Radio frequency amplifier with a waveguide filter for isolating amplifying elements

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.

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.

FIG. 1 is a sectional view of a radio frequency amplifier according to a first embodiment;

FIG. 2 is a plan view of the radio frequency amplifier with a cover removed;

FIG. 3 is a plan view of the radio frequency amplifier with the cover and a main body removed;

FIG. 4 is a sectional view taken along the line IV—IV of FIG. 1;

FIG. 5 is an exploded perspective view of the radio frequency amplifier;

FIG. 6 is a sectional view of a conventional radio frequency amplifier; and

FIG. 7 is a plan view of the conventional radio frequency amplifier of FIG. 6 .

Referring to FIGS. 1 and 5, a radio frequency amplifier preferably used in a millimeter-wave band (having frequency ranges from about 20 to about 40 GHz) transceiver or receiver and encompassing a preferred embodiment is described. A casing 1 , preferably made of metal, such as brass or the like, absorbs heat like a heat sink. The casing 1 includes a storage part, such as the illustrated concave storage part 1 a having an opening at an upper part or side of the storage part 1 a . Preferably, a side wall 1 b surrounds the storage part 1 a and a substantially rectangular concave cavity 1 d is preferably positioned at a bottom portion 1 c of the storage part 1 a . A pair of fastening holes 1 e shown in FIG. 5 is preferably positioned near the cavity 1 d.

As shown in FIG. 1, a circuit board 2 , which is preferably a printed circuit board, includes a pair of holes 2 a and 2 b separated by a predetermined distance therebetween. A substantially rectangular through hole 2 c having a shorter length than the cavity 1 d of the casing 1 is positioned between holes 2 a and 2 b . As shown in FIG. 3, a pair of mounting holes 2 d are positioned across from each other with the through hole 2 c positioned therebetween. A plurality of small holes 2 e surround sides of the through hole 2 c.

Wiring patterns 3 a and 3 b made of conductive materials and a grounding pattern 4 made of a conductive material are positioned on a top surface of the circuit board 2 . The through hole 2 c separates the top surface of the circuit board 2 into first and second regions R 1 and R 2 .

Portions of the wiring patterns 3 a and 3 b are positioned in the first and second regions R 1 and R 2 . The wiring patterns 3 a and 3 b are positioned across from each other, with the through hole 2 c provided therebetween. Each wiring pattern 3 a and 3 b extend to substantially the middle of the through hole 2 c , and preferably are electrically coupled to probes 5 a and 5 b . The grounding pattern 4 is preferably formed around the side peripheries of the through hole 2 c and the mounting holes 2 d away from the probes 5 a and 5 b . The grounding pattern 4 is connected to a ground pattern formed on an entire back surface of the circuit board 2 by a connecting conductor provided through the small holes 2 e.

The preferred circuit board 2 is preferably stored in the storage part 1 a such that the ground pattern is disposed on the bottom portion 1 c of the storage part 1 a . In this embodiment, the through hole 2 c provides access to the cavity 1 d shown in FIG. 4 provided on the bottom portion 1 e , and the probes 5 a and 5 b shown in FIG. 3, which are positioned above the cavity 1 d and terminate near ends of the cavity 1 d.

Referring to FIGS. 1 and 3, amplifying elements 6 a and 6 b such as non-packaged or bare chips FETs are preferably inserted within the holes 2 a and 2 b (see FIG. 1) of the circuit board 2 . The amplifying elements 6 a and 6 b are secured or coupled to the bottom portion 1 c of the casing 1 through an adhesive, such as an electrically conductive adhesive. Wires 7 are preferably bonded to the amplifying elements 6 a and 6 b , and hence, the amplifying elements 6 a and 6 b are connected to the wiring patterns 3 a and 3 b positioned in the first and second regions R 1 and R 2 , respectively.

Various electrical components are preferably connected to the wiring patterns 3 a and 3 b formed or positioned in the first and second regions R 1 and R 2 , respectively. Through these electrical components and the amplifying elements 6 a and 6 b , a first amplifier circuit 8 a that includes a bias circuit or the like is formed or positioned in the first region R 1 , and a second amplifier circuit 8 b that includes a bias circuit or the like is formed or positioned in the second region R 2 .

As shown in FIG 5 , a substantially rectangular main body 9 , preferably made of metal, includes a cavity, preferably a concave cavity 9 a having an opening accessible from the underside or bottom surface of the main body 9 . A side wall 9 b substantially surrounds the cavity 9 a and a plurality of concave portions 9 c or arches are positioned at the edge of the side wall 9 b to provide access to the cavity 9 a from the longitudinal sides of the main body 9 . A pair of mounting holes 9 d is configured to receive fasteners 13 , such as screws to couple the main body 9 to the circuit board 2 .

A lower opening of the main body 9 is preferably supported by the bottom portion 1 c of the casing 1 . The cavity 9 a of the main body 9 is preferably aligned or opposed to the cavity 1 d of the casing 1 . The main body 9 is coupled to the grounding pattern 4 on the circuit board 2 via fasteners 13 , such as the illustrated screws.

The main body 9 is grounded by the grounding pattern 4 , and the circuit board 2 is held between the main body 9 and the bottom portion 1 c . Preferably, the probes 5 a and 5 b are aligned with one or at least one concave portion 9 c or arch of the main body 9 , and thus, the electrical insulating property of the main body 9 is preserved. The probes 5 a and 5 b , the main body 9 , and the bottom portion 1 c preferably comprise a waveguide filter 10 shown in FIGS. 1 and 2. The main body 9 of the waveguide filter 10 is preferably arranged substantially parallel to the side wall 1 b defining the storage part 1 a . Referring to FIGS. 1 and 5, the main body 9 separates the storage part 1 a into first and second chambers 11 a and 11 b (see FIG. 1 ). In the first chamber 11 a , the first amplifier circuit 6 a is arranged. In the second chamber 11 b , the second amplifier circuit 6 b is arranged. The main body 9 , which preferably forms part of the waveguide filter 10 , provides electrical shielding between the first and second amplifier circuits 6 a and 6 b.

A cover 12 which preferably comprises a metal plate includes a pair of mounting holes 12 a passing there through. The cover 12 is laid over the opening of the casing 1 to protect and electrically shield the first and second chambers 11 a and 11 b. A pair of fasteners 13 , pass through the mounting holes 12 a of the cover 12 , the mounting holes 9 d of the main body 9 , and the mounting holes 2 d of the circuit board 2 . The fasteners 13 are received by the fastening holes 1 e of the casing 1 . The cover 12 , the main body 9 , and the circuit board 2 are mounted to the casing 1 using the screws in this embodiment, although other fasteners can be used in alternative embodiments.

By securing the fasteners 13 , preferably the interior of the cover 12 is brought into contact with the top surface of the main body 9 , which preferably comprises part of the waveguide filter 10 . Electrical shielding between the first and second chambers 11 a and 11 b and heat dissipation is improved by this substantially continuous or continuous ground that preferably interconnects the grounds on the top and bottom surfaces of the circuit board 2 to the cover 12 and the casing 1 . By pressing the main body 9 downward using the cover 12 , the circuit board 2 is securely held between the main body 9 and the bottom portion 1 c . Hence, the circuit board 2 is secure, and contact between the main body 9 and the grounding pattern 4 is ensured. Electrical insulation is preferably provided by the entire or substantially the entire bottom surface of the circuit board 2 interconnected to the grounded runs of the top surface of the circuit board 2 , the grounded main body 9 , and the grounded casing 1 and cover 12 With the above arrangement, a radio frequency amplifier according to a preferred embodiment is preferably assembled.

While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. For example, the waveguide filter 10 is not limited to the above described structures, as the waveguide filter 10 can encompass any system or material that guides electromagnetic waves including, but not limited to, a hollow conductor, a solid dielectric, or a dielectric filled conductor. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.