Datasheet RF2485, RF2485PCBA Datasheet (RF Micro Devices)

5-55

5

MODULATORS AND

UPCONVERTERS

Preliminary

Product Description

Ordering Information

Typical Applications

Features

Functional Block Diagram

RF Micro Devices, Inc.
7625 Thorndike Road
Greensboro,NC 27409, USA

Tel [phone]

Fax [phone]

http://www.rfmd.com

Optimum Technology Matching® Applied

Si BJT GaAs MESFETGaAs HBT
Si Bi-CMOS

ü

SiGe HBT

Si CMOS

1

2

3

4

5

6

7

14

13

12

11

10

9

8

VDD2

VDD1

NC

ISIG

IREF

QREF

QSIG

RF OUT

GND2

GND

GND

GND1

PHASE

LO IN

POWER

CONTROL

Σ

+45°

-45°

RF2485

VHF QUADRATURE MODULATOR

• Digital and Spread-Spectrum Systems

• GMSK, QPSK, DQPSK, QAM Modulation

• Private Mobile Radio and TETRA systems

• AM, SSB, DSB Modulation

• Image-Reject Upconverters

The RF2485 is a monolithic integrated universal modula­tion system capable of generating m odulated AM, PM, or
compound carriers in the VHF and UHF frequency range.
The IC contains all of the required components to imple­ment the modulation function including differential amplifi­ers 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
50 Ω load. Component matching, which can only be
accomplished with monolithic construction, is used to full
advantageto obtain excellent amplitude balance and high
phase accuracy. The unit features low power consump­tion, single power supply operation and adjustment free
operation with no external parts required to operate the
part as specified.

• Single 5V Power Supply

•LowPower

• Excellent Amplitude and Phase Balance

• Extremely Low Broadband Noise Floor

• 200MHz to 600MHz Operation

RF2485 VHF Quadrature Modulator
RF2485 PCBA Fully Assembled Evaluation Board

5

Rev A3 010820

0.156

0.148

0

.

0

5

9

0

.

0

5

7

0

.

2

5

2

0

.

2

3

6

0

.

0

1

0

0

.

0

0

4

.

0

1

8

.

0

1

4

8° MAX

0° MIN

0.0500

0.0164

0.010

0.007

0.347

0.339

0.050

Package Style: SOIC-14

Preliminary

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RF2485

Rev A3 010820

5

MODULATORS AND

UPCONVERTERS

Absolute Maximum Ratings

Parameter Rating Unit

Supply Voltage -0.5 to +7.5 V

DC

Input LO and RF Levels +10 dBm
Operating Ambient Temperature -40 to +85 °C
Storage Temperature -40 to +150 °C

Parameter

Specification

Unit Condition

Min. Typ. Max.

LO Input

T= 25°C, VDD=5VDC, I&Q inputs=2V

PP

Frequency Range 200 600 MHz
Power Level -3 +6 dBm
Input VSWR 1.2:1 With external 50Ω termination; see applica-

tion schematic, note A.

Modulation Input

Frequency Range DC 100 MHz
Reference Voltage (V

REF

)2.0 3.0V

Modulation (I&Q) V

REF

±0.7 V I & Q signals for -0.5dBm output power.

Modulation (I&Q) V

REF

±1.5 V I & Q signals for +5dBm output power.

Maximum Modulation (I&Q) V

REF

±2.5 V In-phase and quadrature signals.

Input Resistance 3000 Ω
DC Offset 50 150 mV I

SIG-IREF

and Q

SIG-QREF

; to achieve maxi-

mum carrier suppression.
Amplitude Error (I/Q) 0.2 dB
Quadrature P hase Error ±1 ±3 ° From 350MHz to 450MHz.

RF Output

VDD=5V, LO Power=0dBm,LO

Freq=400MHz, SSB, I& Q input=0.7V

P

Output Power -1.5 -0.5 dBm
Output Impedance 50 Ω
Output VSWR 1.5:1
Broadband Noise Floor -149 -147 dBm/Hz At 5MHz offset
Sideband Suppression 30 43 dB Unadjusted
Carrier Suppression 20 26 dB Modulation DC offset can be externally

adjusted for optimum suppression. Suppres-

sion is typically better than 25dB without

adjustment.
IM3 -40 -52 dBc

TETRA Modulation

Channel Power -3.0 -2.5 -2.0 dBm 1.7V

P-P

TETRA Modulation

LO, 450MHz@-5.0dBm, V

REF

2.5V

Adjacent Channel Power

Rejection

dBc VCC=5.0V

25kHz -47.0 -48.0 -49.0 dBc
50kHz -67.0 -68.5 -70.0 dBc

Power Supply

Voltage 5 V Specifications

4.5 5.5 V Operating Limits

Current 28 39 mA Operating

Caution! ESD sensitive device.

RF Micro Devices believesthe 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 responsibilityfor the use of the described product(s).

Preliminary

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RF2485

Rev A3 010820

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MODULATORS AND

UPCONVERTERS

Pin Function Description Interface Schematic

1VDD2

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.

2VDD1

Power supply for all other circuits. An external RF bypass capacitor is
needed.

3NC

No connection.

4ISIG

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 nee d 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.

5IREF

Reference voltage for the I mixer. This voltage should be the same as
the DC voltage supplied to the I SIG pin. To obtain a carrier suppres­sion of better than 40dB it may be tuned ±0.15V (relati ve to the I SIG
DC voltage). Without tuning, it will typically be better than 25dB.

See pin 4.

6QREF

Reference voltage for the Q mixer. This voltage should be the same as
the DC voltage supplied to the Q SIG pin. To obtain a carrier suppres­sion of better than 40dB it may be tuned ±0.15V (relati ve to the Q SIG
DC voltage). Without tuning, it will typically be better than 25dB. The
SIG a nd 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 cor­rect phase. It is also po ssible to drive the SIG and REF inputs in a bal­anced mode. This will increase the gain.

Same as pin 3.

7QSIG

Baseband input to the Q mixer. This pin is D C 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.

Same as pin 4.

8LOIN

The input of the phase shifting network. This high impedance input can
bematchedwithanexternal56Ω termination resi stor. 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.

9 PHASE

This pin allows to adjust the phase of the I/Q signals. However, the con­trol is very sensitive and hard to control. C ontrol 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 recom­mended 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.

10 GND1

Ground connection of the LO phase shift network. This pin sho uld be
connected directly to the ground plane.

11 GND

Ground connection for other circuits. Keep traces short and connect to
ground plane immediately.

12 GND

Same as pin 11.

13 GND2

Ground connection for the RF output stage. A good ground connection
is especially important at this pin to avoid interference with other cir­cuits.

ISIGIREF

LO IN

P

HASE

Preliminary

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RF2485

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5

MODULATORS AND

UPCONVERTERS

Pin Function Description Interface Schematic

14 RF OUT

50Ω output. This pin carries a DC voltage, and an external blocking
capacitor is recommended.

RF OUT

Preliminary

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RF2485

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MODULATORS AND

UPCONVERTERS

Application Schematic

POWER

CONTROL

Σ

+45°

-45°

RF OUTPUT

LO INPUT

V

DD

I INPUT
Z

IN

=100

V

REF

Q INPUT
Z

IN

=100

50 Ωµstrip

Coupling Capacitor

Coupling Capacitor

100 Ω

100 Ω

100 Ω

100 Ω

100 pF

100 nF

56 Ω

Note A

100 pF

100 pF

50 Ωµstrip

Optional; input impedance is about 79-J158 Ω at 400 MHz
without resistor. SMD resistor mounted adjacent to package pin,
grounded through a via to the ground plane.

NOTE A:

1

2

3

4

5

6

7

14

13

12

11

10

9

8

NC

Preliminary

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RF2485

Rev A3 010820

5

MODULATORS AND

UPCONVERTERS

Evaluation Board Schema t ic

(Download Bill of Materials from www.rfmd.com.)

1

2

3

4

5

6

7

14

13

12

11

10

9

8

POWER

CONTROL

Σ

+45°

-45°

P1-1

C2

100 nFC133 pF

P1-3

C5

33 pF

R1

56 Ω

J2

QSIG

J3

LO IN

J4

RF OUT

50 Ωµstrip

J1

ISIG

50 Ωµstrip

C3

100 pF

50 Ωµstrip

C4

100 pF

50 Ωµstrip

P1-3 VREF

GND

P1-1 VDD

P1

1
2
3

CON3

2485400, Rev. -

Preliminary

5-61

RF2485

Rev A3 010820

5

MODULATORS AND

UPCONVERTERS

Evaluation Board Layout

Board Size 2.0” x 2.0”

Board Thickness 0.031”, Board Material FR-4

Preliminary

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RF2485

Rev A3 010820

5

MODULATORS AND

UPCONVERTERS