T/R Module
Understanding T/R Modules
T/R modules are what make modern phased arrays possible. Each antenna element has its own T/R module, providing independent amplitude and phase control for beam steering, and amplification for both transmit and receive paths. The performance, size, and cost of T/R modules largely determine the phased array system capability.
T/R Module Architecture
- Transmit path: Phase shifter, variable attenuator, driver amplifier, power amplifier, harmonic filter.
- Receive path: LNA, phase shifter, variable attenuator, protection limiter.
- T/R switch: Antenna switch or circulator to share the antenna element between TX and RX.
- Control: Serial interface for setting phase, attenuation, and T/R mode.
Key Specifications
- Transmit power: 1-20W per module (frequency dependent).
- Receive noise figure: 2-4 dB.
- Phase shifter: 6-bit (5.625-degree resolution).
- Size: Half-wavelength spacing (~15mm at X-band).
Frequently Asked Questions
What is a T/R module?
A T/R module is the self-contained RF front end for one element of a phased array. It contains the PA, LNA, phase shifter, attenuator, and switch needed for both transmit and receive beam steering. Modern phased arrays use hundreds to thousands of T/R modules.
Why are T/R modules needed?
Active phased arrays require independent amplitude and phase control at every element. Passive phased arrays (using a centralized PA) have prohibitive feed network losses at element counts above ~100. T/R modules place amplification at each element, eliminating feed losses.
What semiconductor technology is used in T/R modules?
GaN is increasingly dominant for the PA stage due to high power density. GaAs pHEMT is common for LNAs and switches. SiGe is used in some receive-only or lower-power modules. Silicon CMOS is emerging for mmWave 5G T/R modules.