Skip to main content

Line coding 1011000010000000000111

Short answer

Polar NRZ: +V for 1, -V for 0, no transitions in long zero run. Polar RZ: +V/-V for first half of bit then 0; self-clocking but double bandwidth. Manchester: +V then -V for 1, -V then +V for 0; always a mid-bit transition. Unipolar RZ: +V half-bit for 1, 0 for 0; loses timing during zeros.

Draw the timing diagram of Polar NRZ, Polar RZ, Manchester and unipolar RZ for the following binary sequence 1011000010000000000111.

Conventions (bit period TbT_b, amplitude VV):

CodeBit 1Bit 0
Polar NRZ+V+V for full bit−V-V for full bit
Polar RZ+V+V first half, then 0−V-V first half, then 0
Manchester+V+V then −V-V (high-to-low at mid-bit)−V-V then +V+V (low-to-high)
Unipolar RZ+V+V first half, then 00 for full bit

Bit sequence (22 bits): 1 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 1

Each character below is half a bit period.

bits 1 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 1 

Polar NRZ:
+V  |‾‾  ‾‾‾‾        ‾‾                    ‾‾‾‾‾‾
 0  |
-V  |  __    ________  ____________________

Polar RZ:
+V  |‾   ‾ ‾         ‾                     ‾ ‾ ‾
 0  | - - - - - - - - - - - - - - - - - - - - - -
-V  |  _     _ _ _ _   _ _ _ _ _ _ _ _ _ _

Manchester:
+V  |‾  ‾‾ ‾  ‾ ‾ ‾ ‾‾  ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾ ‾‾ ‾ ‾
 0  |
-V  | __  _ __ _ _ _  __ _ _ _ _ _ _ _ _ _  _ _ _

Unipolar RZ:
+V  |‾   ‾ ‾         ‾                     ‾ ‾ ‾
 0  | --- - --------- --------------------- - - -

Observations:

  • Polar NRZ stays at −V-V for the long run of ten 0s (bits 10–19): no transitions, so the receiver can lose bit timing.
  • Polar RZ returns to zero in every bit, so every bit has an edge, but it needs twice the bandwidth of NRZ.
  • Manchester has a transition at the middle of every bit even in the long zero run, so it is self-clocking and has no DC component; its bandwidth is twice that of NRZ.
  • Unipolar RZ gives no pulse at all during the run of zeros, so timing is lost there, and it has a DC component.

✓ Answer checked by Claude Opus 5.5 (high effort)

All Communication Systems chapter 6 questions →