RF90 Degree vs 180 Degree Hybrid: Key Differences Explained
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This article explains the key differences between 90-degree and 180-degree hybrids. Both are RF devices commonly used for equally splitting or combining power across two ports. Let’s dive into the details.
Hybrids as Power Splitters
Both 90-degree and 180-degree hybrids can function as power splitters, dividing an input signal into two equal outputs. For further understanding, you might find these resources helpful:
90 Degree Hybrid
Functionality
A 90-degree hybrid splits the input signal such that the signals at the output ports (P2 and P3) are 90 degrees out of phase with each other.
Construction
The image below illustrates the construction of a 3dB 90-degree hybrid using a microstrip line.
Image: 90 degree hybrid
As shown in the diagram:
- Port 1: Input port
- Port 2: Direct output
- Port 3: Coupled output
- Port 4: Isolated port
180 Degree Hybrid
Functionality
The 180-degree hybrid also splits the input signal, but in this case, the signals at the output ports (P2 and P3) are 180 degrees out of phase.
Construction
The following image depicts the construction of a 3dB 180-degree hybrid using a microstrip line.
Image: 180 degree hybrid
Similar to the 90-degree hybrid:
- Port 1: Input port
- Port 2: Direct output
- Port 3: Coupled output
- Port 4: Isolated port
Key Specifications for Selection
When choosing between a 90-degree and 180-degree hybrid for your specific application, consider the following specifications:
- Frequency Range of Operation: The range of frequencies over which the hybrid operates effectively.
- Isolation (dB): The amount of signal that is isolated between the isolated port and the input ports. Higher isolation is generally better.
- Insertion Loss (dB): The signal loss between the input and output ports. Lower insertion loss is desired.
- Phase Unbalance (degrees): The difference in phase between the two output signals. Ideally, this should be as close to 90 or 180 degrees as possible, depending on the type of hybrid.
- Amplitude Unbalance (dB): The difference in amplitude between the two output signals. Smaller amplitude unbalance indicates better performance.
