Download Application Note

AN RFMD® APPLICATION NOTE
Application Note
RFG1M09180, 865MHz to 895MHz, 48V, 400Wpk Doherty
Reference Design
Abstract
This application note is a reference point for an amplifier circuit design using RFMD’s RFG1M09180 in a
Symmetrical Doherty configuration using two RFG1M09180 devices. The frequency of operation is optimized
for the 869MHz to 895MHz frequency range. The operating drain voltage is 48VDC at an output power of
+50dBm, with >17dB gain, and >50% drain efficiency.
The RFG1M09180 is optimized for commercial infrastructure applications in the 700MHz to 1000MHz
frequency band, ideal for WCDMA and LTE applications. Using an advanced 48V high power density Gallium
Nitride (GaN) semiconductor process optimized for high peak to average ratio applications, these highperformance amplifiers achieve high efficiency and flat gain over a broad frequency range in a single amplifier
design. The RFG1M09180 is an input pre-matched GaN transistor packaged in an air cavity ceramic package,
which provides excellent thermal stability. Ease of integration is accomplished through the incorporation of
simple optimized matching networks external to the package that provide wideband gain, efficiency, and
linearizable performance in a single amplifier.
Introduction
The reference design circuit described in this document was designed to achieve a maximum back-off
efficiency and linearity through trade-offs between output power, gain, distortion, and efficiency. All
recommended components are standard values available from well-known manufacturers. Components
specified in the bill of materials (BOM) have known parasitics, which may affect the circuit’s performance.
Deviating from the recommended BOM or design layout may result in a performance shift due to different
parasitics, line impedances, and line lengths. Component placement, line impedances, and line lengths are
critical to each circuit’s performance.
Circuit Details
The circuit recommended for this application note was designed using the following PCB material:
• Material: Taconic, RF-60A
• Core thickness: 0.025 inch
• Copper cladding: 1.0oz with plating
• Dielectric constant: 6.15 at 10GHz
• Dissipation Factor: 0.0038 at 10GHz
http://www.taconic-add.com/en--index.php
http://www.taconic-add.com/pdf/rf60a.pdf
A 0.25” thick copper plate interface was used between device flange and aluminum heat sink.
Aluminum heat sink is Cool Innovations dense pin configuration #3-505017R
http://www.coolinnovations.com/
http://www.coolinnovations.com/includes/pdf/heatsinks/3-5050XXR.pdf
RF MICRO DEVICES® and RFMD® are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks, and registered trademarks are the property of their respective owners. ©2013, RF Micro Devices, Inc.
AN130410
7628 Thorndike Road, Greensboro, NC 27409-9421 – For sales or technical
Support, contact RFMD at (+1) 336-678-5570 or [email protected]
1 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Design Background
B
Information
As system
ms move to complex modulations, am
mplifier design
ns are requirred to handle
e the peak power
requireme
ents in order to
t keep nonlinearity levels at a minimu
um. One tradiitional straighttforward meth
hod to
combat no
onlinearity is to design an
n amplifier us
sing the large
est power tra
ansistor availa
able. As the power
transistor size reaches a maximum, adding additio
onal transistorrs in parallel (in a balanced
d configuratio
on) will
increase the peak powe
er capability. The
T issue bec
comes average
e power (backk-off) efficienccy. Even thoug
gh the
balanced amplifier is de
esigned and tuned for peak
k power and e
efficiency, the
e efficiency at the average power
c
wavefforms is much
h less. The Do
oherty amplifie
er design imprroves the averrage power ba
ack-off
levels in complex
efficiency without a majo
or degradation
n in RF perform
mance.
erty amplifier transistors
t
are
e biased differrently from th
heir balanced amplifier coun
nterparts. Typ
pically,
The Dohe
balanced amplifiers
a
are biased equally, so they turrn on and ope
erate in unison
n. The Dohertty amplifier ha
as one
transistor that operates
s as the carrie
er (or main) amplifier and one or more
e transistors tthat operate a
as the
peaking amplifier.
a
For this
t
reference
e design, the carrier ampliffier transistor is biased in cclass AB, so it can
amplify the
e incoming sig
gnal under all levels of power. The peakin
ng amplifier iss biased in cla
ass C, thereforre, will
only amplify signals wh
hen they reach
h a large enough level (the
e peaks) to tu
urn on the gatte. Also, the d
design
w
the peaking amplifierr is “turned offf” incorporatess quarterwave
e lines
configuration of the carrrier amplifier while
hing structures
s effectively sh
hifting the load
d impedance tto a state thatt increases the
e efficiency at lower
and match
power leve
els. In a Dohe
erty amplifier, the
t efficiency and linearity ttrade-off can be shifted eassily by changin
ng the
amount off bias voltage applied
a
to the gate of the ca
arrier and peakking amplifier.
wing informattion describes
s the fundam
mental differe nces between traditional balanced am
mplifier
The follow
configuration and the Do
oherty configu
uration. Additio
onal informatio
on on Dohertyy amplifier dessign can be fou
und at
w.rfmd.com/cs//documents/C
CommDRunton
nPASymposium
m11.pdf
http://www
xplore.ieee.org/xpl/login.jsp?tp=&arnumber=5616135&
&url=http%3A%
%2F%2Fieeexxplore.ieee.org
g%2Fi
http://ieeex
el5%2F5606055%2F5614756%2F056
616135.pdf%3
3Farnumber%
%3D5616135
http://www
w.home.agilentt.com/upload/c
cmc_upload/A
All/7March2013
3Webcast.pdff?&cc=US&lc=
=eng
TRADITION
NAL AMPLIFIER:
Good for High
H
power op
peration
Both amplifier A1 and A2
A contribute equally
e
to POUTT
ciency versus POUT characte
eristics
Both have standard Effic
SYMMETRICAL DOHERTY
Y AMPLIFIER:
Good for 3 to 7dB Back--off operation
A1 and A2
2 operate independently whe
en needed
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
2 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
A1 operate
es most of the
e time - handle
es average sig
gnal
A2 operate
es only when peak power is
s needed
ed carrier pow
wer by 3dB
Load Modulation droppe
es the efficienc
cy enhanceme
ent point back
This move
Even more
e suitable for CDMA
C
type sig
gnals
ASYMMETR
RICAL DOHERT
TY AMPLIFIER:
Good for 7dB
7 to 10dB back-off operattion
Change th
he ratio of the carrier/peaking amplifier pow
wer
Equal pow
wer creates ma
aximum efficie
ency at -6dB
Size the ca
arrier amplifier smaller to efffectively move
e the maximum
m efficiency po
oint lower in average powerr,
suitable fo
or higher peak to average ra
atio signals
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
3 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Typical Performa
ance
RFG1M09180, 865
5MHz to 895MHz, 48V,, 400Wpk S
Symmetrical Doherty Re
eference De
esign
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
4 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Sc
chematic
RFG1M09180, 865
5MHz to 895MHz, 48V, 400Wpk S
Symmetrical Doherty Re
eference De
esign
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
5 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Bill of
o Materia
als
RFG1M09180, 865
5MHz to 895MHz, 48V, 400Wpk S
Symmetrical Doherty Re
eference De
esign
Component
Value
Manufaacturer
Part Num
mber
C1-C4
100pF
ATC
C
ATC800A1
101JT
C5-C6
8.2pF
ATC
C
ATC800A8
8R2CT
C7-C12
56pF
ATC
C
ATC100B5
560JT
C13-C14
6.8pF
ATC
C
ATC100B6
6R8CT
C15-C20
4.7F
Muraata
GRM55ER72A475KA01L
C21-C26
0.1F
Muraata
GRM32NR72A
A104KA01L
C27-C28
100F
Panassonic
ECE-V1HA1
101UP
C29-C30
330F
Panassonic
EEU-FC2A
A331
R1-R2
100
Panassonic
ERJ-1TYJ1
101U
R3-R4
10
Panassonic
ERJ-8GEYJJ100V
X1
90° Hybrid
H
Coupler
Anarren
XC0900LL-03S
Photo
RFG1M09180, 865
5MHz to 895MHz, 48V,, 400Wpk S
Symmetrical Doherty Re
eference De
esign
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
6 of 9
AN RFMD® APPLICATION NOTE
Parts Layout
RFG1M09180, 865MHz to 895MHz, 48V, 400Wpk Symmetrical Doherty Reference Design
RF MICRO DEVICES® and RFMD® are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks, and registered trademarks are the property of their respective owners. ©2013, RF Micro Devices, Inc.
AN130410
7628 Thorndike Road, Greensboro, NC 27409-9421 – For sales or technical
Support, contact RFMD at (+1) 336-678-5570 or [email protected]
7 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Thermal Managemen
nt
As with mo
ost power amp
plifiers, the circuit must have
e adequate the
ermal manage
ement in orderr to operate
effectively and reliably. Therefore,
T
an external fan and
a thermal co
ompound betw
ween flange off the device an
nd
a recommen
nded.
heat sink are
Mounting
g Instruction
ns
STEPS FOR
R MOUNTING A FLANGED DEV
VICE
1. Heat-sink
H
surface flatness control.
a. Surface finish = average deviation
d
of the mean
m
value of thee surface height.
b. Surface roughness (Ra) = 0.8m ( 0.03mills)
2. A clean interface surface
s
on both th
he heat-sink and flange.
f
3. Device
D
mounting holes
h
need to be clean
c
and flat (no
o burrs).
4. Apply
A
a “thin” and even layer of the
ermal compound to
t the surface of tthe flange.
5. Place
P
the device, “flange-side-down
“
n”, into the recesss of the PCB.
6. Attach
A
the device to the PBC/Heat-sink with the specified the screw aand washer assem
mbly.
(S
SS #4-40 X ¾ captive SHCS and RND
R
Shim-bearingg. .178”O.D. X .12
23” ID X .01” Thic k)
7. Use
U a Two Step torque sequence:
a. 1st step torque the screw
w and washer on each
e
side = 0.5kgg.cm.
b. 2nd step
p torque the screw
w and washer on each side = 6kg.ccm (+- 1kg.cm).
Caution: excessive torque
e may damage the
e flanged device.
8. Solder
S
the device leads to the PCB..
ustry standard is to
t use a Pb-free alloy
a
(typically SAC
C305; 96.5%Sn, 3
3%Ag, 0.5%Cu) with a liquidus
a. One indu
tempera
ature of 221°C.
b. Tempera
ature at the device lead interface should
s
be <400°C
C (750°F) for <10
0 seconds.
c.
Pre-tin th
he leads to reduce any effects of ‘ggold embrittlemennt’.
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
8 of 9
AN RFMD
D® APPLICA
ATION NOTE
E
Biasing instructions for
f the RFG1
1M09180 Syymmetrical D
Doherty
1.
2.
3.
4.
5.
6.
7.
8.
Connect
C
RF cables at RFIN and RFO
OUT
Connect
C
ground to
o the ground supp
ply terminal, and ensure
e
that both tthe VG and VD grrounds are also co
onnected to this gground
terminal
Apply
A
-6.5V to VG_
_PEAK
Apply
A
-5.5V to VG_
_CARRIER
Apply
A
48V to VG
In
ncrease VG_CARRIER until drain curren
nt reaches 600mA
A or desired bias point.
Turn
T
on the RF inp
put power
Readjust
R
VG_PEAK fo
or desired linearityy versus efficienccy
RF MICRO DEVICES
S® and RFMD® are trademarks of RFMD
D, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other tradee names, trademarks, and registered traademarks are the property of their resp
pective owners. ©2013, RF Micro Devicces, Inc.
AN13
30410
7628 Thorndike Road, Gree
ensboro, NC 27409
9-9421 – For sales oor technical
Supportt, contact RFMD at (+1) 336-678-5570 or [email protected]
9 of 9