High power termination for radio frequency (RF) circuits
In an embodiment, a termination for a transmission line (or high frequency circuit) includes a matching circuit which provides a matching impedance for the transmission line and an electrical connection between the two, e.g., a bond wire. The electrical connection has a reactance matrix, which, when combined with the impedance provided by the matching circuit, provides a resultant termination resistance.
1. An apparatus for terminating a transmission line, the apparatus comprising:
a substrate separate from the transmission line; and
a matching circuit operative to provide a matching impedance for the transmission line and an electrical connection between the transmission line and the apparatus, the matching circuit including a resistor having dimensions and a geometry selected to generate a negative inductance having a magnitude substantially equal to an inductance of the electrical connection.
2. The apparatus of claim 1 , wherein the resistor comprises a thin film resistor.
3. The apparatus of claim 1 , wherein the resistor comprises a multi-section resistor.
4. The apparatus of claim 1 , wherein the matching circuit further comprises:
means for providing a ground potential;
one or more passive elements; and
an electrical connection between the resistor, grounding means, and passive elements to form a network having a network impedance.
5. The apparatus of claim 4 , wherein the grounding means comprise via holes.
6. The apparatus of claim 4 , wherein when connected between the transmission line and the apparatus, the electrical connection has a reactance matrix, and
wherein the combination of the reactance and the network impedance provides a resultant predetermined termination resistance.
7. The apparatus of claim 1 , wherein the electrical connection comprises a bonding wire.
8. The apparatus of claim 1 , wherein the electrical connection comprises a ribbon.
9. The apparatus of claim 1 , wherein the matching circuit is operative to absorb greater than 1 W of power.
10. The apparatus of claim 1 , wherein the matching circuit has a high frequency broadband width.
11. The apparatus of claim 10 , wherein the matching circuit is capable of providing a return loss of less than 20 dB from DC-to-40 GHz.
12. The apparatus of claim 1 , wherein the substrate comprises a microstrip.
13. A method comprising:
determining an inductance of an electrical connection used to connect a transmission line on a first planar medium to a termination circuit on a second planar medium; and
selecting dimensions and a geometry for a thin film resistor operative to generate a negative inductance substantially equal in magnitude to the electrical connection inductance.
14. An apparatus for providing a termination for a high frequency circuit, the apparatus comprising:
a planar matching circuit comprising at least a resistor and a grounding means; and
an electrical connection from said circuit to said planar matching circuit having a connection reactance matrix,
wherein said electrical connection when combined with said planar matching circuit provides a predetermined termination resistance to said circuit, and wherein said at least one resistor is operative to generate a negative inductance.
15. The apparatus of claim 14 , wherein the planar matching circuit further comprises a positive inductance to cancel with the negative inductance.
16. The apparatus of claim 14 , wherein said at least one resistor comprises a plurality of resistors operative to provide a broad frequency bandwidth.
17. The apparatus of claim 14 , wherein the electrical connection comprises one of a bond wire and a ribbon.