Wideband RF Matching Network Design

Single Section vs Multi-Section Matching

  Single L-network bandwidth: BW ≈ f₀/Q_min
  For 10Ω→50Ω: Q_min=2 → BW ≈ f₀/2 (50% fractional BW, limited by Bode-Fano)

  Multi-section N-element transformer:
  Adds N−1 intermediate stages
  Each stage handles √(Z_high/Z_low) impedance ratio
  Much wider bandwidth for same matching quality

Two-Section Stepped Impedance

  Goal: match 5Ω PA → 50Ω over 3.3–3.8 GHz (n78, 500 MHz BW)
  
  Two-section (intermediate at √(5×50) = 15.8Ω):
  Section 1: 5Ω → 15.8Ω (L-network at 3.55 GHz)
    Q₁ = √(15.8/5 − 1) = 1.48
    BW₁ ≈ 3550/1.48 = 2398 MHz (much wider than needed)
  
  Section 2: 15.8Ω → 50Ω (second L-network)
    Q₂ = √(50/15.8 − 1) = 1.48
    BW₂ ≈ 2398 MHz
  
  Combined: 500 MHz BW easily achieved with S11 <−10 dB ✓

Verification in RF View

1. Build 2-stage L-network in Circuit Simulator with PA S2P DUT block
2. Simulate → verify S11 <−10 dB from 3.3–3.8 GHz
3. BW Marker → reads actual −10 dB BW (should be >500 MHz)
4. Monte Carlo ±5% tolerance → verify 90%+ yield at 3.3–3.8 GHz

Related Topics

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