What is directivity in directional coupler?
The Directivity in a coupler is the ratio between the input signal at the coupled port and the unwanted reflected signal at the coupled port. It is a measure of how well the coupler isolates two opposite-traveling (forward and reverse) signals at the coupled port.
How do you measure directivity of a directional coupler?
For example, the reflection port (Port 4) of a directional coupler measures -20 dBm when Port 2 is terminated with a short and -55 dBm with a perfect termination, the directivity is simply the difference of the two, 35 dB.
What is the principle of directional coupler?
Directional couplers are an important type of signal processing device. Their basic function is to sample RF signals at a predetermined degree of coupling, with high isolation between the signal ports and the sampled ports — which supports analysis, measurement and processing for many applications.
What should be the distance between the holes in the multi hole directional coupler?
λg/4 distance
This is a directional coupler with same main and auxiliary waveguides, but with two small holes that are common between them. These holes are a λg/4 distance apart where λg is the guide wavelength. The below figure shows the image of a two-hole directional coupler.
What is the ideal value of directivity in directional coupler?
The single most important parameter in a directional coupler used for reflection measurement is the Directivity. This parameter should be in these ranges to be useful: 10dB minimum for any minimally indicative measurement, no accuracy expected. 20dB minimum for reliable measurement.
What is the directivity of a directional coupler Mcq?
12. Directivity of a directional coupler signifies the direction of power flow in the coupler. Explanation: Directivity is the measure of the directional coupler’s ability to isolate forward and backward waves. Directivity is also defined as the ratio of power at the output port to the power at the isolated port.
What is the difference between a directional coupler and a splitter?
The way we define it, a coupler (usually) has four ports, uses no “internal” resistors and has one isolated port that is terminated. A splitter is (usually) a three-port, is non-directional, and requires internal resistors (like a Wilkinson) and has no isolated port.
What is a dual directional coupler?
Pasternack dual directional couplers (also known as bi-directional couplers) are passive devices that couple part of the transmission power in a transmission line. RF dual directional couplers often use two transmission lines set close together so that energy passing through one is coupled to the other.
What is the primary purpose of a directional coupler?
The basic function of a directional coupler is to operate on an input so that two output signals are available. However, when the input is applied to the opposite port of an internally terminated coupler, only one output signal is produced.
What are the types of directional coupler?
Directional couplers
- Coupled transmission lines.
- Branch-line coupler.
- Lange coupler.
- Wilkinson power divider.
- Hybrid coupler.
- Hybrid ring coupler.
- Multiple output dividers.
- Waveguide branch-line coupler.
What are the scattering parameters of directional coupler?
A directional coupler is a four-port device that uses waveguides to distribute power. A directional coupler is characterized by its coupling factor, isolation, and directivity. The scattering matrix of a directional coupler is the most convenient representation of its behavior in complex systems.
What is total draw length of directional coupler?
The mode-coupling coefficient of the directional coupler with the core center separation of D = 3a is calculated to be ĸ = 0.638 mm−1. The coupling length of this coupler is obtained as Lc = π/2κ = 2.46 mm.
What are the characteristics of a directional coupler?
There is high isolation between the coupled port and the output of the main-line. A schematic representation of the coupler is as follows; the arrows show signal flow: Key characteristics of a directional coupler include coupling coefficient, coupling flatness, main-line loss and directivity, defined on the next page.
How to calculate the directivity of a coupler?
In linear terms, the textbook equation for calculating a coupler’s directivity is: Directivity = Isolation – (Coupling + Loss) Using log rules, this equation becomes: Directivity = Isolation / (Coupling * Loss) The PNA equation editor has all the underlying data structures in complex real/imag (linear) values.
What is the coupling factor of a coupler?
COUPLING FACTOR The coupling factor is defined as: where P 1 is the input power at port 1 and P 3 is the output power from the coupled port (see Figure 1).
How does a PNA connect to a directional coupler?
Set up the connections between the PNA and a directional coupler as shown below. Connect PNA Port 1 to coupler’s input port. Connect PNA Port 2 to coupler’s output port. Connect PNA Port 3 to coupler’s coupled port. Set up basic stimulus conditions for directional coupler’s measurement.