MAX2452ISE 查看數據表（PDF） - Maxim Integrated

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MAX2452ISE

3V, Ultra-Low-Power Quadrature Modulator

Maxim Integrated 

3V, Ultra-Low-Power

Quadrature Modulator

I

DSP

PROCESSING

Q

0°

Σ

90°

÷8

MAX2452

Figure 2. Typical Application Block Diagram

UP CONVERTER

Applications Information

The MAX2452 quadrature modulator is designed to

upconvert I and Q baseband signals to IF frequencies

up to 80MHz. Figure 2 shows a typical application

block diagram, in which the MAX2452 is used for the

first upconversion in a dual-conversion transmitter.

Figure 3 shows an implementation of a resonant tank

circuit. The inductor, two capacitors, and a dual varac-

tor form the resonant circuit of the oscillator. The fre-

quency range of the oscillator shown in Figure 3 is

130MHz to 160MHz. The inductor is directly connected

across the local oscillator’s tank ports so that it will not

lock up the oscillator in a stable state during start-up.

The two 33pF capacitors increase the Q of the resonant

circuit and reduce the VCO gain. They can be changed

to meet individual applications requirements. The oscil-

lation frequency can be determined using the following

formula:

fo =

1

2π LEQ CEQ

where

CEQ =

1+

1

1+

2

C1 C2 CVAR

and

LEQ = L + LSTRAY

+ CSTRAY

CSTRAY, LSTRAY: parasitic capacitance and induc-

tance.

To alter the oscillation frequency range, change the

inductance, the capacitance, or both. Make sure the Q

of the resonant tank does not drop below 35.

Q = REQ

CEQ

LEQ

where REQ = 10kΩ (see Figure 1).

The oscillation frequency can be changed by altering

the control voltage, VCTRL.

TANK

TANK

C1 = 33pF

47k

L = 100nH

C2 = 33pF

1/2KV1410

10k

1/2KV1410

47k

0.1µF

VCTRL

Figure 3. Typical Resonant Tank Circuit

6 _______________________________________________________________________________________

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