PIN Diode Switch
A PIN diode acts as a current-controlled RF resistor: forward-biased it is a small resistance Rf, reverse-biased it is a small junction capacitance Cj. Mounted in series with the line it passes the signal when forward-biased and blocks it when reverse-biased; mounted in shunt it does the opposite. This tool evaluates the two states of a single-diode SPST switch and reports the insertion loss and isolation for either topology.
Equations & Parameters ▸
series diode \(Z_d\): \(A=20\log_{10}\Big|1+\dfrac{Z_d}{2Z_0}\Big|\) (dB)
shunt diode \(Z_d\): \(A=20\log_{10}\Big|1+\dfrac{Z_0}{2Z_d}\Big|\) (dB)
forward \(Z_d=R_f\); reverse \(Z_d=R_r-\dfrac{j}{\omega C_j}\)
shunt diode \(Z_d\): \(A=20\log_{10}\Big|1+\dfrac{Z_0}{2Z_d}\Big|\) (dB)
forward \(Z_d=R_f\); reverse \(Z_d=R_r-\dfrac{j}{\omega C_j}\)
| Topology | Series or shunt mounting of the diode. |
| Rf | Forward (ON) series resistance (Ω). |
| Cj | Reverse junction capacitance (pF). |
| Rr | Reverse series resistance (Ω, often ~0). |
| Z0, f | System impedance and frequency. |
Reference: D. M. Pozar, Microwave Engineering, 4th ed., §10.4.
Inputs
Mounting
Ω
ONpF
OFFΩ
OptionalΩ
SystemGHz
OperatingResults
Switch performance
Insertion loss (ON)—
Isolation (OFF)—
On/off ratio—
Diode impedance
Forward Zd—
Reverse |XCj|—
Reverse Zd—
Switch topology