US 4,646,038 AGranted

Ceramic resonator filter with electromagnetic shielding

AssigneeMotorola, Inc.

InventorRonald J. Wanat

Life of this patent

Estimating the term…

Loading patent…

Abstract

Transmitter combining apparatus includes up to five RF filters (100) coupled to a microstrip combiner (300) for combining up to five input signals for application to a common antenna. The RF filter (100) includes a ceramic resonator (116) sandwiched between first and second compensating discs (114 and 120) and first and second shield plates (142 and 148) for temperature compensation, low loss mounting and heat sinking of the ceramic resonator (116). Good thermal contact between the ceramic resonator (116), discs (114 and 120) and shield plates (142 and 148) is produced by a compressive force exerted by springs (144-147) of shield plate (142) when the top cover (112) is attached to the aluminum housing (124). The resonant frequency of the RF filter is tuned by means of an aluminum tuning shaft (102) and ceramic tuning core (118) which are positioned by brass bushing (133) in top cover (112). Input signals are coupled to each RF filter via respective input coupling loops (122) and output signals are coupled via corresponding output coupling loops (311) to the microstrip combiner (300). The microstrip combiner (300) includes a circuit board (310) having five transmission lines (601-605) and a short-circuited tuning transmission line (610), all coupled to a junction (620). The microstrip combiner (300) is tuned by means a variable impedance produced by varying the position of a dielectric tuning plate (630) with respect to the tuning transmission line (610).

Claims24

Dependent claims

A radio frequency (RF) filter comprising:

resonating means having top and bottom surfaces and being comprised of a ceramic material having a predetermined thermal conductivity and a predetermined rate of change of resonant frequency with temperature;
first and second compensating means being disposed above and below the resonating means, respectively, and each having top and bottom surfaces, the bottom surface of the first compensating means and the top surface of the second compensating means being thermally coupled to the top and bottom surfaces of the resonating means, respectively, and the first and second compensating means being comprised of a dielectric material having a rate of change of resonant frequency with temperature opposite in polarity to said predetermined rate of change, and the dielectric material of the first and second compensating means further having a thermal conductivity greater than the thermal conductivity of air;
first and second shield means being comprised of a metallic material and being thermally coupled to and disposed above and below the the first and second compensating means, respectively, for producing a low-loss electromagnetic path above and below said resonating means;
and
housing means being comprised of a metallic material having an electrical conductivity less than that of the metallic material of said first and second shield means and further including top, bottom and side surfaces;
input coupling means and output coupling means disposed on the side surface of said housing means opposite to said resonating means and at a pre-selected distance from one another for coupling respective input and output signals to said RF filter;
and
said housing means substantially enclosing and retaining the resonating means between the first and second compensating means and the first and second shield means, the top and bottom surfaces of the housing means being thermally coupled to first and second shield means, respectively, whereby a low thermal resistance path is produced between the resonating means, first and second compensating means, first and second shield means and the housing means for conducting away from said resonating means heat dissipated therein thereby minimizing the temperature rise of said resonating means due to power dissipation.

5 more elements

A radio frequency (RF) filter comprising:

resonating means having top and bottom surfaces and being comprised of a ceramic material having a predetermined thermal conductivity;
first and second compensating means each having top and bottom surfaces and being disposed above and below the resonating means, respectively, the bottom surface of the first compensating means and the top surface of the second compensating means being thermally coupled to the top and bottom surfaces of the resonating means, respectively, and the first and second compensating means being comprised of a dielectric material having a thermal conductivity greater than the the thermal conductivity of air;
first and second shield means being comprised of a metallic material and being thermally coupled to and disposed above and below the the first and second compensating means, respectively, for producing a low-loss electromagnetic path above and below said resonating means;
housing means being comprised of a metallic material having an electrical conductivity less than that of the metallic material of said first and second shield means and further including top, bottom and side surfaces;
input coupling means and ouput coupling means disposed on the side surface of said housing means opposite to said resonating means and at a pre-selected distance from one another for coupling respective input and output signals to said RF filter;
and
said housing means substantially enclosing and retaining the resonating means between the first and second compensating means and the first and second shield means, the top and bottom surfaces of the housing means being thermally coupled to the first and second shield means, respectively, whereby a low thermal resistance path is produced between the resonating means, first and second compensating means, first and second shield means and the housing means for conducting away from said resonating means heat dissipated therein thereby minimizing the temperature rise of said resonating means due to power dissipation.

4 more elements

A radio frequency (RF) filter comprising:

resonating means having top and bottom surfaces and being comprised of a ceramic material having a predetermined thermal conductivity and a predetermined rate of change of resonant frequency with temperature;
first and second compensating means being disposed above and below the resonating means, respectively, and each having top and bottom surfaces, the bottom surface of the first compensating means and the top surface of the second compensating means being thermally coupled to the top and bottom surfaces of the resonating means, respectively, and the first and second compensating means being comprised of a dielectric material having a rate of change of resonant frequency with temperature opposite in polarity to said predetermined rate of change, and the dielectric material of the first and second compensating means further having a thermal conductivity greater than the thermal conductivity of air;
first and second shield means being substantially comprised of copper and being thermally coupled to and disposed above and below the the first and second compensating means, respectively, for producing a low-loss electromagnetic path above and below said resonating means;
housing means being substantially comprised of aluminum and including top, bottom and side surfaces;
an input coupling loop and an output coupling loop disposed on the side surface of said housing means opposite to said resonating means and at a pre-selected distance from one another for coupling respective input and output signals to said RF filter;
and
said housing means substantially enclosing and retaining the resonating means between the first and second compensating means and the first and second shield means, the top and bottom surfaces of the housing means being thermally coupled to first and second shield means, respectively, whereby a low thermal resistance path is produced between the resonating means, first and second compensating means, first and second shield means and the housing means for conducting away from said resonating means heat dissipated therein thereby minimizing the temperature rise of said resonating means due to power dissipation.

4 more elements

Dependencies are inferred from the claim text.