Embedded System

Diversity GNSS Antenna FPGA

25 fixed L1 beams to 25 GNSS receivers, with an FPGA mux selecting the best position solution

Overview

A 25-element GNSS antenna array operated as a static beam array: the elements form 25 fixed beams of differing pattern coverage, and each beam feeds its own L1 GNSS receiver. An FPGA mux aggregates the 25 receiver streams and selects the best position solution across the array. The beam geometry is fixed by the array itself — the patterns are not shaped, pointed or adapted at run time.

The 25 beams run in parallel: each of the 25 beams has its own receiver producing its own data stream, and the FPGA mux gathers those streams into a single host data path while preserving which stream came from which beam. That correspondence is what makes the array usable at all — a position solution is only worth anything if it can still be attributed to the beam that produced it.

The project is single-band: L1 (1575.42 MHz) only, no second band and no band selection. The selection rule the mux applies across the 25 streams, its update rate and the host interface are [TBD] and are not asserted here.

Bench Prototype

Bench setup for the diversity GNSS antenna work: the FPGA board at the left, a taped rainbow ribbon harness running to the right, and a whip antenna on a stand on a blue bench mat. — Bench setup: the FPGA board, the taped ribbon harness and a whip antenna on a stand — prototype wiring on the bench, not a finished assembly.

Close-up of a GNSS receiver module on the bench: a white antenna lead, taped wire joins and jumper wires running to a pin header. — Receiver module close up: antenna lead, taped joins and jumpers to the header.

The FPGA development board used for the receiver mux: a 2x20 header carrying the ribbon harness, a USB-C port, debugging silk and a QR code on the board. — The FPGA board carrying the receiver mux: the 2x20 header with the ribbon harness, USB-C and debug silk.

Key Specifications

Parameter	Value
Antenna Beams	25 fixed beams, static geometry (pattern diversity)
GNSS Receivers	25 — one L1 receiver per beam
Frequency Bands	L1 (1575.42 MHz) only
Bandwidth	Up to 10 MHz
Beam Architecture	Fixed beams, static geometry — no adaptive processing
Antenna Aggregation	FPGA mux — 25 receiver streams aggregated, best position solution selected
Supported Signals	GPS L1 C/A; Galileo E1; BeiDou B1

Key Features

25 Fixed Beams — 25 antenna elements form 25 beams whose coverage is set by the array geometry and does not change at run time
25 L1 Receivers — One GNSS receiver per beam, so every beam produces its own position solution
FPGA Mux — The 25 receiver streams are aggregated, and the best position solution across the 25 beams is selected from them
Single-Band Simplicity — L1 only (1575.42 MHz); no second-band hardware and no band switching
Compact Form Factor — Designed for integration into UAVs, ground vehicles, and fixed installations

Applications

High-integrity GNSS receivers for critical infrastructure and autonomous systems
High-integrity positioning for autonomous vehicles
GNSS signal monitoring and spectrum analysis
Research and development for advanced navigation systems

Draft Specifications — Mid-Design · content not final

Detailed Specifications (Preliminary)

Values marked [TBD] are unresolved. Board-level and part-level detail is deliberately not stated — no FPGA part, receiver part, antenna part, pinout or clock plan is asserted on this page.

RF / Electrical

Parameter	Min	Typ	Max	Unit
RF Input Frequency (L1)	—	1575.42	—	MHz
Instantaneous Bandwidth	—	10	[TBD]	MHz
Number of RF Channels	—	25	—
Noise Figure	—	[TBD]	—	dB
Gain	—	[TBD]	—	dB
Phase Noise @ 10 kHz	—	[TBD]	—	dBc/Hz
ADC Resolution	—	[TBD]	—	bits
Input IP3	—	[TBD]	—	dBm
Channel-to-Channel Phase Stability	—	[TBD]	—	deg
Power Supply	[TBD]	[TBD]	[TBD]	V DC
Power Consumption	—	[TBD]	—	W

Digital / Processing

Parameter	Value
Beam Mux	FPGA-based ([TBD] part)
Front-End Multiplexing	25 L1 receiver streams aggregated by the FPGA mux
Position Selection	Best position solution across the 25 beams ([TBD] rule)
Host Interface	[TBD] (USB / Ethernet / PCIe)
Data Output Format	[TBD]
Update Rate	[TBD]
Onboard Storage	[TBD]

Mechanical

Parameter	Value
Dimensions	[TBD]
Weight	[TBD]
Enclosure	[TBD] (e.g., milled aluminum, shielded)
Antenna Connectors	[TBD] (e.g., SMA, MMCX)
Mounting	[TBD]

Environmental

Parameter	Value
Operating Temperature	[TBD]
Storage Temperature	[TBD]
Vibration / Shock	[TBD]
Ingress Protection	[TBD] (IP rating)

Documentation

The draft product specification collects this page's structure, document control and specification tables into one document. It is stamped as content not final on every page and is not a released specification.

Download spec (PDF) — 4 pages, draft

Status

Product in active design phase. Preliminary specifications subject to change; no figure on this page is final.

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