Self-Cooling GaN Power Amplifier Enabled by Harmonic Injection for Scalable High-Density Array Integration

This work presents a new self-cooling power amplifier (PA) architecture based on active second-harmonic injection for RF transmitter systems. Unlike conventional thermal solutions that rely on bulky heat sinks or liquid cooling, the proposed architecture reduces thermal stress at the device level through harmonic injection. By injecting a precisely tuned second-harmonic current, the Class-E switching transitions are reshaped to minimize power dissipation, enabling near-100% efficiency operation. Experimental results reveal temperature reductions close to 20°C at saturation and a dramatic improvement in efficiency across the operating band. The results confirm that harmonic injection can serve as an effective thermal-management mechanism, enabling compact and thermally resilient high-power RF transmitter (array) systems.