High frequency via with stripped semi-rigid cable
View Patent ↗A high frequency coax via structure is configured with a stripped semi-rigid cable (no shield), and an inductive compensation loop to mitigate transition discontinuity between that via structure's center conductor and the pad to which the center conductor is connected. The performance of top-to-bottom microwave transitions at high frequencies (e.g., 1 to 12 GHz) for such boards is enhanced. A non-metallized via hole embodiment that is configured with surrounding ground vias provides a greater degree of compensation for connection pads associated with greater capacitance (such as those coupled to a component).
1. A printed wiring board that includes high frequency coax via structures, the board comprising:
a via hole and corresponding connection pads that enable one side of the board to be connected to the other side; and
a semi-rigid cable stripped of its outer conductor inserted into the via hole, so that a dielectric barrel of the stripped cable contacts the via hole wall, and a conductor protrudes from each end of the via hole;
wherein the conductor protruding from one end of the via hole is connected to a corresponding connection pad on one side of the board, so as to provide an inductive compensation loop having dimensions to compensate for transition discontinuity associated with that connection, and
wherein the inductive compensation loop has a length and height that are each about 1/10 or less of a wavelength at a maximum operating frequency associated with the board.
2. The board of claim 1 wherein the conductor protruding from the other end of the via hole is connected to a corresponding connection pad on the other side of the board, so as to provide a second inductive compensation loop having dimensions to compensate for transition discontinuity associated with that connection.
3. The board of claim 1 further comprising:
a ground gap about at least one of the connection pads that is configured to reduce pad capacitance.
4. The board of claim 1 wherein the via hole is non-metallized, and a number of ground vias are provided around the non-metallized via hole so as to provide a signal return.
5. The board of claim 1 wherein the printed wiring board has top and bottom surfaces and includes multiple layers therebetween, and the high frequency coax via structures couple the top surface to the bottom surface.
6. The board of claim 1 wherein at least one of the connection pads couples to a transmission line or a component.
7. The board of claim 1 wherein the printed wiring board has a maximum operating frequency of up to about 12 GHz.
8. A high frequency coax via structure for a printed wiring board, the via structure comprising:
a via hole; and
a semi-rigid cable stripped of its outer conductor inserted into the via hole, so that a dielectric barrel of the stripped cable contacts the via hole wall, and a conductor protrudes from each end of the via hole;
wherein the conductor protruding from one end of the via hole is adapted for connection to a corresponding connection pad on one side of the board, so as to provide an inductive compensation loop having dimensions to compensate for transition discontinuity associated with that connection, and
wherein the inductive compensation loop has a length and height that are each about 1/10 or less of a wavelength at a maximum operating frequency associated with the board.
9. The via of claim 8 wherein the dielectric barrel is Teflon.
10. The via of claim 8 wherein the via hole is non-metallized, and a number of ground vias are provided around the non-metallized via hole so as to provide a signal return.
11. The via of claim 8 wherein the high frequency coax via structure enables connection to at least one of a transmission line and a component.