Wave transmission lines and networks – Wave mode converters
Reexamination Certificate
2002-06-07
2003-10-28
Tokar, Michael (Department: 2819)
Wave transmission lines and networks
Wave mode converters
C333S034000, C333S026000, C333S033000
Reexamination Certificate
active
06639484
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a planar mode converter used in printed microwave integrated circuits, and more particularly, to a planar mode converter with low transmission losses and a simple fabrication process, utilized for printed microwave integrated circuits.
2. Description of the Related Art
Coupled with the flourishing of wireless communication during the recent years, printed integrated circuits with characteristics such as small in size, light in weight, low production cost and adapted to mass production, have become one of the important techniques in the fabrication of communication modules. However, confronting with wireless communication systems in which microwave and millimeter bands are applied, planar printed circuits, such as microstrips and coplanar waveguides, the shortcoming of the planar printed circuit technique due to comparatively larger transmission losses is explicitly exposed. Therefore, for radio front-end modules that are getting more and more stringent and complex day by day, it is an arduous challenge to depend solely on conventional microwave and millimeter wave planar printed circuit techniques in the fabrication process. Hence, in order to minimize energy consumption and enhance system performance, non-radiative dielectric (NRD) guides and rectangular waveguides are widely used to replace certain planar printed integrated circuits and are applied to millimeter wave or higher bands because of their low transmission losses property, thus becoming one of the main-stream guiding structures for high performance band modules. During the past twenty years, Yoneyama et al. have invented the non-radiative dielectric(NRD) guide
10
by inserting a dielectric strip
13
, represented as the rectangular dielectric rod
13
in
FIG. 1
into a parallel-plate metal waveguide
11
so that signals are propagated in the dielectric rod without radiating energy. Yoneyama et al. in the meanwhile analyzed the characteristics of non-radiative dielectric guide and derived numerous related applications, including transmitter-receiver modules and array antennas.
Referring to
FIG. 2
, as another application structure that has low power losses and has been proficiently used, as disclosed in the U.S. Pat. No. 6,127,901, a rectangular waveguide
20
is shown. However, its structure is non-planar and therefore many interface converters are developed so that the rectangular waveguide
20
can be integrated with planar active or passive components. For instance, a planar microstrip
21
in
FIG. 2
is integrated with the rectangular waveguide
20
by a square aperture
22
. The known converters in the present time are classified into four categories below:
1. A broadband coplanar-strips quasi-yagi antenna similar to outdoor television antennas is made by using a printed circuit board, which is then inserted into the E-plane of the metal waveguide. The radiation pattern of the antenna is then able to correspond with the pattern of the dominant mode (TE
10
) of the rectangular waveguide, in a way that the energy is propagated by the dominant mode of the waveguide instead of the microstrip. The antenna has been disclosed both in “A systematic optimum design of waveguide-to-microstrip transition,” IEEE trans. Microwave Theory Tech., vol. 45, no.5, May 1997, written by H. B. Lee and T. ltoh, and “A Broad-band microstrip-to-waveguide transition using quasi-yagi antenna,” IEEE trans. Microwave Theory Tech., vol. 47, no. 12,pp. 2562-2567, December 1999, written by N. Kaneda, Y. Qian and T. ltoh,. The disclosures are incorporated herein by reference.
2.A patch antenna made by using printed circuit board is placed upon the E-plane of the rectangular waveguide. Then, the propagation energy on the microstrip is coupled into the rectangular waveguide by implementing the aperture-coupling concept so that the patch antenna radiates and further stimulates the dominant mode of the rectangular waveguide, thus completing the mode conversion. The antenna has been disclosed both in “Microstrip-to-waveguide transition compatible with MM-wave integrated circuits,” IEEE trans. Microwave Theory Tech., vol. 42, no.9,pp. 1842-1843, September 1994, written by W. Grapher, B. Hudler and W. Menzel, and “Waveguide-microstrip transmission line transition structure having an integral slot and antenna coupling arrangement,” U.S. Pat. No. 5,793,263 1996, written by D. M. Pozar. The disclosures are incorporated herein by reference.
3. A microstrip probe made by using printed circuit board is inserted into the E-plane of the rectangular waveguide about a quarter of the wavelength in depth. Then, the ground plane of the microstrip probe is connected to the ground metal wall of the rectangular waveguide, thus achieving the mode conversion. The antenna has been disclosed in “Spectral-domain analysis of E-plane waveguide to microstrip transitions,” IEEE Trans. Microwave Theory Tech., vol. 37, pp. 388-392, February 1989, written by T. Q. Ho, and Y. C. Shih, which is incorporated herein by reference.
4. A microstrip made by using printed circuit board is connected to a ridged waveguide, and full-wave analysis is performed to design an impedence matching circuit between the microstrip and the ridged waveguide so that the microstrip mode can be converted into the waveguide mode. The antenna has been disclosed in “A New Rectangular Waveguide to Coplanar Waveguide Transition,” IEEE MTT-S Int. Microwave Symp. Dig., Dallsa, Tex., vol.1, pp.491-492, May 8-10, 1990, written by G. E. Ponchak and R. N. Simons, which is incorporated herein by reference.
As a conclusion drawn from the above, non-radiative dielectric guides, metal rectangular guides, with the aid of the transformation circuits are indeed able to demonstrate considerable outstanding low-loss characteristics. Nevertheless, all of the structures are three-dimensional instead of planar with complicated design, fabrication difficulty and expensive cost; these factors cause difficulties when interfaced with the planar printed circuit. In addition, due to different fabrication processes required by waveguide and planar printed circuits used, fabrication complexity issues arise during the construction of the entire circuit module. Consequently, it is laborious to make adjustments causing the production cost increase significantly and therefore inappropriate for mass production.
For the past few years, to captivate a larger communication market, wireless communication integrated circuits, which are light in weight with low profile and artistic in appearance, are prone to become the trend in the future.
However, as deduced from above, the main drawbacks of these mode converters currently available handicap the integrations of the integrated circuits since complicated fabrication processes are involved.
SUMMARY OF THE INVENTION
The invention relates to a planar mode converter used in a printed microwave integrated circuit; it includes a rectangular waveguide, a microstrip feed-in circuit and a microstrip feed-out circuit.
One object of the invention is to realize the feed-in/feed-out mode converter, the rectangular waveguide, and microstrip coupling in one unified fabrication process, and achieve mode conversion by utilizing electromagnetic coupling of the microstrip.
Another object of the invention is to utilize the feed-in/feed-out mode converter of the microstrip coupling to design and create a rectangular waveguide band filter.
The interior of the rectangular waveguide is filled with a plurality of dielectric layers which are closely adhered on top of one another, wherein the top surface of the uppermost layer, the bottom surface of the lowermost layer, and the right and left sides of the dielectric layers, are covered with metal materials. The lowermost dielectric layer usually has largest dielectric constant and thickness. Except for the lowermost dielectric layer, each dielectric layer has a rectangular aperture at its front-end and back-end, respectively. The rectangular apertures at the front-end are closely situated
Lee Cheng-jung
Tzuang Ching-kuang
Mai Lam
Martine & Penilla LLP
National Chiao Tung University
Tokar Michael
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