Dual Linear Driver for Vector Modulators

Rev. V7

MADRCC0002

1

1

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1

Features

 Linearizes M/A-COM’s PIN Diode Vector

 Dual Channels Allow One Driver per Vector

Modulator

 Guaranteed Minimum Output Currents of 20 mA

 Operates with a Single Supply Voltage of +5V

 Low Quiescent Currents

 Single Control Voltage for Each Channel

 6 x 4 mm Chip Scale Package

 Test Boards with Vector Modulators are Available

 Tape and Reel Packaging Available

 PQFN Package

Description

M/A-COM's MADRCC0002 is a dual, break point

free driver that produces a logarithmic output current

suitable for linearizing PIN diode based vector

modulators. This driver, in conjunction with the

external components, as defined in Figure 1,

produces a linearized transfer function between the

input control voltage of the driver and the

attenuation / phase output of the vector modulator.

The

MADRCC0002

has

been

optimized

for

linearizing M/A-COM’s Vector Modulators (see Table

1), but will function well with most types of cathode

grounded vector modulators. The driver is packaged

in a 6 x 4 mm Chip Scale Package for commercial

SMT applications. A typical schematic for a dual

linearizer driving a vector modulator is shown in

Figure 1.

Ordering Information

Note: Reference Application Note M513 for reel size

information.

Circuit Description:

(Reference Figures 1, 2 and 3)

Note that this is a dual driver. Only the top circuit

will be described, because the bottom circuit is

identical. The input divider, R1 and the sum of R2

and R3, sets the overall transfer function of the cir-

cuit. To increase the transfer function, decrease the

Control Voltage and the value of R1. Temperature

compensation is a function of the temperature

coefficient of the thermistor, R3, and the ratio of R2

to R3, and can only be optimized once the transfer

function and linearity component values have been

established. Varying the value of R4 will optimize

the linearity of the VVA. One can achieve a more

linear transfer function by driving the attenuator

over a smaller portion of its dynamic range. Note

that when the vector modulators called out in Table

1 are driven with the dual linearizer, both amplitude

and phase are affected, which makes it hard to de-

fine linearity. The individual transfer function of

each voltage variable attenuator in the vector

modulator (See Figure 2 for the block diagram) is

linearized as a function of voltage. The two VVAs in

the block diagram are the quad hybrids that are

terminated by two PIN diodes. See Figure 3 for

the transfer function of the SA90-0001 vector

modulator (phase and attenuation vs. control volt-

ages).

Part Number

Package

MADRCC0002

Bulk Packaging

MADRCC0002TR

Tape & Reel (1K Reel)

MAMDCC0005-DC000

Test Board with Circuit per

Figure 1

(MAMDCC0005,

GSM Vector Modulator)

MAMDCC0002-DC000

Test Board with Circuit per

Figure 1

(MAMDCC0002,

PCS Vector Modulator)

SA90-0001-DC000

Test Board with Circuit per

Figure 1

(SA90-0001,

UMTS Vector Modulator