Stopping Signal Loss in High-Frequency PCBs: Material & Design Strategies That Work

In high-frequency electronics—where signals race at 10 GHz and beyond—even a 1 dB loss can cripple performance. A 5G base station might drop connections, a radar system could miss targets, or a satellite transceiver may fail to transmit data. Signal loss here isn’t just an annoyance; it’s a critical failure point. The good news? With the right materials and design choices, you can cut signal loss by up to 60%, ensuring your high-frequency PCB performs as intended. Here’s how to do it.

Why Signal Loss Happens in High-Frequency PCBs

Signal loss (often called insertion loss) in high-frequency PCBs stems from three primary culprits. Understanding them is the first step to fixing the problem:

  a.Dielectric Loss: Energy wasted as heat in the PCB substrate, caused by the material’s dielectric constant (Dk) and loss tangent (Df). Higher Df = more loss, especially above 28 GHz.
  b.Conductor Loss: Resistance in copper traces, worsened by skin effect (high-frequency signals traveling on trace surfaces) and surface roughness.
  c.Radiation Loss: Signals “leaking” from traces due to poor routing, inadequate grounding, or excessive trace length.

Material Choices: The Foundation of Low-Loss Performance
Your PCB substrate is the first line of defense against signal loss. Here’s how top materials compare at 60 GHz (a common mmWave frequency for 5G and radar):

Key Takeaway: PTFE and Rogers materials cut total loss by 65–73% compared to FR-4 at 60 GHz. For most high-frequency designs, Rogers RO4830 balances performance and cost.

Design Strategies to Minimize Signal Loss
Even the best materials can’t overcome poor design. Use these techniques to complement your substrate choice:

1. Shorten Trace Lengths
High-frequency signals degrade rapidly over distance. For every 1 inch of trace at 60 GHz:

  a.FR-4 loses ~11 dB (nearly 90% of signal strength).
  b.PTFE loses ~3 dB (50% of strength).

Fix: Route traces directly, avoiding unnecessary bends. Use “dogbone” patterns for component connections to minimize length without sacrificing solderability.

2. Control Impedance Rigorously
Impedance mismatches (when trace impedance strays from the target, e.g., 50 ohms) cause reflection loss—signals bouncing back instead of reaching their destination.

How to fix:
  Use simulation tools (e.g., Ansys SIwave) to calculate trace width/spacing for your material (e.g., 50-ohm traces on Rogers RO4830 need ~7 mil width with 6 mil spacing).
  Add impedance test coupons to your PCB panel to verify consistency post-production.

3. Optimize Ground Planes
A solid ground plane acts as a “mirror” for signals, reducing radiation loss and stabilizing impedance.

Best practices:
  a.Use a continuous ground plane directly below signal traces (no splits or gaps).
  b.For multi-layer PCBs, place ground planes adjacent to signal layers (separated by ≤0.02 inches for high frequencies).

4. Reduce Vias and Stubs
Vias (holes connecting layers) create impedance discontinuities, especially if they’re:

  a.Too large (diameter >10 mils for 50-ohm designs).
  b.Unplated or poorly plated.
  c.Accompanied by “stubs” (unused via length beyond the connection point).

Fix: Use microvias (6–8 mils) with “back drilling” to remove stubs, cutting via-related loss by 40%.

5. Smooth Copper Traces
Rough copper surfaces increase conductor loss by up to 30% at 60 GHz (due to skin effect amplifying resistance).

 a.Solution: Specify “low-profile” copper (surface roughness <0.5 μm) instead of standard copper (1.5–2.0 μm). Rogers and Isola offer substrates with pre-laminated low-profile copper for this purpose.

Real-World Results: A 5G Case Study
A telecom manufacturer switched from FR-4 to Rogers RO4830 for their 28 GHz 5G modules and implemented the design strategies above. The result?

  a.Signal loss dropped from 8 dB to 3.2 dB over 4 inches of trace.
  b.Connection reliability improved by 45% in field tests.
  c.Heat generation (from dielectric loss) decreased by 28%, extending component lifespan.

Conclusion
Stopping signal loss in high-frequency PCBs demands a two-pronged approach: choosing low-Df materials (like Rogers or PTFE) and pairing them with tight design controls (short traces, impedance matching, solid grounds). For 5G, radar, or satellite systems, this combination isn’t optional—it’s the difference between a product that works and one that fails.

By prioritizing both material performance and design discipline, you’ll ensure your high-frequency PCB delivers the speed, range, and reliability your application demands.