IAM-91563 Applications
Information
Introduction
The IAM-91563 is a miniature
downconverter developed for use
in superheterodyne receivers for
commercial wireless applications
with RF bands from 800 MHz to
6 GHz. Operating from only
3 volts, the IAM-91563 is an
excellent choice for use in low
current applications such as:
1.9 GHz Personal Communication
Systems (PCS) & Personal Handy
System (PHS), 2 GHz Digital
European Cordless Telephone
(DECT), and 800 MHz cellular
telephones (e.g., GSM, NADC,
JDC). Combined with Hewlett-
Packard’s other RFICs and dis-
crete components housed in the
same ultra-miniature SOT-363
package, the IAM-91563 also
provides flexible, building-block
solutions for WLAN’s and wireless
datacomm such as PCMCIA RF
modems as well as many Indus-
trial, Scientific and Medical (ISM)
systems operating at 900 MHz,
2.5 GHz, and 5.8 GHz.
The IAM-91563 is a 3-port,
downconverting RFIC mixer of the
cascode (common source -
common gate) type that uses a low
level (-5 dBm) local oscillator (LO)
to convert an RF signal in the
800 MHz to 6 GHz range to an IF
between 50 and 700 MHz. The
basic mixing function takes place
in a cascode connected pair of
FETs as shown in Figure 17.
IF
LO
FET 2
The received RF signal is con-
nected to the gate of FET1 and the
LO is applied to the gate of FET2.
The purpose of FET2 is to vary the
transconductance of FET1 over a
highly nonlinear region at the rate
of the LO frequency. This pro-
duces the nonlinearity required
for frequency mixing to take
place. This type of mixer is also
known as a “transconductance
mixer.” The IF is taken from the
drain of FET2.
An advantage of the cascode type
of design is the inherent isolation
between the gates of the two
FETs which results in very good
LO-to-RF isolation. An integrated
buffer amplifier between the LO
input and the gate of FET2 not
only increases the LO-RF isolation
but also reduces the amount of LO
input power required by the
mixer.
The IAM-91563 uses an innovative
bias regulation circuit that realizes
several benefits to the designer.
First, the IAM-91563 operates with
a single, positive device voltage
from 1.5 to 5 volts with stable
performance over a wide tempera-
ture range. Second, a unique
feature of the IAM-91563 allows
the device current to be easily
increased by adding an external
resistor to boost device current
and increase linearity.
Using a minimum of external
components with a standard bias
of 3 volts/9 mA and LO power of
-5 dBm, the IAM-91563 mixer
achieves an RF to IF conversion
gain of 9 dB at 1.9 GHz with a
noise figure of 8.5 dB and an input
third order intercept point of
-6 dBm. LO-to-IF isolation is
greater than 35 dB. Setting the
bias for the higher linearity/higher
current mode (approximately
16 mA) along with an LO drive
7-140
level of -2 dBm will boost the
input IP
3
to approximately 0 dBm.
Test Circuit
The circuit shown in Figure 18 is
used for 100% RF and DC testing.
The test circuit is impedance
matched for an RF of 1890 MHz
and an IF of 250 MHz. The LO is
set at 1640 MHz and -5 dBm for
low side conversion. (High side
conversion with an LO of
2240 MHz would produce similar
performance.) The RF choke at
the IF port is used to provide DC
bias. Tests in this circuit are used
to guarantee the G
test
, NF
test
, and
Device Current (I
d
) parameters
shown in the table of Electrical
Specifications.
V
d
100 pF
(2)
0.5 pF
Z = 110
I=10.4 mm
RF
1890 MHz
220 nH
Z = 50
500 pF 68 nH
IF
250 MHz
91
Z = 50
LO
1640 MHz
4.7 pF
Figure 18. Test Circuit.
Specifications and
Statistical Parameters
Several categories of parameters
appear within this data sheet.
Parameters may be described with
values that are either “minimum
or maximum,” “typical,” or
“standard deviations.”
The values for parameters are
based on comprehensive product
characterization data, in which
automated measurements are
made on of a minimum of
500 parts taken from 3 non-
consecutive process lots of
semiconductor wafers. The data
derived from product character-
ization tends to be normally
distributed, e.g., fits the standard
“bell curve.”
Parameters considered to be the
most important to system perfor-
mance are bounded by
minimum
RF
FET 1
Figure17. CascodeFETMixer.
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
