High-Precision FPOR for Broadband Dk and Df Testing (10.2 – 52.2 GHz)

High-precision, non-destructive wideband material characterization for low, medium, and high-loss substrates. Utilizing the Rohde & Schwarz ZVA67 Vector Network Analyzer, iEMSL provides industrial-grade extraction of dielectric constant (Dk) and loss tangent (Df) across the K, Ka, and Q bands.

The FPOR Advantage

The Fabry-Perot Open Resonator (FPOR) measures dielectric constant and loss tangent from 10.2 to 52.2 GHz in a single setup. Its high Q-factor suits low-loss materials at mmWave frequencies, resolving Dk to ±0.25% and loss tangent to ±2%.

• Broadband Coverage: Single-setup testing from 10.2 GHz to 52.2 GHz.
• High-Loss Versatility: We characterize low, medium, and high-loss materials. For lossy materials, we utilize smaller sample thicknesses to maintain resonance stability.
• Anisotropy Detection: Identification of in-plane dielectric properties (anisotropy) in polymers and composites.
• Climatic Stability: Advanced climatic compensation is always enabled to ensure drift-free measurements.

Technical Specifications & Typical Data

Our system provides discrete measurements with options for Basic testing (4.5 GHz step), Standard testing (3.0 GHz step), or Advanced testing (1.5 GHz step).

System Precision:

• Dielectric constant: ±0.25% (for Dk = 1 – 15)
• Loss tangent: tanδ < 10, ±2% (for Df >5×10⁻⁶)

Sample Requirements

To achieve valid resonance across the full 10–52 GHz range, samples must adhere to the following:

• Lateral Dimensions: 105 mm × 105 mm (Preferred)
  
• Thickness: 1 µm – 3 mm
  • Low-loss materials: Can be tested at maximum thickness.
  • Medium/High-loss materials (Df > 10⁻³): the sample thickness must be significantly thinner to prevent quenching the resonance.
    For most applications, a thickness in the range of 100 µm to 400 µm provides an excellent balance between measurement accuracy and practical handling, enabling high-precision dielectric and loss measurements (for more information check thickness limitations section).
    
• Form Factor: Flat, uniform, rectangular or circular

In-plane Anisotropy

FPOR can characterize in-plane anisotropy. Any visual inhomogeneity in the XY plane, such as fiber, creates a directional bias. However, even for samples that appear uniform, anisotropy can occur due to molecular-level crystallization or polymer chain orientation established during manufacturing. In either case, these internal “grains” interact differently with the electric field, resulting in peak or resonance splitting.

If an anisotropic MUT is arbitrarily inserted into the FPOR, the in-plane anisotropic axes will not be aligned with the electric field, causing the resonant curve to split. When that happens, we have to rotate the sample smoothly inside the resonator until one of the two resonant modes is suppressed (mode B) and the other is still present (mode A). To fully characterize the material, it is recommended  to repeat this process for the orthogonal axis. This isolates Mode B and suppresses Mode A, capturing the full variance in Dk and Df across both axes.

Clients have the option to choose to characterize:

• Single-Axis: We provide the Dk and Df data for one primary axis.
• Dual-Axis (Orthogonal): We repeat the process for the orthogonal axis (suppressing Mode A to isolate Mode B). This provides a complete picture of the material’s anisotropic behavior. Since this requires a full second measurement cycle, it is billed as an additional sample.

Thickness and Lateral Dimensions Guidelines

Thickness & Dk Limitations

This graph illustrates the relationship between a material’s dielectric constant (Dk) and its thickness, defining the measurable and unmeasurable regions for a specific testing method. The green and tan areas represent valid combinations that can be measured, while the two “prohibited zones” indicate combinations that cannot be reliably tested. For Dk < 3, the maximum thickness is 3mm.

• Green Zone: This is the ideal measurement range, where combinations of Dk and thickness allow for highly reliable and precise results with a low measurement uncertainty of ±0.25%.
• Tan Zone: This area indicates that a measurement can still be obtained, but with a greater uncertainty of ±0.5%.
• Prohibited Zones: These zones represent invalid combinations of Dk and thickness where no reliable data can be acquired.

Thickness & Df Limitations

Limitations are imposed on the maximum loss tangent with respect to thickness. If the material has a very high loss, the resonator curve may not be distinguishable from noise.

Lateral Dimension Requirements

To achieve the full frequency range down to 10.2 GHz, the target sample size should be between 101 mm and 109 mm. For rectangular samples, one dimension can be up to 150 mm, but the other must be less than 110 mm. Preferred sample size is 105 mm × 105 mm.

Pricing (per sample)

What you receive

• Extracted Dk and Df Charts and tables (vs frequency)
• Raw data (CSV) with resonance/Q data on request
• Technical Report on request (for extra charge)

View our example measurements. See also: WR-90, SPDR, custom characterization, all material characterization services.

Frequently Asked Questions