Introduction (or Why Make Transmission Line Measurements?) A transmission line (or cable) transfers electrical energy from one point to another. Time delay and Attenuation (distortion and losses) are also important parameters for high speed busses.
Attenuation Lossy lines are becoming increasingly important in high speed Yet, there is much confusion in the industry about the origin of the losses and how to account for their effects in practical ways.
Attenuation (cont.) The power loss in a cable. It is due to heating loss because of conductor resistance and skin effects. Dielectric loss caused by poor dielectric materials. The total loss is expressed in decibels (dB) per unit length of cable (ratio between two amounts of power existing at two points) dB = 10 log P1/P2
Attenuation (cont.)
The most important effect arising from a lossy transmission line is rise time degradation. The losses behave in a way that causes higher frequency components of the signal to be attenuated more than low frequency components
RG223
K02252D
Connectors cascade compare between 4 connectors cascade (1 male-male,1 male- female and 2 female- female) to 2 connectors cascade (1 female- male and 1 female-female) and 1 female- female
Cascade of connectors 1 adaptor 2 connectors 4 connectors Attenuation [db] Vs. freq [Hz]
Cascade - conclusion As expected, connector in serial cause signal decrease While concatenate a few elements, minimize number connectors
Two cables and connector manipulation Cable rg58 measurement 2 Cables rg58 plus connector between Two rg58 attenuation by mathematical multiple on single cable
Two cables and connector manipulation 1 rg58 cable 2 rg58 without any connector 2 rg58 with connector Attenuation [db] Vs. freq [Hz]
Two cables and connector manipulation conclusions As we can see, the multiply by 2 of the single 1m cable characters an attenuation of 2m cable. The lower curve present the influence of the connector. It’s better to use one single long cable than two cascade of short cables.
Good/Bad cables, connectors and relationship Rg58 with / without connectors Sucoflex100 (8274/4E) with/without connectors. Substrate a different and comparison
Good/Bad cables, connectors and relationship Good cable 2 cable + connector Bad cable Bad cable + connector Attenuation [db] Vs. freq [Hz]
Manipulation on the couple of curves above ( substract the attenuation,show that there is no relationship between good cale + connector VS. bad cable + connector. Attenuation [db] Vs. freq [Hz]
Conclusion- The quality of the cable does not relate to the connector influence, The attenuation behaves in serial effect. Assumption – the gap between the diff curve result from measure mistakes.
Elements location cable – connector – cable connector –cable – cable cable – cable – connector
Location of the elements in cascade Attenuation [db] Vs. freq [Hz]
element location - conclusions There has no different in arrangement of elements As known, VNA measures and calculates the DUT (passive elements) between the calibration edges as whole component and ignore the inner order.
Measurement sensitivity Flexibility. Connection tightening between elements.
Flexibility based on the vendor parameters. Little radius Big radius Attenuation [db] Vs. freq [Hz]
Connection tightening between elements Tight connection with Newton key Tight connection with hand Weakly connection Attenuation [db] Vs. freq [Hz]