LEYBOLD 737 01 User manual

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Please read this instruction sheet carefully before putting the unit into operation!
Prescribed use
The Gunn oscillator is used to generate microwave power for experiment purposes in voca-
tional training and education.
1. Safety instructions
• Avoid looking directly into the end of the radiating waveguide.
• Any eventual disassembly of the oscillator during experimentation into its 4 main com-
ponents is performed using the quick connectors and the thumb screws. Any further di-
sassembly of the componets may not be carried out.
• During operation make sure that all of the components of the Gunn oscillator are securely
fastened, i.e. tighten the thumb screws securely.
• The DC power supply of the Gunn oscillator may only be supplied using the LD power
supply equipment. This rules out any accidental interchanging of the polarity. Any excess
voltage – even in the form of a "brief voltage surge" – leads to irreparable damage to the
Gunn diode.
Instruction sheet
Gunn Oscillator 737 01
Bb 6/98
Fig. 1

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2 Description
The equipment set MTS 7.4.1 contains a completely assembled Gunn oscillator (c.f. Fig. 1) for a
fixed frequency of 9.40 GHz.This oscillator was especially developed for the requirements of the
training system.
(a) This device can be disassembled into four parts, and is thus well suited for experiment pur-
poses. These four parts are connected using LD quick connectors and are: the Gunn-diode
module, the housing rear panel, a diaphragm, and a adapter (see Fig. 2).
(b) In the training system MTS 7.4.6, it can be modified into a mechanically tuneable oscillator
in the frequency range of 8.5 to 12.4 GHz, using a moveable short.
The function of the Gunn oscillator, which is explained in more detail and practically applied in
MTS 7.4.2, is based on the reduced damping of the cavity resonator using the Gunn diode.
The current of the DC circuit (Fig. 3) flows via the internal conductor (negative pole) of the coaxi-
al BNC socket, the internal conductor of the coaxial low-pass filter and the upper section of the
metal post to the Gunn diode and from there via the lower section of the metal post to the hou-
sing.The heat of the Gunn diode is drained to the housing via the metal post.
The design of the low-pass filter prevents a portion of the microwave power generated in the
Gunn diode from being diverted to the DC circuit; this can be deduced in Fig. 3. It consists of two
cascaded coaxial line segments with considerably different characteristic impedances, which
just reach l/4 at an operating frequency of 9.40 GHz.Thus the microwave signal is almost shor-
ted at the transition point between the coaxial line and the waveguide.
Before the oscillator was delivered, fine tuning of the frequency was carried out by changing the
penetration depth of the stub using the dielectric tuning screw.Therefore, this penetration depth
may not be altered by the user.
Fig. 2: Components of the Gunn oscillator
1Gunn diode module with:
2Metal post (incl. Gunn diode)
3Dielectric tuning screw
4BNC socket
5Rear housing wall
6Diaphragm with aperture
7Adapter

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Fig. 3: DC circuit of the Gunn oscillator
1Gunn diode
2Upper and lower section of the metal post
3Low-pass filter
4Internal conductor of the BNC socket
5External conductor of the BNC socket
3 Technical specifications
Operating DC voltage of the Gunn-diode: 8 bis 10 V
Operating DC current: 115 bis 150 mA
Frequency of microwave signal: 9,40 (± 0,002) GHz
Microwave power: 6 dBm
Suppression of harmonic signals: 30 dB
Suppression of non-harmonic signals: 50 dB
Efficiency of the oscillator: approx. 1 %
Power loss: approx. 1 W