Oscillators – With distributed parameter resonator
Reexamination Certificate
1999-10-06
2001-07-10
Kinkead, Arnold (Department: 2817)
Oscillators
With distributed parameter resonator
C331S099000, C331S1070SL, C331S1170FE, C333S204000
Reexamination Certificate
active
06259332
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microwave oscillator for oscillating a microwave and a millimeter-wave, in particular, to a microwave oscillator for allowing a phase noise of degrading a spectral purity to reduce.
2. Description of the Related Art
With reference to accompanying drawings, a conventional microwave oscillator will be described.
FIG. 1
is a circuit diagram showing the structure of a first example of a conventional microwave oscillator. The microwave oscillator shown in
FIG. 1
is a series feedback oscillator of which a feedback short-circuited stub
2
is connected to the source terminal of a field effect transistor (FET)
1
. A transmission line
11
and a capacitor
6
are connected in series to the gate terminal of the FET
1
. A gate bias circuit
3
supplies a DC bias to the gate terminal of the FET
1
through a spurious oscillation suppression resistor
14
and a transmission line
11
. A drain bias circuit
4
supplies a DC bias to the drain terminal of the FET
1
through a transmission line
11
.
Each of the bias circuits
3
and
4
is composed of a ½ wavelength line
5
, a capacitor
6
short-circuited in a high frequency band region, and a DC power supply
7
. An oscillated output signal is extracted from a load resistor
10
through a transmission line
11
and an output matching circuit
8
that are connected in series to the drain terminal of the FET
1
. The output matching circuit
8
is composed of a transmission line
11
and a matching open stub
12
.
FIG. 2
is a circuit diagram showing the structure of a second example of a conventional microwave oscillator. The microwave oscillator shown in
FIG. 2
is composed of the microwave oscillator shown in
FIG. 1 and a
transmission line resonating circuit
9
. The transmission line resonating circuit
9
is composed of a ½ wavelength open stub
25
. Examples of the microwave oscillator shown in
FIG. 2
are disclosed in “1994 The Institute of Electronics, Information and Communication Engineers, Japan, Spring Convention C-43” and “1993 The Institute of Electronics, Information and Communication Engineers, Japan, C-44”, and so forth.
FIG. 3
is a circuit diagram showing the structure of a third example of a conventional microwave oscillator. The microwave oscillator shown in
FIG. 3
is composed of the microwave oscillator shown in
FIG. 1 and a
transmission line resonating circuit
9
. In particularly, the transmission line resonating circuit
9
is composed of a capacitor
6
and a ¼ wavelength short-circuited stub
26
. The capacitor
6
is short-circuited in a high frequency region.
FIG. 4
is a circuit diagram showing the structure of a fourth example of a conventional microwave oscillator. The microwave oscillator shown in
FIG. 4
has a resonating circuit
9
of which the capacitor
6
connected to the gate terminal of the FET
1
in the microwave oscillator shown in
FIG. 1
is substituted with a ¼ wavelength open stub
27
. Examples of the microwave oscillator shown in
FIG. 4
are disclosed in “1994 The Institute of Electronics, Information and Communication Engineers, Japan, Spring Convention C-73” and “1992 The Institute of Electronics, Information and Communication Engineers, Japan, C-60”, and so forth.
FIG. 5
is a circuit diagram showing the structure of a fifth example of a conventional microwave oscillator. The microwave oscillator shown in
FIG. 5
is composed of the microwave oscillator shown in
FIG. 1 and a
resonating circuit
9
. The resonating circuit
9
is composed of a coupling transmission line
28
and a dielectric resonator
29
. Examples of the microwave oscillator shown in
FIG. 5
are disclosed in “IEEE Transaction on Microwave Theory and Techniques, Vol, MTT-31, p. 312” and so forth.
Although microwave oscillators having the above-described dielectric resonator
29
are disclosed in Japanese Patent Laid Open Publication Nos. Sho-61-205009, Hei-3-140003, and Hei-7-176954, these related art references do not mention the reduction of the size of the structure.
However, in the first example of the conventional microwave oscillator shown in
FIG. 1
, since it does not contain a resonant circuit with a sharp frequency characteristic, the quality factor Q value of the circuit is small and the phase noise thereof is large.
On the other hand, since the second to fourth examples of the conventional microwave oscillators shown in
FIGS. 2
to
4
have a transmission line resonating circuit of which one of a transmission line is opened or short-circuited is disposed, the Q value of the circuit increases and thereby the phase noise reduces. These transmission line resonators can be easily structured with small planar circuits. However, since the unloaded Q value is not large, the phase noise cannot be sufficiently reduced.
On the other hand, in the fifth example of the conventional microwave oscillator shown in
FIG. 5
, with a resonating circuit
9
of which a dielectric resonator
29
is magnetically coupled with a coupling transmission line
28
, the phase noise is reduced. Since the dielectric resonator has a very large unloaded Q value, the phase noise can be remarkably reduced. However, the size and cost of the circuit and the module become large. In addition, the fabrication cost becomes large.
SUMMARY OF THE INVENTION
The present invention is made from the above-described point of view. An object of the present invention is to provide a microwave oscillator that is small in size and low in fabrication cost and that has an excellent phase noise characteristic.
The present invention is a microwave oscillator for oscillating a microwave signal, comprising a resonating circuit having a first open stub and a second open stub connected in parallel, the length of the first open stub being shorter than (2n−1)/4 (where n=1, 2, . . . ) of the wavelength of a fundamental wave by &dgr; (where &dgr; is sufficiently shorter than the wavelength of the fundamental wave), the length of the second open stub being longer than (2n−1)/4 of the wavelength of the fundamental wave by &dgr;.
The present invention is a microwave oscillator for oscillating a microwave signal, comprising a plurality of resonating circuits each of which has a first open stub and a second open stub, the resonating circuits being connected in parallel, the length of the first open stub being shorter than (2n−1)/4 (where n=1, 2, . . . ) of the wavelength of a fundamental wave by &dgr; (where &dgr; is sufficiently shorter than the wavelength of the fundamental wave), the length of the second open stub being longer than (2n−1)/4 of the wavelength of the fundamental wave by &dgr;, the values of n of the resonating circuits being always not the same, the values of &dgr; of the resonating circuits being always not the same.
The present invention is a microwave oscillator for oscillating a microwave signal, comprising a resonating circuit having a first short stub and a second short stub connected in parallel, the length of the first short stub being shorter than n/2 (where n=1, 2, . . . ) of the wavelength of a fundamental wave by &dgr; (where &dgr; is sufficiently shorter than the wavelength of the fundamental wave), the length of the second short stub being longer than n/2 of the wavelength of the fundamental wave by &dgr;.
The present invention is a microwave oscillator for oscillating a microwave signal, comprising a plurality of resonating circuits each of which has a first short stub and a second short stub, the resonating circuits being connected in parallel, the length of the first short stub being shorter than n/2 (where n=1, 2, . . . ) of the wavelength of a fundamental wave by &dgr; (where &dgr; is sufficiently shorter than the wavelength of the fundamental wave), the length of the second short stub being longer than n/2 of the wavelength of the fundamental wave by &dgr;, the values of n of the resonating circuits being always not the same, the values of &dgr; of the resona
Kinkead Arnold
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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