Transmission line characteristic impedance

Modeling of High-Speed Interconnections. Modeling the electrical behavior of an interconnection involves two steps. First, the transmission line characteristics, such as the characteristic impedance, propagation constant, capacitance, resistance, dielectric conductance, and coupling parameters, must be calculated from the physical dimensions and material properties of the interconnection. In addition, structures, such as wire bonds, vias, and pins, must be represented by lumped resistance (R), inductance (L), and capacitance (C) elements. 

In studies of these and other items, the impedance method is often invoked because of the diagnostic value of complex impedance or admittance plots, determined in an extremely wide frequency range (typically from 104 Hz down to 10 2 or 10 3 Hz). The data contained in these plots are analyzed by fitting them to equivalent circuits constructed of simple elements like resistances, capacitors, Warburg impedances or transmission line networks [101, 102]. Frequently, the complete equivalent circuit is a network made of sub-circuits, each with its own characteristic relaxation time or its own frequency spectrum. 

A variety of transmission line structures can be fabricated in planar layers of conductor and dielectric (Figure 9). The stripline and offset stripline are best suited for multilayer structures. The offset stripline, with two orthogonal signal layers between a pair of reference voltage planes, eliminates one intermediate plane and achieves higher characteristic impedance for a given dielectric thickness than do two stripline layers but increases the possibility for crosstalk between layers. 

That is, the characteristic impedance G is the impedance at any point of the transmission line. 

These expressions indicate that the input impedance is the same at any point of the line. Alternatively, if the final impedance of a transmission line is the characteristic impedance, such a line behaves as an infinite line. 

Here, the impedance response is independent of the working point, and the frequency dependence is determined solely by the material parameters of the composite. For / <linear branch appears only at frequencies co > a/Cfr). Doublelayer charging and proton transport dominate the overall electrode response in this regime, whereas Faradaic processes are insignificant due to the high frequencies. An equivalent representation of this system is an RC-transmission line [130], Since no fractality or branching of the network is assumed, the response resembles that of a Warburg impedance with a characteristic proportionality Z a where... 

The dielectric constant of the substrate is the prime property because the propagation speed of the signal is inversely related to it. At these speeds the system has to be designed as a transmission line which must match the impedance of the devices used. Impedance mismatch can lead to reflected signals, and hence to signal distortion. The characteristic impedance of the line is also dependent on the dielectric constant, and for the devices now being used higher impedances are required and, therefore, low dielectric constant substrates. In addition, it is also important to have low-loss materials to prevent distortion of the pulses. 

C. Antenna. The antenna is used to make a transition from a guided wave (from the transmission line) to a radiated electromagnetic wave. The design of the antenna is influenced by many factors such as size, frequency, and electrical impedance. Antennas are normally of two types - omnidirectional and directional. The omnidirectional antennas are element type antennas such as monopoles or dipoles. The directional are horn-type antennas, parabolic dish type antennas such as a satellite communications antenna (SATCOM), or a phased-array antenna which can emit many beams at once. The characteristics of the antenna are a very important aspect of hazard evaluation. 

To understand how a negative resistance oscillator works, it is easiest to consider the electrical characteristics of the waveguide cavity in which the device is housed. A waveguide cavity is in its simplest form a short piece of transmission line terminated in a short-circuit at one end and an impedance matching device coupled to the rest of the circuit at the other end (Section 2.1). 

The frequency dependency of the characteristic Impedance of a Transmission Line (TL) r can be described by the following equations ... 

In order to prevent reflectitMis at the load terminal, the characteristic impedance of the transmission line must be equal to the input impedance of the load. In most microwave systems, 50 Q is used as standard characteristic impedance for transmissimi lines and input impedance for other components. 

Microwave in Mkrofluidks, Fig. 4 When a transmission line is terminated by a load, the ratio of total voltage to the total current (summation of incident and reflected voltage and current) must be equal to the impedance of the load. In order to have a reflection equal to zero, the impedance of the load must be equal to the characteristic impedance of the transmissirai line. No reflection means that all the power sent to the load is consumed by the load... 

Each type of transmission line has different characteristic impedance and propagation constant which are functions of the complex permittivity of the substrate and superstate. The complex permittivity of methanol is extracted in this method for the frequency up to 40 GHz using a hybrid method that combines experimental data with finite element analysis. 

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