1. Introduction

When designing RF circuits, coplanar waveguide with ground (CPWG) offers enhanced isolation and controlled impedance. This article demonstrates kicad how to draw curved coplanar waveguide on your PCB, ensuring that even flexible routing maintains performance integrity. By combining theoretical principles and practical steps, HCJMPCBA enables OEM engineers and procurement teams to implement high-precision RF paths with confidence.

2. Understanding Coplanar Waveguide and Its Benefits

A coplanar waveguide (CPW) is a planar transmission line consisting of a central signal trace flanked by ground conductors on the same PCB layer. The grounded coplanar waveguide variant—also known as CPWG—adds a full ground plane underneath, further stabilizing impedance and reducing radiation.CPWG supports impedance control, improves signal integrity, and is preferred in high-frequency and microwave applications over standard microstrip traces.

3. Key Principles of Grounded Coplanar Waveguide Design

3.1 Layer Stack-up and Ground Planes

Effective CPWG requires:

    A consistent ground pour on both sides of the signal trace on the same layer

    A solid ground plane layer underneath for stable reference potential
    This arrangement supports impedance control pcb and reduces EMI.

3.2 Geometry and Impedance Calculation

Impedance is governed by:

    The width of the signal trace (W)

    The gap between the signal trace and ground pour (S)

    PCB dielectric thickness (h) and substrate permittivity (ε_r)
    Use a coplanar waveguide calculator—input your parameters to get Zo and effective dielectric constant. Advanced tools account for dispersion, copper roughness, and skin effects.

4. Step-by-Step: kicad how to draw curved coplanar waveguide

Step 1: Stack-up Setup

Define your PCB stack-up to include:

    Top signal layer with copper pour

    Ground reference plane on the back or inner layer
    This establishes the CPWG structure.

Step 2: Draw Curved Trace

Within KiCad, use the layout tools to draw the curved signal trace. Assign a net class with a specific width (W) and clearance (S) to maintain consistent spacing with adjacent ground pours.

Step 3: Apply Ground Pours

Add copper pours to either side of the trace, connected to ground. Ensure kept clearances match the calculator’s gap specifications to preserve impedances.

Step 4: Via Fence for Isolation

Enhance shielding with via fences—rows of ground vias flanking the trace. This greatly reduces parasitic coupling.

Step 5: Verify Impedance

Use a preferred coplanar waveguide calculator or KiCad-backed plugin to compute final impedance and adjust W/S as needed.

5. Why Use Grounded CPWG?

    Superior Signal Integrity: Reduced dispersion and cross-talk – ideal for RF or mmWave applications.

    Structural Simplicity: Easier routing with curved paths while maintaining impedance control.

    Efficient Isolation: Ground pours and via fences minimize electromagnetic interference.

6. Best Practices & Layout Guidelines

    Ground Continuity: Ensure uninterrupted ground pours and stencil connections.

    Via Density: Sufficient via fencing increases shielding effectiveness.

    Trace Curvature: Gentle curves maintain impedance better than sharp corners.

    Mixed-Signal Designs: Keep RF CPWG paths separate from noisy digital circuits.

7. Summary Table