Power, Linearity, and Distortion Additional Power System Questions Informational

How do I calculate the efficiency of a power combining network with N amplifier modules?

Calculating the efficiency of a power combining network with N amplifier modules involves accounting for: the individual PA module efficiency, the combining network's insertion loss, and the power distribution uniformity. The total system efficiency: eta_system = eta_PA × eta_combiner, where eta_PA is the average efficiency of each PA module, and eta_combiner is the efficiency of the combining network (the fraction of the PA modules' combined output power that reaches the combiner's output port). The combiner efficiency: eta_combiner = P_output / (N × P_per_module) = 1 / (10^(IL_combiner/10)), where IL_combiner is the combiner's insertion loss in dB. For common combining architectures: Wilkinson combiner (2-way): insertion loss approximately 0.1-0.3 dB (eta approximately 93-97%). Gysel combiner (2-way, high power): insertion loss approximately 0.2-0.5 dB (eta approximately 89-95%). N-way radial combiner: insertion loss approximately 0.3-0.8 dB for N = 4-16 (eta approximately 83-93%). Reactive (Gysel) tree combiner (N-way using cascaded 2-way stages): insertion loss approximately 0.2-0.5 dB per stage × log2(N) stages. For N=8 (3 stages): total IL approximately 0.6-1.5 dB (eta approximately 71-87%). The total efficiency: for N=8 PAs each with 40% efficiency, combined with a 3-stage Wilkinson tree (1.0 dB IL): eta_system = 0.40 × 10^(-1.0/10) = 0.40 × 0.794 = 31.8%. The combining loss reduces the system efficiency by approximately 20%. This loss must be justified by the increased output power (8× or 9 dB more power than a single module).
Category: Power, Linearity, and Distortion
Updated: April 2026
Product Tie-In: Power Amplifiers, Power Supplies

Power Combiner Efficiency

Power combining is essential when a single PA cannot provide the required output power. The combining efficiency determines whether the approach is cost-effective compared to a single higher-power PA.

ParameterClass AClass ABClass F/Doherty
Max Efficiency50%50-78%70-90%
LinearityExcellentGoodModerate (needs DPD)
P1dB Backoff0-3 dB3-6 dB6-10 dB
ComplexityLowLowHigh
Common UseTest, small signalGeneral PABase station, broadcast

Compression Behavior

When evaluating calculate the efficiency of a power combining network with n amplifier modules?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

Efficiency Trade-offs

When evaluating calculate the efficiency of a power combining network with n amplifier modules?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

  1. Performance verification: confirm specifications against the application requirements before finalizing the design
  2. Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
  3. Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
  4. Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture

Thermal Budget

When evaluating calculate the efficiency of a power combining network with n amplifier modules?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

Common Questions

Frequently Asked Questions

When is combining worth it?

Power combining is worth it when: a single PA cannot provide the required output power (the available PA technology is limited; e.g., GaN PAs at 28 GHz are limited to approximately 5-10 W per die; to get 50-100 W: combine 8-16 PAs). The combining loss is acceptable (the total efficiency with combining is still better than an alternative approach). The cost of N smaller PAs + combiner is less than one larger PA (at higher frequencies, this is often the case because: larger PA die have lower yield and higher cost; combining smaller, proven die is more reliable). Combining also provides graceful degradation: if one PA module fails, the output power decreases by only 10×log10((N-1)/N) dB, rather than a complete loss.

What about amplitude and phase imbalance?

Amplitude and phase imbalance between PA modules degrades combining efficiency: if the PA modules have different gain and phase: the combined output is less than the ideal N×P_per_module. Combining efficiency under random module imbalances is given by η_comb ≈ e^(-(σ_φ)²)/(1 + (σ_A)²), where σ_φ is the RMS phase error in radians (σ_φ = Δφ_deg × π/180) and σ_A is the RMS fractional amplitude error (σ_A ≈ ΔA_dB / 8.686). The combining loss (in dB) is L_comb = -10·log10(η_comb). For 10° RMS phase error (0.175 rad) and 1 dB RMS amplitude error (σ_A ≈ 0.115): η_comb ≈ e^(-0.175²)/(1 + 0.115²) ≈ 0.957, yielding a combining loss of approximately 0.2 dB (small). For 30° RMS phase error (0.524 rad) and 3 dB RMS amplitude error (σ_A ≈ 0.345): η_comb ≈ e^(-0.524²)/(1 + 0.345²) ≈ 0.679, yielding a combining loss of approximately 1.7 dB (significant). Maintaining RMS phase error < 10° and RMS amplitude error < 1 dB across all modules is essential.

What about spatial combining?

Spatial combining (combining in free space using an antenna array) avoids the losses of circuit-level combiners. In a phased array: each PA drives its own antenna element, and the power combining happens in the radiated field (coherent addition of the electromagnetic waves from each element). The spatial combining efficiency is ideally 100% (no combiner hardware, no combiner loss). In practice: the spatial combining efficiency is limited by: element-to-element amplitude and phase errors, scan-angle-dependent efficiency, and aperture efficiency. Spatial combining is used in: 5G FR2 beamforming arrays, radar phased arrays, and satellite communication terminals.

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