Oscillators – With outer casing or housing
Reexamination Certificate
2001-05-02
2003-04-08
Pascal, Robert (Department: 2817)
Oscillators
With outer casing or housing
C331S096000, C331S1070DP, C331S1070DP
Reexamination Certificate
active
06545552
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a local oscillator for millimeter wave, and more particularly, to a local oscillator utilizing a non-radiative dielectric waveguide (hereinafter referred to “NRD guide”) which can be used in millimeter wave integrated circuits.
BACKGROUND OF THE INVENTION
An NRD guide circuit has been widely used as a transmission line for a millimeter wave band above 30 GHz as it has a low transmission loss and can be easily fabricated as compared with a conventional microstrip line. The NRD guide circuit has a structure that a dielectric line along which an electromagnetic wave is transmitted is installed between two parallel conductive plates. A distance between the two parallel plates is smaller than half a wavelength of a using signal. Accordingly, the electromagnetic wave is shielded by the two parallel conductive plates not to pass through them, so that the electromagnetic wave can be transmitted along the dielectric line with a low transmission loss. Based on such a good transmission feature of the NRD guide circuit, local oscillators of 35 GHz and 60 GHZ, which are constructed by combining a Gunn diode and the NRD guide circuit, have been suggested.
FIGS. 1
to
3
show a conventional millimeter wave local oscillator. Referring to
FIGS. 1
to
3
, an NRD guide
8
is installed between upper and lower parallel conductive plates
11
a
and
11
b
in such a manner that an antenna portion
10
which is an output portion of the NRD guide
8
is protruded to an exterior. A diode mount
21
, on which a Gunn diode
1
and a bias choke
22
are mounted, is parallel arranged near to an input terminal of the NRD guide
8
. In order to form a longitudinal-section magnetic (LSM) mode in the NRD guide
8
, a microstrip resonator
23
is transversely coupled to the input terminal of the NRD guide
8
in such a manner that the microstrip resonator
23
extends towards an anode of the Gunn diode
1
. A mode suppressor
4
is accommodated in the input terminal of the NRD guide
8
in perpendicular to the microstrip resonator
23
. The mode suppressor
4
is fixed by a fixing block
18
. An oscillating signal of a high frequency generated from the Gunn diode
1
is outputted through the NRD guide
8
via the microstrip resonator
23
.
However, the conventional local oscillator requires the diode mount
21
for installing the Gunn diode
1
and the bias choke
22
. Accordingly, the diode mount
21
is provided with a cylindrical cavity
24
formed with a female screw portion therein so as to mount the Gunn diode
1
. In addition, when the diode mount
21
is installed between the upper and lower conductive plates
11
a
and
11
b
, a fine gap is formed between the diode mount
21
and the upper and lower conductive plates
11
a
and
11
b
. The fine gap acts as a capacitance in a short wavelength of the millimeter wave band so that problems of an oscillation of harmonics and a poor grounding are resulted. In particular, in order to shield a leaky wave, it is required to form a plurality of slots
25
having a width of &lgr;/4 and a predetermined depth on an upper surface of the diode mount
21
, so the structure of the diode mount
21
becomes complicated. Accordingly, the diode mount
21
increases manufacturing costs. In addition, the upper and lower conductive plates
11
a
and
11
b
have to be formed with a recess for fixing the diode mount
21
so the structures of the upper and lower conductive plates
11
a
and
11
b
become complicated.
A heat emission is closely related to an oscillating efficiency of the local oscillator. The Gunn diode
1
generates a heat when it produces the oscillating signal, and the generated heat has to be effectively emitted so as to stably maintain an oscillating power and an oscillating frequency. Accordingly, the diode mount
21
is usually made of copper which is good in heat conductivity. The heat generated from the Gunn diode
1
is transferred to the upper and lower conductive plates
11
a
and
11
b
, which act as a heat sink, and is cooled by the upper and lower conductive plates
11
a
and
11
b
. However, the heat is indirectly transferred to the upper and lower conductive plates
11
a
and
11
b
via the diode mount
21
, so the heat cannot be rapidly emitted. When the Gunn diode
1
is operated for a long time, a latent heat is fed back to the Gunn diode
1
so that a temperature of the Gunn diode
1
continuously increases. In this case, the Gunn diode
1
may generate an undesired oscillating power and an undesired oscillating frequency, thereby resulting a fatal fault to the system.
On the other hand, the Gunn diode
1
receives a direct current (DC) bias through the bias choke
22
mounted on the diode mount
21
and an oscillating signal produced by the Gunn diode
1
is transmitted to the NRD guide
8
through the microstrip resonator
23
. The oscillating power and the oscillating frequency can be controlled by adjusting a width of a microstrip
23
b
and a length thereof. That is, the oscillating frequency becomes higher as the length of the microstrip
23
b
becomes shorter. On the contrary, the oscillating power becomes lower as the length of the microstrip
23
b
becomes shorter. The microstrip
23
b
is a thin conductive film which is formed on a dielectric substrate
23
a
by an etching process. Accordingly, the microstrip
23
b
increases manufacturing costs.
Furthermore, a center of the microstrip
23
b
has to be precisely arranged on the anode of the Gunn diode
1
. In addition, a gap between the microstrip
23
b
and the anode of the Gunn diode
1
is one of the frequency tuning factors. Accordingly, it is required to precisely arrange the microstrip
23
b
and to finely maintain the gap in order to obtain a desired oscillating power and a desired oscillating frequency. However, it is very difficult to precisely arrange the microstrip
23
b
and the Gunn diode
1
in assembling them, so working efficiency is lowered.
On the other hand, as described above, the conventional local oscillator utilizes the length of the microstrip resonator
23
and the gap between the microstrip
23
b
and the anode of the Gunn diode
1
as tuning factors of the power and the frequency of the oscillating signal. However, the two tuning factors may be insufficient under certain circumstances.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems of the prior art, and accordingly, it is a first object of the present invention to provide a local oscillator in which a Gunn diode is directly mounted on a conductive plate in such a manner that a heat generated from the Gunn diode can be rapidly emitted, thereby stably carrying out an oscillating operation, and which allow low manufacturing costs and improve productivity by removing a diode mount.
A second object of the present invention is to provide a local oscillator capable of improving an oscillating characteristic in which a metal rod resonator, which is easily manufactured and has a superiority in power and frequency stability as compared with a microstrip resonator, and a cavity forming member for device protections and frequency tuning are installed.
According to the present invention, there is provided a local oscillator having a Gunn diode for generating an oscillating signal of millimeter wavelength by using a bias voltage, a resonating member for transferring the oscillating signal by adjusting a power of the oscillating signal and a frequency thereof, an NRD guide for guiding the oscillating signal inputted into an input terminal thereof to an output terminal thereof, and an LSE mode suppressor inserted into the input terminal of the NRD guide, for preventing an LSE mode of the oscillating signal transferred from the resonating member from passing therethrough while allowing an LSM mode of the oscillating signal to pass therethrough. The local oscillator also has a housing including an upper conductive plate and a lower conductive plate, for accommodating the Gunn diode, the resonating member, the NRD guide
Kim Young Su
Yoo Young Geun
Glenn Kimberly
NRD Co. Ltd.
Pascal Robert
LandOfFree
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