VSWR is 1 because it signifies a perfectly matched system where there are no voltage variations along the transmission line.
Understanding VSWR = 1
The Voltage Standing Wave Ratio (VSWR) is a crucial measurement in radio frequency (RF) and microwave engineering. It indicates how efficiently radio frequency power is transmitted from a power source through a transmission line into a load (like an antenna).
What is VSWR?
According to the provided reference, VSWR is defined as:
- "the ratio between voltage minima and maxima along a transmission line."
Mathematically, VSWR is calculated as:
VSWR = Voltage Maximum / Voltage Minimum
When energy travels down a transmission line and encounters a mismatch (where the impedance of the line doesn't match the impedance of the load), some of the energy is reflected back towards the source. These forward and reflected waves interfere with each other, creating a standing wave pattern of voltage and current along the line, with points of maximum and minimum voltage.
The Significance of VSWR = 1
A VSWR of 1 (often expressed as 1:1) represents the ideal scenario: a perfectly matched system.
The reference states:
- "A perfectly matched system have no voltage differences along the line,"
In a perfectly matched system, there are no reflections from the load back towards the source. All the power sent down the line is absorbed by the load.
This lack of reflections means there is no standing wave pattern. The voltage magnitude is constant at every point along the transmission line.
- If the voltage is constant along the line, then the maximum voltage (Voltage Maximum) and the minimum voltage (Voltage Minimum) are equal to the same constant voltage value (let's call it V).
Therefore, the VSWR calculation becomes:
VSWR = Voltage Maximum / Voltage Minimum = V / V = 1
As the reference concludes, "so the VSWR is 1, usually expressed as 1:1."
Key Takeaway: Why VSWR is 1
- Definition: VSWR is the ratio of the maximum to minimum voltage on a transmission line.
- Perfect Match: A VSWR of 1 occurs in a perfectly matched system.
- No Voltage Differences: In a perfectly matched system, "have no voltage differences along the line".
- Constant Voltage: This means the voltage is constant everywhere.
- Ratio is One: With constant voltage, the maximum and minimum voltages are the same, making their ratio 1.
