Aperture-coupled microstrip antenna array
A radio frequency (RF) antenna array for an RF printed circuit board (RF-PCB) having a PCB ground layer includes an interposer assembly, conductive pillars, and load element. The interposer assembly includes a substrate, a ground layer defining one or more apertures, a dielectric layer, and a microstrip trace. The substrate is spaced apart from the RF-PCB. The interposer ground layer is deposited onto the substrate. The dielectric layer is deposited onto the interposer ground layer. The microstrip trace, positioned on the dielectric layer, receives and directs incident RF energy along the longitudinal axis. The pillars electrically connect the ground layers and structurally support the substrate, such that RF energy along the trace couples to the upper surface of the interposer assembly through the aperture(s). The load element connects in series to the microstrip trace at a distal/terminal end of the array.
1. A radio frequency (RF) antenna array for use with an RF printed circuit board (RF-PCB) having a PCB ground layer, the RF antenna array having a longitudinal axis and comprising:
an interposer assembly comprising:
a substrate spaced apart from the RF-PCB, and having an upper major surface and a lower major surface;
an interposer ground layer deposited onto the lower major surface of the substrate and defining one or more apertures along the longitudinal axis;
a dielectric layer deposited onto the interposer ground layer; and
a linear microstrip trace configured as an antenna feed line and positioned on the dielectric layer, wherein the linear microstrip trace is configured to direct incident RF energy of a predetermined frequency range along the longitudinal axis;
a plurality of conductive pillars electrically connecting the PCB ground layer to the interposer ground layer and structurally supporting the substrate, such that the RF energy propagating along the linear microstrip trace is coupled to the upper major surface of the interposer assembly through the one or more apertures; and
a load element connected in series with the linear microstrip trace at a terminal end of the RF antenna array.
2. The RF antenna array of claim 1 , wherein the RF antenna array is characterized by an absence of discrete patch antennas.
3. The RF antenna array of claim 1 , further comprising: at least one discrete patch antenna connected to the upper major surface of the substrate opposite a corresponding one of the aperatures.
4. The RF antenna array of claim 3 , wherein the substrate is constructed of silicon, quartz, ceramic, or organic material, the at least one discrete patch antenna is constructed of copper foil, and the dielectric layer is constructed of bisbenzocyclobutene (BCB).
5. The RF antenna array of claim 1 , wherein the load element is a circuitous meander line forming a serial extension of the linear microstrip trace, and wherein the circuitous meander line is thinner than the linear microstrip trace.
6. The RF antenna array of claim 5 , wherein the circuitous meander line has sinuous first and second segments of approximately equal lengths, the first and second segments being positioned on opposing sides of the longitudinal axis.
7. The RF antenna array of claim 5 , wherein the load element includes a resistor connected in series with the linear microstrip trace and coupled to an electrical ground.
8. The RF antenna array of claim 1 , wherein the linear microstrip trace tapers toward a common centerline of the at least one aperture and the load element along the longitudinal axis of the RF antenna array.
9. The RF antenna array of claim 1 , wherein the one or more apertures includes a plurality of aperatures spaced apart from each other along the longitudinal axis.
10. The RF antenna array of claim 1 , wherein the predetermined frequency range is about 228-GHz to 240-GHz.
11. The RF antenna array of claim 1 , further comprising the PCB ground layer.
12. The RF antenna array of claim 1 , wherein the aperatures have a rectangular shape in a plan view, and wherein the pillars are cylindrical.
13. The RF antenna array of claim 1 , further comprising a monolithic microwave integrated circuit (MMIC) electrically connected to the linear microstrip trace.
14. A radio frequency (RF) antenna array for use with an RF printed circuit board (RF-PCB) having a PCB ground layer, the RF antenna array having a longitudinal axis and comprising:
a load element;
one or more antenna elements collectively terminating in the load element, each of the one or more antenna elements having:
a multi-layer interposer segment comprising:
a substrate segment having upper and lower major surfaces;
a ground layer segment deposited onto the lower major surface of the substrate segment and defining an aperture;
a dielectric layer segment deposited onto the ground layer segment;
a linear microstrip trace segment positioned on or within the dielectric layer segment, and configured to direct incident RF energy in a frequency range of at least about 228-GHz along the longitudinal axis toward the load element, wherein the linear microstrip trace segment is not parallel to the longitudinal axis of the RF antenna array; and
a plurality of conductive pillars electrically connecting the PCB ground layer to the ground layer segment, and structurally supporting the substrate segment, such that the RF energy propagating along the linear microstrip trace is coupled to the upper major surface of the interposer segments through the aperture.
15. The RF antenna array of claim 14 , wherein the RF antenna assembly is characterized by an absence of discrete patch antennas.
16. The RF antenna array of claim 14 , wherein the RF antenna array includes a serially-connected plurality of the antenna elements.
17. The RF antenna array of claim 14 , wherein the multi-layer interposer segment includes a discrete patch antenna connected to the upper major surface of the substrate segment opposite the aperture.
18. The RF antenna array of claim 14 , wherein the load element includes a circuitous meander line forming a sinuous extension of the linear microstrip trace.
19. The RF antenna array of claim 14 , wherein the linear microstrip trace segment tapers or angles toward the longitudinal axis.
20. The RF antenna array of claim 14 , further comprising a monolithic microwave integrated circuit (MMIC) that is electrically connected to the linear microstrip trace.