Image-Reject Front End for Dual or Tri-Band GSM Applications
The RF212 device is available as a dual-band (EGSM900/DCS1800) front end or
as a tri-band (EGSM900/DCS1800/PCS1900) front end for Global System for
Mobile Communications (GSM) mobile telephony applications. Each device
integrates all the required front-end components after the frequency pre-select
filters. These components include the Low Noise Amplifiers (LNAs), the internal
image-reject filters, mixers, and a Local Oscillator (LO) amplifier.
The main advantage of the RF212 is its ability to provide a minimum of 35 dB of
image rejection for each band. The block diagrams of the devices are shown in
Figures 1 and 2. The device packages and pin configurations are shown in Figures
3 and 4.
Features
• Supports EGSM
• LNA and mixer for RF to IF conversion
• 12 dB or 20 dB switchable gain step
• Minimum 35 dB of image rejection
• No external post-LNA filters required
• Common Intermediate Frequency (IF) port for all
bands
• IF range from 350 MHz to 450 MHz
• High isolation LO input buffer
• Differential IF output
• High dynamic range with low current consumption
• Three-cell battery operation (2.7 to 3.6 V)
• 20-pin Exposed paddle, Thin Shrink Small Outline
Package (ETSSOP)
Applications
• Dual/tri-band digital cellular mobile telephony
(EGSM900/DCS1800, or
EGSM900/DCS1800/PCS1900)
LOIN
LNA900INIFout
LNA1800IN
control
Gain
Step
Sel
Sel
Figure 1. RF212 Dual-Band Device Block Diagram
Data Sheet
Proprietary Information and Specifications are Subject to ChangeMay 24, 2000
Both RF212 devices form front ends of a dual-band or a tri-band
super-heterodyne receiver. The RF212 dual-band device is
optimized for an EGSM900/DCS1800 design, while the RF212
tri-band device is suitable for EGSM900, DCS1800, and PCS
1900. Each frequency band has its own separate front-end
receiver path. Each receiver path contains an LNA, an imagereject filter, and a mixer. The IF and LO ports are common to all
frequency bands. The image rejection achievable by this frontend design without any additional external components is 35 dB
minimum for an IF of 400 MHz. Both devices operate over a
supply voltage range of 2.7 V to 3.6 V.
The RF212 dual-band device has one band selection pin
(BANDSEL1 on pin 14). When BANDSEL1 is set to logic “0,” the
EGSM900 receiver path is active. The LO frequency needs to
be higher than the RF input frequency (i.e., a high side injection
is used). When BANDSEL1 is set to logic “1,” the DCS1800
receiver path is active. The LO frequency needs to be less than
the RF input frequency (i.e., a low-side injection is used). With a
400 MHz IF, this arrangement allows a single, wide-range
Voltage Controlled Oscillator (VCO) to be used for each band of
operation.
Similarly, the RF212 tri-band device has two band selection pins
(BANDSEL1 and BANDSEL2, pins 14 and 15, respectively). The
EGSM900 path uses the high side injection for the LO, while
DCS1800 and PCS1900 paths use the low side injection. Tables
1 and 2 provide the frequency band selection settings for the
dual and tri-band devices, respectively.
All the LNAs have switchable gain. The gain mode is selectable
using the GAINSEL signal (pin 7). Low gain mode is selected by
driving the GAINSEL signal to a logic “1”; high gain mode is
selected by driving the signal to a logic “0.” Depending on the
need of the handset design on the gain distribution, the gain
step between the high gain and low gain modes can be set to
either a 12 dB step or a 20 dB step. This gain step is selectable
with the STEPSEL signal (pin 18).
Electrical and Mechanical Specifications________________
The RF212 signal pin assignments and functional pin
descriptions are found in Table 3 (dual-band) and Table 4 (triband). The absolute maximum ratings of the RF212 are
provided in Table 5, the operating conditions are specified in
Table 6, and electrical specifications are provided in Table 7.
Figure 3 shows the diagram for a typical application circuit using
the RF212 front end. Figure 4 provides the package dimensions
for both of the 20-pin ETSSOP devices.
ESD Sensitivity
The RF212 is a static-sensitive electronic device. Do not operate
or store near strong electrostatic fields. Take proper ESD
precautions.
2
May 24, 2000Proprietary Information and Specifications are Subject to Change
Conexant
100780D
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Image-Reject Front EndRF212
Table 1. RF212 Dual-Band Selection
BANDSEL1, pin 14Mode
0EGSM900
1DCS1800
Table 2. RF212 Tri-Band Selection
BANDSEL1, pin 14BANDSEL2, pin 15Mode
0
0
10DCS1800
11PCS1900
0
1
EGSM900
Table 3. RF212 Dual-Band Device Signal Description
Pin #NameDescriptionPin #NameDescription
1NCNo connect (recommend c onnecting to
ground)
2GNDGround12LOGNDLO input ground
3GNDGround13LOINLO input
4LNA900IN900 MHz LNA input14BANDSEL1Band select control
5VCCSupply15GNDGround
6VCCSupply16
7GAINSELLNA gain select17IFOUT+Mixer posi tive output
8LNA1800IN1800 MHz LNA input18STEPSELGain step select. STEPSEL= 0 selects a
9GNDGround19GNDGround
10ENADevice enable, active high20VCCSupply
11NCNo connect (recommend c onnecting to
IFOUT−
ground)
Mixer negative output
12 dB gain step; STEPSEL = 1 selec ts a
20 dB gain step
Table 4. RF212 Tri-Band Device Signal Description
Pin #NameDescriptionPin #NameDescription
1NCNo connect (recommend c onnecting to
2GNDGround12LOGNDLO input ground
3GNDGround13LOINLO input
4LNA900IN900 MHz LNA input14BANDSEL1Band select control 1
5VCCSupply15BANDSEL2Band select control 2
6VCCSupply16
7GAINSELLNA gain select17IFOUT+Mixer posi tive output
8LNA1800IN1800 MHz LNA input18STEPSELGain step select. STEPSEL= 0 selects a
9LNA1900IN1900 MHz LNA input19GNDGround
10ENADevice enable, active high20VCCSupply
100956A
ground)
Conexant – Preliminary
11NCNo connect (recommend c onnecting to
IFOUT−
ground)
Mixer negative output
12 dB gain step; STEPSEL = 1 selec ts a
20 dB gain step
May 18, 2000Proprietary Information and Specifications are Subject to Change
3
Page 4
RF212Image-Reject Front End
Table 5. Absolute Maximum Ratings
ParameterMinimumMaximumUnits
Storage Temperature
Supply Voltage (VCC)
Input Voltage Range
−40
−0.3
−0.3
+125°C
+3.6V
VccV
Table 6. RF212 Recommended Operating Conditions
ParameterMinTypicalMaxUnits
Supply Voltage2.73.03.6V
Operating Temperature
−30
+25+85
°C
Table 7. RF212 Electrical Specifications (1 of 3)
(TA = 25 °°°°C, Vcc = 2.7 V, f
IF
= 400 MHz, Plo = −−−−10 dBm)
ParameterSymbolTest ConditionMinTypicalMaxUnits
EGSM900 Mode
Supply current::
Enable mode
Sleep mode
RF Input frequency925960MHz
IF frequencyf
IF
LO to RF input isolation30dB
Input impedance50
Power gain (for 2 kΩ differ ential output impedance):
MAX
High gain mode
Low gain mode 1
Low gain mode 2
Gain step 1
Gain step 2
Temperature coefficient
G
MIN
G
MIN
G
STEP
G
STEP
G
TC
F
Gain variation ver sus frequency
Noise figure:
High gain
Low gain mode 1
Low gain mode 2
Noise figure degradati on with blocker:
High gain
Input 1 dB compression pointIP1
D
Input third order i ntercept pointIP3
Differential IF shunt output resistance2
Image rejection:
May 24, 2000Proprietary Information and Specifications are Subject to Change
100780D
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Image-Reject Front EndRF212
Table 7. RF212 Electrical Specifications (2 of 3)
(TA = 25 °°°°C, Vcc = 2.7 V, f
IF
= 400 MHz, Plo = −−−−10 dBm)
ParameterSymbolTest ConditionMinTypicalMaxUnits
DCS1800 Mode
Supply current:
Enable mode
Sleep mode
RF input frequency18051880MHz
IF frequency350400450MHz
LO to RF input isolation30dB
Input impedance50
Power gain (for 2 kΩ differ ential output impedance):
MAX
High gain mode
Low gain mode 1
Low gain mode 2
Gain step 1
Gain step 2
Temperature coefficient
G
MIN
G
MIN
G
STEP
G
STEP
G
TC
F
Gain variation ver sus frequency
Noise figure:
High gain
Low gain mode 1
Low gain mode 2
Noise figure degradati on with blocker:
High gain
Input 1 dB compression pointIP1
D
Input third order i ntercept pointIP3
Differential IF shunt output resistance2
Image rejection:
IF
= 400 MHz
f
IF
= 350 or 450 MHz
f
PCS1900 Mode (for tri-band devi ce only)
Supply current:
Enable mode
Sleep mode
RF input frequency19301990MHz
IF frequency350400450MHz
LO to RF input isolation30dB
Input impedance50
Power gain (for 2 kΩ differ ential output impedance):
MAX
High gain mode
Low gain mode 1
Low gain mode 2
Gain step 1
Gain step 2
Temperature coefficient
G
MIN
G
MIN
G
STEP
G
STEP
G
TC
F
Gain variation ver sus frequency
Noise figure:
High gain
Low gain mode 1
Low gain mode 2
Noise figure degradati on with blocker:
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