Resistor for microwave applications
A resistor assembly for use at microwave frequencies, has a substrate with first and second contacts or metalizations at either end of the substrate. A third contact or metallization is provided on one side of the substrate generally in the middle thereof. First and second resistors, as thin film resistors, are provided on the substrate extending between the first and second contacts and the third, central contact. A third resistor is provided on the other side of the substrate, connecting the first and second contacts, so as to form a delta configuration of three resistors. This then provides a resistor configuration that can be used to implement a three port Wilkinson splitter or combiner.
1. A resistor assembly, for use at microwave frequencies, the resistor assembly comprising:
a) a substrate;
b) first and second contacts mounted on the substrate;
c) a third contact mounted on the substrate between the first and second contacts;
d) first and second resistors mounted on the substrate, the first resistor extending between the first and third contacts, and the second resistor extending between the second and third contacts; and
e) a third resistor mounted on the substrate and extending between the first and second contacts,
wherein the resistors are maintained spaced from one another by the substrate,
wherein the first and second contacts are provided along opposing edges of the substrate,
wherein the third contact is provided as a middle contact provided on one side of the substrate and spaced between the first and second contacts,
wherein the first and second resistors are provided on said one side of the substrate, and
wherein the third resistor is provided on the other side of the substrate.
2. A resistor assembly as claimed in claim 1 , including a cover for the third resistor and mounted covering the third resistor and portions of the first and second contacts on the other side of the substrate.
3. A resistor assembly as claimed in claim 1 , wherein the substrate comprises beryllia ceramic with a thickness of 25 thou.
4. A resistor assembly as claimed in claim 2 , wherein the substrate comprises beryllia ceramic with a thickness of 25 thousandths of an inch and the cover comprises beryllia ceramic with a thickness of 10 thousandths of an inch.
5. A resistor assembly as claimed in claim 1 , 2 , 3 or 4 , wherein the substrate is generally rectangular and each of the resistors is a generally rectangular thin film resistor.
6. A resistor assembly as claimed in claim 5 , wherein each of the resistors is inwardly spaced from edges of the substrate to leave portions of the substrate surface exposed, and wherein via holes are provided through the substrate opening onto the exposed portions thereof, to provide required frequency response characteristics.
7. In combination, the resistor assembly of claim 1 and a microstrip, the microstrip comprising:
a common connection;
first, second and third line elements connected between the common connection and the first, third and second contacts of the resistor assembly, respectively; and
first, second and third connecting strips arranged on another side of the resistor assembly relative to the line elements, the first, second and third connecting strips connected to the first, third and second contacts of the resistor assembly, respectively.