UPC2533GS Просмотр технического описания (PDF) - NEC => Renesas Technology

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UPC2533GS

AM TUNER FOR ELECTRONIC TUNING CAR RADIOS

NEC => Renesas Technology 

µPC2533

2.3 MIX2 Block

Fig. 2-3 MIX2 Block

From 10.7 MHz BPF

VCC

Note

Xtal

+

To IF amplifier

28

23 17 24

25

14 13

12 11 22

21

R211

Current control

circuit

R212

Bias

circuit

R210

Q201

Q202

Q205

Q206

Q204

Q203

Q208

Q207

Q203

OSC2

Buff2

Note

R209

R207

R208

To RF AGC circuit (Fig. 2-4)

From IF AGC (Fig. 2-6)

Note Output impedance and input impedance of Buff2 are 2 kΩ and 30 kΩ, respectively.

MIX2 (Q201 to Q208) is a DBM with a configuration similar to that of MIX1.

The major difference from the MIX1 is that MIX2 is equipped with a current control circuit for output and is controlled

by the AGC.

Input impedance of MIX2 is 330 Ω to match the 10.7 MHz ceramic filter. Output impedance of Buff2 is 2 kΩ to

match the 450 kHz ceramic filter.

IF signal input from pin 23 is also input to the detector of the RF AGC. The RF AGC is detected by both MIX1 and

MIX2 blocks.

The Buff1 and Buff2 ensure impedance matching between MIX1 and MIX2 outputs and each ceramic filter. As

a result, IFT design is not restricted by the need to match ceramic filter impedance. For turn ratio, etc., only conversion

gain need be taken input account, so it is easy to design.

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