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https://designers-guide.org/forum/YaBB.pl Measurements >> RF Measurements >> Measure CPW (47/90/47) with probe pitch 200 um https://designers-guide.org/forum/YaBB.pl?num=1236164999 Message started by giorgilloz on Mar 4th, 2009, 3:09am |
Title: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 4th, 2009, 3:09am Hi I'm measuring a MEMS Switch on CPW line with a slot of 47/90/47 using Karl Suss Probe pitch 200 um., TRL calibration and SOLT calibration but in both cases the Insertion Loss is characterized by oscillation. Otherwise the width of the Ground Planes are 793 um Someone have any suggestion? |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 4th, 2009, 4:34am giorgilloz wrote on Mar 4th, 2009, 3:09am:
Or 90um is width of center line and 47um is width of slit between planar ground and center line ? Attached S21 is insertion loss of MEMS Switch ? If so, your MEMS Switch have same attenuation maximal point(around 27.5GHz) regardless of calibration methods ? giorgilloz wrote on Mar 4th, 2009, 3:09am:
Generally it is very difficult to prepare reliable calibration kits for SOLT calibration. giorgilloz wrote on Mar 4th, 2009, 3:09am:
giorgilloz wrote on Mar 4th, 2009, 3:09am:
But there are frequencies(around 35GHz) where S21 is larger than 0dB in TRL calibration. You should confirm validity of your calibration kits. |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 9th, 2009, 4:14am Hi pancho_hideboo 90 um is the width of the central conductor and 47 um is the distance between the central conductor and the ground plane (board to board) For the SOLT calibration, of course, i used a commercial SOLT kit calibration of Karl SUSS. I report also the width of the ground plane ("Otherwise the width of the Ground Planes are 793 um ") because i think the oscillations are due to the finite ground dimension of the line respect the pitch of the probe so RF signal can be reflected by the external boarder of the Ground plane. What do you thinck about it? |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 9th, 2009, 5:12am giorgilloz wrote on Mar 9th, 2009, 4:14am:
What do you mean by "board to board" ? giorgilloz wrote on Mar 4th, 2009, 3:09am:
Do you mean this 793um as width of ground of CPW ? If your CPW is compared to MACLIN3 of Chapter 2 in the following, http://cp.literature.agilent.com/litweb/pdf/ads2005a/pdf/ccdist.pdf Sizes are W1=W3=793um, S1=S2=47um, W2=90um. These are correct ? giorgilloz wrote on Mar 9th, 2009, 4:14am:
I can't understand what you mean. Explain in detail. Oscillation in the above is same as the following oscillation ? giorgilloz wrote on Mar 4th, 2009, 3:09am:
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Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 10th, 2009, 3:13am Ok in the picture you can see the dimensions of the CPW. My question is if the oscillations in the measurement are due to the finite ground plane configuration of the CPW. I mean, in the case of the commercial standards used for the SOLT, the THRU has, usually, absorbers on the edges, to minimize the edge reflections and to simulate the ideal case of a CPW with infinite grounds, which is not my case. Moreover, I guess that the oscillation is enhanced around the 35 GHz frequency because the pitch I am using is wider than the CPW geometry and I am not far from the edges, with possible enhancement of the higher frequencies reflections. Which is your opinion ? |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 10th, 2009, 4:02am Answer my following questions. pancho_hideboo wrote on Mar 4th, 2009, 4:34am:
giorgilloz wrote on Mar 9th, 2009, 4:14am:
For both SOLT and TRL calibration fixtures you used, sizes are same as "ScreenHunter_01_Mar__10_10_04.gif" ? Any taper geometry is used for relaxing sudden size change ? giorgilloz wrote on Mar 10th, 2009, 3:13am:
If you mean radiation toward CPW groud plane edge direction due to resonance, it is arouid 27.5GHz of "Insertion_Loss.gif". giorgilloz wrote on Mar 10th, 2009, 3:13am:
Using SOLT calibration, show me following two S21. (1) S21 of THRU pattern of SOLT (2) S21 of THRU pattern of TRL |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 10th, 2009, 4:57am Attached S21 is insertion loss of MEMS Switch ? Yes You seemed to use commercial calibration fixture for SOLT. But what calibration fixture did you use for TRL ? Did you make it by yourself ? Yes i make it and tihis are the dimensions of the standards TRL (47/90/47) εeff ~ 5.6 1. THRUE Lenght=500 um Delay Time=3.94 psec 2. Line1 3-16 GHz Phisical Lenght=3385um+500um DelayTime=30.64psec ( Lenght=3385um ---> 28.94° at 3 GHz --- 154.4° at 16 GHz ) 3. Line2 10-40 GHz Phisical Lenght=1068 um+500um DelayTime=12.37psec ( Lenght=1068um ---> 30.44° at 10 GHz --- 121.73° at 40 GHz ) And like reflect standard i use a short standard For SOLT and TRL calibration fixtures you used, sizes are same as "ScreenHunter_01_Mar__10_10_04.gif" ? For the TRL calibration the size is the same. For SOLT calibration i use the KIT Karl Suss CS 3 (150 to 250 pitch) |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 10th, 2009, 5:11am Answer my question in http://www.designers-guide.org/Forum/YaBB.pl?num=1236164999/5#5. giorgilloz wrote on Mar 10th, 2009, 4:57am:
giorgilloz wrote on Mar 10th, 2009, 4:57am:
You mean you used different probe from TRL calibration ? Anyway sizes of CPW in DUT are same as TRL fixtures not SOLT fixtures. Is this correct ? Using SOLT calibration, show me following two S21. (1) S21 of THRU pattern of SOLT (2) S21 of THRU pattern of TRL In actual CPW, ground plane width have to be finite never infinite. Sorry the following might not be correct. You have to compare width of ground plane with effective wave length. And this finite width of ground plane is less effective rather for high frequency as far as primary transmission mode. |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 10th, 2009, 5:41am Is it true short ? If not, how to estimate reflection coefficients ? Yes is true short giorgilloz wrote on Today at 4:57am: For SOLT calibration i use the KIT Karl Suss CS 3 (150 to 250 pitch) What do you mean by 150 to 250 pitch ? You mean you used different probe from TRL calibration ? No i use the same probe for TRL calibration and SOLT calibration. 150 to 250 means that kit is valid for probe with pitch from 150 um to 250 um Anyway sizes of CPW in DUT are same as TRL fixtures not SOLT fixtures. Is this correct ? Yes it's correct Using SOLT calibration, show me following two S21. (1) S21 of THRU pattern of SOLT (2) S21 of THRU pattern of TRL I haven't this measure but after the several calibration i measured the thrue and i checked the overlap of S21 and S12 and of the S11 and S22 and i checked if the medium value of the S21 and S12 was 0 dB and if the S11 and S22 are under -20dB and all was Ok! like in the case attached. |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 10th, 2009, 5:52am giorgilloz wrote on Mar 10th, 2009, 5:41am:
giorgilloz wrote on Mar 10th, 2009, 5:41am:
"R" is suspicious in your TRL calibration. If you want to know reflections from finite groud plane edge and reflection from contact point between CPW and Probe, analyze IFFT of S11. If your Vector Network Analyzer have time domain analysis ability, you can do it easily. |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by giorgilloz on Mar 10th, 2009, 5:57am In actual CPW, ground plane width have to be finite never infinite. Sorry the following might not be correct. You have to compare width of ground plane with effective wave length. And this finite width of ground plane is less effective rather for high frequency as far as primary transmission mode. If i understand the width of the Ground plane at 28 GHz (resonace) is a Lamda/4 (wavelenght 4000 um) so this can be the problem? |
Title: Re: Measure CPW (47/90/47) with probe pitch 200 um Post by pancho_hideboo on Mar 10th, 2009, 6:05am giorgilloz wrote on Mar 10th, 2009, 5:57am:
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