Philips Semiconductors
Objective specification
Dual-band, CDMA/AMPS LNA
and downconverter mixers
SA9503
DESCRIPTION
The SA9503 is an integrated CDMA/AMPS low noise amplifier
(LNA) plus a downconverter, for both the 900 MHz Cellular band and
the 1.9 GHz PCS band. The LNA incorporates 5 settings of digitally
selected stepped gain in the Cellular band and in the PCS band.
One of the modes (high linearity mode) in each of the Cellular and
PCS bands, includes a high IP3 setting in order to meet the 1-tone
CDMA desensitization test. The gain, noise figure and IP3 for the
remaining 4 low current modes in the Cellular band, are designed in
order to have sufficient separation between the antenna power
levels at which the LNA gains are changed, based on multi-tone
interference levels. A 3 dB overlap is allowed in the antenna power
levels for the adjacent modes. Table 1 indicates a typical scenario.
The downconverter portion is based on our SA9502 and is designed
to meet all the stringent spurious rejections that are required in the
Cellular and PCS bands. There are three individual mixer blocks,
each optimized for high linearity with low power consumption for
operation in one of the following modes: 1900 MHz PCS CDMA,
800 MHz Cellular CDMA, or 800 MHz analog FM AMPS/TACS
modes.
The circuit has been designed in our advanced QUBiC3 BiCMOS
process with 30 GHz f
T
.
Downconverter typical performance
PARAMETER
Gain (dB)
Noise Figure (dB)
Input IP3 (dBm)
Current (mA)
(Tx) LO output
buffer off
Cellular FM
7.5
10
5
6.8
Cellular CDMA
11.5
9
3.5
13
PCS CDMA
12.5
9
4
16
•
Separate, selectable IF outputs to suit FM and CDMA bandwidths
•
Buffered Cellular and PCS LO inputs
•
Integrated frequency doubler for PCS mixer LO
•
Differential (Tx) LO output buffer (can be switched on or off)
•
Low voltage operation down to 2.7 volts
•
Mixers current consumption with (Tx) LO buffer on:
–
Cellular FM: 16.8 mA
–
Cellular CDMA: 23 mA
–
PCS: 26 mA
FEATURES
Versatile step gain LNA
•
Low standby current in sleep mode: <50
µA
•
BCC32++™ package
APPLICATIONS
•
Can meet single tone CDMA desensitization requirements
•
Can meet CDMA two tone interference requirements
•
Cellular
PARAMETER
Gain (dB)
Noise figure (dB)
Input IP3 (dBm)
Current (mA)
MODE
CEL_L
17
2
5.5
13.2
CEL_1
15.5
1.6
–2
4.9
CEL_2
9
1.9
–3.5
4.9
CEL_3
3
4.5
2
4.9
CEL_4
–4
11
15
3.7
•
800 MHz analog FM and CDMA digital receivers
•
1900 MHz PCS band CDMA digital receivers
•
Supports dual-band and triple-mode operation
•
Digital mobile communications equipment
•
Portable, low power radio equipment
•
PCS
PARAMETER
Gain (dB)
Noise figure (dB)
Input IP3 (dBm)
Current (mA)
MODE
PCS_L
15.2
2.5
4.5
13.3
PCS_1
14.3
2
1
5.9
PCS_2
8
2.5
–2
5.9
PCS_3
2
3.7
–1
5.9
PCS_4
–4.5
11.5
16
3.7
BCC32++ is a trademark of Fujitsu Microelectronics.
1999 Jul 29
2
Philips Semiconductors
Objective specification
Dual-band, CDMA/AMPS LNA
and downconverter mixers
SA9503
FUNCTIONAL DESCRIPTION
Mode selection
The SA9503 has several modes of operation for which the selection
logic is defined in Tables 2 and 3. Different mode selections require
different portions of the circuit to be active. Modes from unlisted
combinations of logic pins are not permitted. The LNA and
downconverter together can be programmed to operate in the PCS
or cellular bands using the PCS/CEL logic input pin, and in CDMA or
FM modes using the CDMA/FM logic input pin.
The LNA can be set to four different gain values and one special
high linearity setting. Thus, the LNA can be programmed into five
different modes with associated gain, noise figure, and input IP3,
using the S0, S1, and S2 control lines. The whole circuit (LNAs and
mixers) is powered down when control lines S0 = 1, S1 = 0, and
S2 = 0. It is also possible to independently switch off the LNAs and
keep the mixers on, as shown in Table 3.
Downconverter
The SA9503 has three mixers, one for Cellular FM, one for Cellular
CDMA, and one for PCS CDMA. Each one is individually optimized
for their specific requirements. The Cellular CDMA and FM mixers
have a common single-ended RF input.
The PCS mixer’s RF input port is differential, and requires an
external balun when used with a single-ended source. Both the PCS
and the Cellular mixer RF inputs should be AC coupled.
Local oscillator drive for the mixers is provided through pins
CEL LO_IN and/or PCS LO_IN. The local oscillator inputs are
single-ended, AC-coupled. The CEL LO_IN signal is internally
buffered to drive the following:
– (Tx) LO output buffer,
– cellular FM mixer,
– cellular CDMA mixer,
– PCS LO frequency doubler.
In the PCS mode, mixer LO drive can be either direct (PCS LO_IN)
or through the frequency doubler after CEL LO_IN. The mixer local
oscillator signal is made available externally via the (Tx) LO output
buffer for potential use elsewhere in the radio. For example, this
signal typically can be used with the transmitter circuitry. The
(Tx) LO output buffer can be powered down independently, using
the (Tx) LO_ENABLE logic input. The (Tx) LO output buffer has
open collector differential outputs which are internally biased to
V
CC
2 supply rail.
The PCS and Cellular CDMA mixers have open collector differential
IF outputs. The two IF outputs can either supply two separate IF
filters, or they can be connected together externally for use with one
common receive IF filter. The differential IF outputs must be biased
at the supply voltage through external inductors that may also be
part of the matching circuit to the SAW filter. The cellular band FM
mixer also has a differential open collector IF output.
LNA
External components can be used to match the LNA inputs, and if
required, the outputs, for the Cellular and PCS bands. The input and
output return loss of better than 10 dB can be achieved in all modes.
For Cellular band FM, only the CEL_1 mode is required for the LNA.
For CDMA, LNA modes CEL_1 and PCS_1 are used for normal
operation, as they have the highest gains and lowest noise figures.
For higher levels of multi-tone interference, other modes with lower
gains are to be used. The high linearity CEL_L and PCS_L modes
are used when there is a very strong adjacent channel interference,
while at the same time the mobile is transmitting close to its full
power. The high linearity is required in order to reduce the cross
modulation of the LNA from the mobile’s transmitter, in the presence
of strong adjacent channel interferer. The maximum transmitter
power leakage which can be tolerated at the LNA input is
approximately –30dBm to meet the single tone desensitization
requirements. The cross modulation power can be derived from:
Cellular band: (2
×
P
TX
+ P
JAMMER
– 8) dBm
PCS band:
(2
×
P
TX
+ P
JAMMER
– 10.5) dBm
The LNA requires less than one hundred microseconds to settle
when it changes from one mode to another. This is expected to have
insignificant impact on the CDMA frame error rate.
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GAIN, dB
16.5
9
3
MAXIMUM ANTENNA IN-BAND POWER, dBm
–95
–90.5
–86.7
MINIMUM ANTENNA IN-BAND POWER, dBm
< –104
–98.5
–93.5
–89.7
–3
> –79
1999 Jul 29
4
Table 1. Typical Cellular Mode LNA Gain Change Points for 2-tone CDMA Interference Test
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