K&L Microwave Filtering Modules for IMD Measurements over 4G-LTE Bands
September 12th, 2013
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Objectives • Typical IMD Levels and Applications
• Emission Monitoring Solutions – Measuring without Disrupting
• Low PIM Filtering Solutions - Building Blocks for Reducing Un-certainty of Measurement
High-Pass/Low-Pass Duplexer (HP/LP)
Band-Pass/Band-Stop Duplexer (BP/BS)
Duplexers (BP/BP, LP/BP)
Triplexers (BP/BP/BP)
Band-Reject Filters with Band-Extenders (BRF/BE)
• Build Your Own IMD Test Setups - Control your Dynamic Range
• The “Blockers” are everywhere: New Filtering Solutions …
The “Quadraplexer”: BRF/BP/BP
• “Triple Beat Test”- a Real Challenge
• The Road Map to a Complete and Customized Switched Test System
• Q/A
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Typical IMD Levels and Applications
IMD[dBc]
P[dBm]
IM[dBm]
IP3[dBm]
3rd
3rd
5th
5th
f1
f2
f
[dBm]
Tx Rx Rx
P[dBm] IM[dBm] IMD[dBc] Application
2x(+43) -113* 156 Base Station, PA,
Antenna:
“High-Power”
2x(+43) -118 161 Distributed Antenna
Systems (DAS)
2x(+26),
(+26)+(+16),
(+26)+(-16)
-140 166 Semi-con., Small Cell,
Chipsets, Switches,
Tunable Caps, IC, etc.:
“Low-Power”
2x(+43) -128 171 PIM Analyzers
•1dBm reduction in power carriers (f1 and f2) yields ~2.2dBm reduction in IM 3rd
IM 3rd = (2*f1-f2) and (2*f2-f1) IMD = P-IM For n=3: IP3 = P+IMD/2 “PIM” is IM created by a Passive Source
1n
IMDPIPn
Can you tell which measurement is tougher? Answer:
Only 10dBm difference!
150.426)(432.2113
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Spectrum Analyzer
SPDT
Carriers
Near Zone (LPF) Far Zone (HPF)
Notes: • Emission monitoring is also “Forward” IMD measurement • The HPF and BRF need to reject the carriers such that -60dBm
max. can travel to the spectrum analyzer • Avoid reflected waves back to the DUT or to the source • Low PIM 50Ω Termination (marked with a in this
presentation) is used only if the carriers are passing through • The SPDT is non-reflective, but not specified for PIM, since
carriers don’t travel through
Low PIM 50Ω Termination
Non-Reflective
Emission Monitoring Solutions: Near and Far Zones
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BP/BS Duplexer Applications
S11 “Matched” Band-Reject Filter
S11 “Matched” Band-Pass Filter Attenuator
Attenuator
FDD
TDD
Often used to increase the Dynamic Range of the S/A by attenuating the unwanted signal from mixing …
Often used to improve Impedance Match with the DUT, while drawing more power from the PA …
Traditional Setup
Improved Setup
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BP/BS Duplexer
A complete list of available Band-Pass/Band-Stop duplexers is available at the following link: http://www.klmicrowave.com/product_attach/1/_plk287_1_lowpimhp.pdf If your specific need is not covered here, contact K&L for a custom design.
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BP/BS Typical Data
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BP/BS Typical Data
The flatter the PIM response, the fewer the IMD sources.
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High-Pass/Low-Pass Duplexer
Applications: • Emission Monitoring • 2nd and 3rd Harmonic Tests from a Single Tone
Notes: • The LPF passes the fundamental carrier and rejects the Harmonics, preventing them
from entering the DUT • The HPF terminates Harmonics generated by the PA
DUT
Spectrum Analyzer
2fo, 3fo….
fo
fo
PA
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Low PIM High-Pass and Low-Pass Filters
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Typical Data (Two +43dBm Tones)
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Two Tones-Single Amp-IMD in Rx Band Setup #1a
Notes: • Signals are combined pre-amplification state. • Single amplifier produces two-tones and large IMD levels. • Isolator is an IMD source. • Tx filter is required of high rejection levels >-115dBc. Carriers are rejected back into the
isolator. • Rx filter is required to attenuate the carriers to <-60dBm, to reduce IM products inside the
Spectrum Analyzer. • Hard to obtain low IMD base line.
Applications: • Two Tones - 3rd IM “Reflected” and “Forward” in the Rx Band
DUT
Tx
Rx
Tx
Rx
Spectrum Analyzer
SPDT
Non-Reflective
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Two Tones-Single Amp-IMD in Rx Band Setup #1b
Notes:
• “Reflected Mode” only
• Difficult to obtain a base line
DUT
Tx
Rx
Spectrum Analyzer
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Two Tones-Two Amps-IMD in Rx Band Setup #2a
Notes: • Most popular; cheap, easy to assemble • Amplifiers seem to be isolated by roughly 50dB • Reflected TX1 and TX2 signals are travelling back to isolators, by nature ferromagnetic
devices • Secondary IM products are generated, due to reflections, which tends to raise the base line of
the setup • Tx filter must present at least 100dB rejection to the Rx band, preventing IM products from
the iso-coupler from travelling to the Spectrum Analyzer • Rx filter needs to present 100dB to Tx band, reducing +43dBm tones from mixing inside the
Spectrum Analyzer • Amplifiers need to present extra 3.5dB gain to compensate for the 3dB hybrid and isolators
DUT
Tx
Rx
Tx
Rx
Spectrum Analyzer
SPDT
Non-Reflective
TX1
TX2
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Notes:
• “Reflected Mode” only
Two Tones-Two Amps-IMD in Rx Band Setup #2b
DUT
Tx
Rx
Spectrum Analyzer
TX1
TX2
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Notes:
• Two narrow band filters substituted for the -3dB Hybrid
• The output duplexer covers the entire down-link and up-link bands
• Input duplexer must be of high quality (always), since it’s difficult to pinpoint IMD sources
IMD Test Setup #3
DUT
Spectrum Analyzer
Tx2
Tx1
Tx2
Tx
Rx
Tx1
Applications:
• Inter-Cell Interference in “Forward” mode
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Duplexers (BP/BP) – 100dB Tx-Rx & 161dBc PIM (Two +43dBm Tones)
A complete list of available Low PIM Band-Pass/Band-Pass Duplexers is available at the following link: http://www.klmicrowave.com/product_attach/2/_plk315_1_DASLowPIMds.pdf If your specific need is not covered here, contact K&L for a custom design.
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Notes: • IM test in “Reverse” and “Forward” mode • Base line is easy to maintain • All ports are tuned for -20dB return loss • Easy to maintain and debug problems
Two Signals-BP/BP/BP (Triplexer)-IMD Test Setup #4a
DUT
Spectrum Analyzer
Tx2
Tx1
Tx2
Rx
Tx1
Tx2
Rx
SPDT
Tx1
Non-Reflective
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Notes: • Amplifiers are isolated by 75dB • Rx filter presents 100dB in Tx band • Tx1 and Tx2 are relatively narrow (about 1/3 of down-link bandwidth), reducing the out-of-band
noise of the amplifiers • Tx2 can be dedicated to a “Blocker” signal • Triplexer can be self-tested - easy to maintain
Tx1
DUT
Spectrum Analyzer
Tx1
Tx2 Tx2
Rx
Two Signals-BP/BP/BP (Triplexer)-IMD Test Setup #4b
A complete list of available Low PIM Triplexers is available at the following link: http://www.klmicrowave.com/_upload/3GPPTriplexers.pdf If your specific need is not covered here, contact K&L for a custom design.
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Notes: • DUT is subjected to two signals, one from each port • Filtering the signals provides flow and avoids reflections, reducing possible IMD sources
DUT
Spectrum Analyzer
Tx2
Tx1
Tx2
Rx
Tx1
Tx2
Rx
SPDT
Tx1
Non-Reflective
Two Signals-Both Ports of DUT-IMD Test Setup #5
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Low PIM Triplexers (BP/BP/BP)
RX
f1 f2 f3 f4 f5 f6
75 dB
100 dB
1.5dB
TX1 TX2
• Triplexers can be self- tested
• Easy to maintain the base line
Tx1
Spectrum Analyzer
Tx1
Tx2 Tx2
Rx
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The “Blockers” are Everywhere! BRF/BPF/BPF
Notes: • Tx, Rx, and BRF are isolated by 75dB • All three filters are tuned for 20dB return loss to reduce uncertainty of measurement • BRF provides 20dB of match over all specified “Blockers”
Electrical Scheme Frequency Response
Tx
Rx
BRF Tx+Rx
(Quadraplexer)
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Extending the Passband of the Triplexer-“Reverse” IMD
The Quadraplexer:
• Enables all combinations of “Blockers” and Tx signals
Tx
Rx
BRF Tx+Rx
“Bloc-kers”
DUT
Tx
Spectrum Analyzer
SPDT
Non-Reflective
“Blocker” Signal Gen.
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LTE Band 2: Actual Data
Tx: 1850-1910MHz (1880MHz)
Rx: 1930-1990MHz (1960MHz)
Blockers: 80MHz, 1800MHz, 3800MHz, and 5800MHz
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LTE Band 2: Actual Data (continued)
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• Enables mixing the Tx signal with many “Blockers” through the BRF
• Limited only by the BRF upper-passband match
• Easy to maintain
Tx + “Blocker” IMD Test Data
Tx1 (+26dBm) @ 1855MHz Tx2 (+16dBm) @ 1775MHz 3rd IMD (-147dBm) @ 1935MHz
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LTE Band 2: Actual Data (continued)
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LTE Band 2: Tx signal and “Blockers”
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Tx + “Blocker”-IMD Test Setup #6a
Notes:
• “Reverse” and “Forward” IMD measurements
• Easy to maintain and debug
Spectrum Analyzer
Tx Tx
Rx
BRF Tx+Rx
Tx
Rx
BRF Tx+Rx DUT
SPDT
Non-Reflective
“Blocker” Signal Gen.
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• Enables exposing the DUT to one Tx signal and any “Blockers” with port “swapping” capability
• Enables measurements for “Reverse” and “Forward”
Tx + “Blocker” Port Swapping-IMD Test Setup #6b
Tx
Rx
BRF Tx+Rx
“Bloc-kers”
DUT
Spectrum Analyzer
SP4T
Non-Reflective
“Blocker” Signal Gen.
Tx
Rx
BRF Tx+Rx
“Bloc-kers”
Tx SP2T
Non-Reflective
SP2T
Non-Reflective
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Mix-n-Match (LTE Band 7)
DUT
BPF2620-2635
BPF2675-2690
BPF2550-2595
BPF2620-2690
BPF2500-2570
SpectrumAnalyzer
Triplexer/Duplexer
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Triple Beat & 3rd IMD for RF Switches Triple Beat and IMD for RF Switches emulates two Transmit carriers of the mobile up-link,
separated by 1MHz, entering the DUT, along with a “Jammer” (“Blocker”), representing a weaker signal in the mobile down-link (Receive) band, from a different system.
http://www.ni.com/white-paper/14506/en
• IM 3rd are f3-(f2-f1) and f3-(f2+f1)
• Concerns with the proposed block diagram : The two Tx carriers mix
with the “Jammer” in the CW source
Limited isolation between the amplifiers - return loss limit.
“Jammer” signal travels directly into the Spectrum Analyzer
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Triple Beat Filter Based - Phase 1
Notes:
• “Jammer” CW source is now protected from the two TX signals
• One problem remains: Energy of TX1 and TX2 is reflected back from Tx Filter and DUT, F1 goes to AMP1 and AMP2 and vice versa
• Further mixing is taking place at the isolators
Tx
Rx
DUT
Tx
Rx
“Blocker” Source
Spectrum Analyzer
TX1
TX2
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Triple Beat Filter Based - Phase 2
Notes:
• Hi Q ceramic puck filter can provide ~40dB rejection
• Adding isolators can increase the isolation to ~60dB
• Carriers are terminated after passing through the DUT
• Depending on “Jammer” power level, this setup should be able to provide a good base line
DUT
Spectrum Analyzer
f2
f1
f2
IM
f1+f2
f3
f1
f3
IM in Rx Band = f3-(f2-f1) & f3+(f2-f1)
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Triple Beat Filter Based - Phase 3
• The Band-Pass filter is passed f3 and rejects the IMD products by 40dB.
• The Band-Stop filter passes the IMD products and rejects f3 by 40dB.
• The Band-Pass filter (or Band-Stop filter) can be terminated, providing a broadband match to common port.
Introducing the narrow band BP/BS Duplexer
2MHz
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Triple Beat Filter Based - Phase 4
Notes:
• Units enclosed in dashed line are all integrated
• Number of external connections and jumpers kept to a minimum
DUT
Spectrum Analyzer
f2
f1
f2
IM
f1+f2
f3
f1
f3
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The Road Map to Test Rack System
ATE Integrations • Supports automated production testing of wireless systems and semiconductor
product families covering all LTE bands • Provides emission monitoring while maintaining a good impedance match with the
device under test (DUT) • Can be used to measure IM products and NF and for Triple Beat tests
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Switch Matrix
Modular Architecture
flexibility
reconfigurable
expandable
Compact Structure
reduce 10X10 rack space
from 4U to 3U
Trouble-free Maintenance
field serviceable
field upgradable
Removable Power Supply
easy access
redundant power
supplies available
Fast Switching Time
< 50ms
Interface Options
Ethernet (TCP/IP), HTTP
Server, LabVIEW-based
Web Services, RS-232,
USB, GPIB, ...
Mounting Brackets for Switches
Power Module (Mounts Vertically for 3U and 4U
Enclosures)
2U Model
Next Generation Matrix
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Custom Solutions
Low PIM Test Station for….
Cell Phone Tester for…..
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Coaxial Switch - Data
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The Road Map to Test Rack System (cont.)
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Interface Options
Most switchable RF devices provide a combination of remote and local interfaces. A typical unit is equipped with one or two of the following options:
o SNMP SNMP v.1 SNMP v.3 (coming soon)
o LabVIEW-based Web Services o GPIB o Ethernet (Built-in Web Server) o USB o RS-232 o CAN-bus
-- load the Lua VISA wrapper
require "visa"
-- open connection to equipment
if interface == "GPIB" then
-- use GPIB interface 0 at address 16
c = visa.open "GPIB0::16::INSTR"
else if interface == "SERIAL" then
-- use serial (RS-232, RS-485, etc) interface 1
c = visa.open "ASRL1::INSTR"
else if interface == "TCP" then
-- use TCP/IP over interface 0
c = visa.open "TCPIP0::192.168.1.5::7::SOCKET"
end
-- set switch 1 to position 2
c:write "CT1.2"
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Further questions on this topic can be addressed to the author, Rafi Hershtig, at [email protected].
www.klmicrowave.com
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Further questions on this topic can be addressed to the author, Rafi Hershtig, at [email protected].
www.klmicrowave.com