RF Transformer Calculator

RF Transformer Calculator. An RF transformer matches impedances between a signal source and a load in radio-frequency circuits — getting this ratio right maximizes power transfer and minimizes signal loss. Enter your Input Impedance and Output Impedance into the RF Transformer Calculator to get the Primary to Secondary Turns Ratio (Np/Ns). Secondary outputs include the inverse turns ratio (Ns/Np), the impedance ratio (Zout/Zin), and the turns ratio expressed in dB. Also try the Current Transformer Ratio Calculator.

Input Impedance *

Source impedance in ohms

Output Impedance *

Load impedance in ohms

Results

Primary to Secondary Ratio (Np/Ns)

Secondary to Primary Ratio (Ns/Np)

Impedance Ratio (Zout/Zin)

Turns Ratio (dB)

What is an RF Transformer?

An RF transformer is a passive component used to match impedances between different parts of an RF circuit. It uses magnetic coupling to transfer energy while providing impedance transformation, ensuring maximum power transfer and minimal reflections. See also our Transformer Impedance Calculator.

How do I calculate the turns ratio for impedance matching?

The turns ratio is calculated as the square root of the impedance ratio. For primary to secondary: Np/Ns = √(Zin/Zout). This relationship ensures proper impedance matching between source and load.

What is the difference between Np/Ns and Ns/Np ratios?

Np/Ns is the primary-to-secondary turns ratio (step-down when >1, step-up when <1), while Ns/Np is the inverse secondary-to-primary ratio. Both ratios are commonly specified depending on the transformer orientation and application.

What are typical RF impedance values?

Common RF impedances include 50Ω (most RF systems), 75Ω (cable TV, video), 300Ω (antenna feedlines), and 600Ω (audio/telecom). The choice depends on the specific application and system requirements.

How does frequency affect RF transformer design?

Frequency determines the transformer's core material, winding technique, and parasitic effects. Higher frequencies require careful attention to core losses, leakage inductance, and inter-winding capacitance to maintain performance.

Can I use this calculator for broadband transformers?

This calculator provides the basic turns ratio for any impedance transformation. For broadband applications, additional considerations like core material, winding configuration, and transmission line effects must be evaluated separately.

What happens if impedances are not properly matched?

Impedance mismatch causes signal reflections, power loss, and potential damage to transmitters. The VSWR increases, reducing system efficiency and potentially causing frequency-dependent amplitude variations.

How accurate are the calculated ratios?

The calculated ratios are mathematically exact for ideal transformers. Real-world performance depends on core material, construction quality, frequency response, and parasitic elements that aren't accounted for in this basic calculation. You might also find our calculate Duty Cycle, Turns Ratio (Np:Ns1) & Primary Inductance — Flyback Transformer useful.