Electronic – signal types and wire types

coaxdifferentialmanchester-codingsignalwire

I am trying to understand the selection criterion for choosing between a signal types and wire type out of the following:

Signal types:

  1. Gnd reference uni-polar signal
  2. Gnd reference bi-polar signal
  3. Differential signal
  4. Balanced signal
  5. Encoded signal eg., Manchester encoded

Wire types:

  1. Single core wire
  2. Multi-core wire
  3. Braided wire
  4. Flexible wire
  5. Co-axial wire
  6. Shielded wire
  7. Twisted-pair wires

I want to understand when to use which signal type and which wire type when designing any electronic system? Are there any guidelines for these selection?

Best Answer

Gnd reference uni-polar signal

normal Signals I would say. they are cheap to generate, cheep to receive. Not generally good for longer distances and higher speeds, you need to prepare to cope with EMI Problems.

Gnd reference bi-polar signal

hmm, yes in anlog applications maybe, for digital signals the only advantage would be combined with a dc-free code the average potential is equal to GND.

Differential signal

reduces EMI problems by magnitudes combined with good signal encodings and shields that's the gold standard for least signal distortion ar at least well predictable signal distortion, acceptable impedance, plus good EMI performance

Balanced signal

You want your differential signal to be balanced. It's part to get the performance you want, also you want the signal to be DC-Free, so your signal does not drift to a point where the receiver is no longer able to detect it without errors

Encoded signal eg., Manchester encoded

Well all digital signals are encoded somehow. A multi level code like the Manchester Code gives you a improved data rate above a simple 2 level Pulse-Amplitude Modulation (more bits per clock cycle). Multilevel codes are more complex and suffer from higher susceptibility to EMI (signal to Noise ratio of the transmission channel...) But even schemes like QAM64,128,... are already in use. In most cases combined with some error detection and correction stages.

Wire types:

Single core wire

normally not used for signals, good for GND/Earth connection, Power distribution, with signals you suffer from gnd-loops, at least you want em to be short.

Multi-core wire

pure multicore without combination of shields and e.g. twisted pairs is good for power distribution and only used for low speed analog stuff or low speed busses. Suffer from all kinds of EMI problems.

With additional technologies these cables can be among the best - ethernet and USB show you can transfer Gigabit/sec

Braided wire

low resistance GND connection but suffers from parasitic inductance, which e.g. fails to guide high frequency EMI from a shield to Earth. Single Core Wires are much better here

Flexible wire

more expensive, bit more parasitic inductance

Co-axial wire

very good for high frequency. Most High speed messurement equipment is connected with Coax

Shielded wire

Shields are the Multitool for EMI problems, can be combined with almost any form of cable. Shields are a complex topic of their own. desity of the shield, how to connect with the shield,...