Phase shift module



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

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

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) [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]