Isolation slots for an antenna and printed circuit board interface
This document describes techniques and systems relating to isolation slots for an antenna and printed circuit board (PCB) interface of a radar system. For example, isolation slots may be etched on a metal surface layer of a PCB for a radar control module on each side of each transmission line (e.g., microstrip line) that forms an array of channels (e.g., transmit channels, receive channels). When the PCB and an antenna structure are mated, a gap exists along the mating plane in which energy leakage between the channels can occur. The isolation slots create a stop band for a certain range of frequencies of interest and may reduce this energy leakage even when the gap is uneven along the mating plane. The isolation slots may be relatively easy and inexpensive to manufacture. The gap along the mating plane is not required to be constant, further simplifying the manufacturing process.
1. A printed circuit board (PCB) comprising: an array of transmission lines having at least one row of multiple columns, each transmission line configured to transmit or receive electromagnetic energy; and a metal layer comprising: waveguide interface openings for surrounding each transmission line in the array of transmission lines, each waveguide interface opening being a portion of the metal layer where the metal has been removed; and multiple isolation slots configured to form a stop band for a frequency band of the electromagnetic energy, an isolation slot being disposed on each side of each column in the array of transmission lines such that an isolation slot is aligned in the at least one row on each side of each waveguide interface opening, each isolation slot being a portion of the metal layer where the metal has been removed.
2. The PCB of claim 1 , wherein each isolation slot comprises: one or more first branches aligned in parallel with a longitudinal direction of a waveguide interface opening; and one or more second branches aligned orthogonal to the longitudinal direction of a waveguide interface opening, wherein each of the one or more second branches is bisected by at least one of the first branches.
3. The PCB of claim 2 , wherein:
dimensions of the one or more first branches and dimensions of the one or more second branches are configured to form the stop band; and
a quantity and arrangement of the one or more first branches and the one or more second branches are configured to form the stop band.
4. The PCB of claim 3 , wherein:
the frequency band has a center frequency of 76.5 Gigahertz; and
lengths of the one or more first branches and the one or more second branches are based on a quarter wavelength of the center frequency.
5. The PCB of claim 1 , wherein the frequency band comprises at least a portion of the E-Band or at least a portion of the W-Band.
6. The PCB of claim 1 , wherein:
the metal layer is a first metal layer; and
the PCB further comprises:
a dielectric substrate layer; and
a second metal layer configured as a ground plane, wherein the dielectric substrate layer is disposed between the first metal layer and the second metal layer.
7. The PCB of claim 1 , wherein: the array of transmission lines is a first array of transmission lines; and the PCB further comprises: a second array of transmission lines arranged in another array separate from the first array of transmission lines, and the metal layer further comprises: waveguide interface openings for surrounding each respective transmission line in the second array of transmission lines, each waveguide interface opening being a portion of the metal layer where the metal has been removed; and multiple isolation slots, an isolation slot being disposed on each side of each column in the second array of transmission lines such that an isolation slot is positioned on each side of each waveguide interface opening, each isolation slot being a portion of the metal layer where the metal has been removed.
8. The PCB of claim 1 , wherein the PCB is a radar control module.
9. The PCB of claim 1 , wherein the PCB further comprises a monolithic microwave integrated circuit electrically coupled to each transmission line in the array of transmission lines.
10. The PCB of claim 1 , wherein each transmission line in the array of transmission lines comprises:
a microstrip line.
11. The PCB of claim 1 , wherein:
the PCB is configured to be mated with an antenna structure; and
the isolation slots are configured to block energy leakage, related to an operating frequency of the electromagnetic energy, through a gap formed between the PCB and the antenna structure.
12. A system comprising: an antenna structure including waveguides; and a printed circuit board (PCB) comprising: an array of transmission lines having at least one row of multiple columns, each transmission line configured to transmit or receive electromagnetic energy; and a metal layer comprising: waveguide interface openings for surrounding each transmission line in the array of transmission lines, each waveguide interface opening being a portion of the metal layer where the metal has been removed; and multiple isolation slots, configured to form a stop band for a frequency band of the electromagnetic energy, an isolation slot being disposed on each side of each column in the array of transmission lines such that an isolation slot is aligned in the at least one row on each side of each waveguide interface opening, each isolation slot being a portion of the metal layer where the metal has been removed.
13. The system of claim 12 , wherein each isolation slot comprises: one or more first branches aligned in parallel with a longitudinal direction of a waveguide interface opening; and one or more second branches aligned orthogonal to the longitudinal direction of a waveguide interface opening, wherein each of the one or more second branches is bisected by at least one of the first branches.
14. The system of claim 13 , wherein:
dimensions of the one or more first branches and dimensions of the one or more second branches are configured to form the stop band; and
a quantity and arrangement of the one or more first branches and the one or more second branches are configured to form the stop band.
15. The system of claim 14 , wherein:
the frequency band has a center frequency of 76.5 Gigahertz; and
lengths of the one or more first branches and the one or more second branches are based on a quarter wavelength of the center frequency.
16. The system of claim 12 , wherein the frequency band comprises at least a portion of the E-Band or at least a portion of the W-Band.
17. The system of claim 12 , wherein:
the metal layer is a first metal layer; and
the PCB further comprises:
a dielectric substrate layer; and
a second metal layer configured as a ground plane, wherein the dielectric substrate layer is disposed between the first metal layer and the second metal layer.
18. The system of claim 12 , wherein: the array of transmission lines is a first array of transmission lines, and the PCB further comprises: a second array of transmission lines arranged in another array separate from the first array of transmission lines, and the metal layer further comprises: waveguide interface openings for surrounding each respective transmission line in the second array of transmission lines, each waveguide interface opening being a portion of the metal layer where the metal has been removed; and multiple isolation slots, an isolation slot being disposed on each side of each column in the second array of transmission lines such that an isolation slot is positioned on each side of each waveguide interface opening, each isolation slot being a portion of the metal layer where the metal has been removed.
19. The system of claim 12 , wherein the system is a radar system.
20. A method comprising: forming a printed circuit board (PCB), the PCB comprising: an array of transmission lines having at least one row of multiple columns, each transmission line configured to transmit or receive electromagnetic energy; and a first metal layer comprising: waveguide interface openings for surrounding each transmission line in the array of transmission lines, each waveguide interface opening being a portion of the metal layer where the metal has been removed; and multiple isolation slots, configured to form a stop band for a frequency band of the electromagnetic energy, an isolation slot being disposed on each side of each column in the array of transmission lines such that an isolation slot is aligned in the at least one row on each side of each waveguide interface opening, each isolation slot being a portion of the metal layer where the metal has been removed; a second metal layer configured as a ground plane; a dielectric substrate layer disposed between the first metal layer and the second metal layer; mating the PCB to an antenna structure; and installing the mated PCB and antenna structure in a vehicle to detect and track objects in a field-of-view.