# How do you measure group delay?

## How do you measure group delay?

- During a group delay measurement, the analyzer measures the phase at two closely spaced frequencies and then computes the phase slope.
- The analyzer’s default setting for group delay aperture is the frequency span divided by the number of points across the display.

**What does group delay tell you?**

In signal processing, group delay is the time delay of the amplitude envelopes of the various sinusoidal components of a signal through a device under test, and is a function of frequency for each component. If this timing does not sufficiently meet certain requirements, the device will contribute to signal distortion.

**What is a group delay?**

Group delay is: A measure of device phase distortion. The transit time of a signal through a device versus frequency. The derivative of the device’s phase characteristic with respect to frequency.

### What is group delay in RF?

Group delay is the time it takes for a signal to pass through a device like a Filter or an Amplifier or a complete complex RF product from the Input to Output. The simplest way to calculate Group delay is in the frequency domain.

**Why is it called group delay?**

The so-called “group delay” is simply the time lag between the envelope of input burst and the envelope of the amplitude of the output burst. Linear-phase filters delay the envelope of every signal by the same amount of time, called group delay, no matter what is the carrier frequency of the signal.

**How do you measure group delay in advertising?**

To calculate group delay:

- Proceed as in Simulating an Amplifier, setting frequencies and sweep parameters as needed.
- Edit the S-Parameters component, select the Parameters tab, and enable Group delay.
- Group delay aperture is an option that is found on network analyzers and behaves similarly here.

## What is true time delay?

True time delay is similar to phase shifting, but in most cases you are shifting sections of line that are many wavelengths. True time delay is used in some phased arrays to improve bandwidth. It is not used at the element, but at the subarray level.

**How do you calculate filter delay?**

The formula is simple: given a FIR filter which has N taps, the delay is: (N – 1) / (2 * Fs), where Fs is the sampling frequency. So, for example, a 21 tap linear-phase FIR filter operating at a 1 kHz rate has delay: (21 – 1) / (2 * 1 kHz)=10 milliseconds.

**What causes filter delay?**

Filtering a signal introduces a delay. This means that the output signal is shifted in time with respect to the input. When the shift is constant, you can correct for the delay by shifting the signal in time. Sometimes the filter delays some frequency components more than others.

### What is the advantage of having constant group delay?

By far the most common applications for FIR filters are linear phase FIR filters because of the benefit of constant group delay which is the result of linear phase. Thus the focus of time on FIR filtering should be spent there. But frequently students walk away from a DSP course only knowing linear phase FIR filters.

**How do I plot a group delay in advertising?**

**Can group delays negative?**

The envelope of the carrier signal is delayed by the group delay. However, negative group delays do not imply time advance (at least not in causal systems). Rather, for signals in the band where the group delay is negative the filter tries to predict the input.