5.8 GHz Phased Array Antenna

An electronically-steered phased array for drone use: the entire RF PCB is generated programmatically from Python, on a hybrid Rogers 4350B stackup with blind vias.

The goal

High bandwidth communications / data link with beam steering for maximum gain. This is also the stepping stone toward the counter-UAS radar work on the RF roadmap.

Two boards, one architecture

	3×3 v1	4×4 v2
Elements	9	16
Phase shifters	MAPS-010145, 4-bit (22.5°)	HMC1133, 6-bit (5.625°)
Gain	~9.5 dBi	~12 dBi
Steering	±60°	±60°
Cost	~$450	~$2,750

The 3×3 exists to de-risk the architecture at 83% lower cost before committing to the expensive board. Both target >1 kHz beam updates with IMU compensation, so the beam stays locked while the airframe moves.

Programmatic PCB

There is no hand-drawn schematic. Netlist, component placement, and routing are all generated from Python through KiCad’s scripting API: change the element count or spacing and regenerate the board. RF details are handled in code: 1.077 mm traces for 50 Ω on the Rogers layer, 0.3 mm neck-downs at component pads, curved corners, λ/2 patch spacing at 25.84 mm.

The stackup is the part I’m most pleased with: Rogers 4350B (0.508 mm, tan δ 0.0037) only on the top layer where the RF lives, FR4 below, joined with blind vias from two controlled-depth drill passes. About 30% cheaper than a full Rogers board with no meaningful RF penalty.

Control is an STM32H743: native SPI with 9 chip-selects on the 3×3, and twelve daisy-chained 74HC595 shift registers on the 4×4.

Status

Rev A of the 3×3 is back from fab: hybrid Rogers 4350B / FR4 stackup, two-depth blind vias, ENIG finish, purple mask. The boards look good, and assembly is the next milestone; the project is waiting on funding to order the component set (the nine MAPS-010145 phase shifters are the bulk of the cost).

Fabricated Rev A 3x3 phased array PCB with purple soldermask, held in hand over an electronics workbench — Rev A of the 3×3, back from fab: 150 × 180 mm, nine patch elements on the Rogers layer, ENIG over the RF traces.

One Rev A quirk, visible above: the patch footprint’s radiating pad omitted the mask layer, so the nine antenna elements are etched in the top copper but sit under the soldermask instead of being exposed. That slightly detunes the patches (the mask adds a thin dielectric layer over the fringing fields) but should not block bring-up; the one-line footprint fix is queued for Rev B.

The 4×4 has RF layout done, routing pending. The companion simulator stays live so the beamforming work continues in software.