Oscillators – Solid state active element oscillator – Transistors
Reexamination Certificate
2002-11-13
2004-09-28
Pascal, Robert (Department: 2817)
Oscillators
Solid state active element oscillator
Transistors
C331S1070SL
Reexamination Certificate
active
06798305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high frequency oscillator for use in a microwave band or a millimeter band, and more particularly, to a circuit configuration which can implement a push-push oscillator for generating a signal at a frequency twice as high as an oscillation frequency and a push-pull oscillator for combining oscillation outputs, and improve the performance of these oscillators.
2. Description of the Related Arts
A high frequency oscillator for use in a microwave band or a millimeter band is a core component among others in high frequency hardware, and simultaneously accounts for a large proportion of the device cost in the high frequency hardware, so that higher performance and economization are required for the high frequency oscillator. Particularly, a high frequency oscillator for use in a millimeter-wave region of 30 GHz or higher experiences lower oscillation power and deteriorated noise characteristic associated with a degraded performance of semiconductor devices and an increased circuit loss, and encounters difficulties in a reduction in the cost because a highly accurate assembling process, a high frequency testing process, and the like are required for manufacturing such a high frequency oscillator. These disadvantages also constitute main factors which impede the progress in applications of radio waves in the millimeter band. Remedies contemplated for the impediment may include the use of multiple oscillator elements, power combination based on a push-pull operation, oscillation of a high frequency twice as high as a fundamental frequency through push-push oscillation, and the like.
FIG. 1
illustrates the configuration of a conventional high frequency oscillator. This high frequency oscillator comprises dielectric resonator
2
X as a high frequency (microwave) resonator installed on substrate
1
; two active devices
3
for oscillation each including negative resistance elements, amplifier elements, and circuits associated therewith; and combiner circuit
4
. Two active devices
3
each employ, for example, an FET (field effect transistor) as an amplifier element, and share dielectric resonator
2
X to form two oscillation systems. A ground conductor (not shown) is deposited substantially over the entire back surface of substrate
1
.
Each FET
3
has a gate connected to one end of associated microstrip line
5
. These microstrip lines
5
are positioned on both sides of dielectric resonator
2
X and electromagnetically coupled to the same. Each microstrip line
5
has the other end grounded through terminal resistor
10
. FET
3
, the source of which is grounded, generates an oscillation output at its drain Here, the respective oscillation systems are designed to oscillate in opposite phase to each other, so that two FETs
3
provide oscillation outputs in opposite phase at their drains.
The drains of respective FETs
3
are connected to combiner circuit
4
. Combiner circuit
4
comprises a Wilkinson type power combiner circuit when it is designed, for example, for in-phase combination, and additionally includes a phase inversion circuit connected to one input of the Wilkinson type power combiner circuit when it is designed for antiphase combination. Combiner circuit
4
receives and combines respective oscillation outputs from the drains of the active devices for oscillation, i.e., FETs
3
.
For example, for configuring a push-push oscillator which generates oscillation frequency 2f
0
twice as high as oscillation frequency f
0
in each oscillation system, combiner circuit
4
receives oscillation outputs from respective FETs
3
as they are, and combines the oscillation outputs in phase. In this event, since FETs
3
themselves have oscillation outputs in opposite phase to each other, the fundamental component f
0
and its odd-numbered harmonic components in the oscillation output of each oscillation system are canceled out, while second-order and higher even-numbered harmonic components are combined and delivered from the output of combiner circuit
4
.
FIGS. 2A
to
2
C show the waveforms observed around combiner circuit
4
when the circuit illustrated in
FIG. 1
is used as a push-push oscillator.
FIGS. 2A and 2B
show the waveforms at two input terminals of combiner circuit
4
, respectively, while
FIG. 2C
shows the waveform at the output of combiner circuit
4
.
When the high frequency oscillator illustrated in
FIG. 1
is designed to function as a push-pull oscillator for generating combined output P
o
from the oscillation outputs of both oscillation systems at an output frequency remaining equal to fundamental frequency f
0
, combiner circuit
4
is configured to perform an antiphase combination. Specifically, for the antiphase combination, combiner circuit
4
combines the oscillation output from one FET
3
, after it is inverted, with the oscillation output from the other FET
3
which remains as it is. In this way, since the oscillation outputs are combined with fundamental wave f
0
remaining unchanged, combiner circuit
4
generates combined output P
o
which has the oscillation frequency equal to fundamental wave f
0
and an increased amplitude.
As described above, this type of high frequency oscillator which operates as a push-push oscillator or a push-pull oscillator comprises high frequency (microwave) resonator
2
; two active devices
3
for oscillation (e.g., FET); and combiner circuit
4
for performing an in-phase or an antiphase combination.
FIG. 3
illustrates this configuration in block diagram form. As is apparent from this block diagram, in the conventional high frequency oscillator, high frequency resonator
2
and combiner circuit
4
are designed as completely different components. This designing policy results in a correspondingly complicated circuit configuration. With the trend of increasingly higher oscillation frequency, a more complicated design is generally required for the three components, giving rise to difficulties in reducing the size of the circuit. Combiner circuit
4
disposed in the high frequency oscillator also causes a larger increase in loss.
The aforementioned Wilkinson type combiner circuit routes lines for combining two oscillation outputs to form the combiner circuit, giving rise to a problem that a complicated design is required therefor including an oscillator circuit.
Moreover, if mutually synchronized oscillations can be realized, for example, at four phase angles, i.e., synchronized oscillations with mutual phase differences being at 0 degree, 90 degrees, 180 degrees and 270 degrees, it is possible to generate an oscillation output at a frequency four times as high as the oscillation frequency (fundamental wave f
0
) in oscillation systems based on the principles of the push-push oscillator. However, any four-phase push-push oscillator has not been reported up to now. In other words, it is contemplated that the conventional circuit configuration can hardly be based to design this type of four-phase push-push oscillator.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high frequency oscillator which is suitable for reducing the size and loss of the circuit and is capable of realizing, for example, even a four-phase push-push oscillator.
The object of the present invention is achieved by a high frequency oscillator which includes a transmission line resonator; a pair of active devices for oscillation connected to a pair of resonant wave points, respectively, located on the transmission line resonator in an opposite phase relationship to each other, and a combiner line connected to an electric symmetric point of the transmission line resonator. The pair of active devices constitute a pair of oscillation systems which share the transmission line resonator as a high frequency resonator, and the combiner line is configured to combine outputs from the pair of oscillation systems to generate a high frequency output.
In the present invention, the active devices for oscillation are connected, for example, t
Aikawa Masayoshi
Asamura Fumio
Oita Takeo
Tanaka Takayuki
Chang Joseph
Katten Muchin Zavis & Rosenman
Nibon Dempa Kogyo Co., Ltd.
Pascal Robert
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