AN11024
SDARS active antenna 2nd stage LNA with BFU690, 2.33 GHz
Rev. 1 — 24 March 2011
Application note
Document information
Info
Keywords
Abstract
Content
LNA, 2.33 GHz, BFU690, SDARS
This application note provides circuit, layout, BOM and performance
information for 2.33GHz LNA equipped with NXP Semiconductors
BFU690 wideband transistor
NXP Semiconductors
AN11024
SDARS active antenna 2nd stage LNA with BFU690, 2.33 GHz
Revision history
Rev
v.1
Date
20110324
Description
initial version
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN11024
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1 — 24 March 2011
2 of 19
NXP Semiconductors
AN11024
SDARS active antenna 2nd stage LNA with BFU690, 2.33 GHz
1. Introduction
The BFU690 is a wideband Silicon Germanium Amplifier transistor intended for high
speed, low noise applications. It is designed to be used for LNA applications such as
GPS, satellite radio, cordless phone and wireless LAN. The BFU690 comes in a
SOT343F package providing 2 emitter pins for better grounding.
The BFU690 is ideal in all kind of applications where cost matters. It also gives the
designer flexibility in his design work.
The BFU690 SiGe low noise transistor is shown here in a Satellite Digital Audio Service
(SDARS) active antenna LNA application. It is intended for use as the 2nd stage in a
3 stage SIRIUS LNA chain.
NXP
BFU730
NXP
Bandpass Filter
BFU690
G = 15.3 dB
I
DC
= 30 mA
NF = 1.47 dB
P
1dB
= +13.9 dBm
NXP
BFU
019aab735
2320-2332.5 (SIRIUS, 3 stages)
Fig 1.
Overview of SDARS active antenna LNA
The 2.33 GHz LNA evaluation board (EVB) is designed to evaluate the performance of
the BFU690 transistor applied as the 2nd stage in a 3 stage SIRIUS LNA chain. In this
document, the application diagram, board layout, bill of material, and some typical results
are given.
The evaluation board is shown in
Figure 2
AN11024
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1 — 24 March 2011
3 of 19
NXP Semiconductors
AN11024
SDARS active antenna 2nd stage LNA with BFU690, 2.33 GHz
019aab736
Fig 2.
BFU690, 2.33 GHz LNA evaluation board
2. General description
The BFU690 is a NPN silicon germanium microwave transistor for high speed, low noise
applications in a plastic, 4-pin dual-emitter SOT343F package.
Table 1
shows a summary
of the transistor performance in terms of noise and gain.
Table 1.
BFU690 performance in terms of noise and gain measured at V
CE
= 2 V;
I
C
= 25 mA
Noise figure (dB)
1.13
1.51
BFU690 pinning information
Description
emitter
base
emitter
collector
1, 3
2
1
mbb159
Frequency (GHz)
1.5
2.4
Table 2.
Pin
1
2
3
4
Associated gain (dB)
19.5
15.7
Simplified outline
3
4
Graphic symbol
4
2
AN11024
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1 — 24 March 2011
4 of 19
NXP Semiconductors
AN11024
SDARS active antenna 2nd stage LNA with BFU690, 2.33 GHz
3. Application board
The BFU690 2.33GHz EVB simplifies the evaluation of the BFU690 wideband transistor,
for this frequency range. The EVB enables testing of the device performance and requires
no additional support circuitry. The board is fully assembled with the BFU690, including
input and output matching, to optimize the performance. The input match was a
compromise between the best noise figure and a low input return loss. The board is
mounted with signal input and output SMA connectors for connection to RF test
equipment:
3.1 Application circuit
The application diagram as supplied on the evaluation board is shown in
Figure 3.
V
CC
= 3.3 V
X3
R3
R1
C6
C4
R2
C5
C3
L3
C2
L2
RF out
X2
RF in
X1
L1
C1
BFU690
L4
019aab738
Fig 3.
Evaluation board circuit diagram
3.2 Board layout
Figure 2
shows the board layout with components.
AN11024
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 1 — 24 March 2011
5 of 19
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