Phase shift module

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 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 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

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.

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

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

Number of effective bits, if digital [bit]
Biasing: current-driven, high-voltage electrostatic [mA, V]
DC power consumption [mW]
Distortion: group velocity dispersion (GVD) [ps²/nm]
Gain [dB] if active, loss [dB] if passive
Linearity: IP3, P1dB [dBm]
Phase shift / noise figure [°/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]

^ 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 Archived 2003-03-27 at the Wayback Machine information from Herley General Microwave

"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]}