Gain Equalization Technique for a Broadband Ka-Band Gyrotron Traveling-Wave Tube

Gain fluctuations in broadband Ka-band gyrotron traveling-wave tubes (gyro-TWTs) degrade spectrum flatness, compromising imaging performance in long-range surveillance radars. To address this, we designed four waveguide-based gain equalizers: three transmission-type variants (initial and improved single-stage and two-stage) and one reflection-type device. Vector network analyzer (VNA) measurements agree with simulations for all configurations. During gyro-TWT hot tests across 32–35.5GHz, these equalizers achieved remarkable ripple suppression, reducing gain fluctuations from ±5.75dB (unequalized) to ±2.05 dB (improved single-stage), ±2.55dB (two-stage), and ±2.2 dB (reflection-type). This significant improvement in gain flatness meets the stringent requirements for high-resolution remote radar imaging.