Abstract:
A dielectric resonator antenna that has active components on a selected surface. Also a feed element in the form of a slot may be formed on the surface to efficiently generate the proper resonance mode within the bulk of the dielectric resonator antenna. The entire dielectric resonator antenna may be flip-chip mounted onto a suitable microwave substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/483,319 filed Jun. 26, 2003, the disclosure of which is hereby incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The invention relates to dielectric resonator antennas. 
     BACKGROUND 
     Existing dielectric resonator antennas do not incorporate active devices within or mounted directly on the physical antenna element. Instead they integrate active devices off the antenna, for example, by using a microstrip path and/or a slot. That is, active electronics and antenna elements are connected, side by side. When the antenna is located on the chip next to the active electronics, the chip itself can adversely affect antenna performance due to the presence of wire bonds, microwave substrates, solder bumps, etc. 
     The prior includes: 
     (1) McAllister, Long, Conway “Rectangular dielectric resonator antenna,”  Electron. Lett,  vol 19, March 1983; 
     (2) Esselle, “A low profile rectangular dielectric resonator antenna,”  IEEE Trans on Ant. and Prop. , vol. 44, September 1996; 
     (3) Petosa, Simons, Siushansian, Ittipiboon, Cuhaci,  IEEE Trans on Ant. and Prop. , vol. 48, May 2000; 
     (4) Roberson, I. D. “Millimeter Wave Back Face Patch Antenna for Multilayer MMICs”  Electron. Lett , vol 29, April 1993. 
     The present invention avoids these deficiencies improving performance of the active antenna. 
     SUMMARY OF THE INVENTION 
     The present invention incorporates active devices mounted on the body of a dielectric resonator antenna. In one aspect, the dielectric resonator antenna is constructed as a flip-chip device having one or more active elements integrated on its bottom surface. In another aspect, a slot feed element is formed from a metallization film on the selected surface along with any other selected active elements. In yet another aspect, the dielectric resonator antenna is a receiving antenna and in addition to the feed element the active element on it can be an amplifier. In another aspect the dielectric resonator antenna is a transmitting antenna and in addition to the feed element the active element on it can be a frequency multiplier or an upconverter. In still another aspect, the invention is especially advantageous when any of its various configurations is used at very high frequencies such as at or above W band, and more especially in the receiving mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic bottom view of a dielectric resonator antenna having active circuit components on a bottom surface and configured for flip-chip application; 
         FIG. 2  is a diagrammatic side view of the active dielectric resonator antenna of  FIG. 1 ; 
         FIG. 3  is a schematic representation of a transmitter embodiment of the dielectric resonator antenna; 
         FIG. 4  is a schematic representation of a receiver embodiment of the dielectric resonator antenna; 
         FIG. 5  shows the dimensions and material constants used for a computer simulation of the antenna; 
         FIG. 6  shows the resulting input reflection coefficient, from 75 to 150 GHz, indicating a low Q resonance near 135 GHz for the simulated antenna; and 
         FIG. 7  shows a well-behaved radiation pattern at 125 GHz for the simulated antenna. 
     
    
    
     DESCRIPTION 
     The present invention comprises a dielectric resonator antenna of the type, for example, formed as a dielectric body, such as a cube, cuboid or other parallelepiped, or of other geometric configuration such as a cylinder, in which, on a selected surface, one or more active electronic components are formed. One such active component may be a microwave slot feed element formed from a metallization film on the surface, the film also functioning as a ground plane for the antenna. 
     The slot feed element functions as a feed element to energize the dielectric resonator antenna in the transmit mode, or to receive the incoming signal in the receive mode and is referred to herein as a feed element with reference to either transmit or receive modes. 
     This invention increases the performance of transmit and receive antennas, especially at very high frequencies, for example above 75 GHz. At very high frequencies performance is limited by losses in the circuitry and transitions on and off chip. The present invention allows the incorporation of up- or down-conversion on the antenna chip, co-located with the antenna. This is especially advantageous at high millimeter wave frequencies because transitions on and off chip are extremely difficult to make without serious signal degradation. For example, wire bonds at those frequencies are electrically large and produce uncontrollable reflections. Consequently the invention is useful for any high frequency application, especially W band (75-110 GHz) and above, where it is necessary to radiate energy to and from electronic components in an efficient manner. 
       FIGS. 1 and 2  respectively show diagrammatically a bottom view and a side view of exemplary implementation of an active dielectric resonator antenna as a flip-chip form of the present invention. As shown in the figures, the dielectric resonator antenna  10 , for example being 20×20×20 mils, is flip-chip mounted on a microwave substrate (for example alumina)  12 . The size of the dielectric resonator antenna  10  may be engineered to give a resonant mode at the desired frequency of interest, for example, 125 GHz. The dielectric resonator antenna  10  is electromagnetically coupled to metal circuitry located on the bottom surface  14  of the dielectric resonator antenna  10 . A slot antenna feed element  16  is formed from a metallization film  18  and can be operated in either a transmitting or a receiving mode according to the principle of reciprocity in antenna operation. In its transmitting mode, the slot antenna feed element  16  feeds the resonant mode of the dielectric resonator antenna  10  and is preferably connected to active electronic devices, such as an InP HEMT transistor  20 . Solder bumps  22   a ,  22   b ,  22   c  and  22   d  are preferably used to connect the electronics on the surface  14  to circuitry located on the microwave substrate  24 , where the solder bumps  22   a  and  22   b  are connected to the source of transistor  20 , solder bump  22   c  is connected to the drain of transistor  20  and solder bump  22   d  is connected to the gate of transistor  20 , for example. 
     Solder bumps  22   a ,  22   b ,  22   e  and  22   f  are all connected to the ground plane surrounding the slot antenna and are preferably formed from metallization film  18 . Due to the proximity of the edges of the feed structure  16  to the adjacent edges of the ground plane formed by metallization  18 , high frequency RF signals are shorted to ground and a gate bias is applied to solder bump  22   d . The output of the antenna is derived from solder bump  22   c.    
     Additional RF components could be placed on surface  14  for example an oscillator and mixer could follow the HEMT  20  and provide down conversion to a lower frequency signal. If this occurs on the dielectric resonator antenna  10 , then signal losses through the off-chip transition and subsequent circuitry will be minimized. 
     In a transmitting embodiment, the transmitter chip preferably contains a frequency multiplier  24  and power amplifier  26  located on the dielectric chip antenna  10 , indicated with dashed box in  FIG. 3 , with an oscillator input source  28  located off chip  10 . Any one or all of these blocks  24 ,  26 ,  28  could be located on or off the antenna chip dielectric  10 , but the embodiment of  FIG. 3  has the advantage of providing lower frequency transitions onto the chip  10  (by feeding the on-chip multiplier  24 ), thus reducing the degradation which would otherwise occur due to high frequency chip transitions at the solder bumps. The power amplifier  26  may or may not be required, depending on the application. Another possible embodiment would have the power amplifier  26  preceding the multiplier  24  and located off chip (i.e. the multiplier  24  but not the amplifier  26  is on chip in such an embodiment). That embodiment has an advantage of minimizing the on-chip high frequency circuitry. Multipliers can be made very small (e.g. Heterojunction Barrier Varactor (HBV) Diode multipliers) and may be readily integrated onto the antenna chip dielectric  10 . 
     In a receiving embodiment, the receiver chip  10  preferably contains a Low Noise Amplifier (LNA)  36  and a downconverter  24  (also called a mixer) located on-chip, and a Local Oscillator  38  located off chip. See  FIG. 4 . This embodiment also has the advantage of eliminating high frequency transitions at the solder bumps, since the transitions off chip are made at the LO (Local Oscillator) and IF (Intermediate Frequency) frequencies. In place of the mixer  34  one could use an HBV diode frequency divider to reduce the frequency. This would have the advantage of significantly reducing the transition frequency (typically a factor of three from the RF input frequency), but has the disadvantage of higher conversion loss. The LNA  36  would have to be included on chip  10  for most applications since a high received signal to noise ratio (SNR) is commonly required and placing LNA  36  facilitates that. The primary advantage of this on-chip circuitry is that the received signal gets amplified by the LNA  36  immediately following reception. This significantly improves the SNR and results in a more sensitive receiver. As with the transmitter chip of  FIG. 3 , any one or all of these components may be included on or off chip. For example, one may wish to place the downconverter  34  off chip. This has the disadvantage of requiring a high frequency transition, yet reduces the number of active on-chip components. 
     Disposing the electronics as close to the antenna feed  16  as possible is generally more important for the receiving embodiment of  FIG. 4  than the transmitting embodiment of  FIG. 3 . The reason for this is that receivers generally pick up very small signals and lots of noise. Additional noise gets added as one moves down the signal path away from the antenna feed  16  (due to thermal noise, lossy transitions, interference, etc.). For this reason, it is advantageous to boost the received signal as soon as possible after reception, thereby mitigating the effects of additional noise. Thus, putting the LNA  36  on the antenna chip  10  allows the signal to be boosted very soon after reception and yields a higher (better) Signal to Noise Ratio (SNR). Also, boosting the signal prior to off chip transitions, which tend to be lossy (and therefore noisy), helps improve the receiver SNR. 
     The disclosed dielectric resonator active antenna has dimensions that are determined, at least partly, by the operating frequency. As the frequency gets higher, the chip size must be reduced in order to achieve the desired impedance response. Thus, at higher frequencies, the active chip area gets smaller, hence limiting the area available to active circuitry. At W band frequencies (75 to 110 GHz) it is reasonable to include a simple amplifier and a passive multiplier or downconverter on chip  10 . More circuitry than this is apt to require more chip area than is available using current fabrication technologies. Above W band, the amplifier circuitry will have to be kept very small to fit it on a chip. 
     The manufacturing processes for this dielectric antenna will be substantially the same as the existing process used for conventional W band MMIC components, appropriately modified to yield the disclosed devices. 
     The placement of the slot on the chip surface will affect the amount of coupling between the CPW line on the chip and the chip resonance. Generally, the slot is disposed close to the center of the chip for strong coupling, whether or not there is an active device on the chip. 
     The invention is useful in a wide variety of devices operating in millimeter wave ranges. For example, it can be incorporated into a millimeter wave collision avoidance or adaptive cruise control systems for automotive applications in which the ability to operate well above 77 GHz frequency allows the device to be made much smaller. It could also be used in passive imaging systems since it allows a low noise amplifier to boost the received signal immediately after receiving it, avoiding performance degradation due to off-chip transitions and circuit losses. 
     The disclosed flip-chip dielectric resonator antenna was modeled using commercial finite element electromagnetic simulation software (Ansoft&#39;s HFSS).  FIG. 5  shows the dimensions and material constants used for the simulation.  FIG. 6  shows the resulting input reflection coefficient, from 75 to 150 GHz, indicating a low Q resonance near 135 GHz.  FIG. 7  shows a well-behaved radiation pattern at 125 GHz. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be apparent to those skilled in the art without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except by the following claims including the literal interpretation and permitted scope of equivalents thereof.