![]() This is called double-stub matching and allows for the adjustment of the load impedance. Instead of having a single stub shunted across the line, we may have two stubs. Since we have two possible shunted stubs, we normally choose to match the shorter stub or one at a position closer to the load. Thus we obtain d = d A and d = d B, corresponding to A and B, respectively, as shown in Figure 11.20. Similarly, we obtain d = d B as the distance from Psc to B' (ys = jb). For the stub at A, we obtain d = dA as the distance from P to A', where A' corresponds to ys = -jb located on the periphery of the chart as in Figure 11.20. At A, ys = -jb, l= l A and at B, ys = jb, l = l B as in Figure 11.20.ĭue to the fact that the stub is shorted (y' L =∞), we determine the length d of the stub by finding the distance from Psc (at which z'L = 0 j0) to the required stub admittance ys. Since b could be positive or negative, two possible values of l (<λ/2) can be found on the line. If a shunt stub of admittance y s = -jb is introduced at A, thenĪs desired. Consequently, shunt short-circuited parallel stubs are preferred.Īs we intend that Z in = Z o, that is, z in = 1 or y in = 1 at point A on the line, we first draw the locus y = 1 jb(r = 1 circle) on the Smith chart as shown in Figure 11.20. It is more difficult to use a series stub although it is theoretically feasible.Īn open-circuited stub radiates some energy at high frequencies. Notice that the stub has the same characteristic impedance as the main line. The tuner consists of an open or shorted section of transmission line of length d connected in parallel with the main line at some distance from the load as in Figure 11.19. Design single stub and double stub using Smith chart. Understand the mathematical principle behind the stub matching technique. Understand the concept of matching stub and different types of it. Summary Objectives After completing this module, you will be able to 1. The major drawback of using a quarter-wave transformer as a line-matching device is eliminated by using a single-stub tuner. Design of Double stub using Smith Chart: 9. Shorted stubs are usually preferred because opened stubs may radiate from their opened ends. In coaxial cable or two-wire line applications, the stubs are obtained by cutting appropriate lengths of the main line. They consist of shorted or opened segments of the line, connected in parallel or in series with the line at a appropriate distances from the load. ![]() Stub matches are widely used to match any complex load to a transmission line. Reflection of a Plane wave at oblique incidence.Reflection of a plain wave in a normal incidence.Link between electric and magnetic fields EE334 - Single Stub Impedance Matching 10 Lecture pp 85 92 2-10 Matched impedance when Z0 ZLÎ 0 must get to origin of Smith Chart If not matched insert a matching network Insert an L or C to match impedance, Why no R Avoid Ohmic Losses Stick in a second transmission line that acts as L or C called a stub.Waves and applications and Electromagnetic wave propagation.Forces due to magnetic field-Between Two Current Elements.Forces due to magnetic field-Current Element.Forces due to magnetic field-moving charged particle.Infinitely Long Coaxial Transmission Line-Ampere's Law.Magnetostatics and Magnetic forcesmaterials and devices.A Line Charge above a Grounded Conducting Plane.A Point Charge Above a Grounded Conducting Plane.General procedures for solving Poission’s or Laplace’s equations.Conductor-Free Space Boundary Conditions.Conductor-Dielectric Boundary Conditions.Dielectric-Dielectric Boundary Conditions.Relationship between E and V-maxwell's Equation.Electric field due to charge distribution.Electrostatics and Electric field in material space.Differential Lengths in Spherical Coordinates.Differential length in Cylindrical Coordinates.Differential Lengths in Cartesian Coordinates.Spherical to Rectangular Coordinate Transformation.Rectangular to Spherical Coordinate Transformation.For a coaxial line, it is not possible to determine the location of a voltage minimum. This requirement frequently calls for placement of the stub at an undesirable place from a mechanical view point. Cylindrical to Rectangular Coordinate Transformation Single stub impedance matching requires the stub to be located at a definite point on the line.Rectangular to Cylindrical Coordinate Transformation.Coordinate systems and transformation and Vector calculus.
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