Push-push oscillator

Oscillators – With distributed parameter resonator

Reexamination Certificate

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C331S056000, C331S060000, C331S076000, C331S100000, C331S114000, C331S1170FE, C331S102000, C331S101000, C331S17700V, C331S03600C, C455S260000

Reexamination Certificate

active

06275118

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a push—push oscillator employed in a wireless communication apparatus and measuring instrument, both of which handle high-frequency-bands.
BACKGROUND OF THE INVENTION
The push—push oscillator, in general, uses a resonator which electrically resonates at an oscillating frequency. FIG.
10
A through
FIG. 10C
illustrate this prior art. FIG.
10
A and
FIG. 10B
depict resonators employed in the prior art. The resonator in
FIG. 10B
is a hairpin resonator which is transformed from the resonator in FIG.
10
A. Both the resonators are electrically almost identical. Resonators formed by a transmission line such as a stripline have been widely used. This resonator is disclosed in the document of “Integrated Circuit for Microwave” written by Yoshihiro Konishi and published from “SAMPO” in 1973.
FIG. 10C
illustrates an entire circuit of the oscillator, which is disclosed in the document of “Push—Push VCO Design with CAD Tools” written by Zvi Nativ and Yair Shur, and published from Microwave Journal in February 1989. Japanese Utility Model Publication No. H06-73910 also teaches this idea. The oscillator in
FIG. 10C
comprises the following elements.
(a) resonator circuit
102
comprising a transmission line which length being one-half wavelength of a fundamental wave, and both the ends being left open;
(b) oscillator circuit
105
comprising two branch oscillators
103
and
104
employing Colpitts oscillator and the like, the two branch oscillators being electrically identical;
(c) in-phase addition circuit
106
comprising two transmission lines having an equal electrical length and another transmission line; and
(d) output terminal
107
.
Two output signals tapped off from circuit
105
include fundamental wave components, and its odd-order as well as even-order harmonics-wave-components. The fundamental wave component and its odd-order harmonic-wave-component are cancelled by circuit
106
, whereby they are scarcely supplied to output terminal
107
; however, the even-order harmonic-wave-component is added in-phase by circuit
106
and supplied from terminal
107
. This oscillator yet has one output terminal as
FIG. 10C
illustrates and an output signal obtained therefrom is thus nothing but a single phase. Comparing with a regular circuit which obtains even-order-harmonics by multiplying an output signal supplied from a single oscillator, this oscillator needs an in-phase addition circuit which occupies a physically large space. Further, when this oscillator is employed in a PLL frequency synthesizer, the output signal of the oscillator must be supplied to two circuits, i.e. a PLL circuit and an external circuit, although the oscillator has one output terminal, which eventually demands additional circuits.
The conventional oscillator discussed above has the following problems:
(1) The oscillator is not adequate for devices and instruments which need to be smaller in size, because it requires not only large dimensions but also needs a complex structure.
(2) When the oscillator is employed in the PLL frequency synthesizer, the output cannot be fed into a differential amplifier in double phases. As a result, a noise suppression function proper to the differential amplifier cannot be utilized, which entails the needs of improving the noise immunity of the PLL frequency synthesizer.
(3) Since a stripline is used in a transmission line of the resonator circuit, the quality factor (Q) of the resonator is obliged to be suppressed at a certain level. The phase noise characteristics of the oscillator thus remains at unsatisfactory level.
The conventional oscillators and the devices or instruments employing the oscillators have a limit to be downsized, and need improvement in noise characteristics.
SUMMARY OF THE INVENTION
The present invention aims to address the problems discussed above and provide a push—push oscillator smaller as well as simpler and having better noise characteristics than the conventional one. The present invention also aims to provide devices or instruments which can accommodate and utilize this push—push oscillator.
The push—push oscillator of the present invention comprises the following elements:
(a) a resonator circuit comprising a transmission line of which both ends are left open and a frequency-control-capacitance coupled to the transmission line in parallel;
(b) an oscillator circuit comprising two branch oscillators of which ends are coupled to the input side of respective branch oscillators;
(c) two output terminals of a fundamental wave, coupled to the outside of respective branch oscillators; and
(d) an even-order harmonic output terminal coupled to a midpoint on the transmission line of the resonator circuit.
The construction discussed above allows the oscillator to supply output signals as a fundamental wave and an even-order harmonic from respective output terminals separately provided thereon. Further, this oscillator can eliminate an in-phase addition circuit which has been employed in a conventional oscillator. When this oscillator is employed in a PLL frequency synthesizer (hereinafter called a PLL synthesizer), the fundamental wave can be input into a differential amplifier—an element of a phase-lock-loop integrated circuit (PLL IC)—in double phases so that noise immunity can be improved. In this specification, the “double phases” means two signals in different phases by 180°, and a “single phase” does not always mean a single signal but it is used in contrast with the meaning of this “double phase”.
An even-order harmonic output terminal of the oscillator can be replaced with an even-order harmonic input terminal. Further, when the even-order harmonic is fed into this input terminal, fundamental waves in an injection-locked condition can be taken out from the two output terminals of fundamental wave. In other words, this oscillator functions as a frequency divider.
The oscillator of the present invention can be further equipped with the following elements in addition to the resonator circuit and oscillator circuit.
an in-phase addition circuit for adding output signals from the respective branch oscillators;
an even-order harmonic output terminal coupled to an output side of this in-phase addition circuit;
a transmission line coupled by rf magnetic field with the transmission line near its midpoint in the resonator circuit; and
two fundamental-wave-output-terminals coupled to both the ends of the coupled transmission line.
The construction discussed above allows the oscillator to supply output signals as a fundamental wave and an even-order harmonics from respective output terminals separately provided thereon. When this oscillator is employed in a PLL synthesizer, the fundamental wave can be input into a differential amplifier an element of a phase-lock-loop integrated circuit (PLL IC) in double phases so that a noise immunity cam be improved.
The construction discussed above can be reworded as follows:
(1) a fundamental wave is tapped off in double phases from the oscillator circuit, and the even-order-harmonic is tapped off in a single phase by coupling with rf electric field at the midpoint on the transmission line;
(2) the even-order-harmonic is fed into the oscillator circuit in a single phase by coupling with rf electric field at the midpoint on the transmission line; and
(3) a fundamental wave is tapped off in double phases from the oscillator circuit by coupling with rf magnetic field at the midpoint on the transmission line, and the even-order-harmonic is tapped off in a single phase from the oscillator circuit via the in-phase addition circuit.
This construction allows the oscillator and a PLL synthesizer or a wireless communication apparatus employing the oscillator to be downsized and simplified, which eventually contributes to power saving of these devices. This construction also improves noise immunity as well as phase noise characteristics. This oscillator operates as an injection-locked oscillator so that it functions as a frequency divider.


REFERENCES:
patent: 4754236

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