Beam voltage = 10 KV

Beam Current = 500 mA

Characteristics impedance of helix = 25 Ω

Current length = 20 cm

Frequency = 4 GHz

Determine gain parameter and power gain.

Given,

Beam voltage = $V_0$ = 10 KV

Beam Current = $I_0$ =500 mA

Characteristics impedance of helix = $Z_0= 25 Ω$

Current length = N = 20 cm

Frequency = f = 4 GHz

1. Gain Parameter C

Gain Parameter of TWT can be express as,

$C=\bigg(\frac{I_0 Z_0}{4 V_0 }\bigg)^{\frac{1}{3}}=\bigg(\frac{500×10^{-3}×25}{4×10×10^3}\bigg)^{\frac{1}{3}} \\ ∴C=67.86×10^{-3}$

2. Power Gain AP

$A_P=-9.54+4.73 (N×C) \\ =-9.54+4.73 (20×10^{-2}×67.86×10^{-3}) \\ ∴A_P=-9.47 dB$