Phase shift module

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^[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
    - $\pi$ 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

# 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]‏

References

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

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

[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 information from Herley General Microwave

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