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
- Active:
- 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
- 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.
- 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
- One-conductor or dielectric transmission line (optical fibre, finline, waveguide):
- 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
- Non semi-conducting (ferrite, ferro-electric, RF MEMS, liquid crystal):
- Design
- Loaded-line:
- Distortion:
- Distorted if lumped
- Undistorted and TTD if distributed
- Distortion:
- 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
- Network:
- Switched-line
- Applications: UWB beam steering
- Distortion: undistorted and TTD
- Vector summing
- Loaded-line:
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