Frequency extenders are external modules enabling vector network analyzers (VNAs) to operate at mmWave frequencies. Dynamic range is a key figure of merit for VNAs and VNA frequency extenders with the system dynamic range definition commonly applied to both. This definition refers to S21 or S12 measurements at the nominal test signal power level. Eravant’s STO-series of VNA frequency extenders can increase the VNA frequency range to 330 GHz.
System dynamic range is the ratio between the nominal test signal power available at the VNA test ports and the minimum input power that the system can detect. This sensitivity level is set by the receiver’s noise floor and is a function of the IF bandwidth. For a VNA equipped with frequency extenders, the dynamic range is measured after a two-port calibration. The frequency extenders are separated and the test ports are terminated to prevent signal leakage. The VNA’s IF bandwidth is set to a low value, usually 10 Hz and either S21 or S12 is displayed. The average level indicates the system dynamic range.
An IF bandwidth of 10 Hz is typical when specifying or measuring the dynamic range of VNA frequency extenders. This bandwidth limits the VNA sweep rate to about one measurement per second when moderate averaging is applied. Although the sensitivity achieved at this measurement speed is rarely required, 10 Hz is the most common IF bandwidth used for dynamic range specifications.
Antenna testing is one of a few applications requiring more than 100 dB dynamic range. Test systems with greater dynamic range can accommodate a wider variety of antenna types and measurement conditions without configuration changes. Even at mmWave frequencies, 100 dB of dynamic range is usually sufficient.
Eravant, formerly Sage Millimeter Inc.