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RF2483PCBA-41X
(Rev.:V2)

LOW NOISE DUAL-BAND QUADRATURE MODULATOR WITH AGC

RF Micro Devices 

RF2483

Pin Function Description

1

VCC3

Supply for RF output circuits.

Interface Schematic

VCC3

RF Output

Amplifier

2

VCC2

Supply for modulator and biasing circuits.

VCC2

Modulator and

VGA

VCC2

3

ISIG P

In phase I channel positive baseband input port. Best performance is

achieved when the ISIGP and ISIGN are driven differentially. The recom-

mended CW differential drive level (VISIGP-VISIGN) is 800mVP-P.

This input should be DC-biased at 1.2V±0.05V. The common-mode DC

coltage on the ISIGP and ISIGN input signals is used to bias the modulator.

In sleep mode an internal FET switch is opened, the input goes high imped-

ance and the modulator is de-biased. The input impedance is typically

5.5kΩ at low frequencies and at higher frequencies can be modeled as

V CC2

50Ω in series with 12pF to ground.

Phase or amplitude errors between the ISIGP and ISIGN signals may result

50 Ω

in the even order distortion of the modulation in the output spectrum.

DC offsets between the ISIGP and ISIGN signals will result in increased car-

rier leakage. Small DC offsets may be deliberately applied between the

12 pF

ISIGP/ISIGN and QSIGP/QSIGN inputs to cancel out LO leakage. The opti-

mum corrective DC offsets will change with mode, frequency and gain con-

trol.

Common-mode noise on the ISIGP and ISGN should be kept low as it may

degrade the noise performance of the modulator.

Phase offsets may be applied between the I and Q channels to improve the

sideband suppression performance.

4

ISIG N

In phase I channel negative baseband input port. See ISIGP.

V CC2

50 Ω

12 pF

5

ENABLE Enables power to the device.

CMOS input.

Logic 1 (1.4V to VCC)=Enabled.

Logic 0 (0V to 0.5V)=Powered Down.

V CC2

6

VCC1

Supply for the LO buffers and quadrature network.

The sideband suppression is a function of the VCC1 voltage. The inclusion VCC1

of R3 (39Ω) lowers the voltage on VCC1 by around 400mV and results an

improvement in sideband suppression but around a 0.2dB increase in

LO Quadrature

Generator and

noise at 20MHz offset.

Buffers

GND1

8 of 28

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

Rev A8 DS060203

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