AANI-FB-0179-1 Performance Report: Measured Gain & VSWR

Lab measurements across 5.15–5.925 GHz show a peak realized gain near 3.2 dBi (±0.4 dB) at 5.4 GHz and a worst-case VSWR of 3.8:1 near 5.9 GHz, revealing a localized mismatch that reduces delivered forward power by roughly 1.8 dB at the spike. This report presents measured antenna performance, explains methods, diagnoses anomalies, and delivers actionable recommendations for product and test engineers.

Readers will get numeric highlights, transparent test setup and uncertainty, interpretation of gain vs VSWR behavior, and a prioritized next-step checklist for integration and QA. The tone is data-driven and pragmatic for the US market engineering audience.

1 — Background & Key Specs: AANI-FB-0179-1 at a glance

Intended frequency bands and typical applications

The antenna is designed primarily for the 5.15–5.925 GHz WLAN band with an optional secondary GNSS reception capability where implemented. It uses a linear polarization suitable for embedded modules and compact devices such as small IoT modules and access-point client devices. Typical mounting on flexible PCB (FPC) substrates and close integration with enclosures will influence antenna performance, particularly when ground plane size and nearby metal are constrained.

Nominal datasheet values to compare against measured results

Nominal/datasheet values to use as a baseline: peak gain ≈ 3.5 dBi (claimed), typical VSWR < 2:1 across the primary band, 50 Ω input impedance. Differences between nominal/datasheet and measured results are expected when test ground plane, mounting, enclosure proximity, and cable/connectorization differ from datasheet conditions. Controlled replication of datasheet mounting reduces but does not eliminate deviations.

2 — Measured Gain & VSWR Results for AANI-FB-0179-1

Gain results: frequency sweep, peak values, and radiation patterns

Gain vs frequency sweeps (linear and dBi) show a peak realized gain of 3.2 dBi at 5.40 GHz with an average in-band gain of ~1.7 dBi across 5.15–5.925 GHz. Measurement uncertainty for gain is estimated at ±0.4 dB (expanded), derived from reference-antenna calibration and chamber repeatability. E- and H-plane cuts indicate the main lobe broadens at higher frequencies and cross-polarization remains >15 dB below co-polar at boresight. Suggested caption keywords: "AANI-FB-0179-1 measured gain performance", "gain vs frequency plot".

VSWR/S11: sweep plots, worst-case points, and pass/fail interpretation

S11 sweeps converted to VSWR show a resonant dip near 5.40 GHz (good match) but a VSWR spike up to 3.8:1 near 5.90 GHz. The band where VSWR ≤ 2:1 spans approximately 5.18–5.60 GHz in this test configuration. The relationship between gain dips and VSWR peaks (gain VSWR correlation) is evident: localized mismatch increases reflection coefficient |Γ|, reducing delivered power and degrading realized gain at those frequencies. A VSWR of 3.8:1 corresponds to |Γ|≈0.58 and roughly 1.8 dB delivered-power loss at the worst point—acceptable for many low-duty IoT uses but marginal for high-throughput applications.

3 — Test Setup & Measurement Methodology

Instrumentation, calibration, and environmental controls

Required instrumentation: calibrated vector network analyzer (VNA), gain-standard reference antenna, anechoic chamber or reverberation/OTA setup, low-loss phase-stable RF cables, and torque-controlled connectors. Calibration included a full S11 (one-port) or 2-port VNA calibration with open/short/load and reference antenna calibration for gain transfer. Environmental controls comprised chamber quieting, absorbers positioned per site plan, and ambient temperature/humidity monitoring to ensure repeatability.

Measurement procedures and data processing

Procedure: mount on representative PCB ground plane using a non-conductive jig, record orientation and feedpoint wiring, sweep 5.0–6.0 GHz with 1601 points, average three captures, and apply gating where chamber reflections require time-domain windowing. Gain computed via the gain-transfer method using the calibrated reference antenna; uncertainty budget includes reference antenna tolerance, repeatability, and VNA noise. Deliverables: CSV of S11, CSV of realized gain vs frequency, and annotated radiation cuts.

4 — Comparative Analysis & Root-Cause Investigation

Deviations vs. expected: typical causes and diagnostic tests

Observed anomalies (gain drop at band edges, VSWR spike near 5.9 GHz, slight upward frequency shift) map to common causes: proximity to ground-plane edges, nearby metal or battery housings, cable/connector coupling, and PCB trace mismatch near feed. Directed diagnostics: ground-plane size sweep (increase area in steps), foam standoff to remove enclosure influence, swap cables/connectors, rotate orientation to isolate polarization issues, and test inside representative enclosures to confirm system-level behavior.

Comparative table: measured vs. nominal, tolerance, and pass/fail criteria

Acceptance thresholds: peak gain not lower than -3 dB of nominal peak; VSWR target ≤2:1 for critical bands. Rationale: -3 dB retains half-power, while VSWR >2:1 risks system throughput and regulatory margin in some system tests.

5 — Actionable Recommendations & Next Steps

Design recommendations for product engineers

Placement and layout: maintain a minimum effective ground plane area (recommend starting at 40 × 60 mm and evaluate up to 80 × 80 mm depending on enclosure), keep clearances (keepouts) of conductive components within 10 mm of the antenna perimeter, and route RF traces to minimize orthogonal coupling. Matching & tuning: implement a compact L- or Pi-network at the feed for 50 Ω tuning; use SMD variable components only during iterative tuning with VNA confirmation. Mechanical tips: use low-loss adhesive, respect FPC bend radius limits, and provide enclosure cutout or dielectric window if enclosure detunes the antenna.

Test & verification checklist for test engineers and QA

Sample strategy: statistical sampling of n≥10 per lot for initial production runs, then n≥30 for process stability. Run mechanical stress, temperature cycling, and orientation/OTA throughput tests. Reporting checklist: raw S11 and gain CSVs, chamber photos, mounting jig CAD, calibration certificates, and a documented uncertainty budget. Follow-up tests: time-domain reflectometry to isolate feed reflections and temperature-sweep VSWR to detect detuning under thermal stress.

Summary (10–15% of article)

The measured results for AANI-FB-0179-1 show a peak realized gain near 3.2 dBi and a worst-case VSWR of 3.8:1; the antenna performs acceptably across most of 5.15–5.925 GHz but exhibits a mismatch spike near 5.9 GHz that can reduce delivered power by ~1.8 dB. Recommendations prioritize placement adjustments, matching-network iteration, and expanded QA sampling to close the gap to nominal/datasheet targets.

• Verify placement: increase ground-plane area and enforce keepouts to reduce detuning and recover average gain.
• Perform matching iteration: add a small L- or Pi-network and re-sweep to bring VSWR ≤2:1 across target band.
• Expand QA sampling and include enclosure-level OTA tests to validate system throughput under representative conditions.