The present application claims priority to Singapore Patent Application 200907908-8 filed in the Singapore Patent Office on Nov. 25, 2009, the entire contents of which is incorporated herein by reference.
The present invention relates to a millimeter wave (MMW) antenna and a method of manufacturing an antenna, particularly though not solely to tuning the central signal frequency, radiation direction/pattern and/or the bandwidth of a directional bond wire antenna, patch antenna or box/polygon antenna.
In most communications system the antenna is a very important part of the design. In MMW communications systems, the antenna may be very small due to the short wavelength. For such a small size antenna, high radiation efficiency and high coupling efficiency may be important considerations.
A MMW antenna is often made on a printed circuit board (PCB) or other solid substrate. Prior art PCB substrates may have a high loss factor for MMW and hence the radiation efficiency of an antenna built on this kind of substrate may be less than optimal.
One possible improvement is to use special processing on low loss material such as MicroElectroMechanical Systems (MEMS) processing on glass (alumina). However this may involve complex processing and high cost.
The coupler from the IC die to the substrate where the antenna is, may also cause loss. Although the antenna may be located on the IC die (on-chip antenna) to avoid some coupling loss and reduce the size, the radiation efficiency of an on-chip antenna may very low due to the high loss tangent of the IC die.
Another approach is using a bond wire on the signal port on the IC die and design the wire's length and shape so that the bond-wire works as an antenna. Because the bond wire is over air, the loss of the IC die and PCB substrate has little effect to the antenna. Such an antenna is called bond-wire antenna (BWA).
In general terms the invention proposes to tune a MMW antenna by
locating a conducting or dielectric object at a desired tuner location in proximity to the antenna to tune the central signal frequency,
locating a conducting reflector at a desired reflector location in proximity to the antenna to tune the radiation direction or pattern and/or to increase the bandwidth, and/or
selecting a conducting patch or object as a radiator/detector element to modify the bandwidth.
This may have the advantage(s) that:
In a first particular expression of the invention there is provided a method of manufacturing an antenna as claimed in claim 1.
In a second particular expression of the invention there is provided a MMW antenna as claimed in claim 21.
One or more example embodiments of the invention will now be described, with reference to the following figures, in which:
a), is a schematic diagram of a single fed BWA according to a first example embodiment;
b), is a schematic diagram of a differential fed BWA according to a second example embodiment;
a), is a graph of return loss (S11) for the third example embodiment of
b), is a graph of return loss (S11) for the forth example embodiment of
a), is a graph of the radiation pattern for the first example embodiment of
b), is a graph of the return loss for the first example embodiment of
c), is a graph of the radiation pattern for the second example embodiment of
d), is a graph of the return loss for the second example embodiment of
a), is a graph of the radiation pattern for the sixth example embodiment of
b), is a graph of the return loss for the sixth example embodiment of
a), is a graph of the radiation pattern for the seventh example embodiment of
b), is a graph of the return loss for the seventh example embodiment of
a), is a schematic diagram of a single-end fed triangle patch antenna (metal box) according to an eight example embodiment,
b), is a graph of the return loss for the eighth example embodiment of
a), is a schematic diagram of a single-end fed triangular patch antenna (2-layer ceramic PCB box) according to a ninth example embodiment,
b), is a graph of the return loss for the ninth example embodiment of
a), is a schematic diagram of a differential fed triangular patch antenna (2-layer ceramic PCB box) according to an tenth example embodiment,
b), is a graph of the return loss for the tenth example embodiment of
a), is a schematic diagram of a differential fed triangular patch antenna (metal box) according to an eleventh example embodiment,
b), is a graph of the return loss for the eleventh example embodiment of
a), is a schematic diagram of a single-end fed triangle patch antenna (metal box) with reflector according to an twelfth example embodiment,
b), is a graph of the return loss for the twelfth example embodiment of
c), is a graph of the radiation pattern for the twelfth example embodiment of
a), is a schematic diagram of 6-side metal polygon antenna according to an thirteenth example embodiment,
b), is a graph of the return loss for the thirteenth example embodiment of
c), is a graph of the radiation pattern for the thirteenth example embodiment of
In the following description a number of embodiments are described for tuning or adjusting a MMW antenna. These adjustments would normally occur during manufacturing but might also occur during installation, maintenance or retrofitting to improve performance of an existing antenna. Once the adjustments have been made the antenna may either be left as adjusted or encapsulated in dielectric or resin to prohibit further movement of the components (in this case the components would be sized according to the wavelength in that dielectric and a compensation made in the tuning process). The adjustments may be categorised into:
a. tuning of the central signal frequency,
b. tuning of the radiation direction/pattern, and
c. modifying the bandwidth.
a) and 1(b) show a MMW antenna according to the first and second example embodiments. In the first and second example embodiments the antenna is a BWA surrounded by air. In
In
Because the two-wire design, the BWAs' 100, 120 bandwidth may be enlarged. For example, the differential fed BWA 120 according to the second example embodiment may have a bandwidth of 15 GHz at a central signal frequency of 60 GHz (relative bandwidth >25%).
A possible problem for the BWA 100, 120 of the first and second example embodiments may be that the wire bond geometry may make it difficult to consistently manufacture an antenna with parameters within a small tolerance, especially when bonding wires are manually bonded. In certain applications it may be useful for the central signal frequency and/or radiation beam pattern to be within a predetermined tolerance.
Tuning of the Central Signal Frequency
Depending on the application it may be desirable to modify the central signal frequency. Accordingly,
Alternatively, a metal cylinder 218(a) according to the forth example embodiment approaches to the feeding point can make the antenna resonant frequency higher. The cylinder may be a hollow copper cylinder, with the same size as the dielectric cylinder.
In order to tune the antenna 200 according to the third or forth example embodiments, the cylinder 218 is located in various positions and the central signal frequency is tested until it is within the desired range. The cylinder 218 is then fixed in place by pasting it on the substrate 230.
Again in order to tune the antenna 400 according to the fifth example embodiment, the triangular dielectric tuner 418 is located in various positions and the central signal frequency is tested until it is within the desired range. The cylinder 418 is then fixed in place by pasting it on the substrate 430.
Alternatively if the wires are encapsulated in resin the central frequency may be tuned after encapsulation. One method of doing this would be to drill a hole in the resin, where the significance of the hole would be used in tuning, eg: the deeper or wider the hole, the higher the central signal frequency.
Tuning of the Radiation Direction/Pattern
a) to
Depending on the application it may be desirable to modify the radiation direction or pattern. According to the sixth example embodiment 700 shown in
a) shows the radiation pattern 800 change by introducing the reflector 718 in this first location 720. The maximum radiation directions are still two diagonal directions (approximately about x=y and x=−y or 45 and 135 degrees from the x axis) however the radiation is much more uniform becoming more omnidirectional in the positive y direction.
a) shows that the maximum radiation direction may be modified to the vertical direction (z-axis) 1000 and forward direction (y-axis) 1002 if the reflector 918 is at the second location 920. Also as shown in
Modifying the Bandwidth
Depending on the application it may be desirable to modify the bandwidth. For example metal patches as the radiation element may be used to increase the bandwidth.
a) shows an antenna 1100 according to the eighth example embodiment with a single-end fed 1116 triangle patch/metal box 1118 as the radiator/detector element.
The box 1118 is a hollow metal box made from copper. The box 1118 is 1.1 mm wide and 0.6 mm long with a height of 0.3 mm. In plan view it may be an isosceles triangle, with the two equal angles being less than 60 degrees, for example 30 degrees. The feed 1116 is attached to the adjacent apex of the two equal short sides and the long unequal side is distant from the feed 1116. The apex is spaced approximately 50 microns from the integrated circuit. The box 1118 is attached to the substrate and the integrated circuit is attached to a ground plane on the substrate.
a) shows an antenna 1200 according to the ninth embodiment with a single-end fed 1216 triangular patches 1218,1219 as the radiator/detector element separated by a 2-layer ceramic box 1220.
The patches 1218,1219 are 0.7 mm wide and 0.38 mm long. In plan view they may be an isosceles triangle, with the two equal angles being less than 60 degrees, for example 30 degrees. The feed 1216 is attached to the adjacent apex of the two equal short sides of the top patch 1218 and the long unequal side is distant from the feed 1216. The apex is spaced approximately 50 microns from the integrated circuit. The bottom patch 1219 is attached to the substrate and the integrated circuit is attached to a ground plane on the substrate. The ceramic box 1220 is 1 mm long, 3 mm wide and 0.254 mm high. The ceramic box may be made from quart with a dielectric constant of 9.1 and a loss factor of 0.
a) shows an antenna 1300 according to the tenth embodiment with a differential fed 1316 triangular patches 1318, 1319, 1320, 1321 as the radiator/detector element separated by a 2-layer ceramic PCB box 1322.
The patches 1318, 1319, 1320, 1321 are 1.475 mm wide and 0.95 mm long. The are spaced 50 micron from each other and from the integrated circuit. In plan view they may be an isosceles triangle, with the two equal angles being less than 60 degrees, for example 30 degrees. The feed 1316 is attached to the adjacent corner of the two the top patches 1318,1320 and the apex of all of the patches 1318, 1319, 1320, 1321 is distant from the integrated circuit. The ceramic box 1322 may be the same as in the ninth embodiment.
a) shows an antenna 1400 according to the eleventh embodiment with a differential fed 1416 double triangular patch antenna (metal box) 1418,1419 as the radiator/detector element. The geometry and orientation of the boxes 1418,1419 may similar to the patches 1318, 1319, 1320, 1321 in the tenth embodiment except with a height of
a) shows an antenna 1500 according to the twelfth embodiment with a single-end fed 1516 triangle patch (metal box) 1518 as the radiator/detector element with a reflector 1520 in the second location 1522.
While example embodiments of the invention have been described in detail, many variations are possible within the scope of the invention as will be clear to a skilled reader.
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200907908-8 | Nov 2009 | SG | national |
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Number | Date | Country | |
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20110122047 A1 | May 2011 | US |