Oscillators – With distributed parameter resonator – Parallel wire type
Reexamination Certificate
2001-02-02
2003-01-07
Mis, David C. (Department: 2817)
Oscillators
With distributed parameter resonator
Parallel wire type
C331S096000, C331S1170FE
Reexamination Certificate
active
06504440
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric resonance oscillation circuit using a microstrip line, a dielectric resonator and a transistor.
2. Description of the Background Art
In a receiving converter for satellite broadcasting employing Ku-band, a local oscillation signal of extremely high frequency of 10 GHz to 12 GHz has been utilized. Correspondingly, it has become common for a local oscillation circuit to employ a field effect transistor (FET) having a high cutoff frequency (Ft).
FIG. 4
illustrates a pattern and parts arrangement of a dielectric resonance oscillation circuit utilizing such a FET. Specifically, a microstrip line
52
has one end connected to a gate terminal
58
of FET
51
and the other end grounded via a terminating resistance
53
of 50&OHgr;. A dielectric resonator
4
is provided at an appropriate distance maintained from microstrip line
52
within a range where it can be coupled with microstrip line
52
at high frequency. With such an arrangement, a change in location of dielectric resonator
4
is accompanied by a change in impedance of dielectric resonator
4
as seen from gate terminal
58
.
The oscillation circuit above comes to operate for oscillation when the impedance of dielectric resonator
4
as seen from a source terminal
59
of FET
51
exhibits characteristics of negative resistance. As dielectric resonator
4
is moved in parallel with microstrip line
52
, at the time when it arrives at a specific position, the impedance of dielectric resonator
4
seen from source terminal
59
attains such characteristics of negative resistance. Thus, by properly positioning the dielectric resonator
4
, a stable oscillating operation is ensured. A signal generated by such an oscillating operation is output from source terminal
59
. The oscillation signal is then externally taken out from an oscillation signal output terminal
57
, via a stub
55
for output matching and a capacitor
56
for removal of a direct-current (DC) component. In
FIG. 4
,
60
denotes a DC supply terminal.
The characteristics of negative resistance as described above exhibit periodicity in that they appear every time dielectric resonator
4
moves a distance equal to a wavelength of the oscillation frequency. If dielectric resonator
4
is placed close to FET
51
, the loops of the electric field generated from dielectric resonator
4
strongly affect FET
51
, thereby increasing phase noise. Thus, dielectric resonator
4
is placed as far as possible from FET
51
within a range allowed by a size of an enclosure containing the oscillation circuit.
Currently, however, there is a pressing demand for increasing an amount of transmissible data for the Internet, for two-way communications, and in the fields where multi-channel and/or high-definition broadcasting is pursued, e.g., for digital broadcasting by broadcast-satellite (BS) that has recently been introduced to Japan. To meet such a demand, there is a growing tendency to employ 8-value PSK (phase shift keying) as a modulation technique, instead of 4-value PSK.
When such transition from 4-value PSK to 8-value PSK takes place, however, a permissible level of phase rotation in a signal transmission path becomes small. Accordingly, in the specification of a block handling a signal of high frequency, a permissible level of phase noise is set to a small value.
More specifically, in the phase shift keyed modulation techniques, data are identified by phase distribution on a complex plane. Thus, tolerance for phase variation for the 8-value PSK becomes much narrower than that for the 4-value PSK. When performing frequency conversion in the block handling a signal of high frequency, a local oscillation signal is required. Such a local oscillation signal includes undesired phase noise, which causes deviation of the phase distribution of the modulated signal being transmitted. Accordingly, for the frequency conversion of a signal by the 8-value PSK, a signal of low phase noise should be used as the local oscillation signal.
If FET
51
is being used as an oscillation element, it is difficult to decrease the phase noise, since undesired phase noise included in the oscillation signal tends to increase. Thus, a technique has been proposed which employs PLL (phase locked loop) to decrease such undesired phase noise. In order to use this technique, however, a reference signal oscillation circuit employing a temperature compensated type crystal oscillator will be required. Such a reference signal oscillation circuit is expensive, which makes this technique difficult to apply to household appliances.
A technique to address the above-described problems associated with the local oscillation circuit in the converter has conventionally been disclosed in Japanese Patent Laying-Open No. 10-200333.
Specifically, this technique utilizes, as an oscillation element, a transistor that operates in a microwave band. A circuit disclosed therein includes a microwave line connected to a base terminal of the transistor, and a dielectric resonator configured to couple with this microwave line. The microwave line has a length equal to ½ the wavelength of an oscillation frequency and its end is open-circuited. Alternatively, the microwave line may have a length equal to ¼ the wavelength or an odd number of times thereof and its end is short-circuited. The resonance frequency of the dielectric resonator is set equal to the oscillation frequency.
This reference, however, has not disclosed any specific arrangements for interconnecting a plurality of patterns or any specific configurations for achieving stable oscillation. Thus, an attempt to realize a compact oscillation circuit for practical use according to this technique has encountered a number of obstacles.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a dielectric resonance oscillation circuit that facilitates configuration of a feedback type oscillation circuit.
Another object of the present invention is to provide a dielectric resonance oscillation circuit that increases the degree of freedom in pattern designing.
A further object of the present invention is to provide a dielectric resonance oscillation circuit that makes a stable oscillation output obtainable.
A still further object of the present invention is to provide a dielectric resonance oscillation circuit that exhibits an increased degree of coupling with a dielectric resonator.
Yet another object of the present invention is to provide a dielectric resonance oscillation circuit that facilitates supply of power.
A further object of the present invention is to provide a dielectric resonance oscillation circuit that decreases a leakage level of an oscillation signal.
A still further object of the present invention is to provide a dielectric resonance oscillation circuit that facilitates taking of an output signal.
Yet another object of the present invention is to provide a dielectric resonance oscillation circuit that prevents a DC component from appearing at an outputting terminal.
A further object of the present invention is to provide a dielectric resonance oscillation circuit that decreases an effect of a circuit connected to the outputting terminal being posed on oscillation.
The dielectric resonance oscillation circuit according to an aspect of the present invention includes: a microstrip line connected to a signal input terminal of a transistor; a microstrip line connected to a signal output terminal of the transistor; and a dielectric resonator coupled with the microstrip lines at high frequency. Each of the microstrip lines is provided with a pattern that is branched off from the relevant microstrip line at an arbitrary angle.
Accordingly, it is readily possible to realize an arrangement in which the microstrip line connected to the signal output terminal is coupled to the dielectric resonator at high frequency and, at the same time, the dielectric resonator is coupled to the microstrip line connected to the signal input terminal at high
Birch & Stewart Kolasch & Birch, LLP
Mis David C.
Sharp Kabushiki Kaisha
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