Example Data Table
| Case |
Input Powers |
Phases |
Combiner |
Use |
| Two equal amplifiers |
5 W, 5 W |
0°, 0° |
Wilkinson |
Checks normal in-phase addition. |
| Phase error test |
10 W, 10 W |
0°, 35° |
Hybrid |
Shows loss from phase spread. |
| Unequal drive |
8 W, 5 W, 4 W, 3 W |
0°, 5°, -3°, 10° |
Corporate feed |
Reviews imbalance and heating. |
Formula Used
Input conversion: P(W) = 10((dBm - 30) / 10)
Coherent power: Pcoherent = |Σ √Pi × ejθi|² / N
Insertion factor: Floss = 10(-Loss dB / 10)
Mismatch factor: Γ = (VSWR - 1) / (VSWR + 1), then Fmatch = 1 - Γ²
Delivered output: Pout = Pcoherent × Floss × Fmatch × Efficiency
Load voltage: Vrms = √(Pout × Rload)
Load current: Irms = Vrms / Rload
Temperature rise: ΔT = Average heat × Thermal resistance
How to Use This Calculator
Enter each RF input power in watts or dBm. Add matching phase values in degrees. Select a combiner type, then enter measured or estimated loss values. Add VSWR, efficiency, isolation, port rating, and duty cycle. Press Calculate. The result appears above the form, below the page header.
Use CSV for spreadsheet records. Use PDF for quick design reports. For final RF work, compare this estimate with datasheets, calibrated power readings, and network analyzer measurements.
Practical RF Power Combining
RF power combiners join two or more RF sources into one output path. They are used in transmitters, test benches, antenna systems, repeaters, and lab fixtures. A good design does more than add watts. It also controls phase, port balance, isolation, heating, and mismatch. This calculator helps review those points before hardware is selected.
Why Phase Matters
RF sources are vector signals. Two sources with equal power can add fully when phase matched. They can also cancel when one path is shifted. The calculator converts each input power into a square root power vector. It then sums the vectors and divides by the number of ports. This gives a practical coherent output estimate before loss is applied.
Loss, Efficiency, and Match
No real combiner is perfect. Wilkinson, hybrid, corporate, and resistive combiners all have different behavior. Insertion loss reduces delivered power. VSWR reduces accepted power at the load. Efficiency accounts for copper loss, dielectric loss, resistor heating, and other practical effects. The output result therefore includes phase loss, insertion loss, mismatch loss, and total delivered power.
Port Balance and Protection
Unequal inputs may create extra stress. High imbalance can push current into isolation resistors. Poor isolation can allow one amplifier to see another amplifier. That may cause distortion or damage. The tool reports input spread in decibels and checks each port against a safe limit. It also estimates heat from the difference between input power and delivered power.
Using Results in Design
Treat the result as an engineering estimate. Confirm final values with datasheets, load pull data, a power meter, and a network analyzer. Use realistic cable losses and measured phase offsets. Check average power with duty cycle, but also verify peak power ratings. Add margin for temperature, altitude, enclosure airflow, and modulation type. A conservative design lasts longer. It also gives cleaner RF output during real operation.
Common Use Cases
Designers use combiners for amplifier staging, antenna distribution, receiver tests, and power sensor calibration. The same math supports bench comparisons between two paths. It also helps choose attenuators, dummy loads, and cooling plans. When the calculated heat looks high, select a larger rated combiner or reduce drive before testing. Keep cables equal when accuracy matters.
FAQs
What is an RF power combiner?
It is a network that combines two or more RF paths into one output. It may use resistors, transmission lines, transformers, hybrids, or Wilkinson sections.
Why does phase affect output power?
RF signals add as vectors. In-phase signals add strongly. Opposite-phase signals cancel. Even small phase errors can reduce output power.
Does this calculator include insertion loss?
Yes. It includes a preset combiner loss and an extra loss field. Use measured datasheet values when available.
What does VSWR change?
VSWR estimates load mismatch. A higher VSWR reflects more power and lowers delivered power. It may also increase device stress.
Can I enter dBm values?
Yes. Select dBm as the input unit. The calculator converts each value into watts before combining the RF vectors.
What is phase loss?
Phase loss is the difference between simple input power sum and coherent vector output before hardware loss. Large values indicate cancellation.
Why is thermal power estimated?
Power not delivered to the load becomes loss. Some loss becomes heat inside resistors, conductors, or dielectric material.
Is this result enough for final design?
No. Use it for planning. Confirm final power, match, isolation, and heating with real parts and calibrated RF test equipment.