- SMITH CHART STUB MATCHING HOW TO
- SMITH CHART STUB MATCHING GENERATOR
- SMITH CHART STUB MATCHING SERIES
SMITH CHART STUB MATCHING GENERATOR
If one moves from load to generator on the line, the corresponding chart location moves from the reference point, in clockwise motion, according to an angle (indicated by the light green arc) Notice that in this case the load admittance falls outside the unitary conductance circle. This provides on the admittance chart the physical reference for the load location on the transmission line. The red arrow on the example indicates the load admittance. It is very convenient to analyze the possible solutions on a Smith chart. (inductance if negative, or capacitance if positive)Ī stub should be placed at a location where the line admittance has real part equal to Y0ĭepending on the length of the transmission line, there may be a number of possible locations where a stub can be inserted for impedance matching. Note that the input admittance of a stub is always imaginary In order to complete the design, we have to find an appropriate location for the stub.
Since the circuit is based on insertion of a parallel stub, it is more convenient to work with admittances, rather than impedances. On the other hand, an open circuited stub may be more practical for certain types of transmission lines, for example microstrips where one would have to drill the insulating substrate to short circuit the two conductors of the line. A short circuited stub is less prone to leakage ofĮlectromagnetic radiation and is somewhat easier to realize.
The choice of open or shorted stub may depend in practice on a number of factors. In many cases it is also convenient to select the same characteristic impedance used for the main line, although this is not necessary. The transmission line realizing the stub is normally terminated by a short or by an open circuit. The drawback of this approach is that if the load is changed, the location of insertion may have to be moved. There are two design parameters for single stub matching: The location of the stub with reference to the load dstub The length of the stub line Lstub Any load impedance can be matched to the line by using single stub technique. I feel there has to be a way, because otherwise it would be easier to simply use a combined admittance/impedance Smith Chart) thanks for the documents.Single stub impedance matchingImpedance matching can be achieved by inserting another transmission line (stub) as shown in the diagram below Then I mirror the admittance 1/Zin1 to get Zin2 (or just calculate it) What I still find a bit unsatisfying: Is there any way around drawing that 1/Z0 admittance circle? (Without using a combined admittance/impedance Smith Chart). thats 1/(Zin2 + R1) and read the imaginary part of the admittance which represents 1/ZL2. Then I mirror the green dot about the center.
SMITH CHART STUB MATCHING SERIES
Because its length is lambda/8 I know that the shorted series Stub has an input impedance of Zin2 = j*ZL2*tan(2*pi/8) = j*ZL2 So I can calculate ZL2 from that. I walk clockwise along the Real(Z)=const circle until I cut the 1/Z0 circle. I draw the 1/Z0 admittance circle in my impedance Smith chart (the grey circle) 2. Start point is 50Ohm/200Ohm = 0.25 (yellow dot) 1. But I'm not 100% satisfied with my solution. But that was all L and C matching because it was just for a couple 100 MHz, so no transmission line matching there) (All this is kind of embarrassing because 5 years back I worked in an RF lab and working with the SC was a common task for me. I'm totally lost, Monday is exam and I'm totally crapping my pants here So if anyone has a good explanation for a panicking student I'll be incredible grateful. That makes things a bit more complicated.
SMITH CHART STUB MATCHING HOW TO
Matching with Parallel / series L or C But no explanation on how to find the ZL if I have a series open/short stub with a given length Additional "boundary condition" to the solution: AFAIK in the exam we are only given a Impedance Smith chart, no admittance Smith Chart. Inserting parallel Open/short stubs and finding out the length 4. Inserting series open/short stub with ZL=Z0 and finding out the length 3. Matching a real Zload to a real Z by inserting a series Transmission line (not series open/short stub) with ZL unequal to Z0 and finding out ZL 2. I already watched several videos and documents explaining smith chart matching.
3.75GHz 200 Ohm Generator -> lambda/8 Parallel open stub -> lambda/8 series short stub -> 50 Ohm load (Length is lambda/8 because it should filter out 7.5GHz for which the 10mm are lambda/4) The goal is to find the impedances ZL1 and ZL2 of the transmission lines. I have a circuit like in the attached image.
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