================================================================================ SCHEMATIC: 2-WAY WILKINSON POWER DIVIDER TM-HYB-001 Rev A Equal-split, in-phase, resistive isolation 50Ω system, covering 160M through 23cm ham bands ================================================================================ OVERVIEW -------- The Wilkinson power divider splits an input signal into two equal-amplitude, in-phase outputs with resistive isolation between output ports. Design parameters: Port impedance: 50 Ω (all three ports) Quarter-wave arm Z: Z_λ/4 = Z0 × √2 = 70.71 Ω Isolation resistor: R_iso = 2 × Z0 = 100 Ω Split ratio: Equal (3 dB nominal insertion loss each arm) Phase difference: 0° (in-phase) Typical isolation: >20 dB Typical return loss: >20 dB (matched) SCHEMATIC — TRANSMISSION LINE VERSION (VHF/UHF) ------------------------------------------------- PORT 1 (input, 50Ω) │ ├──── λ/4 @ 70.71Ω ─────────── PORT 2 (output A, 50Ω) │ │ │ [R_iso = 100Ω] │ │ └──── λ/4 @ 70.71Ω ─────────── PORT 3 (output B, 50Ω) Each λ/4 arm: coaxial or microstrip, Z = 70.71 Ω Coaxial implementation (50Ω → 70.71Ω): Use RG-59 (75Ω) as 70.71Ω approximation; or Construct semi-rigid coax with calculated OD/ID ratio: Z = (138 / √εr) × log10(D/d) For PTFE (εr = 2.1): D/d = 2.31 for 70.7Ω Or wind on toroid/bead using parallel coaxes (2-wire line). SCHEMATIC — LUMPED ELEMENT VERSION (HF) ----------------------------------------- Each λ/4 arm replaced by low-pass L-C T-network equivalent. T-network: L/2 – C – L/2 (series half-inductors, shunt capacitor) PORT 1 ──┬───[L_a/2]──┬──[L_a/2]─── ─┬─── PORT 2 │ [C_a] │ │ │ │ │ GND [R_iso = 100Ω] │ │ └───[L_b/2]──┬──[L_b/2]─── ─┘─── PORT 3 [C_b] │ GND Values: L_a = L_b, C_a = C_b (identical arms) L (total per arm) = 70.7 / (2πf₀) [in Henrys at f₀ Hz] C (shunt) = 1 / (2πf₀ × 70.7) L/2 each side = L / 2 COMPONENT VALUES — LUMPED ELEMENT WILKINSON 2-WAY --------------------------------------------------- Band f₀ (MHz) L_total (µH) L/2 (µH) C_shunt (pF) R_iso (Ω) ---- -------- ----------- -------- ------------ --------- 160M 1.85 6.08 3.04 1216 100 80M 3.75 3.00 1.50 601 100 40M 7.15 1.574 0.787 315 100 30M 10.125 1.111 0.556 222 100 20M 14.175 0.793 0.397 159 100 17M 18.118 0.621 0.311 124 100 15M 21.225 0.530 0.265 106 100 12M 24.940 0.451 0.226 90 100 10M 28.850 0.390 0.195 78 100 6M 50.500 0.223 0.111 44.7 100 NOTE: Above 50 MHz, use coaxial or microstrip sections (lumped elements degrade rapidly due to parasitic inductance/capacitance of components). COMPONENT VALUES — COAXIAL λ/4 SECTIONS (VHF/UHF/MICROWAVE) -------------------------------------------------------------- Band f₀ (MHz) λ/4 physical length* Coax type (70.7Ω approx) ---- -------- --------------------- ------------------------ 6M 50.5 1480 mm (146 cm) RG-59 (75Ω, VF=0.66): 975 mm 2M 146 512 mm (51 cm) RG-59: 337 mm 1.25M 223.5 335 mm RG-59: 220 mm 70cm 435 172 mm RG-59: 113 mm; or microstrip 33cm 915 82 mm microstrip preferred 23cm 1296 58 mm microstrip preferred * Physical length = (c / (4 × f)) × VF VF = velocity factor of line (0.66 for polyethylene, 0.82 for PTFE foam) For RG-59 (VF=0.66): length = 4919 / f_MHz mm MICROSTRIP WILKINSON (70cm / 33cm / 23cm) ------------------------------------------- 70.71Ω microstrip on FR-4 (εr = 4.4, h = 1.6 mm): w = 1.0 mm (use Saturn PCB Toolkit to verify) Effective εr ≈ 3.3 VF ≈ 1/√3.3 = 0.55 Physical λ/4 at 435 MHz: (68.9/435) × 1000 = 158 mm 100Ω isolation resistor: Use SMD 0402 or 0603. For outdoor/weatherproof use, MELF resistors are preferred. Solder across output port pads (between port 2 and port 3 pads). PERFORMANCE SPECIFICATIONS --------------------------- Parameter Ideal Typical (well-built) --------- ----- -------------------- Insertion loss 3.01 dB 3.0–3.3 dB Return loss (P1) ∞ dB >20 dB Isolation (P2–P3) ∞ dB >20 dB (at design frequency) Amplitude balance 0.0 dB <0.2 dB Phase balance 0.0° <1° Bandwidth (−1 dB) 0.7f–1.5f (approximately 2:1) Maximum power limited by R_iso and transmission line rating POWER HANDLING --------------- R_iso = 100Ω carries current only when outputs are mismatched. For equal matched loads: R_iso dissipates zero power. For fully mismatched (one port open): R_iso dissipates P_in/2. Use 0.25W resistor for HF (< 5 W input). Use 1W resistor for inputs up to 20 W. Use 2W for inputs up to 50 W. WIDEBAND MULTI-SECTION WILKINSON ---------------------------------- For wider bandwidth (>2:1), cascade multiple sections with different λ/4 impedances (Chebyshev-stepped design): 2-section: Z1 = 62.1 Ω, Z2 = 80.2 Ω → 4:1 bandwidth 3-section: Z1 = 58.1 Ω, Z2 = 70.7 Ω, Z3 = 85.9 Ω → 8:1 bandwidth Isolation resistors: one 100Ω at each junction between sections. TOROID IMPLEMENTATION (HF LUMPED, HIGH POWER) ---------------------------------------------- For HF power levels >50 W: Replace L_total with toroidal inductor on mix-2 (yellow) or mix-6 (yellow/white): Band Core Turns Inductance target ---- ---- ----- ---------------- 160M T-94-2 22t 6.1 µH 80M T-94-2 16t 3.0 µH 40M T-68-6 11t 1.57 µH 20M T-50-6 9t 0.79 µH 10M T-50-6 7t 0.39 µH Wind close-spaced (bifilar NOT used — single wire). Use #22 AWG magnet wire for 100W, #18 AWG for 500W. PARTS LIST — 2-WAY WILKINSON (ONE UNIT) ----------------------------------------- Ref Qty Value Description --- --- ----- ----------- L1, L2 2 per table Inductors (see band-specific table above) C1, C2 2 per table NP0/C0G capacitors (see band-specific table) R1 1 100Ω Isolation resistor (0.25W–2W per power level) J1 1 SMA or BNC Input connector J2, J3 2 SMA or BNC Output connectors PCB 1 — Double-sided, 1 oz copper (HF: perfboard with short wires; VHF/UHF: coax or microstrip) ================================================================================