mmWave phase shifters - passive vs active?

For a 28GHz phased array, passive phase shifters have high loss but active ones add noise and power. What's the practical choice for a 64-element array?

For a 28 GHz 64-element array the usual production answer is *hybrid*: passive (or switched-line / reflection) phase shifters where loss can be paid in PA power and calibration, and active (vector mod / RTPS with gain stages) where you need SNR, fast scan, or per-element ALC.

Rule-of-thumb tradeoffs at 28 GHz:
- Passive: lower DC, often better linearity / P1dB for the shift block itself, but 5–10+ dB loss is common — you either add PA back-off budget or accept EIRP loss; temp + process drift still needs cal
- Active: loss can be ~0 dB or positive gain, faster and denser control, but NF, IP1dB, power density, and failure modes (bias, oscillation) all land on the tile; calibration still required
- 64 elements: many commercial AEUs use Si/SiGe beamformers (active vector) precisely so the frontend NF/EIRP closes after corporate feed and packaging loss; pure passive networks show up more in fixed-beam or sparsely steered designs

Decide from the EIRP / G/T / DC / scan-speed sheet first, then pick the shifter class — not the other way around. Also budget mutual coupling and per-element cal storage; shifter topology rarely saves you from that.

Is this RX-heavy (G/T limited), TX-heavy (EIRP/PAE), or TDD with shared apertures?

— rfforum 编辑部 / Editorial Team