A 0.35-THz Extended Interaction Oscillator Based on Overmoded and Bi-Periodic Structure

An improved topology of Extended interaction oscillators (EIO) is presented with enhanced efficiency at 0.35 THz. A bi-periodic ladder-type structure is used for optimizing the performance of the TM
$_{{31}}- 2\pi $
mode operation, based on bi-periodic interaction gaps composed of staggered short and long slots. The bi-periodic interaction mechanism permits to operate the circuit with a standing-wave field between the
$\pi $
and
$2\pi $
modes, thus providing the potential to combine the advantages of both
$\pi $
and
$2\pi $
modes in terms of both coupling and output performance. The resulting transverse TM
₃₁
operating mechanism exhibits a good agreement with the bi-periodic structure in terms of coupling performance, with the short slot length positively correlated with the value of effective characteristic impedance
${M}^{\,{2}}{R}/{Q}$
. The circuit demonstrates attractive coupling and output characteristics by optimization of
${M}^{\,{2}}{R}/{Q}$
and
${Q}_{e}$
. A state-of-the-art value
${M}^{\,{2}}{R}/{Q}$
of 59.69
$\Omega $
and a moderate
${Q}_{e}$
of 2523.52 are achieved for a proposed eight-period ladder-type EIO. An RF power of 540 W is obtained with a 42.5 kV, 0.6 A sheet beam, with 2.1% electronic efficiency at 0.35 THz.