Eliza E1 v0 antenna plan

Date: 2026-05-19 Status: planning. No antenna is laid out on a board. Claim boundary: Planning document. Promotion requires antenna routing on a fabricated board, network-analyzer S11 captures, near-field SAR scans, and regulatory pre-compliance evidence per FCC Part 15 / CE RED.

Scope

v0 carries three radios:

1. Wi-Fi 5 + Bluetooth 5 (Murata Type 1DX via SDIO+UART; see package/wifi/murata-1dx-sdio.yaml).
2. GNSS (GPS L1 + GLONASS L1, single-band).
3. NFC (13.56 MHz tag/peer mode for pairing/payment scaffolding).

Wi-Fi 7, BT 6, cellular (4G/5G), and UWB are explicit non-goals for v0 (research/mobile_platform_2026/02_analysis/wifi_bt_modem.md, "Low confidence recommendations" L-1, L-5).

Antenna assignment

Radio	Band(s)	Antenna type	Location (planning)	Feed network	Match target
Wi-Fi 2.4 GHz	2.400-2.4835 GHz	PIFA, 30 mm trace	Top-left corner of mainboard	π-network	< -10 dB S11
Wi-Fi 5 GHz	5.150-5.850 GHz	shared PIFA dual-band w/ Wi-Fi 2.4	Top-left corner	π-network shared	< -8 dB S11
Bluetooth 5	2.400-2.4835 GHz	shared with Wi-Fi 2.4 (same PIFA)	Top-left corner	shared π	< -10 dB S11
GNSS L1	1.575 GHz	chip antenna (e.g. Inpaq A2503CC)	Top-right corner	LNA pre-tuned series LC	< -10 dB S11 at 1.575 GHz
NFC	13.56 MHz	etched 4-turn loop, 25 × 35 mm	Back of mainboard under battery cover	50-Ω tuned (NXP PN7150 reference)	matched per NXP AN

Isolation and coexistence

• Wi-Fi 2.4 / BT coexistence: shared antenna with Murata Type 1DX internal TDM coexistence engine; no additional isolation needed beyond the module's reference circuit.
• Wi-Fi 2.4 / GNSS: ≥ 100 mm physical separation between PIFA feed and GNSS chip antenna feed; ground-pour discontinuity along the keep-out zone to suppress GNSS desense from Wi-Fi 2nd harmonic.
• NFC / digital noise: NFC loop sits under battery and is shielded from AP/PMIC digital noise by the battery's nickel-plated steel can; verify with a real RFID reader at 5 cm reading distance.

Test points

Each antenna feed needs a U.FL test connector for VNA captures during bring-up. U.FL is removed before regulatory testing.

Open questions (require human decision before board layout)

1. Single PIFA dual-band vs separate 2.4 and 5 GHz antennas.
2. NFC loop placement: top of battery vs along enclosure edge.
3. GNSS LNA: integrated into chip antenna module vs discrete (e.g. Skyworks SKY65809).

Cross-references

• package/wifi/murata-1dx-sdio.yaml
• docs/arch/wifi.md
• docs/architecture-optimization/phone-platform.md
• research/mobile_platform_2026/02_analysis/wifi_bt_modem.md