Application Note: High CSO Push-Pull CATV Amplifier

DESIGN
APPLICATION
NOTE
-- AN077
DESIGN
APPLICATION
NOTE
--- AN077
SBB-2089 High CSO Push-Pull CATV Amplifier
Abstract:
With the abundance of data and voice traffic being transmitted across standard cable and wireless pathways and the
ever increasing linearity requirements of CATV amplifiers, there is a great need for amplification that optimizes gain,
VSWR, efficiency and linearity. This application note demonstrates the use of two SBB-2089 amplifiers in a pushpull configuration to achieve excellent CSO/CTB/XMOD performance from 50-860 MHz.
Introduction:
Inherent in push-pull amplifiers is the distinct cancellation of second order harmonics and intermodulation products.
The low cost of RFMD amplifiers, coupled with their excellent linearity, makes them an easy choice
for use in high linearity CATV applications. Table 1 contains a summary of performance of the SBB-2089 push-pull
amplifier. Figures 2 and 3 illustrate the push-pull application circuit schematic and PCB layout. All measurements
in this application note were taken in a 75 Ohm system.
Symbol
Parameter
Freq.(MHz )
Min.
Typ.
Units
17.8
17.0
16.4
16.2
dB
G
Small Signal Gain
50
500
870
1000
IRL
Input Return Loss
500
100-870
15.0
ORL
Output Return Loss
500
100-870
16.0
C SO
Worst Case Over Band, 79 Ch., Flat, +34dBmV
70
dB c
CTB
Worst Case Over Band, 79 Ch., Flat, +34dBmV
73
dB c
XMOD
Worst Case Over Band, 79 Ch., Flat, +34dBmV
67
dB c
24.0
16.0
dB
dB
Table 1: Typical RF Performance: VS=5V, ID=180mA @ TL=+25°C, Push-Pull Config.
CTB/CSO/XMOD 34dBmV/Chan., 79 Chan., Flat
100
95
90
dBc
85
80
75
70
65
Xmod
CTB
CSO+
CSO-
60
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
Freq. (MHz)
The information provided herein is believed to be reliable at press time.RFMD assumes no responsibility for inaccuracies or omissions.RFMD assumes no responsibility for
the use of this information, and all such information shall be entirely at the user’s own risk. Prices and specifications are
subject to change without notice. No patent rights or licenses to any of the circuits described
herein are implied or granted to any thirdparty. RFMD does not authorize or warrant anyRFMD product for use in life-support devices and/or systems.
Copyright 2005 RFMD. All worldwide rights reserved.
303 S. Technology Ct., Broomfield, CO
Phone: (800) SMI-MMIC
1
http://www.RFMD.com
EAN-104613 Rev A
DESIGN APPLICATION NOTE -- AN077
SBB-2089 High CSO Push-Pull CATV Amplifier
Gain vs. Frequency
20
18
Gain (dB)
16
14
12
10
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950 1000
Frequency (MHz)
Return Loss (dB) vs. Frequency
0
-5
Return Loss (dB)
-10
-15
-20
-25
IRL
-30
ORL
-35
-40
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950 1000
Frequency (MHz)
303 S. Technology Ct., Broomfield, CO 80021
Phone: (800) SMI-MMIC
2
http://www.RFMD.com
EAN-104613 Rev A
DESIGN APPLICATION NOTE -- AN077
SBB-2089 High CSO Push-Pull CATV Amplifier
Vs = +5 V
1200 pF
1 uF
1200 nH
SBB2089
8200 pF
Macom
ETC1-1-13
Macom
ETC1-1-13
SBB2089
1200 nH
Vs = +5 V
1 uF
1200 pF
S
P
3
4
S
S
P
3
5
4
1
1
5
P
Figure 2: SBB-2089 Push-Pull Schematic
+
S
P
Figure 3: SBB-2089 Push-Pull PCB Layout
303 S. Technology Ct., Broomfield, CO 80021
Phone: (800) SMI-MMIC
3
http://www.RFMD.com
EAN-104613 Rev A

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