Time Domain Reflectometry (TDR) Analysis of Transmission Lines

T
ime Domain Reflectometry is the analysis of a conductor lines (interconnects)by sending a pulsed signal into the conductor, and then examining the reflection of that pulse. A TDR transmits a short rise time pulse along the conductor. If the conductor is of a uniform impedance and is properly terminated, the entire transmitted pulse will be absorbed in the far-end termination and no signal will be reflected toward the TDR. Any impedance discontinuities will cause some of the incident signal to be sent back towards the source. By examining the polarity, amplitude, frequencies and other electrical signatures of all reflections; tampering or interconnect discontinuity may be precisely located

Time Domain Reflectometry is the analysis of a conductor lines (interconnects) by sending a pulsed signal into the conductor, and then examining the reflection of that pulse. A TDR transmits a short rise time pulse along the conductor. If the conductor is of a uniform impedance and is properly terminated, the entire transmitted pulse will be absorbed in the far-end termination and no signal will be reflected toward the TDR. Any impedance discontinuities will cause some of the incident signal to be sent back towards the source.
By examining the polarity, amplitude, frequencies and other electrical signatures of all reflections; tampering or interconnect discontinuity may be precisely located.


TDR Analysis Need in Signal Net

TDR : Working Principle

With TDR, step pulse voltage is input into the transmission circuit and the voltage reflected in the transmission circuit is measured over time. The characteristic impedance of the circuit board is then calculated from the voltage drop in the reflected voltage.


TDR Simulation Result of Transmission Line in Smart phone from USB to Chip

TDR Pulse (step waveform) is very important. Rise Time value specifies the rise time of incident TDR pulse. The resolution of a TDR measurement system is directly related to the rise/fall time of the incident pulse. Rise time is specified with either a 10%-90% or a 20%-80% definition.


For example, consider a 20* timestep rise time for a 10%-90% definition, there will be 20 time steps between the time where the waveform has a value of 0.1 to the time it reaches a value of 0.9.


Initial glitch on TDR response Since the instantaneous TDR response is directly calculated from V/I, it reveals the initial glitch on TDR response. It is due to the zero current flowing through at the time = 0

Comments

Post a Comment

Popular posts from this blog

Image
Slotted Waveguide Array Antenna Slotted antenna arrays used with waveguides are a popular antenna in navigation, radar, and other high-frequency systems. A waveguide is a very low loss transmission line. It allows propagating signals to a number of smaller antennas (slots). Each of these slots allows a little of the energy to radiate. Slot impedance and resonant behavior for a single slot are dependent on slot placement and size. Its exceptional directivity in the elevation plane gives it quite high power gain. The slotted waveguide has achieved most of its success when used in an omnidirectional role To make the unidirectional antenna radiate over the entire 360 degrees of azimuth, the second set of slots are cut on the back face of the waveguide. An 8×8 planar four pole X-band Tchebyshev dual inductive post substrate integrated waveguide filter from 10.15 GHz to 10.7 GHz is designed for terrestrial broadcasting. The filter is designed on the 5870 with a relative dielectric
Read more

EMI & EMC Compliance of Smartphone

EMC within electronic components has become an increasingly important issue for embedded designers to contend with. As system frequencies and the need for lower supply voltages increase, the end application becomes more and more vulnerable to the negative affects of EMI. These electrical influences can be generated by either radiated or conductive EMI sources. Radiated sources include anything electrical or electromechanical, including motors, power lines, antennas, traces on a PCB (Printed Circuit Board), and even the silicon components on the PCB. Conductive EMI primarily shows itself as electrical “noise” on the power supply lines of an application and can be caused by induced voltage spikes from other devices within a system. Electromagnetic Interference (EMI): Electromagnetic emissions from a device or system that  interfere with the normal operation of another device or system. EMI is also referred to as Radio Frequency Interference (RFI) Electromagnetic Compatibility (E
Read more

QFN Package Simulation

Image
he Quad Flat No-lead (QFN) package is a CSP (plastic encapsulated package) with a copper lead frame substrate. QFN type package is one of the most cutting-edge IC packaging technologies in the electronics. The QFN is a leadless package where electrical contact to the PCB is made by soldering the leads on the bottom surface of the package to the PCB, instead of the conventional formed perimeter gull wing leads. The QFN-type package is known for its small size, cost-effectiveness and good production yields. QFN also possess certain mechanical advantages for high-speed circuits including improved co-planarity and heat dissipation. The QFN has pins on 4 edges of the bottom surface of the package. The QFN can have either a square or rectangle body as well as symmetric or asymmetric terminal patterns. The QFN was introduced to replace the gull wing lead Quad Flat Package (QFP) because the component leads are embedded in the plastic and cannot be bent during handling to insure consistent
Read more