connecting an LC parallel
• The oscillator signal is injected into the phase shifter circuit.
Phase shifter circuit
• This is a phase shifter having CR configuration.
AGC amplifier circuit
• An IF signal (480 MHz band) from the tuner stage is input to Pins 9 and 10.
• The gain can be adjusted by applying the AGC voltage to Pin 8.
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
• The output is low impedance.
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.
This circuit produces two local signals having a 90° phase difference at 479.5 MHz and injects these signals
to the IQ mixer circuit.
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 applied AGC voltage ranges from 0 to 4 V, with the minimum gain at 0 V and the maximum gain at 4 V.
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.
—10—
(See the Electrical Characteristics Measurement Circuit.)
CXA3038N