ltp: tft025 version 1.1 01.11.00 ______________________________________________________________________________________________________ vi telefilter application note tfs 246m - 1/2 ______________________________________________________________________________________________________ _____________________________________________________________________________________________ vi telefilter vectron international, inc. potsdamer stra?e 18 267 lowell road d 14 513 teltow / germany hudson, nh 03051 / usa tel: (+49) 3328 4784-52 / fax: (+49) 3328 4784-30 tel: (603) 598-0070 fax: (603) 598-0075 e-mail: tft@telefilter.com e-mail: vti@vtinh.com _____________________________________________________________________________________________ vi telefilter reserves the right to make changes to the product(s) and/or information contained herein without notice. no liab ility is assumed as a result of their use or application. no rights under any patent accompany the sale of any such product(s) or infor mation 1. general the filter is symmetrical, i.e. input and output are exchangeable with each other. but the external coupling coil has to be connected to pin 3 in any case. the filter can be driven balanced only. to get a balanced signal for test measurements with the network analyzer we use two wideband 1:1 transformers at each port: smt 4, vendor neosid, pn 88 8529 10 the termination impedances are : 600 ? || -1.45 pf this impedance is equal for the input and the output. it has to be realized at the point were the filter is mounted. to match this impedance to the impedance of the system a matching circuit is required. 2. theoretical matching for the matching to 50 ohm there can be used two different matching circuits: 50 ohm test circuit 1 2 1 6 5 4,7,8 lb-in lb-out saw c1 l1 c2 l4 l2 l3 l5 3 c3 the theoretical values of the stated elements are: l1 = l2 =l3 = l4 = 53 nh c1 = c2 = 2.1 pf c3 = 0 pf l5 = 108 nh
ltp: tft025 version 1.1 01.11.00 ______________________________________________________________________________________________________ vi telefilter application note tfs 246m - 2/2 ______________________________________________________________________________________________________ _____________________________________________________________________________________________ vi telefilter vectron international, inc. potsdamer stra?e 18 267 lowell road d 14 513 teltow / germany hudson, nh 03051 / usa tel: (+49) 3328 4784-52 / fax: (+49) 3328 4784-30 tel: (603) 598-0070 fax: (603) 598-0075 e-mail: tft@telefilter.com e-mail: vti@vtinh.com _____________________________________________________________________________________________ vi telefilter reserves the right to make changes to the product(s) and/or information contained herein without notice. no liab ility is assumed as a result of their use or application. no rights under any patent accompany the sale of any such product(s) or infor mation 50 ohm test circuit 2 2 1 6 5 4,7,8 lb-in lb-out saw l1 c1 l2 c4 c2 3 l3 c3 the theoretical values of the stated elements are: c1 = c2 = c3 = c4 = 7.8 pf, l1 = l2 = 83.3 nh, l5 = 108 nh the calculation was made without consideration of parasitics. the elements which have to be used on the pcb are slightly different from the stated due to these parasitics. 3. matching on pcb for example: pcb with 50 ? test circuit 1 l1 = l2 = l4 = 68 nh l3 = 56 nh c1 = c2 = c3 = 0.5 pf l5 = 100 nh the calibration is made at the 50 ohm ports. thus, the measured characteristics will include the losses of the two transformers (about 0.7 db each). in case of questions please contact us to
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