1. Twinax
A Twinax is a dual coaxial cable with a common shield (“Extension” of TWP).
3 custom prototypes were produced for R&D purposes.
Currently Cu wire (later CCAl), low density polyethylene dielectric, Al foil shield, PU or polyester jacket.
AWG
Width/mm
Height/mm
Mass (kg/km) 28
2.39
1.32
5.2 30
1.75
0.97
2.55 34
1.12
0.64
1.1
Martin Kocian (SLAC)
Twinax
14 September 2016

2. Bit Error Rate Tests
Used a Virtex 4 bit error rate tester with a number of fixed rates to determine the maximum rates at which the transmission is
error-free.
The table shows the max rates in Mbps.
The eye pattern is for 6 m of AWG 28 at 5 Gbps.
AWG
length(m)
Raw
DC bal./preem. 28 6
3110
8000 30
1555
6220 34 4
Martin Kocian (SLAC)
Twinax
14 September 2016

3. New Bit Error Rate Tester
Kintex 7 instead of Virtex 4.
Xilinx-supplied ibert core.
Max rate is about 10 Gbps.
PRBS-31 pattern is random non-DC-balanced.
No 8b10b capability but PRBS-7 pattern is equivalent to 8b10b.
2 types of adaptive equalizers: LPM and DFE (high performance).
AWG/l (m)
PRBS31
PRBS31/pre
PRBS31/DFE
PRBS7
PRBS7/pre
PRBS7/DFE
28/6
6.4 8 10
30/6 5
34/4
=⇒ Higher rates with the new board.
Much improvement on transceivers between Virtex 4 and Kintex 7.
The equalizer on the Kintex 7 makes a big difference.
Martin Kocian (SLAC)
Twinax
14 September 2016

4. New Prototype
We plan to order a new Twinax prototype in about a month:
CCAl wires instead of copper.
Lower impedance (70 Ω?) for smaller cable size.
AWG 30?
• ft.
Any input on specs or requests for cables is welcome.
Martin Kocian (SLAC)
Twinax
14 September 2016

5. Connections
Interposer
The twinax cable has to be connected on both ends (opto/EOS).
Fuzz buttons provide a technology to do this.
Interposer with two PC boards attached on boths sides.
Twinax soldered to PC board.
+ Reliable and reasonably high density.
- Expensive (about 4 Fr. per button).
An alternative could be a ZIF connector with kapton flex soldered to the Twinax.
Martin Kocian (SLAC)
Twinax
14 September 2016

6. Twisted Wire Pair Solution
TWP is low-mass solution high-density electrical data transmission solution for inner pixel layers
Achieves 5 Gbps bandwidth for short lengths [O(1m)], but bandwidth drops quicklywith increased length
Most likely final solution continues twisted wire pair with longer impedance-matched twin-axial cable
We expect the total module-to-optobox distance to be 1.2 m + 6 m (more input on optobox location needed)
100 Ω twisted-pair requires large conductor separation
120
✓ 2s ◆
z(Ohms) = p✏ ln d
Signal propagation in skin-effect region (multistrand conductor)
– Large number of strands should approximate solid-core performance
J. Nielsen (UCSC/SCIPP)
ITk Week /09/14

7. Twisted Wire Pair Solution
J. Nielsen (UCSC/SCIPP)
ITk Week /09/14

8. Current Models Under Test
TWP 36 AWG multistrand w/ PEEK dielectric and shield
TWP 36 AWG multistrand w/ PEEK dielectric, no shield
TWP 40 AWG MS Rad-Soft (used for comparison)
Hybrid [6m 28 AWG twinax + 1m 36 AWG MS TWP]: soldered connection between twinax and TWP
Hybrid [6m 30 AWG twinax + 1m 36 AWG MS TWP]: soldered connection between twinax and TWP
We are working on detailed material calculations for comparisons of current and future designs
J. Nielsen (UCSC/SCIPP)
ITk Week /09/14

9. Summary of Bit-Error Rate Results
Comparison of solid core and multi-strand, 36 vs 40 AWG
We also see large variations in results for different PRBS
– With PRBS-7, BER< , even at 8.25 Gbps! Need a standard for testing
J. Nielsen (UCSC/SCIPP)
ITk Week /09/14

10. Design Adjustments p✏ ln
Even if the TWP is low-mass solution, non-negligible volume complicates stave loading
Current cables have outside diameter of 1100 microns (area 1 mm2)
PEEK insulation contributes 660 microns of the total
Shield contributes microns
Can we reduce the volume and number of X0?
– Reduce conductor diameter d from 150 microns to 100 microns (36 to 38 AWG), maintaining multistrand conductor for strength
PEEK reduced by corresponding amount –
– Total diameter > 900 microns
120
z(Ohms) =
✓ 2s ◆ d
p✏ ln
Reduce impedance from 100 Ω to 70 Ω?
Allows larger reduction of PEEK
Reduce outside diameter to 700 microns (0.4 mm2)?
Power considerations for long low-impedance cables
Drain wire for ease in connecting shields (no effect at high freq.)
J. Nielsen (UCSC/SCIPP)
ITk Week /09/14

11. Cables tested: TWISTED PAIR
CABLES TESTS
Cables tested: TWISTED PAIR
36 AWG (American Wire Gauge) ≈ mm diameter
Multi-stranded Copper : 7 strands/ cable
Each conductor is insulated with PEEK (is a colourless organic thermoplastic polymer, Poly-Ether-Ether-Ketone)
- Different thicknesses has been measured for this insulator
390 µm for “transparent” PEEK
307 µm for “blue” PEEK
Both conductors are shielded with 10 μm aluminium foil
Backed with kapton insulator, 25um thick
390 µm
307 µm
Signal
1.10 mm
0.7 mm
Peek Insulator
Foil Shield (10 µm)
Kapton insulator (25 µm)
14 September 2016
Leyre Flores

12. Cables tested: TWINAXIAL (3 different versions)
CABLES TESTS
Cables tested: TWINAXIAL (3 different versions)
TwinAx Type/ parts
Cu28
Cu30
Cu34
Signal Wire Cu
Signal wire OD (µm)
321
255
160
Drain wire OD (µm)
202
127
Dielectric material
Polyethylene
Dielectric diameter (µm)
1060
840
480
Al shield thickness (µm) 25
Jacket material
Polyurathane
Polyester
Jacket thickness (µm)
100
Cable width (mm)
2.39
1.75
1.12
Cable height (mm)
1.32
0.97
0.635
Weight (kg/km)
5.2
2.55
1.1
14 September 2016
Leyre Flores

13. Cables tested: SPACEWIRE
CABLE TESTS
Cables tested: SPACEWIRE
It was given by a cable company AXON for us to test it
28 AWG
Conductor is aluminium coated with silver
Silver is not possible to use in the experiment!!!
Multistranded wire
Insulator is expanded PTFE
14 September 2016
Leyre Flores

14. CABLE TESTS RESULTS TABLE
***We will need to calculate the spacewire mass
Type of cable
AWG
Length
S21 (dB 2.5 Gbps
Twisted pair 36
1 meter
-3.36 dB
3 meters
-8.66 dB
5 meters dB
Twinaxial 28
8 meters dB 30 dB 34 dB
Spacewire
-4.77 dB
7 meters
-9.79 dB
Band-width completely dependent on the distance and AWG
We consider any result up to -12dB (thumb rule)
14 September 2016
Leyre Flores