Scalar vs. Vector Network Analyzers: Core Technology Differences

Scalar network analyzers measure transmission and reflection characteristics solely in terms of amplitude. Devices such as the Anritsu 560 and Keysight 8757D measure insertion loss, gain, return loss, SWR, and power. Because they do not capture phase information, they cannot characterize complex impedance, electrical delay, or group delay.

Vector network analyzers, represented by models like the Keysight E5071C and Keysight 8753ES, measure both amplitude and phase. This complete vector measurement enables the calculation of S-parameters (such as S11 through S22 for 2-port configurations, or up to S44 for 4-port systems). Consequently, VNAs support advanced display formats including phase, group delay, polar charts, and Smith charts, which are essential for impedance matching and phase-sensitive RF design.

The hardware layout of these systems differs substantially. Scalar analyzers are frequently modular systems. The Anritsu 560 and Keysight 8757D function as mainframes requiring an external signal source, directional bridges, and external detectors—such as the Agilent 85037 series—to complete the test setup. The Keysight 8757D supports both AC and DC detection modes, requiring a specific 27.778 kHz square wave AC modulation frequency when operating in AC detection mode.

Conversely, modern VNAs integrate the signal source, test set, and receivers into a single enclosure. The Keysight E5071C, for example, is available with 2 or 4 test ports, contains internal bias tees, and features a synthesizer with 1 Hz frequency resolution. VNAs use narrow intermediate frequency bandwidth (IFBW) filtering—ranging from 10 Hz to 500 kHz on the E5071C—to achieve low trace noise (0.004 dB rms) and high dynamic range.

Calibration represents a major point of divergence between the two technologies. Because SNAs lack phase detection, they rely on scalar calibration. This method cannot mathematically isolate or remove systematic reflection errors caused by cable mismatches and test port adapters, which limits overall measurement accuracy.

VNAs utilize vector error correction to overcome these systematic limitations. By measuring both magnitude and phase of known calibration standards, instruments like the Keysight 8753ES can execute full two-port or adaptive calibrations. This mathematical correction removes the magnitude and phase effects of cables, adapters, and fixtures, providing much higher measurement accuracy and repeatability.