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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]

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.^[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

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
    • ${\displaystyle \pi }$ 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
• Biasing: current-driven, high-voltage electrostatic
• DC power consumption
• Distortion: group velocity dispersion (GVD)
• Gain if active, loss if passive
• Linearity: IP3, P1dB
• Phase shift / noise figure (phase shifter) or time delay / noise figure (TTD phase shifter)
• Power handling
• Reliability
• Size
• Switching time

References

External links

• "Phase Shifters", Micorwaves101.com
• 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^{[dead link]}