Circuit Analysis
Unilateral
A device or network characteristic where signal flow occurs in only one direction, meaning the output has no influence on the input, simplifying gain and stability analysis
Understanding Unilateral
A perfectly unilateral device has S12 = 0, meaning there is no reverse transmission. Real transistors and amplifiers have non-zero S12, but when S12 is sufficiently small, the unilateral approximation simplifies design by decoupling input and output matching networks.
The unilateral figure of merit U quantifies the error introduced by the unilateral assumption. When U is small (< 0.1), the unilateral gain approximation is within 1 dB of the actual transducer gain.
Common Questions
Frequently Asked Questions
When is the unilateral approximation valid?
When the device S12 is small enough that the unilateral figure of merit U < 0.1, meaning the approximation introduces less than about 1 dB error.
What is unilateral gain?
Unilateral transducer gain GTU is the gain with independently conjugate-matched input and output, calculated assuming S12 = 0.
See Also