Phase shift module

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A microwave (6 to 18 GHz) Phase Shifter and Frequency Translator

A phase shift module is a microwave network module which provides a controllable phase shift of the RF signal.[1][2][3] Phase shifters are used in phased arrays.[4][5][6]


Active versus passive[edit]

Active phase shifters provide gain, while passive phase shifters are lossy.

Analog versus digital[edit]

  • Analog phase shifters provide a continuously variable phase shift or time delay.[7]
  • Digital phase shifters provide a discrete set of phase shifts or time delays. Discretization leads to quantization errors. Digital phase shifters require parallel bus control.
  • Differential, single-ended or waveguide:
    • Differential transmission line: A differential transmission line is a balanced two-conductor transmission line in which the phase difference between currents is 180 degrees. The differential mode is less susceptible to common mode noise and cross talk.
    • Antenna selection: dipole, tapered slot antenna (TSA)
    • Examples: coplanar strip, slotline
  • Single-ended transmission line: A single-ended transmission line is a two-conductor transmission line in which one conductor is referenced to a common ground, the second conductor. The single-ended mode is more susceptible to common-mode noise and cross talk.
    • Antenna selection: double folded slot (DFS), microstrip, monopole
    • Examples: CPW, microstrip, stripline
  • Waveguide
    • Antenna selection: waveguide, horn

Frequency band[edit]

One-conductor or dielectric transmission line versus two-conductor transmission line[edit]

  • One-conductor or dielectric transmission line (optical fibre, finline, waveguide):
  • Two-conductor transmission line (CPW, microstrip, slotline, stripline):
    • Differential or single-ended
    • TEM or quasi-TEM mode is TTD or quasi-TTD
  • Phase shifters versus TTD phase shifter
    • A phase shifter provides an invariable phase shift with frequency, and is used for fixed-beam frequency-invariant pattern synthesis.
    • A TTD phase shifter provides an invariable time delay with frequency, and is used for squint-free and ultra wideband (UWB) beam steering.

Reciprocal versus non-reciprocal[edit]

    • Reciprocal: T/R
    • Non-reciprocal: T or R


  • Non semi-conducting (ferrite, ferro-electric, RF MEMS, liquid crystal):
    • Passive
  • Semi-conducting (RF CMOS, GaAs. SiGe, InP, GaN or Sb):


  • Loaded-line:
    • Distortion:
      • Distorted if lumped
      • Undistorted and TTD if distributed
  • Reflect-type:
    • Applications: reflect arrays (S11 phase shifters)
    • Distortion:
      • Distorted if S21 phase shifter, because of 3 dB coupler
      • Undistorted and TTD if S11 phase shifter
  • Switched-network
    • Network:
      • High-pass or low-pass
      • or T
    • Distortion:
      • Undistorted if the left-handed high-pass sections cancel out the distortion of the right-handed low-pass sections
  • Switched-line
    • Applications: UWB beam steering
    • Distortion: undistorted and TTD
  • Vector summing

Figures of Merit[edit]

  • Number of Effective bits, if digital [Bit]
  • Biasing: current-driven, high-voltage electrostatic [mA,V]
  • DC power consumption [mW]
  • Distortion: group velocity dispersion (GVD) [ps/(km.nm)]
  • Gain [dB] if active, loss [dB] if passive
  • Linearity: IP3, P1dB [dBm]
  • Phase shift / noise figure [deg/dB] (phase shifter) or time delay / noise figure [ps/dB] (TTD phase shifter)
  • Power handling [mW, dBm]
  • Reliability [Cycles, MTBF]
  • Size [mm2]
  • Switching time [ns]


  1. ^ Microwave Solid State Circuit Design, 2nd Ed., by Inder Bahl and Prakash Bhartia, John Wiley & Sons, 2003 (Chapter 12)
  2. ^ RF MEMS Theory, Design and Technology by Gabriel Rebeiz, John Wiley & Sons, 2003 (Chapter 9-10)
  3. ^ Antenna Engineering Handbook, 4th Ed., by John Volakis, McGraw-Hill, 2007 (Chapter 21)
  4. ^ Phased Array Antennas, 2nd Ed., by R. C. Hansen, John Wiley & Sons, 1998
  5. ^ Phased Array Antenna Handbook, 2nd Ed., by Robert Mailloux, Artech House, 2005
  6. ^ Phased Array Antennas by Arun K. Bhattacharyya, John Wiley & Sons, 2006
  7. ^ Microwave Phase Shifter Archived 2003-03-27 at the Wayback Machine information from Herley General Microwave

External links[edit]