What is the difference between a passive phased array and an active electronically scanned array?
PESA vs AESA
The PESA architecture uses a single high-power tube transmitter (TWT or klystron) that generates the full transmit power. This power is distributed to all elements through a corporate feed network, with phase shifters at each element for beam steering. The feed network must handle the full transmit power, which limits the bandwidth and increases losses. A single transmitter failure disables the entire array.
| Parameter | Low Gain | Medium Gain | High Gain |
|---|---|---|---|
| Gain Range | 2-6 dBi | 6-15 dBi | 15-45 dBi |
| Beamwidth | 60-360° | 15-60° | 1-15° |
| Typical Types | Dipole, monopole, patch | Yagi, helical, horn | Parabolic, array, Cassegrain |
| Bandwidth | Narrow to wide | Moderate | Narrow to moderate |
| Complexity | Low | Medium | High |
Frequently Asked Questions
What is the cost difference?
PESA is cheaper to build (one centralized transmitter vs N T/R modules). However, PESA requires expensive high-power tubes with limited lifetime (5000-20000 hours). AESA T/R modules use solid-state components with much longer lifetime (>100,000 hours). Over the system life, AESA can have lower total ownership cost.
What about for commercial applications?
5G base stations use a simplified AESA architecture (active antenna units). Each element has a small PA and LNA integrated into an RFIC. The per-element cost is much lower than military T/R modules ($1-10 vs $100-1000) due to mass production in semiconductor processes.
Can I upgrade a PESA to AESA?
Not easily. The architectures are fundamentally different: PESA distributes high-power RF through the feed network, while AESA distributes low-power RF and DC power. A PESA-to-AESA upgrade typically requires a complete redesign of the antenna face, feed network, and power distribution system.