Amplifiers – Involving structure other than that of transformers per se – With printed circuits
Reexamination Certificate
2001-04-17
2003-09-23
Lee, Benny (Department: 2817)
Amplifiers
Involving structure other than that of transformers per se
With printed circuits
C330S068000, C333S247000, C333S208000
Reexamination Certificate
active
06624692
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to radio frequency amplifiers preferably used in satellite communication transmitters and transceivers.
2. Description of the Related Art
A radio frequency amplifier used in a millimeter-wave band (which has a frequency range from 20 to 40 GHz) is illustrated in
FIGS. 6 and 7
. A casing
31
made of metal, such as brass serves as a heat sink. The casing
31
includes a storage part
31
a
having an opening at an upper part and a side wall
31
b
(see
FIG. 6
) that surrounds the storage part
31
a.
A circuit board
32
, which is a printed circuit board, includes a pair of holes
32
a
and
32
b
shown in FIG.
6
. As shown in
FIG. 7
, wiring patterns
33
a
and
33
b
, which are conductive, are positioned on a top surface of the circuit board
32
. A filter
34
, which is made of oblique conductive patterns, is positioned between the wiring patterns
33
a
and
33
b
between the holes
32
a
and
32
b.
The filter
34
separates the top surface of the circuit board
32
into first and second regions R
1
and R
2
(see FIG.
7
). As shown in
FIG. 6
, a ground pattern is positioned on the back surface of the circuit board
32
. The ground pattern is disposed on a bottom portion
31
c
of the storage part
31
a
and the circuit board
32
is mounted in the storage part
31
a
by appropriate means.
Field effect transistors (FETs)
35
a
and
35
b
are inserted into the holes
32
a
and
32
b
of the circuit board
32
. The FETs
35
a
and
35
b
are fixed through the holes to the bottom portion
31
c
of the casing
31
using electrically conductive adhesive. Wires
36
are bonded to the FETs
35
a
and
35
b
, and hence, the FETs
35
a
and
35
b
are connected to the wiring patterns
33
a
and
33
b
, which are formed in the first and second regions R
1
and R
2
, respectively.
Various electrical components are soldered to the wiring patterns
33
a
and
33
b
formed in the first and second regions R
1
and R
2
, respectively. With these electrical components and the FETs
35
a
and
35
b
, a first amplifier circuit
37
a
that includes a bias circuit is assembled in the first region R
1
, and a second amplifier circuit
37
b
that includes a bias circuit is assembled in the second region R
2
. A metal cover is mounted by appropriate means to cover the opening of the casing
31
to shield the storage part
31
a.
In this conventional radio frequency amplifier, the filter
34
is formed of oblique conductive patterns. These conductive patterns can cause large transmission losses and can create distortion in the amplifier circuits
37
a
and
37
b
. Thus, the performance of this radio frequency amplifier is not always efficient and isolation between the first and second amplifier circuits
37
a
and
37
b
can be compromised.
SUMMARY OF THE INVENTION
A radio frequency amplifier includes a casing, preferably made of metal, which includes a storage part. A circuit board is positioned within the storage part, on which first and second amplifier circuits are positioned. A filter is positioned between the first and second amplifier circuits. The filter includes a waveguide filter that is preferably configured to attenuate or dampen interfering electrical signals, such as noise or electromagnetic interference that can adversely affect the first and second amplifier. The waveguide filter is positioned within the storage part between the first and second amplifier circuits and preferably provides electrical shielding between the first and second amplifier circuits.
The first and second amplifier circuits preferably include first and second amplifying elements, respectively, and the amplifying elements may be non-packaged or bare chips. The first and second amplifying elements can be connected to a wiring pattern on the circuit board, with the waveguide filter positioned between the amplifying elements.
The waveguide filter preferably includes a main body preferably formed of metal and having a cavity. The main body preferably separates the storage part into first and second chambers. The first amplifier circuit is preferably formed within the first chamber. The second amplifier circuit is preferably formed within the second chamber.
The cavity of the main body is preferably a concave cavity that that opens from the underside of the main body. The opening is preferably positioned above a bottom portion of the casing, wherein the bottom portion and the main body comprise the waveguide filter.
The bottom portion of the casing preferably includes a cavity that is also preferably a concave cavity. The cavity of the casing and the cavity of the main body is preferably arranged such that the cavities substantially align with each other, with a circuit board positioned between the bottom portion and the main body. A probe, preferably comprised of a portion of the wiring pattern of the circuit board, is preferably located in the storage part. The radio frequency amplifier may further include a cover that conceals the opening of the storage part. An interior surface of the cover preferably contacts a top surface of the waveguide filter.
According to a preferred embodiment, the transmission loss and distortion of amplifier circuits are relatively small in comparison to some conventional circuits, which provide a high-performance radio frequency amplifier. Unlike some conventional circuits, the first and second amplifier circuits are not directly coupled, and hence, electrical isolation is improved. Moreover, the structure of a radio frequency amplifier is simplified, and the radio frequency amplifier can be fabricated at a low cost. Furthermore, reliable electrical shielding between the first and second amplifier circuits is provided by a main body, further improving electrical isolation. Since a casing can preferably comprise a part of the waveguide filter, the structure of the waveguide filter is simplified. The waveguide filter preferably has a reduced height which reduces the cost of the waveguide filter. A circuit board can be easily mounted, and probes are preferably comprised of wiring patterns.
REFERENCES:
patent: 5274340 (1993-12-01), Deki et al.
patent: 5412340 (1995-05-01), Tanikoshi
patent: 5581217 (1996-12-01), Macdonald
patent: 6005455 (1999-12-01), Lindell et al.
patent: 314401 (1989-12-01), None
patent: 01 314408 (1989-12-01), None
patent: 11-330760 (1999-11-01), None
patent: 2000-77954 (2000-03-01), None
Suzuki Shigetaka
Takayama Akira
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
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