Frequency multiplier, dielectric transmission line device...

Wave transmission lines and networks – Frequency multipliers

Reexamination Certificate

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Details

C333S033000

Reexamination Certificate

active

06262641

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a frequency multiplier, a dielectric transmission line device, and a radio device, for use in a high frequency range such as a millimeter wave or sub-millimeter wave range.
2. Description of the Related Art
A signal source having a sufficiently high capability of directly generating a signal in the millimeter wave or sub-millimeter wave range is not known in the art. Therefore, in the millimeter wave or sub-millimeter wave range, frequency multipliers are widely used to generate a signal at a desired frequency by multiplying the frequency of an input signal by an integral factor. Frequency multipliers are generally realized using non-linearity in the current vs. voltage characteristic of a device such as a Schottky barrier diode, step recovery diode, bipolar transistor, FET, etc.
FIG. 6
illustrates a conventional frequency multiplier. As shown in
FIG. 6
, the frequency multiplier includes an FET for generating a multiplied frequency, an input matching circuit disposed between an input terminal and the FET, and an output matching circuit disposed between the FET and an output terminal. The frequency multiplier is designed taking into account both the fundamental-frequency signal input via the input terminal and the multiplied-frequency signal output via the output terminal. For example, the output matching circuit is designed such that the signal at the fundamental frequency is absolutely reflected but, at a desired harmonic frequency, a signal having a maximum power is transferred to the output terminal. In
FIG. 6
, a fundamental frequency reflecting stub reflects the fundamental frequency and a multiplied frequency matching stub provides matching with the FET so that the multiplied frequency is output in a most efficient manner.
In the conventional frequency multiplier, as shown in
FIG. 6
, input and output matching circuits with a large size and a complicated structure are required to provide matching for both the fundamental frequency and the multiplied frequency. In circuits used in the millimeter or sub-millimeter wave ranges, a dielectric transmission line such as an NRD (Non-Radiative Dielectric) waveguide is known to be advantageous in that a low transmission loss can be achieved. However, in practice, no frequency multiplier is known which provides an output signal directly through a NRD waveguide.
In order to output a signal via an NRD waveguide, it is required to provide a transmission line transformer between a conventional type frequency multiplier with a microstrip line and the NRD waveguide as shown in FIG.
7
. However, when the output matching circuit is constructed in the form of a planar circuit as shown in
FIG. 6
, a transmission line transformer circuit for providing a connection between the planar circuit and the NRD waveguide is needed to be connected to the output terminal of the frequency multiplier. This causes the frequency multiplier to become greater in total size and more complex in structure.
In view of the above, it is an object of the present invention to provide a frequency multiplier with an output matching circuit having a simplified structure in which an output signal is obtained directly through a dielectric transmission line.
It is another object of the present invention to provide a dielectric transmission line device in which a small-sized frequency multiplier is employed so as to achieve a reduction in the total size.
It is still another object of the present invention to provide a radio device using a dielectric transmission line of the above-described type as a transmission line for transmitting a transmission signal.
SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided a frequency multiplier including an element for generating a harmonic and an output matching circuit disposed between the above-described element and an output terminal wherein the output matching circuit includes a dielectric transmission line which passes a multiplied frequency and also includes an open-ended transmission line coupled with an electromagnetic field of the dielectric transmission line.
An FET may be employed as the above-described element for generating a harmonic. In this case, the source of the FET is grounded and the gate of the FET is connected to an input matching circuit. This configuration makes it possible to generate a harmonic or a multiplied-frequency signal more efficiently.
The dielectric transmission line may be constructed in the form of a non-radiative dielectric (NRD) waveguide to reduce the transmission loss due to electromagnetic wave radiation. The NRD waveguide may be disposed in close proximity to another transmission line without causing unwanted coupling with that transmission line. This makes it possible to achieve a further reduction in the total size.
The above-described transmission line serving as the output matching circuit may include a part having a width different from the width of the other part of the transmission line wherein the part with the different width has a length one-quarter the wavelength of the multiplied frequency such that the part serves as an impedance transformer. This allows the transmission line to be electromagnetically coupled with the dielectric transmission line with a particular characteristic impedance in a most efficient fashion. It also provides good matching between the transmission line and the harmonic-generating element, such as an FET, thereby making it possible to efficiently output the multiplied-frequency signal.
According to still another aspect of the invention, there is provided a dielectric transmission line device including a frequency multiplier according to any of the above-described aspects of the invention wherein the frequency multiplier is disposed between an oscillator device and a dielectric transmission line. This makes it possible to realize a dielectric transmission line device including a small-sized high-efficiency frequency multiplier.
According to still another aspect of the invention, a small-sized high-efficiency radio device includes a dielectric transmission line device according to the above aspect of the invention as a transmission line for transmitting a transmission signal.


REFERENCES:
patent: 5886595 (1999-03-01), Von Stein
patent: 6031433 (2000-02-01), Tanizaki et al.
patent: 9-083216 (1997-03-01), None
Patent Abstracts of Japan, vol. 1997, No. 07, Jul. 31, 1997, & JP 09 083216 A (Mitsubishi Electric Corp; Yoneyama Tsutomu), Mar. 28, 1997, abstract, p. 8, col. 1, line 13-line 42; Figure 31, p. 9, col. 1, line 1-line 10.
Iyama et al., “Second Harmonic Reflection Type High-Gain FET Frequency Doubler Operating in K-Band”, Intl. Microwave Symposium, New York, Jun. 13-15, 1989, pp. 1291-1294, p. 1291, col. 2 lines 1-10, Fig. 1.

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