O-type BWO Backward-wave oscillator

1 o-type bwo

1.1 o-bwo spectral purity , noise

1.1.1 frequency stability
1.1.2 noise

o-type bwo

the o-type carcinotron, or o-type backward wave oscillator, uses electron beam longitudinally focused magnetic field, , slow-wave circuit interacting beam. collector collects beam @ end of tube.

o-bwo spectral purity , noise

the bwo voltage tunable oscillator, voltage tuning rate directly related propagation characteristics of circuit. oscillation starts @ frequency wave propagating on circuit synchronous slow space charge wave of beam. inherently bwo more sensitive other oscillators external fluctuations. nevertheless, ability phase- or frequency-locked has been demonstrated, leading successful operation heterodyne local oscillator.

frequency stability

the frequency–voltage sensitivity, given relation

Δ


{\displaystyle \delta }

f/f = 1/2 [1/(1 + |vΦ/vg|)] (



Δ


{\displaystyle \delta }

v0/v0)

the oscillation frequency sensitive beam current (called frequency pushing ). current fluctuations @ low frequencies due anode voltage supply, , sensitivity anode voltage given by

Δ


{\displaystyle \delta }

f/f = 3/4 [ωq/ω/(1 + |vΦ/vg|)] (



Δ


{\displaystyle \delta }

va/va)

this sensitivity compared cathode voltage sensitivity, reduced ratio ωq/ω, ωq angular plasma frequency; ratio of order of few times 10.

noise

measurements on submillimeter-wave bwo s (de graauw et al., 1978) have shown signal-to-noise ratio of 120 db per mhz expected in wavelength range. in heterodyne detection using bwo local oscillator, figure corresponds noise temperature added oscillator of 1000–3000 k.