Patent Application
20190089042
Radar and other detection systems have a variety of uses. More recently, automotive vehicles have included increasing amounts of detection technology that utilizes radar signaling or principles for detecting objects in the vicinity or pathway of a vehicle.
There are a variety of configurations of antennas for vehicle sensor devices. Some include a substrate integrated waveguide (SIW) on a printed circuit board. Various techniques have been proposed to couple the radiated energy or signal into the SIW. One proposal that is useful for differential radio frequency signals includes coupling the differential radio frequency signal terminals to a balun to establish a single-ended output. That output can be coupled to a single-ended microstrip, which in turn can be coupled with the SIW.
The transition between the balun and the microstrip and the transition between the microstrip and the SIW each introduce a loss of power and limit bandwidth. Improved performance is desirable without such transition-induced losses.
An illustrative example transmission device includes a substrate having a metal layer near one surface of the substrate and a waveguide area in the substrate. The metal layer includes a slot that at least partially overlaps the waveguide area. A source of radiation includes a first source output situated on a first side of the slot and a second source output situated on a second, opposite side of the slot.
In an example embodiment having one or more features of the transmission device of the previous paragraph, the first and second source outputs are coupled to the waveguide area to provide the radiation directly into the waveguide area.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the slot is situated offset from a center of the waveguide area.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the radiation comprises radio frequency radiation and the radio frequency radiation radiates outward from the waveguide area of the substrate.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the slot has a first portion oriented in a first direction and a second portion oriented in a second direction.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the first direction is transverse to the second direction.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the first direction is perpendicular to the second direction.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the source of radiation comprises a ball grid array, the first source output comprises a first ball of the ball grid array, and the second source output comprises a second ball of the ball grid array.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the slot has a length that corresponds to one-half a wavelength of the radiation.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the slot has a dimension that establishes a resonant frequency of the radiation in the waveguide area.
In an example embodiment having one or more features of the transmission device of any of the previous paragraphs, the metal layer defines an outer surface of one side of the substrate, the metal layer has a thickness, and the slot has a depth that is equal to the thickness.
An example embodiment having one or more features of the transmission device of any of the previous paragraphs includes a solder mask between the metal layer and the source of radiation, the solder mask including a first source solder pad on the first side of the slot and a second source solder pad on the second side of the slot.
An illustrative example method of making a transmission device includes establishing a slot in a metal layer on a first surface of a substrate overlapping a waveguide area of the substrate, situating a first output of a source of radiation on a first side of the slot, situating a second output of the source of radiation on a second side of the slot, and establishing a connection between the first and second outputs and the waveguide area of the substrate that facilitates the source providing the radiation directly into the waveguide area.
An example embodiment having one or more features of the method of the previous paragraph includes situating the slot in a position that is offset from a center of the waveguide portion.
An example embodiment having one or more features of the method of any of the previous paragraphs includes providing the slot with a first portion oriented in a first direction and a second portion oriented in a second, different direction.
In an example embodiment having one or more features of the method of any of the previous paragraphs, the first direction is perpendicular to the second direction.
An example embodiment having one or more features of the method of any of the previous paragraphs includes providing the slot with a length that establishes a resonant frequency of radiation emitted by the waveguide portion.
An example embodiment having one or more features of the method of any of the previous paragraphs includes providing the slot with a length that corresponds to one-half a wavelength of the radiation.
Another illustrative example method of operating a transmission device includes directly coupling radiation from first and second outputs into a waveguide area of a substrate by establishing an electromagnetic field between the first and second outputs across a slot in a metal layer of the substrate where the slot overlaps the waveguide area.
In an example embodiment having one or more features of the method of the previous paragraph, the radiation comprises differential radio frequency radiation.
Various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
Embodiments of this invention provide signaling or detecting devices that are useful, for example, on vehicles that include a differential radiation source and a substrate integrated waveguide (SIW) transmitter with improved power and bandwidth characteristics. Such devices include a slot between radiation source outputs. The slot facilitates directly coupling radiation from the source into the waveguide.
The substrate body 34 includes a plurality of electrically conductive vias 36 arranged to establish a waveguide area 38 in the substrate 30. In this example the waveguide area 38 is a SIW.
The example transmission device 22 includes a slot 40 in the metal layer 32. The slot 40 at least partially overlaps the waveguide area 38. In this example the entire slot 40 is situated in an overlapping relationship with the waveguide area.
A source of radiation or signaling energy 42 includes a first source output 44 situated on one side of the slot 40 and a second source output 46 situated on an opposite side of the slot. Having the slot 40 between the source outputs 44 and 46 allows for establishing an electromagnetic field between the outputs across the slot 40. The slot 40 facilitates directly coupling energy or radiation from the source outputs 44 and 46 directly into the waveguide area 38. Such a direct coupling eliminates any transitions between the source and intermediate connectors such as microstrips that might otherwise be required to couple the radiation from the source to the waveguide area 38. The direct coupling provided by the example embodiment reduces or eliminates power loss and lessens or removes limits on bandwidth that otherwise would exist with intermediate connectors.
In this example, the source 42 comprises a ball grid array source that provides differential radio frequency radiation or energy. The first output 44 and the second output 46 are the positive and negative outputs of the differential radiation. The slot 40 and the outputs 44 and 46 on opposite sides of the slot 40 makes it possible to directly couple such radiation directly into the waveguide area 38. One feature of embodiments of this invention is that they are effective and efficient at handling the positive and negative signal balancing for a differential radio frequency signal, which has otherwise been difficult or challenging.
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The slot 40 has a length that is selected to establish a resonant frequency of the radiation in the waveguide area 38. The length of the slot 40 in this example corresponds to one-half a wavelength of the radiation.
The slot 40 is offset from a center of the waveguide area 38 to maximize the energy or radiation transferred or radiated into the waveguide area 38. The position of the slot 40 may be selected in various embodiments to tune the transmission device to meet the needs of a particular implementation. Those skilled in the art who have the benefit of this description will realize the precise offset position of the slot 40 to meet their needs.
Selecting the slot length and position compensates for die output impedance or circuit discontinuities, for example.
The features represented in the drawings and described above are discussed in connection with a particular embodiment but they are not necessarily limited to that embodiment. Combinations of one or more features from one embodiment with one or more from another embodiment are possible to realize other embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
