AD6459 Datasheet, PDF (1/12 Pages) Analog Devices – GSM 3 V Receiver IF Subsystem

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FEATURES
Fully Compliant with Standard and Enhanced GSM
Specification
–11 dBm Input 1 dB Compression Point
0 dBm Input Third Order Intercept
10 dB SSB Noise Figure (50 ⍀)
DC-500 MHz RF and LO Bandwidths
Linear IF Amplifier
Linear-in-dB and Stable over Temperature
Voltage Gain Control
Quadrature Demodulator
On-Board Phase-Locked Quadrature Oscillator
Demodulates IFs from 5 MHz to 50 MHz
Low Power
8 mA at Midgain
2 ␮A Sleep Mode Operation
2.7 V to 5.5 V Operation
Interfaces to AD7013, AD7015 and AD6421 Baseband
Converters
20-Lead SSOP
GSM 3 V Receiver IF Subsystem
AD6459
FUNCTIONAL BLOCK DIAGRAM
LO
RF
GAIN
CONTROL
FREF
BPF
I
PLL
Q
AD6459
GENERAL DESCRIPTION
The AD6459 is a 3 V, low power receiver IF subsystem for
operation at input frequencies as high as 500 MHz and IFs
from 5 MHz up to 50 MHz. It is optimized for operation in
GSM, DCS1800 and PCS1900 receivers. It consists of a mixer,
an IF amplifier, I and Q demodulators, a phase-locked quadra-
ture oscillator, a precise AGC subsystem, and a biasing system
with external power-down.
The AD6459’s low noise, high intercept mixer is a doubly-
balanced Gilbert-Cell type. It has a nominal –11 dBm input-
referred 1 dB compression point and a 0 dBm input-referred
third-order intercept. The mixer section of the AD6459 also
includes a local oscillator (LO) preamplifier, which lowers the
required LO drive to –16 dBm.
The gain control input accepts an external gain-control voltage
input from an external AGC detector or a DAC. It provides an
80 dB gain range with 27 mV/dB gain scaling.
The I and Q demodulators provide in-phase and quadrature
baseband outputs to interface with Analog Devices’ AD7013
(IS54, TETRA, MSAT) AD7015 and AD6421 (GSM,
DCS1800, PCS1900) baseband converters. An on-board
quadrature VCO that is externally phase-locked to the IF signal
drives the I and Q demodulators. This locked reference signal is
normally provided by an external VCTCXO under the control of
the radio’s digital processor. The AD6459 can also provide
demodulation of N-PSK and N-QAM in many non-TDMA
systems when used with external analog carrier recovery systems
such as the Costas Loop. Finally, the VCO can be phase-locked
to a frequency that is deliberately offset from the IF as in the
case of a Beat-Frequency oscillator (BFO) resulting in the
product detection of CW or SSB.
The AD6459 uses supply voltages from 2.7 V to 5.5 V over the
temperature range of –40°C to +85°C. Operation is enabled by a
CMOS logical level; response time is typically < 80 µs. When
disabled, the standby current is reduced to 2 µA.
The AD6459 comes in a 20-pin shrink small outline (SSOP)
surface mount package.
REV. 0
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© Analog Devices, Inc., 1996