Preliminary
5
Typical Applications
• Digital and Spread-Spectrum Systems
• GMSK, QPSK, DQPSK, QAM Modulation
• Private Mobile Radio and TETRA systems
• AM, SSB, DSB Modulation
• Image-Reject Upconverters
RF2485
VHF QUADRATURE MODULATOR
Product Description
The RF2485 is a monolithic integrated universal modula-
tion system capable of generating modulated AM, PM, or
compound carriers in the VHF and UHF frequency range.
The IC contains all of the required components to imple-
ment the modulation function including differential amplifi-
ers for the baseband inputs, a 90° hybrid phase splitter,
limiting LO amplifiers, two balanced mixers, a combining
amplifier, and an output RF amplifier which will drive a
50Ω load. Component matching, which can only be
accomplished with monolithic construction, is used to full
advantage to obtain excellent amplitude balance and high
phase accuracy. The unit features low power consump-
tion, single power supply operation and adjustment free
operation with no external parts required to operate the
part as specified.
Optimum Technology Matching® Applied
Si BJT
Si Bi-CMOS
GaAs HBT
SiGe HBT
Si CMOS
0.156
0.148
.018
.014
0.010
0.004
5
MODULATORS AND
0.347
0.339
0.050
0.252
0.236
0.059
0.057
8° MAX
0° MIN
0.0500
0.0164
0.010
0.007
ü
GaAs MESFET
Package Style: SOIC-14
Features
• Single 5V Power Supply
• Low Power
• Excellent Amplitude and Phase Balance
• Extremely Low Broadband Noise Floor
• 200MHz to 600MHz Operation
VDD2 1
VDD1 2
NC 3
I SIG 4
I REF 5
Q REF 6
Q SIG 7
POWER
CONTROL
14 RF OUT
13 GND2
12 GND
11 GND
10 GND1
+45°
-45°
Σ
9 PHASE
8 LO IN
Ordering Information
RF2485
RF2485 PCBA
VHF Quadrature Modulator
Fully Assembled Evaluation Board
Functional Block Diagram
RF Micro Devices, Inc.
7625 Thorndike Road
Greensboro, NC 27409, USA
Tel (336) 664 1233
Fax (336) 664 0454
http://www.rfmd.com
Rev A3 010820
5-55
RF2485
Absolute Maximum Ratings
Parameter
Supply Voltage
Input LO and RF Levels
Operating Ambient Temperature
Storage Temperature
Preliminary
Rating
-0.5 to +7.5
+10
-40 to +85
-40 to +150
Unit
V
DC
dBm
°C
°C
Caution!
ESD sensitive device.
RF Micro Devices believes the furnished information is correct and accurate
at the time of this printing. However, RF Micro Devices reserves the right to
make changes to its products without notice. RF Micro Devices does not
assume responsibility for the use of the described product(s).
Parameter
LO Input
Frequency Range
Power Level
Input VSWR
Specification
Min.
Typ.
Max.
200
-3
1.2:1
600
+6
Unit
MHz
dBm
Condition
T=25°C, V
DD
=5V
DC
, I&Q inputs=2V
PP
5
MODULATORS AND
UPCONVERTERS
With external 50Ω termination; see applica-
tion schematic, note A.
100
3.0
MHz
V
V
V
V
Ω
mV
dB
°
Modulation Input
Frequency Range
Reference Voltage (V
REF
)
Modulation (I&Q)
Modulation (I&Q)
Maximum Modulation (I&Q)
Input Resistance
DC Offset
Amplitude Error (I/Q)
Quadrature Phase Error
DC
2.0
V
REF
±0.7
V
REF
±1.5
V
REF
±2.5
3000
50
0.2
±1
I & Q signals for -0.5dBm output power.
I & Q signals for +5dBm output power.
In-phase and quadrature signals.
I
SIG
-I
REF
and Q
SIG
-Q
REF
; to achieve maxi-
mum carrier suppression.
From 350MHz to 450MHz.
V
DD
=5V, LO Power=0dBm, LO
Freq=400MHz, SSB, I&Q input=0.7V
P
150
±3
RF Output
Output Power
Output Impedance
Output VSWR
Broadband Noise Floor
Sideband Suppression
Carrier Suppression
-1.5
-0.5
50
1.5:1
-149
43
26
dBm
Ω
-147
dBm/Hz
dB
dB
30
20
At 5MHz offset
Unadjusted
Modulation DC offset can be externally
adjusted for optimum suppression. Suppres-
sion is typically better than 25dB without
adjustment.
IM3
-40
-3.0
-52
-2.5
-2.0
dBc
dBm
dBc
1.7V
P-P
TETRA Modulation
LO, 450MHz@ -5.0dBm, V
REF
2.5V
VCC=5.0V
TETRA Modulation
Channel Power
Adjacent Channel Power
Rejection
25kHz
50kHz
-47.0
-67.0
-48.0
-68.5
5
4.5
Current
28
5.5
39
-49.0
-70.0
dBc
dBc
V
V
mA
Specifications
Operating Limits
Operating
Power Supply
Voltage
5-56
Rev A3 010820
Preliminary
Pin
1
Function
VDD2
Description
Power supply for the RF Output amplifier. An external RF bypass
capacitor is needed. The trace length between the pin and the bypass
capacitor should be minimized. The ground side of the capacitor should
connect immediately to the ground plane.
Power supply for all other circuits. An external RF bypass capacitor is
needed.
No connection.
Baseband input to the I mixer. This pin is DC coupled. Maximum output
power is obtained when the input signal has a peak to peak amplitude
of 5V. The DC level supplied to this pin should be 2.5±0.5V. The SIG
and REF inputs are inputs of a differential amplifier. Therefore the REF
and SIG inputs are interchangeable. If swapping the I SIG and I REF
pins, the Q SIG and Q REF also need to be swapped to maintain the
correct phase. It is also possible to drive the SIG and REF inputs in a
balanced mode. This will increase the gain.
RF2485
Interface Schematic
2
3
4
VDD1
NC
I SIG
I REF
I SIG
5
5
I REF
Reference voltage for the I mixer. This voltage should be the same as
See pin 4.
the DC voltage supplied to the I SIG pin. To obtain a carrier suppres-
sion of better than 40dB it may be tuned ±0.15V (relative to the I SIG
DC voltage). Without tuning, it will typically be better than 25dB.
Reference voltage for the Q mixer. This voltage should be the same as Same as pin 3.
the DC voltage supplied to the Q SIG pin. To obtain a carrier suppres-
sion of better than 40dB it may be tuned ±0.15V (relative to the Q SIG
DC voltage). Without tuning, it will typically be better than 25dB. The
SIG and REF inputs are inputs of a differential amplifier. Therefore the
REF and SIG inputs are interchangeable. If swapping the I SIG and I
REF pins, Q SIG and Q REF also need to be swapped to maintain cor-
rect phase. It is also possible to drive the SIG and REF inputs in a bal-
anced mode. This will increase the gain.
Baseband input to the Q mixer. This pin is DC coupled. Maximum out- Same as pin 4.
put power is obtained when the input signal has a peak to peak ampli-
tude of 5V. The DC level supplied to this pin should be 2.5±0.5V.
The input of the phase shifting network. This high impedance input can
LO IN
be matched with an external 56Ω termination resistor. This pin is inter-
nally connected to ground through a 4kΩ resistor. Putting a DC voltage
on this pin is not recommended. However, connecting this pin to
ground, e.g., through a shunt inductor, is allowed.
MODULATORS AND
PHASE
6
Q REF
7
8
Q SIG
LO IN
9
PHASE
10
11
12
13
GND1
GND
GND
GND2
This pin allows to adjust the phase of the I/Q signals. However, the con-
trol is very sensitive and hard to control. Control voltage change for a
few degrees adjustment is in the order of 10mV. Device to device and
temperature variation are not characterized. Therefore it is not recom-
mended to use this pin; leave it not connected. Do NOT connect to
ground.For compensating large errors in the I/Q signals supplied to the
device or in control loops this pin may prove useful.
Ground connection of the LO phase shift network. This pin should be
connected directly to the ground plane.
Ground connection for other circuits. Keep traces short and connect to
ground plane immediately.
Same as pin 11.
Ground connection for the RF output stage. A good ground connection
is especially important at this pin to avoid interference with other cir-
cuits.
Rev A3 010820
5-57
京公网安备 11010802033920号
EEWORLD
