Amplitude Balance vs. Phase Balance in RF Power Dividers

This article clarifies the fundamental definitions of amplitude balance and phase balance, specifically focusing on their differences in the context of RF power dividers.

Amplitude Balance

Definition: Amplitude balance is assessed at the output ports of an RF power divider or an RF hybrid coupler.

Essentially, it’s the maximum peak-to-peak amplitude difference observed at the output ports, measured in dB. This specification usually includes a defined frequency range.

Consider a power divider with two output ports, designed as a 3dB power divider. Amplitude balance quantifies how evenly the power is distributed between these two output ports.

It’s important to note that amplitude balance is not relevant for RF directional couplers, as they are designed with uneven power ratios.

Typically, amplitude balance is less than 0.25 dB for a 2-way power divider and around 0.4 dB for a Quad hybrid coupler.

Many products, such as those from Marki Microwave, are designed to meet these stringent requirements.

Image alt: RF Power Divider

Phase Balance

Definition: Phase balance is also measured at the output ports of an RF power divider or coupler.

It represents the maximum peak-to-peak phase difference observed at the output ports across the specified frequency range, and it’s measured in degrees.

In simpler terms, phase balance indicates the differential phase shift between the two output ports.

This is pertinent to components with equal output power, such as power dividers or quadrature hybrids. Ideally, it should be within a few degrees.

It’s worth mentioning that phase balance tends to degrade at higher frequencies.