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.
Classification
Active versus passive
Active phase shifters provide gain, while passive phase shifters are lossy.- Active:
- * Applications: active electronically scanned array, passive electronically scanned array
- * Gain: The phase shifter amplifies while phase shifting
- * Noise figure
- * Reciprocity: not reciprocal
- Passive:
- * Applications: active electronically scanned array, passive electronically scanned array
- * 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
- * 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, 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 :
- * 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 :
- * Differential or single-ended
- * TEM or quasi-TEM mode is TTD or quasi-TTDPhase 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 beam steering.
Reciprocal versus non-reciprocal
- Reciprocal: T/R
- Non-reciprocal: T or R
Technology
- Non semi-conducting :
- * Passive
- Semi-conducting :
- * 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
- * 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
- 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
- Gain if active, loss if passive
- Linearity: IP3, P1dB
- Phase shift / noise figure or time delay / noise figure
- Power handling
- Reliability
- Size
- Switching time