1. What is Coaxial Cable Cutoff Frequency?

The cutoff frequency of a coaxial cable is the frequency above which higher-order modes can propagate, potentially causing signal distortion. For TEM mode, this is an approximate calculation of when the first higher-order mode (TE11) can propagate.

2. How Does the Calculator Work?

The calculator uses the coaxial cable cutoff frequency formula:

Where:

• \( f_c \) — Cutoff frequency (Hz)
• \( c \) — Speed of light (3 × 10⁸ m/s)
• \( a \) — Inner conductor radius (m)
• \( b \) — Outer conductor radius (m)

Explanation: This formula gives the approximate frequency where the first higher-order mode can propagate in the coaxial cable.

3. Importance of Cutoff Frequency

Details: Operating below the cutoff frequency ensures only the TEM mode propagates, which is important for maintaining signal integrity and preventing modal dispersion.

4. Using the Calculator

Tips: Enter the inner and outer radii in meters. The outer radius must be larger than the inner radius. Typical values are in millimeters (convert to meters by dividing by 1000).

5. Frequently Asked Questions (FAQ)

Q1: Why is cutoff frequency important?
A: It determines the maximum frequency for single-mode (TEM) operation, which is crucial for maintaining signal quality in high-frequency applications.

Q2: What happens above the cutoff frequency?
A: Higher-order modes can propagate, potentially causing signal distortion and increased attenuation.

Q3: How can I increase the cutoff frequency?
A: Use a smaller diameter cable (reduce both inner and outer radii while maintaining the same ratio).

Q4: Is this formula exact?
A: It's an approximation. The exact formula for TE11 mode cutoff is \( f_c = \frac{c}{\pi (a + b)} \times 1.0002 \) for typical coaxial cables.

Q5: What about other modes?
A: The TE11 mode has the lowest cutoff frequency. Other modes have higher cutoff frequencies and typically don't propagate if f < f_c.