Study on SLT calibration method of 2-port waveguide DUT

Transcription

1 Interntionl Conference on Advnced Electronic cience nd Technology (AET 206) tudy on LT clibrtion method of 2-port wveguide DUT Wenqing Luo, Anyong Hu, Ki Liu nd Xi Chen chool of Electronics nd Informtion Engineering, Beihng University, Beijing, 00083,Chin Abstrct. LT (hort-offset-hort-lod-through) is clssicl clibrtion method of VNA (Vector Network Anlyser) which needs multiple ssembly of the stndrd prts nd exists the impct of the phse in the millimetre wvebnd. Aimed tht the of the two-port wveguide DUT is less thn -0dB, simple LT (hort-lod-through) clibrtion method is presented in this pper ccording to the simplified error model. This clibrtion method only needs to crry on the clibrtion of short circuit plte nd the mtching lod in the one-port of the VNA, nd the through in the dul-port. The clibrtion process nd the correction lgorithm is simple. Finlly, it is found tht the mplitude reltive error of the LT clibrtion method is less thn 2% nd the phse clibrtion error is less thn 2.5 through the sttistics of severl DUTs. Keywords: 2-port wveguide DUT; LT clibrtion; VNA. Introduction VNA (Vector Network Anlyser) is one of the importnt mesuring instruments of the DUT (Device Under Test) in the microwve or millimetre wvebnd. The clibrtion nd correction of the error model in the VNA is the key to ccurtely mesure the performnce of the DUT []. For the 2-port wveguide DUT, it needs two or more fixtures to connect the wveguide port of the DUT nd the coxil port of the VNA. The -prmeters of those fixtures re consequently introduced into the mesurements results s errors. o it s necessry to remove the effect of the test fixtures by the error clibrtion nd correction of the VNA. OLT (hort-open-lod-through) clibrtion, trditionl VNA clibrtion method of the coxil device, complete the four -prmeters clibrtion of the 2-port DUT by using the four stndrds (short-circuit, open-circuit, mtching lod nd through). For the DUT of wveguide port, the clibrtion method nd stndrds re relted to the chrcteristics of the wveguide. The open circuit of the wveguide is equivlent to poorly mtching lod, so it cn t be replced by the open wveguide. According to the theory of the microwve trnsmission line, short circuit plte with λ/4 offset is equivlent to the open circuit. o short circuit plte with offset replce the wveguide stndrd of the open one [2]. Therefore, we cll this clibrtion method LT (hort Offset hort Lod Through) clibrtion insted of OLT clibrtion. LT clibrtion exists the problem of multiple ssembly stndrd, tht it needs three stndrds of the signl port nd through clibrtion of the two-port. Furthermore, the offset rnge of short circuit plte becomes lrger in the millimetre wve bnd. Additionlly, the clibrtion lgorithm is complex for testing [3-5]. Aimed tht the of the two-port wveguide DUT is less thn -0dB, simple LT Corresponding uthor : luo_wq92@26.com 206. The uthors - Published by Atlntis Press 276

2 AET206 (hort-lod-through) clibrtion method is presented in this pper. This clibrtion method only needs to crry on the short circuit plte nd the mtching lod clibrtion in the one-port of the VNA, nd through clibrtion in the dul-port. Moreover, there is no impct on the ctul phse with offset rnge. This pper is orgnized s follows. ection II gives comprehensive processing of the proposed LT clibrtion. In section III, experimentl results tht verify the usefulness nd ccurcy of the proposed method re presented. Finlly, ection IV gives generl conclusions concerning the LT clibrtion technique. 2 LT clibrtion 2-error model is one of 2-port VNA clibrtion model tht is extensively used in VNA clibrtion [6- -8]. In this pper, 2-error model is simplified to 6-error model combined with the chrcteristics of 2- port wveguide DUT. Error clibrtion nd modified formul, nmely the reltionship between rel vlue of the DUT nd the mesured vlue of the stndrd, is gotten bsed on the reltionship of the error term in the signl flow grph. 2. Error model 2-error model is one of the most widely used error models in the three-chnnel two-port vector network nlyser, which includes forwrd model nd bckwrd model, s shown in figure. The system error includes the direction error E D, the reverse trcking error E R, the equivlent source mismtch error E, the difference error E X, the forwrd trcking error E T nd the lod mismtch error E L. T EX T2 2 ET m2 ED E 22 EL 2 m () Forwrd model ER2 m22 2 EL2 22 E2 ED2 2 m2 ET2 T Figure. chemtic digrm of 2 error models EX2 (b) Bckwrd model The clibrtion nd correction is studied by tking the nd 2 s n exmple, nd the clibrtion of 22 nd 2 is similr to tht of nd 2. Difference error (E X ) is the lekge error of the source nd receiver in the VNA. It is generlly less thn -40dB becuse of excellent hrdwre performnce of commercil VNA. o the difference error (E X ) cn be ignored in the clibrtion process. ource nd lod mismtch error (E /E L ) is cuse by the multiple reflections of the incomplete mtching in the port of incentive port or the non-incentive port of the DUT. In this test, the DUT hs 277 T2

3 AET206 high mtching degree with the tested fixture, nd the of the DUT is less thn -0dB [9-3]. o in this cse, the source nd lod mismtch error (E /E L ) cn be ignored in the clibrtion process. implified 6-error model is gotten, s shown in figure2. ED ET m2 m ER T T2 Figure 2. chemtic digrm of simplified 6-error model 2.2 Error clibrtion LT clibrtion includes the L clibrtion of one-port (short circuit nd mtching lod) nd through clibrtion [4-6]. pecific clibrtion is s follows: 2.2. L clibrtion of one-port L clibrtion is minly clibrting the of the DUT. When the one-port of the VNA connects with the short circuit chip or the mtching lod, the error model cn be simplified to one-port error model, s shown in Figure3. ED Γ(X) m(x) ER Figure 3. One-port error model The expression of the reltionship between the reflection coefficient nd the corresponding mesured vlue of the stndrd ccording to the signl flow grph: (X) = E + E Γ (X) () m D R where Γ(X) is the reflection coefficient of the stndrd X, nd sys the short circuit, nd L sys the mtching lod, nd m (X) is the corresponding mesured vlues of the stndrd. The following expression cn be gotten when the short circuit nd mtching lod is respectively connected to the one-port of VNA: ( L) = E m D ( ) = E + E m D R (2) The vlue of error term E D nd E R of one-port cn be obtined by eqution group (2) s follows: E = ( L) D m E = ( ) ( L) R m m (3) 278

4 AET Through clibrtion Through clibrtion is clibrting the 2 of the DUT. In the through clibrtion, it supposes tht nd 22 of the through connection equl to 0, nd 2 nd 2 mount to. The through clibrtion error model is shown s figure 4. ET m2(t) 2= m(t) ED =0 2= 22=0 Figure4. Through clibrtion error model ER The expression of the reltionship between the error term nd the corresponding mesured vlue of the through ccording to the signl flow grph cn be expressed s: m2 (T) = ET (4) where m2 (T) is the mesured vlue of through clibrtion. The reltionship between error terms nd the stndrds cn be obtined from tht wy. Menwhile, the clibrtion of the 6-error model is completed. 2.3 Error correction On the bsis of error clibrtion, the influence of error term of VNA on the DUT is eliminted by error correction while the 2-port DUT is tested. Becuse the nd 2 of the 2-port wveguide DUT is tested, the error correction is only considered of the incentive of VNA Port. The following cn be obtined from the forwrd model while the port is excited: m ED ER = 0 b (5) o the incident wve nd the reflected wve b of port cn be expressed s: = b = E m D E R (6) imilrly, the incident wve 2 of port cn be expressed s: 2 m2 = (7) E According to the definition of the prmeter nd the expression (6) nd (7), the corrected nd 2 cn be obtined. Correction formultion cn be gotten s follow while expression of error terms tht re gotten from the error clibrtion re tken into the nd 2. T 279

5 AET206 2 = = m m m m m2 m2 () (T) (L) (L) (9) Among them, m () nd m (L) re the mesured dt of bout the short circuit nd mtching lod, nd m2 (T) is the mesured dt of 2 bout the through clibrtion, nd m nd m2 is the tested dt of nd 2 bout the DUT, nd the nd 2 is corrected dt. 3 Mesurement nd result The LNA (Low Noise Amplifier) is selected s the DUT in this pper, which of is less thn -0dB. The comprison between the LT clibrtion nd LT clibrtion bout the mplitude of nd mplitude nd phse of 2 is done following. 3. Mesurement of LT clibrtion is presented ccording tht the source nd lod mismtch error (E /E L ) re ignored, while it is bsed tht the of the DUT is less thn -0dB. o the DUT we select is the LNA with less thn -0dB. The testing result of LT clibrtion nd LT clibrtion is shown in figure5. It cn be seen from the figure tht the of the two clibrtions re bsiclly consistent. Menwhile, the verge vlue of in 2G bndwidth with DUTs nd the reltive error of the two clibrtions re counted, nd the results re shown in Figure6. As cn be seen from the figure, when the of the DUT is more thn -0dB, the error of two clibrtions is reltively lrge, nd while the of DUT is less thn -0dB, the reltive error between two clibrtion is less thn 2% Men of in 2G bnd the reltive error of 0 /db LT LT Men of in 2G bnd /db the reltive error of /% Fre/GHz Figure5. Comprison of test results of LT nd LT clibrtion methods for Num. Figure6. Men of in 2G bnd nd reltive error sttistics of two clibrtion methods 3.2 Mesurement of 2 The 2 testing result of LT clibrtion nd LT clibrtion is shown in figure7, where the grph () is the 2 mplitude result, nd the grph of (b) is the 2 phse result. It cn be seen from the figure tht the 2 of the two clibrtions re bsiclly consistent. Menwhile, the verge vlue of 2 in 2G bndwidth of DUTs nd the reltive error of the two clibrtions re counted, nd the results re shown in Figure8. As cn be seen from the figure8(), the reltive error of the verge vlue of 2 in 2G bndwidth between two clibrtions is less thn 2%. At the sme time, the reltive error of the 2 phse of the two clibrtions is less thn

6 2/dB LT LT 2/ LT LT Fre/GHz () Amplitude Fre/GHz (b) Phse Figure7. Comprison of test results of OLT nd LT clibrtion methods for 2 Men of 2 mplitude in 2G bnd/db Men of 2 mplitude in 2G bnd the reltive error of 2 mplitude Num. () Amplitude 3 2 the reltive error of 2 mplitude/% the reltive error of 2 phse/ Num. (b) Phse Figure8. Men of 2 in 2G bnd nd reltive error sttistics of two clibrtion method 4 Conclusion The LT clibrtion technique, which uses short circuit, mtching lod nd through s clibrtion elements, hs been introduced nd its usefulness nd precision hs been experimentlly demonstrted. This clibrtion method do not need multiple ssembly stndrd. The clibrtion nd the correction lgorithm is simple. Through the mesurement, it cn be seen tht the reltive error of the mgnitude of is below 2%, nd the reltive error of the mgnitude of 2 is less thn 2%, the phse error is less thn 2.5. It meet the ccurcy requirements of the test, nd verify the correctness nd relibility of the LT clibrtion. This clibrtion cn be extended to the field of utomted testing for quickly testing. References. Horibe Mshiro, Kishikw Ryoko. Mesurement uncertinty in wveguide VNA clibrted by offset short clibrtion with oversized wveguide perture t sub-millimetre wve frequency. Microwve Mesurement Conference (ARFTG), th ARFTG, pge(s): Zho X, tudy on Reflection Coefficient Mesurement in Qusi-opticl Millimeter-wve ystem Front-end, BUAA, (20) 3. M. Horibe, et. l. Complete chrcteriztion of rectngulr wveguide mesurement stndrds for vector network nlyzer in the rnge of millimeter nd sub-millimeter wve frequencies. 76th ARFTG Conf. Digest, pp. -5, Dec. (200). 4. Li W, Wng Z G, Li Z Q. Comprison of clibrtion methods of OLT nd TRL in prmeter mesurement nd clibrtion[c]. Proceedings of the Fifth Chin Test Conference.5.-5, (2008) 5. A.A.vin. A novel fctor verifiction technique for one-port vector network nlyzer. 43rd Europen Microwve Conference, Oct. (203). 6. Li E, Xing Z J, Guo G F, Zhng Q X, Reserch on TRL clibrtion technique of ridge wveguide, Journl of instrument nd meter, 09:04-043, (2006). 7. Zho W, Reserch on Clibrtion Technology of multi port vector network nlyzer[d], NUAA, (20). 8. Yun C H. Clibrtion nd correction of multi port vector network nlyzer[d], NUAA, (202) 9. Qin H B, Reserch on Clibrtion Technology of vector network nlyzer, Xidin University, (204) 28

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