Phase Angle, Time Delay and Frequency Relationship
The relationship between the phase angle (φ), time delay (Δt) and frequency (f) is given by the following equations.
Phase Angle (Degrees)
| Equation | Description |
|---|---|
| φ (°) = 360 × f × Δt | Calculate phase angle |
| Δt = φ / (360 × f) | Calculate time delay |
| f = φ / (360 × Δt) | Calculate frequency |
Where:
| Symbol | Description |
|---|---|
| φ | Phase angle (degrees) |
| Δt | Time delay (seconds) |
| f | Frequency (Hz) |
Phase Angle (Radians)
| Equation | Description |
|---|---|
| φ (rad) = 2π × f × Δt | Calculate phase angle |
| Δt = φ / (2π × f) | Calculate time delay |
| f = φ / (2π × Δt) | Calculate frequency |
Wavelength
The wavelength is calculated using:
| Equation | Description |
|---|---|
| λ = c / f | Wavelength |
Where:
| Symbol | Description |
|---|---|
| λ | Wavelength (m) |
| c | Speed of sound (343.2 m/s at 20°C) |
| f | Frequency (Hz) |
Time Delay Due to Distance
| Equation | Description |
|---|---|
| Δt = r / c | Time delay |
| r = Δt × c | Distance travelled |
Where:
| Symbol | Description |
|---|---|
| r | Path length (m) |
| c | Speed of sound (m/s) |
Rule of Thumb:
Sound takes approximately 3 ms to travel 1 metre through air.
Speed of Sound vs Air Temperature
| Temperature (°C) | Speed (m/s) | Time per 1 m (ms) |
|---|---|---|
| +40 | 354.9 | 2.818 |
| +35 | 352.0 | 2.840 |
| +30 | 349.1 | 2.864 |
| +25 | 346.2 | 2.888 |
| +20 | 343.2 | 2.912 |
| +15 | 340.3 | 2.937 |
| +10 | 337.3 | 2.963 |
| +5 | 334.3 | 2.990 |
| 0 | 331.3 | 3.017 |
| -5 | 328.2 | 3.044 |
| -10 | 325.2 | 3.073 |
| -15 | 322.0 | 3.103 |
| -20 | 318.8 | 3.134 |
| -25 | 315.7 | 3.165 |
Example
For a fixed time delay of Δt = 0.5 ms, the resulting phase shift is:
| Phase Angle | Radians | Frequency | Wavelength |
|---|---|---|---|
| 360° | 2π | 2000 Hz | 0.171 m |
| 180° | π | 1000 Hz | 0.343 m |
| 90° | π/2 | 500 Hz | 0.686 m |
| 45° | π/4 | 250 Hz | 1.372 m |
| 22.5° | π/8 | 125 Hz | 2.744 m |
| 11.25° | π/16 | 62.5 Hz | 5.488 m |
Phase Shift from Distance
Since
Δt = a / c
the phase angle becomes
φ = (a × f × 360) / c
| Symbol | Description |
|---|---|
| a | Path length (m) |
| f | Frequency (Hz) |
| c | Speed of sound (m/s) |
Phase Shift vs Polarity Reversal
Phase shift and polarity reversal are often confused, but they are completely different.
- A phase shift introduces a time delay between two versions of the same signal.
- A polarity reversal flips the waveform upside down without introducing any time delay.
Polarity reversal can be achieved using:
- An inverting amplifier
- A transformer
- Swapping pins 2 and 3 of an XLR connector
- Multiplying the digital signal by -1
Therefore, polarity reversal is not the same as a phase shift.
Linear Phase Response
A linear phase response does not mean the phase angle remains constant.
Since
φ = 360 × f × Δt
the phase angle naturally increases with frequency for a fixed time delay.
- Doubling the frequency doubles the phase angle.
- Tripling the frequency triples the phase angle.
This is the expected behaviour of a linear-phase system.
Angular Frequency
| Equation | Description |
|---|---|
| ω = 2π × f | Angular frequency |
| f = ω / (2π) | Frequency |
Example
Given
y = 50 sin (5000t)
| Parameter | Value |
|---|---|
| Amplitude | 50 |
| Angular Frequency | 5000 rad/s |
| Frequency | 795.77 Hz |
Phase / Delay / Frequency Converter
Enter exactly two values and leave the third blank to calculate it.
Frequency ↔ Angular Frequency
| Frequency (f): | Hz |
| Angular Freq (ω): | rad/s |
Discussion & Solutions
Hello Mr. Swagatam
l want Circuit for Creating 90° and 45° Phase Shift for Variable Frequency.
This phase difference must be very precise.
Thank you for your efforts and the time you dedicate to providing responses.
Best regards
Hi Mazloumi,
I think you might find the following concepts useful for satisfying your application needs:
https://www.homemade-circuits.com/phase-shift-oscillators-wien-bridge-buffered-quadrature-bubba/