Phase shift module

This article is about the microwave device. For the guitar effect, see Phaser (effect).

"Phase shifter" redirects here. For the type of electric utility transformer, see quadrature booster.

File:General Microwave Phase Shifter.png

A microwave (6 to 18 GHz) Phase Shifter and Frequency Translator. Picture courtesy of Herley

A phase shifter is a microwave network which provides a controllable phase shift of the RF signal. Phase shifters are used in phased arrays.

Classification

• Active versus passive: Active phase shifters provide gain, while passive phase shifters are lossy.
  • Active:
    • Applications: active electronically scanned array (AESA), passive electronically scanned array (PESA)
    • Gain: The phase shifter amplifies while phase shifting
    • Noise figure (NF)
    • Reciprocity: not reciprocal
  • Passive:
    • Applications: active electronically scanned array (AESA), passive electronically scanned array (PESA)
    • Loss: the phase shifter attenuates while phase shifting
    • NF: NF = loss
    • Reciprocity: reciprocal

• Analog versus digital:
  • Analog phase shifters provide a continuously variable phase shift or time delay.
  • 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

• One-conductor or dielectric transmission line versus two-conductor transmission line
  • One-conductor or dielectric transmission line (optical fibre, finline, waveguide):
    • Modal
    • No TEM or quasi-TEM mode, not TTD or quasi-TTD
    • Higher-order TE, TM, HE or HM modes are distorted
  • 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
  • Reciprocal: T/R
  • Non-reciprocal: T or R

• Technology
  • Non semi-conducting (ferrite, ferro-electric, RF MEMS, liquid crystal):
    • Passive
  • Semi-conducting (RF CMOS, GaAs. SiGe, InP, GaN or Sb):
    • Active: BJT or FET transistor based MMICs, RFICs or optical ICs
    • Passive: PIN diode based hybrids

• Design
  • 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
      • $\pi$ 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

• 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 if [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]

External links

• Website on Phase Shifters in Microwaves
• Microwave Phase Shifter information from Herley General Microwave
• [1] A low cost electro-mechanical phase shifter design, including a brief summary of solid state methods @ www.activefrance.com