RF View for Antenna Impedance Matching

Antenna Matching Design Workflow

Modern mobile antennas (chip antennas, PIFAs, patch antennas) rarely present exactly 50 Ω at the feed point — especially when installed on a PCB with limited ground plane. A two-element matching network (L-network) between the 50 Ω feed line and the antenna transforms the antenna's actual impedance to 50 Ω at the target frequency.

Step 1: Measure and Load Antenna S11

  1. Measure antenna on final PCB with VNA → save as .s1p
  2. Transfer .s1p to Android → open in RF View
  3. Select S11 view → check current resonance:
     - If S11 > −10 dB at target band: needs matching
     - If S11 < −15 dB: already well matched (may not need matching network)
  4. Switch to Smith chart → note impedance location at target frequency

Step 2: One-Tap Auto Matching

  Open Matching tab in RF View:
  - Target: 50 Ω (standard for all cellular systems)
  - Frequency: e.g., 900 MHz for LTE Band 8
  - Topology: Auto (RF View selects optimal L-network topology)
  - Tap "Auto Match"

  RF View outputs:
  - Component values: e.g., "Shunt C = 4.7 pF, Series L = 8.2 nH"
  - Matched S11 response: shows improvement after matching
  - Bandwidth: −10 dB bandwidth of matched antenna

Step 3: Verify Matching Across Full Band

  LTE Band 8 requirement: S11 < −10 dB from 880–960 MHz (TX+RX)

  After RF View Auto Match:
  S11 at 880 MHz: −12.5 dB ✓
  S11 at 920 MHz: −18.2 dB ✓ (best match at center)
  S11 at 960 MHz: −11.3 dB ✓

  All pass LTE Band 8 requirement!
  BW Marker confirms: −10 dB bandwidth = 870–975 MHz (105 MHz)

Step 4: Multiband Antenna Matching

For multi-band operation (e.g., LTE Band 1 + Band 8), a single L-network typically cannot match at both frequencies simultaneously. Options:

• Tunable matching element (varactor diode) that changes with the operating band
• Switched matching network (MEMS or PIN diode switches) — one L-net per band
• Antenna redesign for inherently wider-band operation

Related Topics

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