QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1524A-A
200MHZ TO 6000MHZ QUADRATURE MODULATOR WITH ULTRAHIGH OIP3
1
LTC5588-1
DESCRIPTION
Demonstration circuit 1524A-A is a high linearity direct
quadrature modulator featuring the LTC
®
5588-1.
The LTC5588-1 is a direct conversion I/Q modulator
designed for high performance wireless applications. It
allows direct modulation of an RF signal using differen-
tial baseband I and Q signals. It supports LTE, GSM,
EDGE, TD-SCDMA, CDMA, CDMA2000, W-CDMA, Wi-
Max and other communication standards. It can also be
configured as an image reject upconverting mixer, by
applying 90°
phase-shifted signals to the I and Q inputs.
The LTC5588-1 accepts externally applied balanced I
and Q baseband input signals with a common-mode
voltage level of 0.5V. These voltage signals are con-
verted to currents and translated to RF frequency by
means of double-balanced upconverting mixers. The
mixer outputs are combined to single-ended through an
on-chip RF output balun, which also transforms the
output impedance to 50
Ω
for a wide RF frequency
range. A single-ended or differential LO input signal
drives a precision quadrature phase shifter followed by
LO buffers, which in-turn drive the upconverting mix-
ers.
The LTC5588-1 offers exceptional linearity performance.
An external voltage can be applied to the LINOPT pin to
further improve its output 3rd-order intercept. The
LTC5588-1’s supply voltage range is 3.15V to 3.45V,
and consumes about 303mA current.
Demonstration circuit 1524A-A is designed for evaluat-
ing the LTC5588-1 IC at RF frequencies from 700MHz
to 5GHz. With a few component changes, it can be eas-
ily optimized for evaluations at lower or higher frequen-
cies. Refer to “Application Note” section and the
LTC5588-1 data sheet for details.
Design files for this circuit board are available. Call
the LTC factory.
, LT, LTC, and LTM are registered trademarks of Linear Technology Corp.
All other trademarks are the property of their respective owners.
Table 1. Typical Demo Circuit Performance Summary
T
A
= 25°C; V
CC
= 3.3V, EN = 3.3V; BBPI, BBMI, BBPQ, BBMQ common-mode DC Voltage V
CMBB
= 0.5V
DC
, I and Q baseband input signal = 100kHz CW,
1V
P-P(DIFF)
each (two-tone I and Q baseband input signal are at 4.5MHz and 5.5MHz), I and Q 90° shifted, lower side-band selection; P
LOM
= 0dBm; f
RF
=
f
LO
– f
BB
, unless otherwise noted.
PARAMETER
CONDITIONS
TYPICAL PERFORMANCE
Supply Voltage
3.15V to 3.45V
Supply Current
I
CC1
+I
CC2
, EN = High
303mA
Sleep Current
I
CC1
+I
CC2
, EN = 0V
33µA
Baseband Bandwidth
-1dB Bandwidth, R
SOURCE
= 25
Ω
, Single-ended
430MHz
Baseband Input Current
Single-Ended
-136µA
Baseband Input Resistance
Single-Ended
-3k
Ω
Baseband DC Common-Mode Voltage Externally Applied
0.5V
Baseband Amplitude Swing
No Hard Clipping, Single-Ended
0.86V
P-P
LO Match Frequency Range
Standard Demo Board, S
11
< -10dB
600MHz to 6000MHz
RF Match Frequency Range
Standard Demo Board, S
22
< -10dB
700MHz to 5000MHz
