FSMR26-N_frequency_response_issue_(final).pdf

Ottmar Steffke

FSMR26-N frequency response issue

Investigation status, proposed solution and next steps

COMPANY CONFIDENTIAL

ı Symptom: dips in the frequency response below 3.6 GHz ı Examples:

S# 101383

(shipped 10/2012)

S# 101555

(shipped 12/2014) ı observed on instruments used by the US Navy instruments on Navy stock for ~ 9 months some instruments ~ 3 months after repair without use

FSMR frequency response issue

Symptoms observed

FSMR26-N investigation 2

Summary of investigations since first observation of symptoms ı June 2015 4 FSMR26-N show dip in frequency response at incoming test ı July 2015 Check of cables, RF connectors, preamplifiers and RF frontends

Components suspected:

2x preamplifier, 1x RF frontend, 1x RF input connector

Spare preamplifiers ordered mid July ı August 2015 Preamplifier spare parts arrived mid August.

Dips persisted after replacement.

New suspicion: RF attenuator - dips persisted after replacement.

New suspicion: RF input connector - dips vanished when replaced.

Replaced parts were sent to Munich for analysis on 28th August ı Sept. 2015 Parts were forwarded to supplier after optical inspection by

R&S QA in 1st week of September.

In parallel: investigation by R&S of a large number of service test reports of other spectrum analyzer models using the same connector.

FSMR26-N investigation 3

Summary of investigations since first observation of symptoms ı Investigated spectrum analyzer models:

FSU26, FSQ26, FSUP26, FSMR26, ESU26

production range 2012 to 2015 failure rate < 1% ı Conclusion

The R&S statistics only show individual cases.

No time frames with increased failure rate identified.

Proceed with replacing connectors if identified as out of tolerance ı 15. Oct. 2015 Received first analysis results from supplier:

Conclusion:

mechanical issue caused by manual assembly during connector production

FSMR26-N investigation 4

First investigation of input connector, root cause reported by supplier ı mechanical issue confirmed:

lids of the inner contact found bent and out of tolerance root cause communicated by supplier:

insufficient precision of manual assembly process ı initiated changes to component production:

modified assembly tooling additional optical inspection two measurements of electrical parameters (previously: 1 measurement) ı scope of issues stated by supplier issues are regarded as singular events no relation to specific production lots identified

Insufficient data and frequency of occurence to begin voluntary product recall proceedings

FSMR26-N investigation 5 bent lid

Mechanical design of connector + adapter

FSMR26-N investigation 6

PC3.5 adapter

RF cable connector

Subsequent investigations performed by R&S from

October to December 2015 ı Investigation of impact of vibration during transport no impact on frequency response ı Analysis of repetitive measurements with multiple adapter changes in production no impact on frequency response ı Investigation of impact of temperature changes (cycles from 5 to 45 ° C) no impact on frequency response ı Analysis of torque applied to cables, input connector and adapters in production torque is according to supplier specification ı Impact of production test system on measurement results results are reproduceable independent from test system used ı Conclusion:

production processes on instrument level are ok

FSMR26-N investigation 7

Additional investigations performed by R&S in this time frame ı Impact of service test system on measurement results results are reproduceable independent from test system used ı Visit to Pax River to analyze Navy calibration processes, torque applied to cables, input connectors and adapters as well as the tools / equipment utilized in the process.

processes, accessories and tools meet expectations ı Visit of Navy members to RSA Service Center to observe RSA Calibration process to insure consistency of the Navy process.

processes were found to be consistent.

ı Discussion with end-user to determine whether over-torquing may have occurred in the field or metrology lab.

ı Inspection of instruments taken directly from Navy stock: dips reproduced ı Inspection of instruments 3 months after connector change: dips reproduced

FSMR26-N investigation 8

Recent investigations of more returned input connectors by R&S (Dec. 2015 / Jan. 2016) ı Optical inspection: no issues, especially not at lids of inner contact ı Analysis of mechanical dimensions: no issues ı X-Ray analysis: no issues ı S parameter measurements:

dips in frequency response reproduced ı Time domain measurements:

root cause for dips is definitely inside input connector (not in cable or adapter) ı Influence of lid geometry on frequency and depth of dip was reproduced by bending the lids

FSMR26-N investigation 9

Latest investigations of more returned input connectors by supplier ı Optical inspection: no issues ı Analysis of mechanical dimensions: no issues ı REM analysis: contact areas with traces of aging detected ı Chemical analysis of contact areas: chemical aging confirmed ı No changes to material / suppliers: confirmed ı Confirmed root cause of dips:

aging effects on contact surfaces isolate parts of the connector and thus cause resonances resulting in dips indicator: moving / turning / cleaning the flexible part fixes the dips long storage time of instruments is in favour of the aging effect

FSMR26-N investigation 10

Why is the percentage of affected FSMR26-N higher compared to other instrument models?

ı The aging effect on contact surfaces is supported by long storage time before first use ı The aging effect is also supported if the instrument is not permanently in use ı Frequent change of adapters prevents/minimizes the aging effect

FSMR26-N investigation 11

Proposed solution by supplier (Alternative 1):

Improve current connector design ı Mechanical change:

increase contact force of inner contact ı Material change:

increase thickness of gold and nickel plating layers ı Production process change:

Add an additional test for the quality of the gold and nickel layers ı Time schedule:

Modified connectors will become available in April 2016

FSMR26-N investigation 12

Proposed solution by R&S (Alternative 2):

Precision-N connector ı Replace the current input connector system by a precision N connector, as currently used in the R&S FSWT ı Default configuration:

ı Configuration with

N-to-PC3.5 adapter

(FSMR26-N accessory)

FSMR26-N investigation 13

Proposed solution

Alternative 2: Precision-N connector ı Specified RF performance of FSMR26-N will be maintained up to 26.5 GHz

FSMR26-N today, YIG preselector off

FSWT26 today, YIG preselector off, including PC3.5 adapter

FSMR26-N investigation 14

Proposed solution

Alternative 2: Precision-N connector ı Features:

Mechanically robust

Adapter set shipped with the FSMR26-N can be used without change

Simple modification to existing instruments ı Time schedule:

Implement Precision-N solution and verify specifications at R&S 29-01-2016

Provide 3 prototype instruments for evaluation to USN 12-02-2016

FSMR26-N investigation 15

Question ı How to proceed with the order of 48 units currently in production:

postpone delivery until approval of new concept?

ship with current design and upgrade later?

FSMR26-N investigation 16

Impact on DUTs calibrated with FSMR26-N so far ı FSMR passes incoming inspection:

no impact on DUTs ı FSMR out of specification: no impact during normal use:

dips have no impact on linearity measurements dips have no impact on modulation quality measurements frequency response measurements are usually performed using a power meter and power splitter. Dips have no impact in this case.

FSMR26-N investigation 17