Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
1999-03-04
2001-03-13
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S219000
Reexamination Certificate
active
06201458
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a strip-line filter utilized to filter microwaves in a communication apparatus or a measuring apparatus operated in frequency bands ranging from an ultra high frequency (UHF) band to a super high frequency (SHF) band, and more particularly to a strip-line filter in which a strip line is shortened and is made plane at low cost. Also, the present invention relates generally to a dual mode resonator utilized for an oscillator or a strip-line filter, and more particularly to a dual mode resonator in which two types microwaves are independently resonated.
2. Description of the Related Art
2.1. First Previously Proposed Art
A strip-line resonating filter is manufactured by serially arranging a plurality of one-wavelength type of strip line ring resonators to reduce radiation loss of microwaves transmitting through a strip line of the resonating filter. However, there is a drawback in the strip-line resonating filter that the resonating filter cannot be downsized. Therefore, a dual mode strip-line filter in which microwaves in two orthogonal modes are resonated and filtered has been recently proposed. A conventional dual mode strip-line filter is described with reference to
FIGS. 1 and 2
.
FIG. 1
is a plan view of a conventional dual mode strip-line filter.
FIG. 2A
is a sectional view taken generally along the line II—II of FIG.
1
.
FIG. 2B
is another sectional view taken generally along the line II—II of
FIG. 1
according to a modification.
As shown in
FIG. 1
, a conventional dual mode strip-line filter
11
comprises an input terminal
12
excited by microwaves, a one-wavelength strip line ring resonator
13
in which the microwaves are resonated, an input coupling capacitor
14
connecting the input terminal
12
and a coupling point A of the ring resonator
13
to couple the input terminal
12
excited by the microwaves to the ring resonator
13
in capacitive coupling, an output terminal
15
which is excited by the microwaves resonated in the ring resonator
13
, an output coupling capacitor
16
connecting the output terminal
15
and a coupling point B in the ring resonator
13
to couple the output terminal
15
to the ring resonator
13
in capacitive coupling, a phase-shifting circuit
17
coupled to a coupling point C and a coupling point D of the ring resonator
13
, a first coupling capacitor
18
for coupling a connecting terminal
20
of the phase-shifting circuit
17
to the coupling point C in capacitive coupling, and a second coupling capacitor
19
for coupling another connecting terminal
21
of the phase-shifting circuit
17
to the coupling point D in capacitive coupling.
The ring resonator
13
has a uniform line impedance and an electric length which is equivalent to a resonance wavelength &lgr;
o
. In this specification, the electric length of a closed loop-shaped strip line such as the ring resonator
13
is expressed in an angular unit. For example, the electric length of the ring resonator
13
equivalent to the resonance wavelength &lgr;
o
is called 360 degrees.
The input and output coupling capacitors
14
,
16
and first and second coupling capacitors
18
,
18
are respectively formed of a plate capacitor.
The coupling point B is spaced 90 degrees in the electric length (or a quarter-wave length of the microwaves) apart from the coupling point A. The coupling point C is spaced 180 degrees in the electric length (or a half-wave length of the microwaves) apart from the coupling point A. The coupling point D is spaced 180 degrees in the electric length apart from the coupling point B.
The phase-shifting circuit
17
is made of one or more passive or active elements such as a capacitor, an inductor, a strip line, an amplifier, a combination unit of those elements, or the like. A phase of the microwaves transferred to the phase-shifting circuit
17
shifts by a multiple of a half-wave length of the microwaves to produce phase-shift microwaves.
As shown in
FIG. 2A
, the ring resonator
13
comprises a strip conductive plate
22
, a dielectric substrate
23
mounting the strip conductive plate
22
, and a conductive substrate
24
mounting the dielectric substrate
23
. That is, the ring resonator
13
is formed of a microstrip line. The wavelength of the microwaves depends on a relative dielectric constant &egr;
r
of the dielectric substrate
23
so that the electric length of the ring resonator
13
depends on the relative dielectric constant &egr;
r
.
In a modification, the ring resonator
13
is formed of a balanced strip line shown in FIG.
2
B. As shown in
FIG. 2B
, the ring resonator
13
comprises a strip conductive plate
22
m
, a dielectric substrate
23
m
surrounding the strip conductive plate
22
m
, and a pair of conductive substrates
24
m
sandwiching the dielectric substrate
23
m.
In the above configuration, when the input terminal
12
is excited by microwaves having various wavelengths around the resonance wavelength &lgr;
o
, electric field is induced around the input coupling capacitor
14
so that the intensity of the electric field at the coupling point A of the ring resonator
13
is increased to a maximum value. Therefore, the input terminal
12
is coupled to the ring resonator
13
in the capacitive coupling, and the microwaves are transferred from the input terminal
12
to the coupling point A of the ring resonator
13
. Thereafter, the microwaves are circulated in the ring resonator
13
in clockwise and counterclockwise directions. In this case, the microwaves having the resonance wavelength &lgr;
o
are selectively resonated according to a first resonance mode.
The intensity of the electric field induced by the microwave resonated is minimized at the coupling point B spaced 90 degrees in the electric length apart from the coupling point A because the intensity of the electric field at the coupling point A is increased to the maximum value. Therefore, the microwaves are not directly transferred to the output terminal
15
. Also, the intensity of the electric field is minimized at the coupling point D spaced 90 degrees in the electric length apart from the coupling point A so that the microwaves are not transferred from the coupling point D to the phase-shifting circuit
17
. In contrast, because the coupling point C is spaced 180 degrees in the electric length apart from the coupling point A, the intensity of the electric field at the coupling point C is maximized, and the connecting terminal
20
is excited by the microwaves circulated in the ring resonator
13
. Therefore, the microwaves are transferred from the coupling point C to the phase-shifting circuit
17
through the first coupling capacitor
18
.
In the phase-shifting circuit
17
, the phase of the microwaves shifts to produce phase-shift microwaves. For example, the phase of the microwaves shifts by a half-wave length thereof. Thereafter, the connecting terminal
21
is excited by the phase-shift microwaves, and the phase-shift microwaves are transferred to the coupling point D through the second coupling capacitor
19
. Therefore, the intensity of the electric field at the coupling point D is increased to the maximum value. Thereafter, the phase-shift microwaves are circulated in the ring resonator
13
in the clockwise and counterclockwise directions so that the phase-shift microwaves are resonated according to a second resonance mode.
Thereafter, because the coupling point B is spaced 180 degrees in the electric length apart from the coupling point D, the intensity of the electric field is increased at the coupling point B. Therefore, electric field is induced around the output coupling capacitor
16
, so that the output terminal
15
is coupled to the coupling point B in the capacitive coupling. Thereafter, the phase-shift microwaves are transferred from the coupling point B to the output terminal
15
. In contrast, because the coupling points A, C are respectively spaced 90 degrees in the electric length apart from the coupling point D, the intensity
Makimoto Mitsuo
Matsuo Michiaki
Sagawa Morikazu
Matsushita Electric - Industrial Co., Ltd.
Nguyen Patricia T.
Pascal Robert
Rossi & Associates
LandOfFree
Plane type strip-line filter in which strip line is... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plane type strip-line filter in which strip line is..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plane type strip-line filter in which strip line is... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2494049