ANTENNA ASSEMBLY
BACKGROUND OF THE INVENTION
[0001] The present invention relates to signal transmitting and receiving devices  and more particularly  to antennas with connective elements that interface with cable connectors  e.g.  coaxial cable connectors  in a manner that reduces variability amongst antennas having the same construction.
[0002] Devices for transmitting or receiving signals such as antennas are used in many applications including applications where the attenuation level of a signal is measured as between two antennas. For example  the attenuation of a radio frequency (“RF”) signal can be used to monitor certain performance characteristics of filters such as diesel particulate filters (“DPF filters”)  and related DPF filter systems. These systems deploy antennas on either side of a filter  cause an RF signal to be exchanged between the antennas  and process a measured RF signal to identify the attenuation that results from particulate build-up in the filter.
[0003] Typically these systems are configured to calibrate noise  and other system inconsistencies so as to manage the overall performance  reliability  and quality of the data collected  e.g.  during operation of the DPF filter system. This calibration can take into account  for example  reflection of the RF signal that occurs as a result of the construction of the various components  e.g.  the cables  cable connectors  and the antennas. But this calibration takes time and resources  in effect reducing the efficiency of operation of the equipment on which the DPF system is utilized. It is also likely that such calibration can require specific equipment and technical knowledge  both of which are not necessarily available or cost effective to provide on-site.
[0004] Moreover  calibration and other techniques only mask problems. They do nothing to address the limitations and flaws of the underlying components. These limitations include the reflection of the RF signal in the various components  and more particularly the reflection that occurs in and around the antenna  the cable  and the antenna-cable interface.
[0005] Therefore  there is a need to reduce the reflective characteristics of the antenna so as to reduce the reliance on calibration techniques as they relate to measurement systems like the DPF filter systems mentioned above. It is likewise desirable to provide an antenna that is constructed in a manner so as to permit antennas to be replaced within the DPF filter systems. Still further there is a need to reduce the variability of signal conduction between the antenna and other mated devices  such as coaxial cables that are used in the DPF filer system.
BRIEF DESCRIPTION OF THE INVENTION
[0006] In one embodiment  an antenna that comprises an antenna body with a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween. The antenna also comprises an antenna connector disposed on the connective end  and a transmitting or receiving element aligned with the longitudinal axis. The transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion forming a center conductor of the antenna connector.
[0007] In another embodiment  an antenna that comprises an antenna body comprising a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween. The antenna also comprises an antenna connector disposed on the connective end  the antenna connector comprising an interface comprising an elongated insulating member having an inner bore  and an outer shell in surrounding relation to the elongated insulating member. The antenna further comprises a transmitting or receiving element aligned with the longitudinal axis. The transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion extending into the inner bore of the elongated insulating member in a manner exposing the connecting portion as a center conductor of the antenna connector.
[0008] In yet another embodiment  a sensor that comprises a controller responsive to an RF signal  a cable coupled to the controller  and an antenna secured to the mating connector. The cable comprising a mating connector  and a conductor for conducting the RF signal between the controller and the mating connector. The antenna comprising an antenna body having a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween. The antenna also comprises an antenna connector disposed on the connective end  the antenna connector for receiving the mating connector. The antenna further comprises a transmitting or receiving element aligned with the longitudinal axis  the transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion forming a center conductor of the antenna connector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that the manner in which the above recited features of the present invention can be understood in detail  a more particular description of the invention briefly summarized above  may be had by reference to the embodiments  some of which are illustrated in the accompanying drawings. It is to be noted  however  that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope  for the invention may admit to other equally effective embodiments. The drawings are not necessarily to scale  emphasis generally being placed upon illustrating the principles of certain embodiments of invention.
[0010] Thus  for further understanding of the nature and objects of the invention  references can be made to the following detailed description  read in connection with the drawings in which:
[0011] FIG. 1 is a side view of an example of an antenna that is made in accordance with concepts of the present invention.
[0012] FIG. 2 is a side  cross-sectional view of another example of an antenna that is made in accordance with the present invention.
[0013] FIG. 3 is a schematic diagram of a sensor that comprises sensor electronics  connecting cables  and a pair of antennas  such as the antennas of FIGS. 1 and 2.
[0014] FIG. 4 is a schematic diagram of a DPF filter system that is configured to monitor the amount of soot in a filter of the DPF filter system  the DPF filter system comprises a pair of antennas such as the antennas of FIGS. 1 and 2.
DETAILED DESCRIPTION OF THE INVENTION
[0015] There is provided below embodiments of an antenna that are configured to transmit and receive RF signals. Such embodiments are constructed in a manner that reduces  and effectively eliminates certain operating characteristics generally exhibited by antennas of this type so as to improve RF signal conduction via the antenna. These improvements are realized in some embodiments because the antenna has a reduced number of reflection points  which can cause the RF signal to reflect back towards one end of the antenna. Reflection can disrupt the RF signal conduction  reduce the sensitivity of the antenna  and lead to unacceptably high levels of variability among antennas.
[0016] These challenges  and in particular the variability between antennas  can be burdensome when the antennas are to be replaced  swapped  or otherwise exchanged with other antennas of the same or similar construction  such as is the case in certain systems and applications (e.g.  sensor systems for diesel particulate filters). On the other hand  it will be discussed in more detail below that the antennas that are made in accordance with the concepts of the present invention reduce the variability from antenna to antenna to a level where each antenna can be replaced without effectively changing the performance of the system and/or application. This is particularly beneficial because these antennas can be implemented to collect measurements related to RF signal conduction  and more particularly to collect such measurements where the collected data must fall within specific tolerance levels that are not addressed by the antennas  or the systems discussed in the Background section above.
[0017] So with reference to the drawings generally  and FIGS. 1-4 in particular  embodiments of the antenna can be had  in which these embodiments are characterized so that the attenuation of the signal transmitted from one antenna  and received by another antenna can be measured with a reduced level of variability from antenna to antenna. With reference to FIG. 1  there is illustrated an example of an antenna 100 that is made in accordance with the concepts of the present invention. The antenna 100 can comprise an antenna body 102 with a longitudinal axis 104  a transmitting or receiving end 106  and a connective end 108 for receiving a cable 110 such as more particularly a cable connector 112 on the end of the cable 110. In one example  the antenna 100 can comprise an antenna connector 114  located on the connective end 108  and configured to interface with the cable connector 112.
[0018] The antenna 100 can also comprise a transmitting or receiving element 116  constructed in one embodiment of Inconel alloys and comparable materials. The transmitting or receiving element 116 has an element body 118 extending into the antenna body 102. The element body 118 can comprise a radiating portion 120  which extends out of the antenna body 102 on the transmitting or receiving end 106. The element body 118 can also comprise a connecting portion 122 (shown here in limited view)  which is opposite the radiating portion 120 and proximate the antenna connector 114.
[0019] It is noted here  and also discussed and illustrated in connection with FIG. 2 below  that the connecting portion 122 extends into the antenna connector 114. This configuration permits the connecting portion 122 to be used as the center conductor of the antenna connector 114. This configuration eliminates one or more reflective points. Moreover  the connecting portion 122 can directly contact the center conductor of the cable 110  when the cable connector 112 and the antenna connector 114 are secured together. This direct contact permits signals (e.g.  the RF signals) transmitted or received by the radiating portion 120 to be conducted directly to the center conductor of the cable 110.
[0020] Additional details of this concept  as well as other features and concepts of embodiments of the present invention are discussed below in connection with the example of an antenna 200  which is illustrated in FIG. 2. Here  like numerals are used to identify like components as between the antenna 100 of FIG. 1  except the numerals are increased by 100 (e.g.  100 is now 200). For example  it is seen in this embodiment that the antenna 200 can comprise an antenna body 202 with a longitudinal axis 204  and a transmitting or receiving end 206. The antenna body 202 can also comprise a connective end 208 for  e.g.  receiving a cable 210 with a center conductor 211 via a cable connector 212. The antenna 200 can further comprise an antenna connector 214  a transmitting or receiving element 216 with an element body 218 that has a radiating portion 220  and a connecting portion 222  which is opposite the radiating portion 220.
[0021] The antenna connector 214 can comprise an interface 224  which in one construction has an outer shell 226 that surrounds an inner insulating member 228. In the present example  the insulating member 228 has a bore portion 230 that extends into the inner insulating member 228 from the connective end 208. By way of non-limiting example  the antenna body 202 can have a receptacle area 232 near the connective end 208  the receptacle area 232 being constructed in a manner that it can receive the antenna connector 214 therein. Embodiments of the antenna 200  for example  can be configured where the receptacle area 232 and the outer shell 226 have complementary threads  which engage in a manner that secures the antenna connector 214 to the antenna body 202.
[0022] In one example  the outer shell 226 can comprise a shoulder 234 with a shoulder surface 236  in which the position of the shoulder surface 236 can abut a part of the antenna body 202. This abutment can limit the extent to which the outer shell 226 is received in the receptacle area 232. It is likewise contemplated that the receptacle area 232 and the outer shell 226 can be sized and configured so as to secure the antenna connector 214 to the antenna body 202 without threads or other fastening implements (e.g.  adhesives). The diameters of the outer shell 226 and the receptacle area 232  for example  can be selected so as to create interference  an interference fit  and/or a press-fit  as between the outer dimensions of the outer shell 226 and the inner dimensions of the receptacle area 232.
[0023] The interface 224  and in one example the outer shell 226 can be used to secure the cable connector 212 and the antenna connector 214. The interface 224 can be of standard variety such as is used with coaxial cables  and coaxial cable technology. Exemplary interfaces for use as the interface 224 can include  but are not limited to threaded surfaces  snap fittings  pressure release fittings  deformable fittings  quick-release fittings  and any combinations thereof. In one example  the interface 224 (and the cable connector 212  and the antenna connector 214) can comprise a reverse polarity connector  wherein the male portion resides on the antenna connector 214 and the female portion resides on the cable connector 212. In another example  the interface 224 (and one or both of the cable connector 212  and the antenna connector 214) are compatible with connectors selected from the group of connector interfaces consisting of a BNC connector  a TNC connector  an F-type connector  an RCA-type connector  a 7/16 DIN male connector  a 7/16 female connector  an N male connector  an N female connector  an SMA male connector  and an SMA female connector.
[0024] The bore portion 230 of the insulating member 228 can be likewise configured to receive the cable connector 212 such as if the reverse polarity connector is utilized to connect the cable 210 to the antenna body 202. In one example  the diameter of the bore portion 230 is sized to receive the inner portion of one of the connectors discussed immediately above. This inner portion may comprise a complementary cylindrical shape  and in one implementation the inner portion is sized to fit inside of the bore portion 230  so as to be in surrounding relation to the connecting portion 222 of the element body 218.
[0025] The antenna body 202 can further comprise a seal area 238  which is opposite the receptacle area 232  and for receiving a seal 240. Seals of the type used as the seal 240 are generally constructed so as to fit in surrounding relation to the element body 218  such as by providing an aperture through the seal 240 that is sized to fit over and around the element body 218. A variety of materials can used for the seal 240  with one construction of the seal 240 comprising one or more slugs of glass and/or similar silica-based materials  which is inserted into the seal area 238 and melted to form the seal  e.g.  an air-tight seal.
[0026] Discussing next an implementation of embodiments of the antennas  such as the antennas 100  200 described above  FIG. 3 illustrates an example of a sensor 300 that comprises a first antenna 302 and a second antenna 304  both of which can be made in accordance with concepts of the present invention. The sensor 300 also comprises a controller 306  and cables 308 with connectors 310 that interface with the first antenna 302 and the second antenna 304 (“the antennas”). This interface places the center conductor of the cable in direct contact with the transmitting or receiving element of the first antenna 302 and the second antenna 304. The sensor 300 further comprises an interface cable 312 such as would be used to interface with  e.g.  a computer  a laptop  and/or an equipment condition monitoring (“ECM”) device.
[0027] At a high level  in one embodiment the sensor 300 is configured to cause one of the antennas to transmit a signal such as an RF signal  and to respond to the RF signal as that signal is received by the other  non-transmitting antenna. The RF signal can have frequency that is greater than about 500 mHz  with one particular operation of the sensor 300 providing the frequency from about 700 mHz to about 900 mHz. This frequency is particularly useful in connection with the DPF filters discussed above  an example of which is provided immediately below.
[0028] That is  and with reference to FIG. 4  an example of a DPF filter system 400 comprises a sensor 402 with a first antenna 404  a second antenna 406  a controller 408  and an interface cable 410. The DPF filter system 400 also comprises a filter body 412 with an input side 414 and an output side 416. Inside of the filter body 412 is provided a filter 418  wherein the filter 418 in preferred embodiments of the system 400 can be constructed of materials that are selected for their compatibility with diesel exhaust  and diesel exhaust particulates generated by diesel engines. The DPF filter system 400 can also comprise a first temperature sensor 420  a second temperature sensor 422  and an ECM device 424  which is coupled to each of the sensor 402  the first temperature sensor 420  and the second temperature sensor 422.
[0029] During operation of the DPF filter system 400 (and  also the sensor 402)  diesel exhaust impinges on the filter 418 as the exhaust flows from the input side 418 to the output side 416 of the filter body 412. Based on the construction of the filter 418  particulates are trapped in the material of the filter 418  which clogs the material so as to effectively retard the flow of the diesel exhaust through the filter 418. It is recognized that as more particulates become bound in the material of the filter 418  the effect is to reduce the flow of exhaust through the filter 418 in a manner that can deleteriously impact  e.g.  the diesel engine connected to the DPF filter system 400.
[0030] Sensor 402 is provided  however  so as to monitor the clogging of the filter 418. In one embodiment  an RF signal is transmitted from the first antenna 404  and received by the second antenna 406. The ECM device 424 is configured  typically with an algorithm or other logical circuitry  to compare properties of the transmitted RF signal to properties of the received RF signal so as to determine the level of clogging that has occurred during operation of the filter 418. In one example  this property is the amount of power of the signal  so that the amount of power of the transmitted RF signal is compared to the amount of power of the received RF signal. More particularly  the ECM device 424 is configured to measure the attenuation of the RF signal as between the transmitted RF signal and the received RF signal. The attenuation  in combination with temperature data that is monitored and collected by the temperature sensors 420  422 can be used to monitor clogging of the DPF filter 400.
EXPERIMENTAL EXAMPLES
[0031] In view of the foregoing  it is further noted that antennas of the type disclosed and contemplated herein can be readily replaced in the DPF filter systems because of the limited variability between such antennas. To exemplify this favorable level of variability  reference is had to the experimental data collected from experiments conducted in a system that is similar to the DPF filter system 400 discussed above. That is  an RF signal having a frequency swept between 700 mHz and 900 mHz was transmitted from a first antenna positioned on one side of a filter in a DPF filter system  and received at a second antenna on the other side of the filter. The level of attenuation was measured  as between the transmitted RF signal and the received RF signal.
[0032] Table 1 below summarizes data collected from nine (9) separate antennas  each of the nine antennas being constructed in accordance with the concepts of the present invention so as to have the transmitting or receiving element being used as the center conductor of the antenna connector  which forms a “one-piece” construction.
Table 1

[0033] Table 2 below summarizes the data collected for the nine (9) separate antennas of Table 1  and compares this data to data collected for fifteen (15) separate antennas operated under similar conditions  but with the antenna having a separate center conductor in the antenna connector  which forms a “two-piece” construction.
Table 2

[0034] Examining the data of Tables 1 and 2 it is seen that the performance of antennas where the transmitting and receiving element is used as the center conductor of the antenna connector is superior to antennas that utilize a separate center conductor. For example  it is seen that the range and standard deviation of values for the average S21 is far less for the antenna that is made in accordance with the present invention. This lower value not only indicates superior performance over the antenna with separate center conductor  but also that the variability previously seen in such antenna is effectively reduced.
[0035] It is contemplated that numerical values  as well as other values that are recited herein are modified by the term “about”  whether expressly stated or inherently derived by the discussion of the present disclosure. As used herein  the term “about” defines the numerical boundaries of the modified values so as to include  but not be limited to  tolerances and values up to  and including the numerical value so modified. That is  numerical values can include the actual value that is expressly stated  as well as other values that are  or can be  the decimal  fractional  or other multiple of the actual value indicated  and/or described in the disclosure.
[0036] This written description uses examples to disclose the invention  including the best mode  and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims  and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims  or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

What is claimed is:
1. An antenna comprising:
an antenna body comprising a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween;
an antenna connector disposed on the connective end; and
a transmitting or receiving element aligned with the longitudinal axis  the transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion forming a center conductor of the antenna connector.
2. An antenna according to claim 1  wherein the antenna connector comprises an interface with a threaded surface.
3. An antenna according to claim 2  wherein the interface comprises an outer shell in surrounding relation to the connecting portion of the element body  and an insulating member disposed in the outer shell  the insulating member for insulating the connecting portion from the outer shell.
4. An antenna according to claim 1  wherein the antenna connector comprises a reverse polarity connector  and wherein the center conductor forms a male portion of the reverse polarity connector.
5. An antenna according to claim 1  further comprising a seal disposed on the transmitting or receiving end of the antenna body  the seal comprising an aperture in surrounding relation to the element body.
6. An antenna according to claim 1  wherein the element body comprises a nickel-chromium alloy.
7. An antenna according to claim 1  wherein the antenna connector comprises a TNC connector.
8. An antenna according to claim 1  wherein the connector end comprises a receptacle area that has an inner threaded surface for engaging a portion of the antenna connector.
9. An antenna comprising:
an antenna body comprising a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween;
an antenna connector disposed on the connective end  the antenna connector comprising an interface comprising an elongated insulating member having an inner bore  and an outer shell in surrounding relation to the elongated insulating member; and
a transmitting or receiving element aligned with the longitudinal axis  the transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion extending into the inner bore of the elongated insulating member in a manner exposing the connecting portion as a center conductor of the antenna connector.
10. An antenna according to claim 9  further comprising a seal disposed on the transmitting or receiving end of the antenna body  the seal comprising a glass body having an aperture in surrounding relation to the element body.
11. An antenna according to claim 9  wherein the element body comprises Inconel.
12. An antenna according to claim 9  wherein the outer shell comprises a threaded surface.
13. An antenna according to claim 9  wherein the connective end comprises a receptacle area that has an inner threaded surface for engaging the outer shell.
14. A sensor comprising:
a controller responsive to an RF signal;
a cable coupled to the controller  the cable comprising a mating connector  and a conductor for conducting the RF signal between the controller and the mating connector; and
an antenna secured to the mating connector  the antenna comprising 
an antenna body having a transmitting or receiving end  a connective end opposite the transmitting or receiving end  and a longitudinal axis extending therebetween 
an antenna connector disposed on the connective end  the antenna connector for receiving the mating connector; and
a transmitting or receiving element aligned with the longitudinal axis  the transmitting or receiving element comprising an element body with a radiating portion extending out the transmitting or receiving end  and a connecting portion forming a center conductor of the antenna connector.
15. A sensor according to claim 12  wherein the center conductor of the antenna connector directly contacts the conductor of the cable.
16. A sensor according to claim 12  wherein the RF signal is conducted directly to the conductor of the cable via the element body.
17. A sensor according to claim 12  wherein antenna connector comprises an interface with a reverse polarity connector  the reverse polarity connector forming a male portion for receiving a female portion of the mating connector.
18. A sensor according to claim 12  wherein the element body comprises Inconel.
19. A sensor according to claim 12  wherein the connective end comprises a receptacle area that has an inner threaded surface for engaging the outer shell.
20. A sensor according to claim 12  wherein the element body comprises a nickel-chromium alloy.

ANTENNA ASSEMBLY
ABSTRACT
An antenna configured so as to use a transmitting or receiving element as the center conductor of a connector interface  which can connect to other connectors such as coaxial cable connectors. In one embodiment  the antenna comprises an antenna body that has an antenna connector configured as a reverse polarity connector. The reverse polarity connector comprises features which can position the transmitting or receiving element in direct contact with the center conductor of a mating cable.