RF circuit with multiple-definition RF substrate and conductive material void under a bias line

A radio frequency (RF) circuit comprising:

• a first dielectric material having first and second surfaces and a first dielectric constant;
• a first conductive layer over the first surface of the first dielectric material, wherein the first conductive layer includes a plurality of conductive features that include a signal line and a bias line, wherein the signal line has a first end and a second end, and the bias line has a first section with a first end and a second end, and wherein the first section of the bias line is a quarter wave transmission line;
• a second conductive layer over the second surface of the first dielectric material, wherein the second conductive layer includes a ground plane, and the signal line is formed directly over the ground plane with the first dielectric material disposed therebetween, and wherein a conductive material void is present in the second conductive layer, and the first section of the bias line is aligned with the conductive material void;
• a second dielectric material over the second conductive layer, wherein the second dielectric material has a second dielectric constant that is different from the first dielectric constant;
• and
• a mounting area for an RF device, wherein the first end of the signal line and the first end of the first section of the bias line are located proximate to the mounting area to enable the signal line and the bias line to be electrically coupled with one or more leads of the RF device.

A radio frequency (RF) circuit comprising:

• a first dielectric material having first and second surfaces and a first dielectric constant, wherein the first dielectric material is selected from ceramic-filled polytetrafluoroethylene (PTFE), ceramic-filled PTFE with woven glass, ceramic-filled hydrocarbon, ceramic-filled hydrocarbon with woven glass, random glass filled PTFE, PTFE with woven glass, PTFE with micro glass fiber, e-fibre glass, and high performance FR4;
• a first conductive layer over the first surface of the first dielectric material, wherein the first conductive layer includes a plurality of conductive features that include a signal line and a bias line, wherein the signal line has a first end and a second end, and the bias line has a first section with a first end and a second end;
• a second conductive layer over the second surface of the first dielectric material, wherein the second conductive layer includes a ground plane, and the signal line is formed directly over the ground plane with the first dielectric material disposed therebetween, and wherein a conductive material void is present in the second conductive layer, and the first section of the bias line is aligned with the conductive material void;
• a second dielectric material over the second conductive layer, wherein the second dielectric material has a second dielectric constant that is different from the first dielectric constant, wherein the second dielectric material is selected from PTFE, ceramic-filled PTFE, ceramic-filled PTFE with woven glass, ceramic-filled hydrocarbon, ceramic-filled hydrocarbon with woven glass, random glass filled PTFE, PTFE with woven glass, PTFE with micro glass fiber, high performance FR4, and air;
• and
• a mounting area for an RF device, wherein the first end of the signal line and the first end of the first section of the bias line are located proximate to the mounting area to enable the signal line and the bias line to be electrically coupled with one or more leads of the RF device.

A method for forming a radio frequency (RF) circuit, the method comprising:

• laminating together a substrate that includes a first dielectric material, a first conductive layer, and a second dielectric material, wherein
• the first dielectric material has first and second surfaces and a first dielectric constant,
• the second dielectric material has first and second surfaces and a second dielectric constant that is different from the first dielectric constant, and
• the first conductive layer is between the first surfaces of the first and second dielectric materials, and the first conductive layer includes a ground plane and a conductive material void, and the first and second dielectric materials contact each other through the conductive material void;
• and
• forming a second conductive layer over the second surface of the first dielectric material, wherein the second conductive layer includes a plurality of conductive features that include a signal line and a bias line, wherein the signal line has a first end and a second end, and the signal line is formed directly over the ground plane with the first dielectric material disposed therebetween, and the bias line has a first section with a first end and a second end, the first section of the bias line is aligned with the conductive material void, and a characteristic impedance of the bias line is in a range of 75 ohms to 300 ohms at a frequency in a range of 800 megahertz to 6.0 gigahertz, and
• wherein the substrate includes a mounting area for an RF device, wherein the first end of the signal line and the first end of the bias line are located proximate to the mounting area to enable the signal line and the bias line to be electrically coupled with one or more leads of the RF device.