Applications Note No. 074
Silicon Discretes
A 35 dB Gain-Sloped LNB I.F. Amplifier for Direct Broadcast Satellite
Television Applications using the BGA430 & BGB540 Silicon MMICs
•
Gain = 32 – 37 dB from 950 – 2150 MHz (positive gain slope)
•
Low Power Consumption: 40mA at +5.0 Volts
•
Exceptionally low Noise Figure: less than 3 dB
•
Low Cost, Low Parts Count
•
High Reverse Isolation
•
•
Output Compression point: +1 dBm minimum
(May be increased with higher DC bias level)
Suitable for European, Asian & North American DBS
LNB I.F. Amplifier Chains for 950 – 1450 and 950 – 2150 MHz
1. Overview
describes using the BGA430 MMIC as a standalone DBS I.F. Amplifier block, and covers
design issues unique to BGA430. Section 6
addresses the question “why might one want a
positive gain slope I.F. Amplifier” and Section 7
gives measurement results on the complete
gain-sloped amplifier using both BGA430 &
BGB540.
Infineon’s BGA430 Broad Band High Gain
Low Noise Amplifier and BGB540 Active
Biased Transistor are shown in an
Intermediate-Frequency
(“I.F.”)
amplifier
application targeted for the I.F. chains of
European, Asian and North American DirectBroadcast Satellite (DBS) Low Noise Block
Amplifier / Downconverters (LNBs).
Table 1.
complete
Amplifier.
A summary of key performance parameters for
the complete LNB I.F. Amplifier is given in Table
1 to the right.
The reader is referred to
Appendix A on page 21 for complete electrical
data including minimum, maximum, mean value,
and standard deviation for the lot of Printed
Circuit Boards (PCBs) tested. Appendix B on
page 22 gives information on performance over
the –40 to +85 °C temperature range.
Conditions: Temperature=25°C, V=5.0 Volts, n=25 units,
ZS=ZL=50Ω, network analyzer source power = -40 dBm
Parameter
Input Return Loss, dB
Gain, dB
Reverse Isolation, dB
Output Return Loss, dB
Noise Figure, dB
Output P1dB, dBm
Input IP3, dBm
Section 2 of this applications note provides a
brief description of the BGA430 and BGB540
MMICs. Section 3 gives some general Direct
Broadcast Satellite system information, and is
included to provide a general background.
Section 4 provides details on the PC Board
used, including photos, a Bill of Material (BOM)
and a PCB cross-sectional diagram. Section 5
AN 074 Rev E
Typical performance for the
BGA430+BGB540
LNB
I.F.
Frequency, MHz
950
1450
2150
26.0
27.3
12.0
33.0
37.2
37.2
>50
>50
>50
13.7
13.4
13.1
2.4
2.4
2.6
+1.7
+4.9
+7.9
-20.8
-22.5
-18.9
Please note that the reference planes for all
measurement data shown in Table 1 are at the
PC board’s SMA RF connectors; e.g. no PCB
loss is extracted from the numbers given.
1 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
given in the BGB540 datasheet. For lower
operating currents, the value of RBIAS becomes
large, and therefore RBIAS in series with the
power supply voltage behaves as a near-ideal
constant-current source.
Otherwise, the
BGB540 is treated like a standard RF transistor,
with the normal procedures for impedance
matching, stability analysis, etc. being used.
2. Description of BGA430 and BGB540
The BGA430 is a three-stage, 50 ohm, internally
matched, unconditionally stable MMIC fabricated
in Infineon’s well-proven, consistent and costeffective 25 GHz transition frequency (fT) B6HF
bipolar process. The BGA430 only requires
three external elements – input / output DC
blocking capacitors, and a single decoupling
capacitor on the power supply pin. Depending
on
the
particular
LNB
performance
requirements, the BGA430 may be used as a
stand-alone I.F. amplifier block, or together with
the BGB540.
Figure 1. BGA430 Block Diagram and
Package (SOT363).
The BGB540 is an unmatched, active-biased RF
transistor produced in the 45 GHz fT B6Hfe
bipolar process. B6Hfe, derived from B6HF, is a
more advanced process with higher achievable
gains and lower noise figures. BGB540 uses an
internal current mirror for DC biasing. This
approach achieves some reduction in external
component count due to elimination of a number
of external DC bias circuit elements, while still
preserving the flexibility inherent in a fully
discrete transistor. The device bias current may
be adjusted via a single external resistor.
Furthermore, the internal current-mirror, being
located on the same chip as the RF transistor
cell, has excellent “thermal tracking” of the RF
transistor cell, providing for a more stable DC
operating point over temperature. The BGB540
preserves the cost-advantages of the simple 4pin industry-standard SOT343 package.
3
RFout
5
GND1
2
GND1
6
RFin
Bias
1
Vcc
BGA430 (B6HF) VMAX = 6.5 V, IMAX = 35 mA
Figure 2. BGB540 Block Diagram and
Package (SOT343).
Bias
Pin 4
C
Pin 3
BFP540
1/10 BFP540
Base
Pin 1
BGB 540 B6HFe
VCE MAX = 4.5 V
A block diagram and package drawing for the
BGA430 and BGB540 are given in Figures 1 &
2, respectively. Note that for the BGB540, the
emitter areas of the current-mirror transistor cell
and the RF transistor cell are in the ratio of 1:10.
To set DC bias current for the BGB540, one
injects a current into pin 4, and the current
drawn by the RF transistor cell is 10 times the
current injected into pin 4, by virtue of the
current-mirror principle. The simplest DC bias
configuration for BGB540 involves using just a
single resistor between the power supply and
pin 4 – no RF choke or decoupling capacitor is
required on pin 4. The value of this bias resistor
– referred to as “ RBIAS “ – required for a given
device current can be determined from curves
AN 074 Rev E
4
GND2
Emitter
Pin 2
IC MAX = 80 mA
3. General DBS System Information
A generic block diagram of a Direct Broadcast
Satellite Low Noise Block Amplifier /
Downconverter (LNB) is given in Figure 3 on
page 3. LNBs produced for the Direct Broadcast
Satellite consumer electronics market are
extraordinarily cost-sensitive, and cost issues
are usually the primary consideration in the LNB
design process.
A broadcast signal in the 12 GHz range is
transmitted from an orbiting satellite towards the
Earth’s surface. There are two orthogonal parts
2 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Various approaches and switching schemes are
employed in different LNB designs to enable the
end user(s) to select between channels riding on
either the horizontally or vertically polarized
signals. Each approach has its own unique cost
and performance trade-offs. Optimizing LNB
architectures
to
achieve
performance
requirements while continuously reducing cost
as new, higher-performance and lower cost
semiconductor devices become available is a
challenging task.
of the composite signal – a vertically polarized
component, and a horizontally polarized
component. The two polarizations enable more
efficient use of the available bandwidth and
power. (The isolation between “vertical” and
“horizontal” radio signals permits a greater
number of channels to be simultaneously
broadcast within the available bandwidth than
would otherwise be expected.) The satellite’s
transmitted signal is received by an earth-based
antenna like that shown in the photo on page 1.
The signal is focused by the parabolic “dish”
antenna onto a waveguide integrated into the
LNB.
The received signal travels a short
distance down the waveguide until reaching a
waveguide-to-microstripline
transition
that
carries the signal onto the LNB circuit board
assembly.
A further complication to the switching
requirements is added if one wishes to have a
“dual output LNB” – e.g. an LNB that can drive
two different set-top boxes and television sets
simultaneously, allowing each TV to display a
different channel. (“Quad output” LNBs are also
available). One possible switching scheme for a
“single output LNB” is shown in Figure 3. Note
that the vertical / horizontal switching is done at
the I.F. Amplifier block. The BGA430 and
BGB540 are shown in the shaded I.F. Amplifier
section.
The LNB must be able to receive channels on
both the vertically and horizontally polarized
signals – and one way to do this is to have
essentially two different receiver front-ends as
shown in Figure 3 below.
Figure 3. Generic Block Diagram, "Single Output" Direct
Broadcast Satellite Television Block Downconverter (DBS LNB)
Cascaded Gain: approximately 55 - 60 dB; Cascaded Noise Figure: approximately 1 dB
Approximate Gain, dB =>
10
12
-1.5
-10 to +8
-4
30 to 45
Approximate Noise Figure, dB =>
0.5
0.7
1.5
7 to 12
4
3 to 7
LNB
U.S., Japan, Korea,
Latin America
Horizontal
Polarization
11.45 - 12.75 GHz
(depending on region)
(Components in Shaded Area)
Mixer
(Passive or Active)
LNA
BPF
LNA
U.S., Japan, Korea,
Latin America:
in 10.5 - 11.25 GHz range
Europe
Europe:
10.6 GHz or
9.75 + 10.6 GHz
(dual DRO)
10.7 - 12.75 GHz
(Two L.O.'s required for
full coverage)
Vertical
Polarization
LNA
LNA
Audio + Video
to TV set
AN 074 Rev E
(Vert. / Hor.)
I.F. Amplifier
Local Oscillator
(DRO)
BPF
Switch
BPF
IF Amp
IF Amp
BGA430 + BGB540
Mixer
(Passive or Active)
"Set Top Box"
(Channel Selector,
Demodulator, etc.)
3 / 24
Intermediate Frequency ("I.F.")
950 - 1450 MHz (North America)
950 - 2150 MHz (Europe, Asia)
75 ohm Coaxial Cable
To Set-Top Box
(75 ohm system)
RG-6, RG-6/U
19-November-2002
Applications Note No. 074
Silicon Discretes
signal to the RF input signal. A poor noise figure
in the mixer stage, as well as high conversion
loss, places additional demands (and cost) on
both the LNA block up front, as well as the I.F.
amplifier which follows.
After the waveguide to microstrip transition, the
signals enter a PC Board assembly. The signal
is amplified in two or more low noise amplifier
(LNA) stages and then hits a band pass filter.
The LNAs provide enough gain to boost the
level of the received signal such that the overall
receiver noise figure is dominated by the LNA
block itself. The LNA stages must have enough
gain and a sufficiently low noise figure to
minimize the noise floor for the entire receive
chain. Achieving enough gain and a low enough
noise figure at 12 GHz is costly, and anything
that can reasonably be done to relax the
requirements on the LNA section will reduce
cost.
The down-converted I.F. signal undergoes
further band pass filtering and then is amplified
in the I.F. amplifier block. The I.F. amplifier is
the focus of this applications note, and is the
primary point of discussion regarding the
BGA430 and BGB540 Silicon MMICs. The I.F.
amplifier boosts the signal up to a reasonable
input level for the set top box. It is worth noting
that the system impedance in this area is 75
ohms, not 50 ohms, and that the coaxial cable
typically used (RG-6, RG-6/U or sometimes RG59) is very low cost, and has a relatively high
attenuation per unit length a the intermediate
frequency. Furthermore, the attenuation of the
cable increases with increasing frequency –
coaxial cable loss at 2150 MHz is higher than
cable loss at 950 MHz. Herein lies the reason
for designing an I.F. amplifier with a gain
slope that increases with increasing
frequency – this positive gain slope in the
I.F. amp will help to compensate out the
negative gain slope of the coaxial cable and
other RF front-end blocks.
The LNA is then followed by a band pass filter
(BPF) which provides for some rejection of out –
of-band signals and noise, as well as image
rejection. The amplified and filtered signal then
enters the mixer stage.
The types of simple, inexpensive mixers likely to
be used in an LNB will usually convert both the
desired input signal (12 GHz in this case) and an
undesired “image” frequency (10 GHz) to the
intermediate frequency (1 GHz for this example).
The band pass filter in front of the mixer stage
can attenuate any undesired signals or noise
present at the 10 GHz image frequency before it
hits the mixer stage, preventing the undesired
image from being down-converted on top of the
desired, down-converted 12 GHz input signal.
At present, most LNB manufacturers use one of
three main types of mixers:
4. Information on Printed Circuit Board
The PC board used in this applications note was
simulated within and generated from the
Eagleware GENESYS® [3] software package.
After simulations, CAD files required for PCB
fabrication, including Gerber 274X and Drill files,
were created within and output from GENESYS.
Photos of the PC board are provided in Figures
4, 5 and 6. A cross-sectional diagram is given
in Figure 7. A schematic diagram and a Bill Of
Material (BOM) for the complete BGA430 +
BGB540 I.F. Amplifier are given in Figures 8
and 9, respectively. The PC Board material
used is standard FR4. Note that each MMIC
may be tested individually; capacitor C3 (see
schematic) may be positioned to “steer” the RF
from the BGA430 output to the SMA connector
on the bottom of the PCB, or, C3 may be used
to link the track from this same RF connector to
the input of the BGB540. When testing the
1. GaAs FET used as a simple active mixer
2. GaAs FET with no DC bias applied ( “FET
resistive mixer”)
3. Schottky Diode based mixer
Some references for mixers are given in [1] and
[2] at the end of this applications note.
The FET active mixer will usually have
“conversion gain” while the FET resistive mixer
or Schottky diode mixers have “conversion loss”.
Conversion gain or loss is simply the ratio of the
amplitudes of the down-converted output I.F.
AN 074 Rev E
4 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
BGB540 stage alone, a zero-ohm “jumper”
needs to be used in place of R2. The total PCB
area consumed for the entire BGA430 +
BGB540 I.F. Amplifier is approximately 0.585 x
0.180 inch / 14.9 x 4.6 mm, or approximately 70
mm2.
The total component count, including
both Silicon MMICs, is 16. Note that PCB area
and component count may be reduced markedly
if the end user is able to satisfy his or her I.F.
amplifier requirements by using the BGA430 as
a stand-alone part. The next section describes
the BGA430 as a stand-alone I.F. amplifier.
Figure 6. Close-In Shot of PCB. BGA430 on
left, BGB540 on Right.
Figure 4. Top View of I.F. Amp PC Board.
Figure 7.
Cross-Section Diagram of I.F.
Amplifier Printed Circuit Board.
PCB CROSS SECTION
0.010 inch / 0.254 mm
THIS SPACING CRITICAL !
TOP LAYER
INTERNAL GROUND PLANE
0.031 inch / 0.787 mm ?
LAYER FOR MECHANICAL RIGIDITY OF PCB, THICKNESS HERE NOT
CRITICAL AS LONG AS TOTAL PCB THICKNESS DOES NOT EXCEED
0.045 INCH / 1.14 mm (SPECIFICATION FOR TOTAL PCB THICKNESS:
0.040 + 0.005 / - 0.005 INCH;
1.016 + 0.127 mm / - 0.127 mm )
BOTTOM LAYER
Figure 5. Bottom View of I.F. Amp PC Board
5. Using the BGA430 as a Stand-Alone I.F.
Amplifier Block
Provided that BGA430 gain magnitude, gain
curve and output power are adequate for the
user’s LNB system requirements, BGA430 may
be used as a very low-parts-count, low-cost
stand-alone LNB I.F. amplifier over the 950 –
2150 MHz range. Note that only 3 external
elements are typically required with BGA430:
1) an input DC blocking capacitor 2) an output
DC blocking capacitor 3) an RF bypass / RF
decoupling capacitor on the VCC pin (Pin 1).
Table 2 on page 8 summarizes the BGA430’s
typical performance and Figures 11 – 15 give
network analyzer screen shots of input / output
match, gain, and
(continued on page 7)
AN 074 Rev E
5 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 8. Schematic Diagram of Complete BGA430 + BGB540 LNB I.F. Amplifier
J3
+5.0 Volts
(Total Current Draw = 39.9 mA)
Black Rectangles = Microstriplines on PCB
(PCB Track or Trace)
22.9 mA
17.0 mA
15.45 mA
C6
22 pF
R6
30 ohms
1.55 mA
R1
300 ohms
C2
22 pF
L1
3.0 nH
R4
2K
(R Bias)
J1
RF Input
950 - 2150 MHz
Notes:
C1
22 pF
IC1
MMIC
BGA430
B6HF
R2
18 ohms
C3
22 pF
C4
1.5 pF
R3
300 ohms
High Pass Filter
Butterworth
fC (3 dB) = 1860 MHz
3 dB Pad
Purpose of Pad :
1) Gain Reduction (especially at lower end of band)
2) Provide good input termination for HPF
R5
43 ohms
L2
4.7 nH
C5
22 pF
J2
RF Output
IC2
MMIC
BGB540
B6HFe
Purpose of HPF :
Adjust overall gain
slope of cascade
1) Using C4 as both a DC block and as a Highpass Filter element enables the elimination of one capacitor
2) Bias current of Stage 2 (BGB540 MMIC) can be increased or decreased to vary overall output compression point
3) Stage 1 (BGA430) requires careful attention to proper grounding !
Figure 9. Bill Of Material (BOM) for Complete BGA430 + BGB540 LNB I.F. Amplifier
REFERENCE
DESIGNATOR
C1, C3, C5
C2, C6
C4
VALUE
22 pF
22 pF
1.5 pF
MANUFACTURER
VARIOUS
VARIOUS
VARIOUS
CASE SIZE
0402
0402
0402
L1
L2
3.0 nH
4.7 nH
MURATA LQP15M
MURATA LQP15M
0402
0402
R1, R3
R2
R4
300 OHMS
18 OHMS
2K
VARIOUS
VARIOUS
VARIOUS
0402
0402
0402
R5
43 OHMS
VARIOUS
0402
R6
30 OHMS
VARIOUS
0402
IC1
IC2
-
INFINEON TECHNOLOGIES
INFINEON TECHNOLOGIES
SOT363
SOT343
J1, J2
-
-
J3
-
JOHNSON 142-0701-841
AMP 5 PIN HEADER
MTA-100 SERIES
P/N 640456-5 OR
641215-5 (GOLD PLATING)
AN 074 Rev E
6 / 24
-
FUNCTION
DC BLOCK
RF BYPASS
DC BLOCK & HIGH PASS FILTER
FUNCTION
HIGH PASS FILTER FUNCTION
“RF CHOKE” / DC FEED FOR BGB540,
INFLUENCES BGB540 OUTPUT MATCH
FOR 3 dB ATTENUATOR PAD
FOR 3 dB ATTENUATOR PAD
RBIAS FOR IC2 (BGB540 MMIC) - SETS
DEVICE CURRENT)
RF STABILITY AND OUTPUT MATCH FOR
IC2 (BGB540)
DROP 5V SUPPLY TO ~ 4.5V. MAY BE
OMITTED IF MAXIUM RATINGS OF IC2
ARE NOT EXCEEDED.
BGA430 Si MMIC, B6HF PROCESS
BGB540 ACTIVE BIASED TRANSISTOR
MMIC, B6HFe PROCESS
RF INPUT / OUTPUT CONNECTOR
DC CONNECTOR
PINS 1, 2, 4, 5 = GROUND
PIN 3 = VCC
19-November-2002
Applications Note No. 074
Silicon Discretes
some I.F. amplifier designs, requiring only 3
external elements.
reverse isolation. Note that all of these results
are taken in a 50 ohm system, and that results in
a 75 ohm system will differ slightly.
Figure 10. BGA430 Mounting Position on PC
Board. Compare unpopulated (above) to
populated (below) PCB images.
Note
locations and number of ground vias near
BGA430 MMIC. Pin 1 (VCC) is pad at lower left.
Circuit Design Issues Relevant to BGA430:
1) proper device grounding !!
2) proper bypassing of the VCC pin !
The BGA430 is an extremely high gain device
(>30 dB @ 1 GHz) contained within a single
SMT package. As a result, casual or sloppy
PCB layout techniques which add undesired
parasitic inductance between BGA430 ground
leads and PCB ground plane will add enough
feedback to adversely alter the BGA430’s gain
and return loss. In cases of extremely poor
grounding, sufficient feedback will be present to
enable either gain “peaking” or even an
oscillation. In addition, the VCC pin (Pin 1) needs
to be bypassed with a capacitor that, with its
self-inductance
taken
into
account,
approximates a short-circuit in the 1 to 2 GHz
range. Generally a 0603 or 0402 case-size chip
capacitor in the range of 15 – 22 pF is sufficient.
A photo of a bare I.F. Amp PC board is shown in
Figure 10, with a close-in view of the BGA430
mounting area. Note that seven (7) ground vias
are provided for the BGA430 ground pins,
including three ground vias located immediately
underneath the device. Note the two ground
holes provided for the bypass capacitor C2
(22pF) on the BGA430 VCC pin, and the close
proximity of C2 to the VCC pin.
To summarize:
•
The user must avoid any additional parasitic
ground inductance between BGA430 ground
pins and PCB ground plane. A sufficient
number of ground vias need to be provided
and these vias should be placed as close to
the BGA430 as possible.
•
BGA430 VCC pin (Pin 1) must be bypassed
carefully, and the bypass capacitor used
must have its “cold” side well-grounded.
It needs to be pointed out that the BGA430 is
designed to operate at a nominal supply voltage
of +5 volts, with a current draw of approximately
23mA. However, if a higher output compression
point is desired, the BGA430 may be safely run
up to 6.5 volts, and maximum safe current is
35mA. If an adjustable output voltage regulator
If these two suggestions are carefully followed, a
low-cost, single device solution may be used for
AN 074 Rev E
7 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
is used in the LNB, and if a higher output power
is required of the BGA430 than is available at
the 5V, 23mA condition, the user has the option
of simply cranking up the BGA430 supply
voltage.
Table 2. Summary of stand-Alone BGA430
LNB I.F. Amplifier Performance.
Conditons: Temperature = 25°C, V = 5.0 Volts, PCB = Infineon
P/N 430-051802 Rev B, ZS=ZL=50 Ω, network analyzer source
power = -40 dBm.
Parameter
950
11.1
33.4
40.5
13.7
+3.2
Input Return Loss, dB
Gain, dB
Reverse Isolation, dB
Output Return Loss, dB
Output P1dB, dBm
Frequency, MHz
1450
12.2
33.2
42.5
13.4
+3.9
2150
12.4
27.8
46.1
13.1
+3.2
Figure 11. Stand-Alone BGA430 Amp, Input Return Loss.
CH1
S 11
log MAG
5 dB/
REF 0 dB
31 Jul 2002 00:56:05
2_:-12.193 dB
1 450.000 000 MHz
PRm
1_:-11.101 dB
950 MHz
Cor
3_:-12.448 dB
2.15 GHz
Del
Avg
16
Smo
2
1
3
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 12. Stand-Alone BGA430 Amp, Input Return Loss, Smith Chart.
Reference Plane = PCB Input SMA Connector.
CH1
S 11
1 U FS
31 Jul 2002 00:56:16
24.293
2.6664 nH
2_: 47.119
1 450.000 000 MHz
PRm
1_: 29.082
-7.2041
950 MHz
Cor
3_: 74.199
-17.477
2.15 GHz
Del
Avg
16
Smo
2
3
1
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
8 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 13. Stand-Alone BGA430 Amp, Forward Gain.
CH1
S 21
log MAG
5 dB/
REF 30 dB
31 Jul 2002 00:56:41
2_: 33.205 dB
1 450.000 000 MHz
PRm
Cor
Del
Avg
16
Smo
1_: 33.447 dB
950 MHz
SCALE
5 dB/div
3_: 27.765 dB
2.15 GHz
2
1
3
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 14. Stand-Alone BGA430 Amp, Output Return Loss.
CH1
S 22
log MAG
5 dB/
REF 0 dB
31 Jul 2002 00:57:27
2_:-9.5522 dB
1 450.000 000 MHz
PRm
Cor
Del
Avg
16
Smo
1_:-13.418 dB
950 MHz
SCALE
5 dB/div
3_:-9.7191 dB
2.15 GHz
2
3
1
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
9 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 15. Stand-Alone BGA430 Amp, Output Return Loss, Smith Chart.
Reference Plane = PCB Output SMA Connector.
CH1
S 22
1 U FS
31 Jul 2002 00:57:34
-37.225
2.9486 pF
2_: 58.355
1 450.000 000 MHz
PRm
1_: 38.189
14.771
950 MHz
Cor
3_: 25.271
-1.2881
2.15 GHz
Del
Avg
16
Smo
1
3
2
START 900.000 000 MHz
STOP 2 200.000 000 MHz
is a delta of approximately 4 dB in insertion loss
as we move from 950 to 2150 MHz.
6. Why a Positive Gain Slope LNB I.F.
Amplifier?
The question arises: why would one want an
I.F. amplifier with a positive gain slope? The
reader is referred to Figures 16 – 20 on pages
11 – 13. Two points are worth noting:
I.
The return loss of this 75 ohm cable
appears to be quite reasonable in a
50 ohm measurement system (partly
due to the cable’s insertion loss
characteristic)
II.
The insertion loss of the 15.2 meter
length of cable increases with
increasing frequency. (Figures 18 &
20.)
If an LNB I.F. Amplifier were made with a
positive gain slope, the net gain across the
I.F. bandwidth could be ‘flattened out’
somewhat, and the range of input power that
the set-top box demodulators need to work
over could be reduced. Furthermore, this
description of coaxial cable negative gain
slope only considers gain decrease with
increasing frequency or “gain roll-off” in the
cable itself. In all likelihood, the LNB’s 12
GHz LNA block and mixer stage will have a
gain roll-off of their own, further worsening
the overall net negative gain slope of the
entire LNB and coax cable assembly taken
together.
A 15 meter length of coaxial cable has a
negative gain slope of approximately 2 dB
across the 950 – 2150 MHz range.
An
additional 15 meter section of lower-cost coax
cable (RG-6) was attached via a “barrel”
connector to the first section, making a 30.4
meter cable run, which was then also tested.
For a 30.4 meter / 100 foot length of cable, there
AN 074 Rev E
Table 3 on page 13 summarizes coaxial cable
insertion loss and return loss for both 15.2 meter
and 30.4 meter cable runs. The next section
describes the complete BGA430 + BGB540 LNB
I.F. Amp with positive gain slope.
10 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 16. 15.2 meter / 50 foot section of commercial 75 ohm RG-6 coaxial cable being tested.
Note measurement system impedance is 50 ohms.
Figure 17. Return Loss of 15.2 meters / 50 foot section of 75 ohm RG-6 coaxial cable.
Measurement made in 50 ohm system.
CH1
S 11
log MAG
10 dB/
REF 0 dB
31 Jul 2002 10:11:55
2_:-19.567 dB
1 450.000 000 MHz
PRm
1_:-17.082 dB
950 MHz
Cor
3_:-14.909 dB
2.15 GHz
Del
Avg
8
Smo
2
3
1
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
11 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 18. Insertion loss of 15.2 meter / 50 foot section of 75 ohm RG-6 coax cable. Measurement
system impedance is 50 ohms. Gain slope for this section is approximately - 1.62 dB / GHz.
CH1
S 21
log MAG
1 dB/
REF -3 dB
31 Jul 2002 10:13:22
2_:-4.8872 dB
1 450.000 000 MHz
PRm
1_:-4.0789 dB
950 MHz
Cor
REFERENCE VALUE
-3 dB
Del
Avg
8
Smo
3_:-6.0191 dB
2.15 GHz
2
1
3
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 19. Return Loss of a 30.4 meter / 100 foot section of 75 ohm coaxial cable. Measurement
system impedance is 50 ohms.
CH1
S 11
log MAG
10 dB/
REF 0 dB
31 Jul 2002 10:32:52
2_:-19.192 dB
1 450.000 000 MHz
PRm
1_:-18.677 dB
950 MHz
Cor
3_:-15.959 dB
2.15 GHz
Del
Avg
8
Smo
2
3
1
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
12 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 20. Insertion loss of 30.4 meter / 100 foot section of 75 ohm coaxial cable. Measurement
system impedance is 50 ohms. Gain slope for this section is -3.55 dB / GHz.
CH1
S 21
log MAG
1 dB/
REF -9 dB
31 Jul 2002 10:33:48
2_:-11.134 dB
1 450.000 000 MHz
PRm
Cor
Del
Avg
8
Smo
1_:-9.281 dB
950 MHz
REFERENCE VALUE
-9 dB
3_:-13.537 dB
2.15 GHz
1
2
3
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Table 3. Return Loss & Insertion Loss vs.
Frequency, 15.2 m / 50 ft and 30.4 m / 100 ft
sections of 75 ohm coaxial cable.
Cable
Length
m / ft
Parameter
increases with increasing frequency) via use of a
simple, low-cost High Pass Filter (HPF) between
the BGA430 and BGB540 MMICs. The HPF
between the two MMICs has the effect of
reducing the overall amplifier gain below the
filter’s cutoff frequency, allowing one to achieve
a positive gain slope. Please refer to the
Schematic Diagram, Figure 8 on page 6. Shunt
inductor L1 and series capacitor C4 form a highpass filter with a 3 dB corner frequency near
1860 MHz. Computer simulation in Eagleware’s
GENESYS package, which includes filter
synthesis tools, permitted fast and easy design
optimization for the best overall amplifier gain
response. To give the reader an idea of the
interstage high pass filter’s shape, please refer
to Figure 21 on the next page. This is a plot of
simulated filter insertion loss and return loss
which was exported from GENESYS.
Frequency, MHz
950
1450
2150
15.2 / 50
Input Return Loss, dB
17.1
19.6
14.9
15.2 / 50
Insertion Loss, dB
-4.1
-4.9
-6.0
30.4 / 100
Input Return Loss, dB
18.7
19.2
16.0
30.4 / 100
Insertion Loss, dB
-9.3
-11.1
-13.5
7. Complete Gain-Sloped LNB I.F. Amplifier
with both BGA430 & BGB540 MMICs
The basic approach taken for the complete I.F.
Amp was to create a positive gain slope (gain
AN 074 Rev E
13 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 21. Simulated Return Loss and Insertion Loss for 2 – Element High Pass Filter. Note
insertion loss = 10.3 dB at 950 MHz.
30.4 meters / 100 feet of 75 ohm coaxial cable,
this combination was measured in a network
analyzer. Please refer to Figure 23 on page 16.
A plot of the resulting gain response of the
complete gain-sloped BGA430 + BGB540 I.F.
Amp driving 30 meters / 100 feet of coaxial
cable is given. When this I.F. Amp drives 30
meters of 75 ohm coax, the gain at 950 and
2150 MHz is virtually identical, with a 3 dB
‘hump’ or rise at mid band.
The entire amplifier with the high pass filter was
optimized in simulations.
A significant
improvement in I.F. amplifier gain slope was
achieved. Please refer to Figures 22 – 29 for
Return Loss, Gain and Reverse Isolation plots of
the complete BGA430 + BGB540 I.F. Amplifier,
with and without the I.F. Amp driving a 30 meter
length of coaxial cable.
For the complete I.F. Amplifier, there is a
difference of about 4 dB in gain between 950
and 2150 MHz, with a positive slope – and
that the 30.4 meter / 100 foot length of 75
ohm coaxial cable has about a 4 dB
difference in insertion loss between 950 and
2150 MHz, with a negative slope.
The use of a high pass filter to achieve a
positive gain slope does limit the available
output compression point at the lower end of the
frequency range (950 MHz). However, some of
the output power capability could be bought
back by running the BGA430 at a higher bias
voltage than 5.0 volts as is done here, since the
BGA430 can safely tolerate up to 6.5 volts.
To see the net gain response of the gain-sloped
BGA430 + BGB540 I.F. Amplifier together with
AN 074 Rev E
14 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 22. Gain of Complete Gain-Sloped BGA430 + BGB540 LNB I.F. Amplifier. Note positive
gain slope.
CH1
S 21
log MAG
2 dB/
REF 33 dB
29 Jul 2002 22:58:08
2_: 37.311 dB
1 450.000 000 MHz
PRm
1_: 33.091 dB
950 MHz
Cor
SCALE
2 dB/div
Del
Avg
8
Smo
3_: 37.271 dB
2.15 GHz
2
3
1
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Gain Plot for Figure 22 is taken between points 'A' and 'B'
BGA430 MMIC
BGB540 MMIC
B
A
High Pass Filter
Complete LNB I.F. Amp
AN 074 Rev E
15 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 23. Network Analyzer Screen Shot of Complete Gain-Sloped BGA430 + BGB540 LNB I.F.
Amplifier driving 30 meters / 100 feet of 75 ohm RG-6 Coaxial Cable. The resulting net gain at 950
and 2150 MHz are nearly equal in value, with net gain at 950 MHz = 23.6 dB, and net gain at 2150
MHz = 23.7 dB. The mid band “hump” in gain is approximately 3 dB. Before attaching the 30
meter length of cable to the output of the complete BGA430 + BGB540 I.F. Amplifier, the Amplifier
Gain was 33 dB at 950 MHz and 37 dB at 2150 MHz.
CH1
S 21
log MAG
2 dB/
REF 25 dB
31 Jul 2002 10:50:23
2_: 26.281 dB
1 450.000 000 MHz
PRm
Cor
Del
Avg
8
Smo
1_: 23.624 dB
950 MHz
SCALE
2 dB/div
3_: 23.653 dB
2.15 GHz
2
3
1
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Gain Plot for Figure 23 is taken between points 'A' and 'B'
BGA430 MMIC
BGB540 MMIC
B
A
High Pass Filter
Complete LNB I.F. Amp
30 m / 100 ft
75 ohm RG6 Coax Cable
AN 074 Rev E
16 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
range. Additional output power may be had
from the BGA430 by running it up to a maximum
of +6.5 volts. The exceptionally low noise figure
of the I.F. Amplifier presented – under 3 dB –
may help the LNB designer achieve additional
sensitivity margin for his or her product.
An advantage of either the stand-alone BGA430
or BGA430 + BGB540 I.F. Amp solution is the
exceptionally low noise figure provided. The
complete amplifier with the gain-sloping high
pass filter has a noise figure of well under 3 dB.
A plot of measured noise figure for one complete
unit may be viewed in Appendix C on page 23.
Depending on the gain and noise figure
performance of the LNB’s Low Noise Amplifier
and Mixer sections, the excellent noise figure of
the I.F. amplifier presented here could provide
additional design margin for receiver sensitivity,
and possibly enable the use of lower cost
approaches for the LNA and mixer stages.
The Applications Board shown in this
Applications Note is available from Infineon
Technologies.
References
[1] Mass, Stephen A.
“Microwave Mixers”,
Second Edition. Artech House, 1993. (General
reference is on mixers, including the use of
FETs as active or resistive mixers).
Conclusion
The BGA430 and BGB540 both provide a costeffective and flexible solution for today’s pricesensitive Direct Broadcast Satellite LNB I.F.
Amplifier designs. A simple, low-cost approach
was shown for achieving a positive gain slope in
a 950 – 2150 MHz I.F. Amplifier. The BGA430
used as a stand-alone I.F. Amplifier requires
only 3 external components, and the complete,
gain-sloped I.F. Amplifier using both BGA430
and BGB540 with an interstage high pass filter
allows the LNB designer to compensate for
overall LNB gain roll-off in the Intermediate
Frequency
range,
where
gain
roll-off
compensation is easier and less costly to
achieve than at the 12 GHz RF input frequency
[2] Mass, Stephen A. “The RF and Microwave
Design Cookbook”, First Edition, Artech House,
1998. ISBN 0890069735. Another reference on
mixers, including single-device FET mixers.
[3] Eagleware Corporation, 653 Pinnacle Court,
Norcross,
GA
30071
USA.
Tel:
+1.678.291.0995 http://www.eagleware.com
Eagleware software suite GENESYS Version 8
was used in all simulation, synthesis, and PC
board CAD file generation done for the circuit
described in this Applications Note.
Performance Plots of complete LNB I.F. Amplifier, and Appendixes A – C begin on the following page.
AN 074 Rev E
17 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 24. Input Return Loss of the complete BGA430 + BGB540 I.F. Amplifier. (No coaxial cable
is included).
CH1
S 11
log MAG
10 dB/
29 Jul 2002 22:57:29
2_:-22.315 dB
REF 0 dB
1 450.000 000 MHz
PRm
Cor
Del
Avg
8
Smo
1_:-26.688 dB
950 MHz
SCALE
10 dB/div
3_:-11.932 dB
2.15 GHz
3
2
1
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 25. Input Return Loss of the complete BGA430 + BGB540 I.F. Amplifier, Smith Chart.
Reference Plane = PC Board Input SMA RF Connector. (No coaxial cable is included).
CH1
S 11
1 U FS
29 Jul 2002 22:57:39
4.9746
546.02 pH
2_: 44.748
1 450.000 000 MHz
PRm
1_: 50.229
-4.5684
950 MHz
Cor
3_: 81.805
-10.59
2.15 GHz
Del
Avg
8
Smo
2
1
START 900.000 000 MHz
AN 074 Rev E
3
STOP 2 200.000 000 MHz
18 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 26. Forward Gain, complete BGA430 + BGB540 I.F. Amplifier.
included). Note positive gain slope.
CH1
S 21
log MAG
2 dB/
REF 33 dB
(No coaxial cable is
29 Jul 2002 22:58:08
2_: 37.311 dB
1 450.000 000 MHz
PRm
1_: 33.091 dB
950 MHz
Cor
SCALE
2 dB/div
Del
Avg
8
Smo
3_: 37.271 dB
2.15 GHz
2
3
1
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 27. Reverse Isolation, complete BGA430 + BGB540 I.F. Amplifier. (No coaxial cable is
included).
CH1
S 12
log MAG
10 dB/
REF 0 dB
29 Jul 2002 23:02:05
2_:-68.136 dB
1 450.000 000 MHz
PRm
1_:-65.945 dB
950 MHz
Cor
3_:-70.367 dB
2.15 GHz
Del
Avg
8
Smo
2
1
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
19 / 24
3
19-November-2002
Applications Note No. 074
Silicon Discretes
Figure 28. Output Return Loss, complete BGA430 + BGB540 I.F. Amplifier. (No coaxial cable is
included).
CH1
S 22
log MAG
10 dB/
REF 0 dB
29 Jul 2002 23:02:26
2_:-13.168 dB
1 450.000 000 MHz
PRm
1_:-13.136 dB
950 MHz
Cor
SCALE
10 dB/div
Del
Avg
8
Smo
3_:-12.844 dB
2.15 GHz
2
3
1
START 900.000 000 MHz
STOP 2 200.000 000 MHz
Figure 29. Output Return Loss, complete BGA430 + BGB540 I.F. Amplifier, Smith Chart.
Reference Plane = PC Board Output SMA RF Connector. (No coaxial cable is included).
CH1
S 22
1 U FS
29 Jul 2002 23:02:38
22.004
2.4152 nH
2_: 62.408
1 450.000 000 MHz
PRm
1_: 36.105
13.162
950 MHz
Cor
3_: 61.844
-23.063
2.15 GHz
Del
Avg
8
Smo
2
1
3
START 900.000 000 MHz
AN 074 Rev E
STOP 2 200.000 000 MHz
20 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Appendix A. Data on 25 LNB I.F. Amplifier Circuit Boards, 430-051802 Rev B, taken randomly
from a lot of 40 units. All data taken at room temperature (25°C).
dB[s11]2
Board
S/N
dB[s21]2
dB[s22]2
Noise Figure, dB
Output 1dB
Compression Point,
dBm
950
1450
2150
MHz
MHz
MHz
+1.5
+4.7
+7.7
+1.7
+4.7
+8.0
+1.9
+5.0
+8.1
+1.9
+4.9
+8.0
+1.7
+4.7
+7.9
+1.5
+6.8
+7.8
+1.6
+4.8
+7.9
+1.8
+5.0
+8.0
+1.7
+4.9
+8.2
+1.2
+4.2
+7.4
+1.6
+5.0
+7.9
+1.7
+4.9
+7.9
+2.0
+5.3
+8.2
+1.4
+4.5
+7.7
+1.7
+4.7
+7.8
+1.7
+4.8
+7.8
+2.9
+5.1
+7.7
+1.7
+4.8
+7.9
+1.7
+4.7
+7.8
+2.0
+5.1
+8.2
+1.6
+4.6
+7.9
+1.7
+4.8
+7.9
+1.6
+4.7
+7.9
+1.6
+4.6
+7.8
+2.0
+5.1
+8.2
Current
Consumption
mA
950
MHz
25.9
26.2
27.2
26.1
26.7
27.0
25.3
24.1
27.1
24.6
26.2
25.0
26.9
26.3
27.0
27.4
24.4
26.2
27.6
27.9
25.5
25.6
23.9
24.7
25.6
1450
MHz
18.4
31.9
30.8
25.8
22.5
28.1
22.5
38.1
29.1
30.2
29.4
33.4
22.9
25.3
24.4
25.9
28.1
32.6
27.5
23.7
32.4
23.0
19.5
33.1
23.0
2150
MHz
10.2
12.2
13.4
11.4
12.1
12.1
11.5
11.9
12.3
12.6
11.9
12.6
11.6
12.6
11.7
13.0
12.7
13.0
12.5
11.1
11.5
11.7
11.2
12.4
11.8
950
MHz
32.9
32.7
32.9
33.1
33.0
32.7
33.0
33.0
32.7
32.8
32.8
32.7
33.1
33.1
32.8
32.9
34.1
32.7
33.1
33.2
32.5
32.8
33.4
32.8
33.4
1450
MHz
37.6
36.8
37.0
37.4
37.2
36.9
37.4
37.2
36.7
36.9
36.8
36.7
37.5
37.5
37.2
37.1
38.2
36.7
37.2
37.7
36.8
37.2
37.8
36.9
37.7
2150
MHz
37.3
37.2
37.0
37.4
37.2
37.0
37.3
37.0
37.2
36.8
37.1
36.7
37.6
37.4
37.1
37.3
37.8
36.9
37.2
37.6
37.4
37.3
37.3
37.0
37.5
950
MHz
13.4
13.2
13.2
13.3
13.3
13.4
13.3
13.5
13.4
13.6
13.2
13.2
13.3
13.7
13.5
13.2
21.8
13.0
13.7
13.5
13.4
13.0
13.8
13.4
13.2
1450
MHz
13.2
13.2
12.9
12.8
13.1
13.3
12.8
13.6
13.2
13.4
12.9
12.7
13.3
13.7
13.2
12.8
19.8
12.7
13.5
13.5
13.4
12.9
13.5
13.2
13.3
2150
MHz
13.4
13.2
12.9
12.6
13.0
13.0
12.6
13.3
13.0
12.9
12.9
12.5
13.1
14.1
12.9
13.1
15.9
12.6
12.7
13.8
13.1
13.2
12.8
12.7
13.1
950
MHz
2.3
2.5
2.4
2.3
2.3
2.3
2.9
2.3
2.2
2.3
2.4
2.4
2.3
2.3
2.3
2.3
2.4
2.6
2.3
2.4
2.8
2.3
2.3
2.3
2.3
1450
MHz
2.3
2.5
2.4
2.3
2.4
2.4
3.1
2.4
2.3
2.4
2.4
2.4
2.3
2.4
2.3
2.4
2.4
2.7
2.4
2.4
3.0
2.3
2.3
2.4
2.3
2150
MHz
2.5
2.6
2.5
2.5
2.5
2.5
3.3
2.5
2.4
2.5
2.5
2.5
2.4
2.5
2.5
2.5
2.6
2.8
2.5
2.5
3.1
2.5
2.5
2.5
2.4
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
⇓
Min
23.9
18.4
10.2
32.5
36.7
36.7
13.0
12.7
12.5
2.2
2.3
2.4
+1.2
+4.2
+7.4
39.4
Max
27.9
38.1
13.4
34.1
38.2
37.8
21.8
19.8
15.9
2.8
3.1
3.3
+2.9
+6.8
+8.2
41.4
Mean
26.0
27.3
12.0
33.0
37.2
37.2
13.7
13.4
13.1
2.4
2.4
2.6
+1.7
+4.9
+7.9
40.5
Std.
Dev.
σn
1.11
4.75
0.69
0.32
0.39
0.25
1.67
1.33
0.67
0.16
0.20
0.20
0.30
0.45
0.18
0.45
001
002
003
004
007
009
010
011
012
013
014
015
016
017
019
022
023
027
028
029
031
033
036
037
038
40.0
40.3
40.8
41.0
40.8
39.9
40.7
40.5
40.9
39.4
40.2
40.7
41.4
39.7
40.4
40.5
40.6
40.6
40.3
40.4
40.0
40.7
40.6
40.1
41.2
Note: Population Standard Deviation is used (σn), not sample standard deviation (σn-1)
AN 074 Rev E
21 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Appendix B. Performance of LNB I.F. Amplifier over –40 to +85 °C Temperature Range.
Temperature Test, BGA430 + BGB540 LNB IF Amp, PCB=430-051802 Rev B, -40 to +85 C
Overall Impression:
Good stability of DC operating point over temperature for both BGA430 and BGB540. No
abnormal “peaking” or oscillatory behavior observed for BGA430 at –40 C. Input and Output
match does deteriorate to worse than 10 dB return loss in some cases (see yellow highlights) but
this issue could be remedied with component value tuning on PCB, etc.
Summary Of Data, Stand-Alone BGA430 (e.g. single – MMIC LNB IF Amp Solution)
dB[s11]2
dB[s21]2
dB[s12]2
dB[s22]2
-40 C
-40 C
-40 C
Frequency
MHz
950
1450
2150
12.1
9.4
8.5
33.3
33.5
29.3
>40
40
40
9.8
8.9
13.0
22.5
+25 C
+25 C
+25 C
950
1450
2150
17.7
19.2
12.5
32.7
32.5
27.9
>40
>40
>40
10.2
9.1
13.2
21.8
+85 C
+85 C
+85 C
950
1450
2150
16.7
17.8
11.5
32.2
31.5
26.6
>40
>40
>40
11.0
9.2
13.3
21.1
Temperature
Current,
mA
Summary Of Data, BGA430 + BGB540 --- Complete two MMIC IF Amp
dB[s11]2
dB[s21]2
dB[s12]2
dB[s22]2
-40 C
-40 C
-40 C
Frequency
MHz
950
1450
2150
25.2
14.0
7.5
33.7
37.8
38.8
>50
>50
>50
13.0
13.0
12.0
39.3
+25 C
+25 C
+25 C
950
1450
2150
21.8
29.9
13.6
32.3
36.4
37.2
>50
>50
≈46
13.6
13.7
12.4
38.5
+85 C
+85 C
+85 C
950
1450
2150
15.3
13.4
12.7
31.1
35.1
35.4
>50
>50
>50
14.3
15.7
11.9
37.7
Temperature
AN 074 Rev E
22 / 24
Current,
mA
19-November-2002
Applications Note No. 074
Silicon Discretes
Appendix C. Noise Figure Plot for Complete BGA430 + BGB540 LNB I.F. Amplifier.
AN 074 Rev E
23 / 24
19-November-2002
Applications Note No. 074
Silicon Discretes
Appendix D. Revision Log
Revision Level
Date
A
24-July-2002
Initial Release
B
14-November-2002
First Revision
C
15-November-2002
Description of Modification(s)
•
Addition of Temperature Test Data (Appendix B)
•
Revised System Block Diagram (Figure 3)
•
General text cleanup
•
Revised Schematic and Bill Of Materials
Second Revision
•
D
18-November-2002
Third Revision
•
E
19-November-2002
Text Cleanup
Fourth Revision
•
AN 074 Rev E
General text cleanup
Text Cleanup
24 / 24
19-November-2002