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LT5528

5528f

90°

0°

LT5528

V-I

BALUN

VCC

5528 BD

GND

BBPI

BBMI

BBPQ

BBMQ

GND

The LT5528 consists of I and Q input differential voltage-

to-current converters, I and Q up-conversion mixers, an

RF output balun, an LO quadrature phase generator and

LO buffers.

VCC = 5V

BBPI

BBMI

GND

LOMI

LOPI

FROM

5528 F01

BALUN

VREF = 0.52V

R1B

Ω

R1A

Ω

12pF

R2A

Ω

R2B

Ω

12pF

LT5528

Figure 1. Simpliﬁed Circuit Schematic of the LT5528

(Only I-Half is Drawn)

External I and Q baseband signals are applied to the dif-

ferential baseband input pins, BBPI, BBMI, and BBPQ,

BBMQ. These voltage signals are converted to currents and

translated to RF frequency by means of double-balanced

up-converting mixers. The mixer outputs are combined

in an RF output balun, which also transforms the output

impedance to 50Ω. The center frequency of the resulting

RF signal is equal to the LO signal frequency. The LO input

drives a phase shifter which splits the LO signal into in-

phase and quadrature LO signals. These LO signals are then

applied to on-chip buffers which drive the up-conversion

mixers. Both the LO input and RF output are single-ended,

50Ω-matched and AC coupled.

Baseband Interface

The baseband inputs (BBPI, BBMI), (BBPQ, BBMQ) present

a differential input impedance of about 90Ω. At each of the

four baseband inputs, a ﬁrst-order low-pass ﬁlter using 20Ω

BLOCK DIAGRA

APPLICATIO S I FOR ATIO

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