Mai suna Gunn Diode Oscillator?

Me k'a ce Wani Gun Diode Oscillator?

Gunn Diode Oscillator

Gunn Diode Oscillator (ko da ake kira Gunn oscillators ko transferred electron device oscillator) suna da kayayyakin masu shirya microwave na yanki da suka fi sanya. Suna da Gunn diode ko transferred electron device (TED) a matsayin muhimman komponantoda. Su ne kofin da take sama da Reflex Klystron Oscillators.

A cikin Gunn oscillators, ana jin Gunn diode a cikin resonant cavity. Gunn oscillator an samu biyu masu muhimmiyar komponanta: (i) DC bias da (ii) A tuning circuit.

Yadda Gunn Diode Yake Iya Samun Funtshi a Cikin DC Bias

A cikin Gunn diode, idan an yi tasiri kan DC bias, akwai zama mafi girma har zuwa inda ya shiga threshold voltage. Bayan wannan wuraren, akwai zama mafi gajerar da kuma volts ya ci abin da ya shiga breakdown voltage. Zabubbukan daga takam zuwa wata a cikin wannan kyakkyawan yana nuna ma'anar negative resistance region.

Kyakkyawar Gunn diode a taka negative resistance, ta hanyar sabbin properties, yana iya taimakawa su samun funtshi a cikin oscillator. Wannan yana faru saboda negative resistance yana tsara waɗanda ake koyar da su a cikin kyakkyawan, wanda ke taimakawa inganci mai girma.

Wannan ke haɗa zuwa samun inganci masu girma duka lokacin da ake da DC bias, amma girman wannan inganci suna da damar a cikin boundaries of the negative resistance region. 

Tuning Circuit

A cikin Gunn oscillators, frequency of oscillation yana da nasara mai yawa a kan middle active layer of the gunn diode. Amma frequency of resonance yana iya kunna tushen mekaniki ko electronic. A cikin electronic tuning circuit, control yana iya samun fuskantar waveguide ko microwave cavity ko varactor diode ko YIG sphere.

A cikin wannan, diode an jin a cikin cavity hakan yadda yake iya kansa loss resistance of the resonator, wanda ke bayar da inganci. Duk da haka, a cikin mechanical tuning, size of the cavity ko magnetic field (for YIG spheres) yana iya canzawa mekaniki, misali, by using an adjusting screw, in order to tune the resonant frequency.

Waɗannan types of oscillators suna amfani da su don samun microwave frequencies ranging from 10 GHz to few THz, as decided by the dimensions of the resonant cavity. Usually coaxial and microstrip/planar based oscillator designs suna da low power factor and are less stable in terms of temperature.

Duk da haka, waveguide and dielectric resonator stabilized circuit designs suna da greater power factor and can be made thermally stable, quite easily.Figure 2 shows a coaxial resonator based Gunn oscillator which is used to generate the frequencies ranging from 5 to 65 GHz. Here as the applied voltage Vb is varied, the Gunn diode induced fluctuations travel along the cavity to get reflected from its other end and reach back their starting point after time t given by

Idan, l ita ce length of the cavity and c ita ce speed of light. Daga wannan, equation for the resonant frequency of the Gunn oscillator can be deduced as

idance, n ita ce number of half-waves which can fit into the cavity for a given frequency. This n ranges from 1 to l/ct d where td ita ce time taken by the gunn diode to respond to the changes in the applied voltage.

A cikin wannan, inganci suna faru idan loading of the resonator yana da shi da maximum negative resistance of the device. Ba dangane, wannan inganci suna ci girman da ya hankula har zuwa lokacin da average negative resistance of the gunn diode becomes equal to the resistance of the resonator, then one can get sustained oscillations. 

Duk da haka, waɗannan relaxation oscillators suna da large capacitor connected across the gunn diode so as to avoid burning-out of the device due to the large amplitude signals.Lastly, it is to be noted that the Gunn diode oscillators are extensively used as radio transmitters and receivers, velocity-detecting sensors, parametric amplifiers, radar sources, traffic monitoring sensors, motion detectors, remote vibration detectors, rotational speed tachometers, moisture content monitors, microwave transceivers (Gunnplexers) and in the case of automatic door openers, burglar alarms, police radars, wireless LANs, collision avoidance systems, anti-lock brakes, pedestrian safety systems, etc.