6
V
d
IF
250 MHz
500 pF
4.7 pF
68 nH
Z = 50 Z = 50
Z = 110
I=10.4 mm
0.5 pF
220 nH
100 pF
(2)
LO
1640 MHz
RF
1890 MHz
91
IAM-91563 Applications Information Introduction
The IAM-91563 is a miniature downconverter developed
for use in superheterodyne receivers for commercial wire-
less 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 Avago’s other RFICs and discrete
components housed in the same ultra-miniature SOT-363
package, the IAM-91563 also provides exible, building-
block solutions for WLAN’s and wireless datacomm such
as PCMCIA RF modems as well as many Industrial, Sci-
entic 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.
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 gure of 8.5 dB and an input third order inter-
cept 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 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 cir-
cuit are used to guarantee the G
test
, NF
test
, and Device Current
(I
d
) parameters shown in the table of Electrical Specications.
Figure 17. Cascode FET Mixer.
The received RF signal is connected 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 “transcon-
ductance mixer.” The IF is taken from the drain of FET2.
An advantage of the cascode type of design is the inher-
ent isolation between the gates of the two FETs which re-
sults in very good LO-to-RF isolation. An integrated buer
amplier 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 benets 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
temperature 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.
Figure 18. Test Circuit.
Specications 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 devia-
tions.”
The values for parameters are based on comprehensive
product characterization data, in which automated mea-
surements are made on of a minimum of 500 parts taken
from 3 non-consecutive process lots of semiconductor
wafers. The data derived from product characterization
tends to be normally distributed, e.g., ts the standard “bell
curve.”
Parameters considered to be the most important to system
performance are bounded by minimum or maximum val-
ues. For the IAM-91563, these parameters are: Conversion
Gain (G
test
), Noise Figure (NF
test
), and Device Current (I
d
). Each
of these guaranteed parameters is 100% tested.
Values for most of the parameters in the table of Electri-
cal Specications that are described by typical data are the
mathematical mean (µ), of the normal distribution taken
from the characterization data. For parameters where mea-
surements or mathematical averaging may not be practical,
such as the Typical Reection Coecients table or perfor-
mance curves, the data represents a nominal part taken
from the “center” of the characterization distribution. Typi-
cal values are intended to be used as a basis for electrical
design.
