# What is Loss Tangent

Last Updated: 2023-08-01

## What is Loss Tangent

Loss Tangent, also known as the Dissipation Factor (Df), is a crucial parameter in the PCB industry that measures the amount of signal loss as the signal travels along the transmission line. It is a dimensionless value that signifies the level of electromagnetic wave absorption by the dielectric material used in the PCB. The loss tangent, denoted as tan(δ), is influenced by various factors such as the material’s structure and composition, particularly the glass-resin composition.

A lower loss tangent indicates reduced signal loss, allowing a greater portion of the original transmitted signal to reach its intended destination. This characteristic is especially significant in designs involving transceivers and the transmission of high-frequency signals across long backplane channels. The loss tangent is typically measured in decibels per inch (dB/in) and can be calculated using the attenuation equation.

When selecting a suitable material for a PCB, it is ideal to choose one with a lower loss tangent to minimize signal loss. However, it is important to consider the tradeoff between material performance and cost, as materials with lower loss tangents often come at a higher price. Therefore, it is recommended to evaluate the cost-performance ratio by comparing the signal attenuation for different material options at the target data rate and reach required.

### What Is Loss Tangent for an Ideal Dielectric

The loss tangent (tan δ) of an ideal dielectric represents the quantitative measurement of electrical energy dissipation caused by various physical phenomena, including electrical conduction, dielectric relaxation, dielectric resonance, and non-linear processes .

### What Is the Loss Tangent in Electromagnetic Theory

The loss tangent, denoted as tanδ, is a term used in electromagnetic theory to quantify the effect of loss on the electromagnetic field within a material. It is important to note that the loss tangent is zero for a lossless material (σ≡0) and increases as the loss increases. This provides an alternative method to measure the impact of loss on the electromagnetic field within a material.

### How Is Loss Tangent Calculated

The loss tangent, also known as the dissipation factor, can be calculated by determining the numerical ratio between the active dissipative current and the reactive charging current. Additionally, it can be expressed as the ratio between the real and reactive electrical power.

### How Is Loss Tangent Measured

The loss tangent, also known as tan δ, is determined by calculating the ratio between the imaginary part of the dielectric constant and the real part. It is often referred to as tan delta, tangent loss, or dissipation factor.

### What Is the Difference Between Dielectric Loss and Loss Tangent

Dielectric loss is determined by using a parameter known as the loss tangent or tan delta (tan δ). In simpler terms, tan delta represents the tangent of the angle formed between the alternating field vector and the loss component of the material. Therefore, a higher value of tan δ indicates a more significant dielectric loss.