On high frequency/mm-wave IMD measurements with small tone spacing

Small-tone-spacing intermodulation distortion (IMD) measurements, needed for some memory-effect modeling studies in particular, are traditionally challenging because of the stresses on source phase noise, isolation, measurement system memory effects and dynamic range. These effects are exacerbated in broadband and mm-wave measurements due to (typically) more frequency multiplication and reduced source chain isolation. Through a series of studies on automatic level control (ALC) bandwidth modulation, isolation effects, source coherence improvements and receiver memory control, an improved system will be presented having residual measurement system third-order intercept products (IP3) in excess of 25 dBm at 70 GHz and >20 dBm at 110 GHz with a 100 Hz tone spacing.