Wideband low-reflection transmission lines for bare chip on multilayer PCB

Rashad Ramzan, Jonas Fritzin, Jerzy Dabrowski, Christer Svensson

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The pad pitch of modern radio frequency integrated circuits is in the order of few tens of micrometers. Connecting a large number of high-speed I/Os to the outside world with good signal fidelity at low cost is an extremely challenging task. To cope with this requirement, we need reflection-free transmission lines from an on-chip pad to on-board SMA connectors. Such a transmission line is very hard to design due to the difference in on-chip and on-board feature size and the requirement for extremely large bandwidth. In this paper, we propose the use of narrow tracks close to chip and wide tracks away from the chip. This narrow-to-wide transition in width results in impedance discontinuity. A step change in substrate thickness is utilized to cancel the effect of the width discontinuity, thus achieving a reflection-free microstrip. To verify the concept, several microstrips were designed on multilayer FR4 PCB without any additional manufacturing steps. The TDR measurements reveal that the impedance variation is less than 3 Ω for a 50 Ω microstrip and S11 better than -9 dB for the frequency range 1 GHz to 6 GHz when the width changes from 165 μm to 940 μm, and substrate thickness changes from 100 μm to 500 μm.

Original languageEnglish
Pages (from-to)335-343
Number of pages9
JournalETRI Journal
Issue number3
Publication statusPublished - Jun 2011
Externally publishedYes


  • Bare chip mounting
  • Microstrip discontinuities
  • Microstrip transitions
  • RF testing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Computer Science
  • Electrical and Electronic Engineering


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