AN11010
Single stage Ku band LNA using BFU730F
Rev. 1.0 — 11 January 2011
Application note
Document information
Info
Content
Keywords
Abstract
BFU730F, LNA, Ku band, LNB
The document provides circuit, layout, BOM and performance information
on Ku band LNA equipped with NXP’s BFU730F wide band transistor.
NXP Semiconductors
AN11010
Ku band LNA using BFU730F
Revision history
Rev
Date
1.0
20110111
Description
Initial document
Contact information
For additional information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN11010
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1.0 — 11 January 2011
2 of 20
NXP Semiconductors
AN11010
Ku band LNA using BFU730F
1. Introduction
BFU730F is a discrete HBT produced in NXP’s SiGeC QuBIC4x BiCmos process.
SiGeC is a normal silicon germanium process with the addition of Carbon in the base
layer of the NPN transistor. The presence of carbon in the base layer suppresses the
boron diffusion during wafer processing. This allows steeper and narrower SiGe HBT
base and a heavier doped base. As a result, lower base resistance, lower noise and
higher cut off frequency can be achieved.
2. Requirements for Ku band LNA
The typical application for a Ku band LNA consists of amplification stage in the MW
preamplifier chain of a satellite LNB.
The noise figure requirements for LNBs may vary from standard to standard, however
most of them will set a figure of:
NF
LNB
≤
1.2dB
BFU730F typical values for the minimum noise figure and maximum stable gain at Ku
band frequency of 12GHz and bias of 2V / 10mA are:
NFmin = 1.1dB and Gmax = 12.5dB
This recommends the device as an alternative solution to replace pHemts in Ku band
LNA applications.
IF the target spec for the BFU730F LNA noise and gain is:
NF= 1.4dB and Gain = 11.5dB
The LNB system performance is as it shows up in
Table 1:
Table 1.
BFU730F vs pHemt NF and Gain performance comparison
1 stage
NF/Gain (dB)
st
Preamplifier
2 stage
NF/Gain (dB)
nd
3 stage
NF/Gain (dB)
rd
Mixer stage
NF/Gain (dB)
LNB
NF/Gain (dB)
2 stage
pHemt
0.8 / 12
pHemt
0.8 / 12
pHemt
0.8 / 12
pHemt
1 / 12
BFU730F
1.4 / 11.5
pHemt
1 / 12
pHemt
1 / 12
BFU730F
1.4 / 11.5
N/U
N/U
pHemt
1 / 12
BFU730F
1.4 / 11.5
BFU730F
1.4 / 11.5
active
8/2
active
8/2
diode
12 / -12
diode
12 / -12
diode
12 / -12
0.93 / 26
0.97 / 25.5
0.88 / 24
0.88 / 23.5
0.91 / 23
3 stage
pHemt
0.8 / 12
pHemt
0.8 / 12
The performance of the stand-alone BFU730F amplifier is slightly worse compare to the
pHemt one, however in an LNB chain it gives almost no performance change when used
as LNA3, or minor acceptable degradation when used as LNA2.
AN11010
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1.0 — 11 January 2011
3 of 20
NXP Semiconductors
AN11010
Ku band LNA using BFU730F
3. Design
The Ku band LNA consists of one stage BFU730F amplifier. It is aimed to replace more
costly pHemt transistors in the second and / or third stage of the LNB preamplifier. These
stages have to compensate the higher noise of the following mixer stage, thus their gain
has to be as high as possible. The driving designs criteria for the LNA is the
maximization of its gain. Secondly the noise figure has to be as good as possible, with a
very small compromise on gain. Due to the gain criteria, the input and output match are
also optimized. Stability wise the LNA has to be unconditionally stable over very broad
frequency range. In terms of linearity, the system analysis does not impose stringent
requirements.
The design has been conducted using Agilent’s Advanced Design System (ADS). The
2D EM Momentum tool has been used to design the microwave section and the PCB.
The linear and harmonic balanced circuit tools have been used to simulate the gain,
noise, match, stability and linearity performances of the LNA.
3.1 BFU730F Ku LNA - ADS simulation circuit
Fig 1.
ADS simulation circuit for BFU730F Ku band LNA
AN11010
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1.0 — 11 January 2011
4 of 20
NXP Semiconductors
AN11010
Ku band LNA using BFU730F
3.2 BFU730F Ku LNA - ADS Gain and match simulation results
Fig 2.
ADS Gain and match simulation results for BFU730F Ku band LNA
3.3 BFU730F Ku LNA - ADS NF simulation results
Fig 3.
ADS Noise Figure simulation results for Ku band LNA
AN11010
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1.0 — 11 January 2011
5 of 20
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