Patent Publication Number: US-6903621-B2

Title: In-line attenuator

Description:
FIELD OF THE INVENTION 
   This invention relates to electrical components, and particularly to attenuators. It is disclosed in the context of a microstrip, stripline, or the like, attenuator. However, it is believed to be useful in other applications as well. 
   1. Background of the Invention 
   Various types of attenuators are known. There are, for example, the attenuators illustrated in PCT/US01/43204, assigned to the same assignee as this application. The disclosure of PCT/US01/43204 is hereby incorporated herein by reference. There are also the various types of attenuators illustrated and described at http://www.metcladinternational.com/reference/Microstrip%20Lines/Microstrip.htm, the disclosure of which is hereby incorporated herein by reference. No representation is intended by this listing that a thorough search of all material prior art has been conducted, or that no better art than that listed is available, or that the listed items are material to patentability. Nor should any such representation be inferred. 
   2. Disclosure of the Invention 
   According to the invention, an attenuator includes a substrate having first and second surfaces and a plurality of discrete circuit elements. The first surface includes a first electrically conductive pattern providing circuit contacts providing electrical connections among the discrete circuit elements, and circuit contacts providing electrical connections to components external to the attenuator. The second surface includes a second electrically conductive pattern. 
   Illustratively according to an aspect of the invention, the apparatus further includes a housing for the attenuator. The circuit contacts providing electrical connections to components external to the attenuator include connectors for coupling electrically to complementary connectors provided on the housing. 
   Illustratively, according to an aspect of the invention, the housing includes a BNC connector and the circuit contacts include connectors for coupling electrically to respective terminals of the BNC connector. 
   Illustratively according to an aspect of the invention, the housing includes an SMA connector and the circuit contacts include connectors for coupling electrically to respective terminals of the SMA connector. 
   Illustratively according to an aspect of the invention, the substrate includes a third surface between the first and second surfaces. The third surface includes an electrically conductive portion coupled to at least one of the first and second electrically conductive patterns. The apparatus further includes a connector for coupling the electrically conductive portion of the third surface to the housing. 
   Illustratively according to an aspect of the invention, the attenuator comprises a microstrip attenuator. 
   Illustratively according to an aspect of the invention, the substrate comprises fiber-reinforced resin. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may best be understood by referring to the following detailed descriptions and accompanying drawings which illustrate the invention. In the drawings: 
       FIG. 1  illustrates a perspective view of a device constructed according to the invention; 
       FIG. 2  illustrates a plan view of a device constructed according to the invention; 
       FIG. 3  illustrates a plan view of a device constructed according to the invention; 
       FIGS. 4   a-b  illustrate plan views of details constructed according to the invention; 
       FIGS. 5   a-b  illustrate plan views of details constructed according to the invention; 
       FIGS. 6   a-b  illustrate plan views of details constructed according to the invention; 
       FIGS. 7   a-b  illustrate plan views of details of devices constructed according to the invention; 
       FIGS. 8   a-b  illustrate plan views of details of device constructed according to the invention; 
       FIG. 9  illustrates an exploded perspective view of a device constructed according to the invention; 
       FIG. 10  illustrates an assembled perspective view of the device illustrated in  FIG. 9 ; 
       FIG. 11  illustrates an exploded perspective view of a device constructed according to the invention; 
       FIG. 12  illustrates an assembled perspective view of the device illustrated in  FIG. 11 ; and, 
       FIGS. 13   a-d  through  18   a-d  illustrate performance characteristics of various devices constructed according to the invention. 
   

   DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
   Referring now to  FIG. 1 , a microstrip attenuator  10  includes a substrate  12 , having a front surface  14  and a back surface  16 , longitudinal edges  15  and  17  between surfaces  14  and  16 , and a plurality of chip resistors  18 . Illustratively, substrate  12  is constructed using FR4. FR4 is a fairly ubiquitous, non-low loss, epoxy resin-impregnated fiberglass. Constructing the substrate  12  using FR4 may provide cost benefits Alternatively, substrate  12  may be composed of one of several common dielectric materials known to those of ordinary skill in the art. The front surface  14 , back surface  16 , and edges  15 ,  17  are coated with conductive films using any suitable method such as, for example, plating or vapor deposition of metal film. The method used may depend in part on the material from which the substrate  12  is constructed. The coating of the surfaces  14 ,  15 ,  16 ,  17  creates on each of surfaces  14 ,  15 ,  16 ,  17  a continuous electrically conductive film such as, for example, a copper or other metal or metal composite film. A pattern  20 ,  22 , respectively, of the conductive film (shaded areas in  FIGS. 4   a-b ,  5   a-b ,  6   a-b ,  7   a-b  and  8   a-b ) is then created on each of surfaces  14 ,  16 , by any suitable means, for example, chemically etching. The film on edges  15 ,  17  may be left intact and remain electrically connected to the adjacent remaining film pattern  20 ,  22  on one or the other or both of surfaces  14 ,  16 . The pattern  20 ,  22  generation forms electrically conductive circuit traces  20  on the surface  14  and a patterned ground plane  22  on surface  16 . 
   In other embodiments, the film on edges  15 ,  17  and the conductive film traces  20  and patterned ground plane  22  may be applied by painting or printing of conductive material, selective application of conductive tape, or any other suitable technique. This eliminates the step(s) associated with removing the film from areas where it is not desired. 
   The resistors  18  are soldered or otherwise electrically coupled to conductive pads of the circuit traces  20  of the front surface  14 . The resistors  18  are coupled to the traces  20  to create an attenuator  10  for attenuating electrical signals in an electrical circuit into which the attenuator  10  is subsequently coupled. 
   The circuit traces  20  of the front surface  14  include connector pin interface pads  30 - 1  and  30 - 2  and resistor pads  32 - 1 ,  32 - 2 ,  32 - 3  and, in the embodiment of  FIGS. 3 and 8   a-b ,  32 - 4 . The conductive pads  30 - 1 ,  30 - 2  and  32 - 3  provided points for coupling the attenuator  10  to external circuitry. Specifically, pad  30 - 1  and pad  32 - 3  provide an input or output to/from the attenuator  10  and pad  30 - 2  and pad  32 - 3  provide an output or input port from/to attenuator  10 . Pads  32 - 1 ,  32 - 2  and  32 - 3  and, in the embodiment of  FIGS. 3 and 8   a-b ,  32 - 4 , provide the connection points for the resistors  18  that provide the attenuation provided by attenuator  10 . The illustrative circuit traces  20  with their pads  30 - 1 ,  30 - 2 ,  32 - 1 ,  32 - 2 ,  32 - 3 ,  32 - 4  are configured for three resistors  18 - 1 ,  18 - 2 ,  18 - 3 , or, in the embodiment of  FIGS. 3 and 8   a-b , six resistor  18 - 1 ,  18 - 2 ,  18 - 3 ,  18 - 4 ,  18 - 5 ,  18 - 6 , “Π” attenuator networks. However, the illustrated and described technology is also adaptable to other types of attenuators including, for example, types having other numbers of resistors or other network configurations. In each case, by proper selection of the values of the resistors  18 , a desired amount of attenuation can be provided by attenuator  10 . 
   As best illustrated in  FIGS. 4   a ,  5   a ,  6   a ,  7   a  and  8   a , in plan view, the substrate  12  of each attenuator  10 - 1 , − 2 ,  10 - 3 ,  10 - 6 ,  10 - 10  and  10 - 20  is generally rectangular in shape. Illustratively, each attenuator  10  has a width of about 0.325 inch (about 8.26 mm). Attenuators  10 - 1 , − 2  illustrated in  FIGS. 4   a-b , and attenuators  10 - 3 ,  10 - 6  and  10 - 10  illustrated in  FIGS. 5   a-b ,  6   a-b  and  7   a-b , respectively, illustratively have lengths of 0.62 inch (about 15.75 mm). Attenuator  10 - 20  illustrated in  FIGS. 8   a-b  illustratively has a length of 0.86 inch (about 21.84 mm). However, the lengths, widths, and shapes are clearly within the scope of the invention. Other dimensions of the traces  20 - 1 , − 2 ,  20 - 3 ,  20 - 6 ,  20 - 10  and  20 - 20  and the ground plane patterns  22 - 1 , − 2 ,  22 - 3 ,  22 - 6 ,  22 - 10  and  22 - 20  of attenuators  10 - 1 , − 2 ,  10 - 3 ,  10 - 6 ,  10 - 10  and  10 - 20 , respectively, are as noted in inches (mm in parenthesis) in  FIGS. 4   a-b ,  5   a-b ,  6   a-b ,  7   a-b  and  8   a-b , respectively, referenced to a corner designated 0.0 of the substrate  12 - 1 , − 2 ,  12 - 3 ,  12 - 6 ,  12 - 10  and  12 - 20 , respectively. 
   In an attenuator  10 , the circuit traces  20  of the front surface  14  are generally as illustrated in  FIGS. 4   a ,  5   a ,  6   a ,  7   a  and  8   a . Due at least in part to distributed parasite circuit parameters, such as parasitic capacitance, of such traces  20  at the frequencies of operation at which these types of devices are sometimes used, the ground plane on the back surface  16  is patterned  22 . The pattern  22  depends upon the desired attenuation.  FIG. 4   b  illustrates a ground plane pattern  22 - 1 , − 2  useful for attenuators  10 - 1 ,  10 - 2  useful for providing 1 or 2 decibels (dB), respectively, of attenuation (the same pattern  22 - 1 , - 31 - 2  is used to construct attenuators  10 - 1  and  10 - 2  having 1 dB and 2 dB of attenuation, respectively).  FIG. 5   b  illustrates a ground plane pattern  22 - 3  useful for attenuators  10 - 3  useful for providing 3 dB attenuation.  FIG. 6   b  illustrates a ground plane pattern  22 - 6  useful for attenuators  10 - 6  useful for providing 6 dB attenuation.  FIG. 7   b  illustrates a ground plane pattern  22 - 10  useful for attenuators  10 - 10  useful for providing 10 dB attenuation.  FIG. 8   b  illustrates a ground plane pattern  22 - 20  useful for attenuators  10 - 20  useful for providing 20 dB attenuation. 
   Each back surface  16  includes ground plane pattern  22  and pin connector pads  30 - 1  and  30 - 2  corresponding in location to pin connector pads  30 - 1  and  30 - 2 , respectively, on front surface  14 . The ground plane pattern  22 - 1 ,  22 - 3 ,  22 - 6 ,  22 - 10 ,  22 - 20  varies according to the amount of attenuation, 1 or 2 dB, 3 dB, 6 dB, 10 dB and 20 dB, respectively, which the attenuator  10  is constructed to provide. The ground plane pattern  22 - 1 , − 1 ,  22 - 3 ,  22 - 6 ,  22 - 10 ,  22 - 20  accounts for the effects of these parasite circuit parameters of the attenuator  10 - 1 ,  10 - 2 ,  10 - 3 ,  01 - 6 ,  10 - 10 ,  10 - 20  at the frequencies at which the attenuator  10 - 1 ,  10 - 2 ,  10 - 3 ,  10 - 6 ,  10 - 10 ,  10 - 20  is to operate, providing the desired accuracy to attenuator  10 - 1 ,  10 - 2 ,  10 - 3 ,  10 - 6 ,  10 - 10 ,  10 - 20 . Locating the pin pads  30 - 1 ,  30 - 2  generally along a center line of the substrate  12  promotes a reasonably stable mounting geometry for attenuation  10 . As illustrated, the pin connector pads  30 - 1  and  30 - 2  on surface  16  are electrically isolated from the respective ground plane pattern  22 . 
   There are numerous applications for attenuator  10 . For example, and as illustrated in  FIGS. 9-10 , attenuator  10  may be integrated into an SMA connector  50 . Connector  50  includes an SMA jack  52 , a pin  54 , a strip  58  of resilient springy metal such as beryllium copper, phosphor bronze, or the like, an attenuator  10  providing the desired attenuation, a pin  56 , a fixed pad enclosure  60 , and an SMA plug  62 . Pins  54 ,  56  include slotted heads by which they are soldered or otherwise attached to respective pads  30 - 1 ,  30 - 2  of the attenuator  10 . Illustratively, pins  54 ,  56  are soldered to pads  30 - 1 ,  30 - 2  on both the front  14  and back  16  of substrate  12  for mechanical stability and strength. Illustratively, pins  54 ,  56  extend along the center line of the assembled jack  52  and plug  62 . Spring strip  58  helps to promote electrical contact between pad  32 - 3  and enclosure  60  and between portions of pattern  22  which are to be at reference potential and enclosure  60 . This provides the reference potential on attenuator  10 , typically through enclosure  60 , and jack  52  and plug  62 , both of which are coupled to a shield of a coaxial cable (not shown) by which they are coupled to reference potential of external circuitry, or are mounted to an equipment chassis or frame (not shown) which is maintained at an electrical reference potential, or the like. Attenuator  10  with attached connector pins  54 ,  56  is inserted, along with spring strip  58 , into the interior  61  of enclosure  60 . Jack  52  and plug  62  are then screw threaded onto enclosure  60 . This results in an SMA connector  50  with an integrated attenuator  10 , illustrated in FIG.  10 . 
   Another application for attenuator  10  is the integration of attenuator  10  into a typical BNC connector  80 , as illustrated in  FIGS. 11-12 . Connector  80  includes a BNC jack  82 , a pin  84 , a strip  88  of resilient springy metal such as beryllium copper, phosphor bronze, or the like, attenuator  10 , a pin  86 , a fixed pad enclosure  90 , and a BNC plug  92 . Assembly of the BNC connector  80  with an integrated attenuator  10  is similar to the assembly of the SMA connector  50  described above. Pins  84 ,  86  are soldered or otherwise attached to respective pads  30 - 1 ,  30 - 2  of the attenuator  10 . Illustratively, pins  84 ,  86  are soldered to respective pads  30 - 1 ,  30 - 2  on both the front  14  and back  16  of substrate  12  for mechanical stability and strength. Illustratively, pins  84 ,  86  extend along the center line of the assembled jack  82  and plug  92 . Spring strip  88  helps to promote electrical contact between pad  32 - 3  and enclosure  90  and between portions of pattern  22  which are to be at reference potential and enclosure  90 . This provides an electrical reference potential on attenuator  10 , typically through enclosure  90 , and jack  82  and plug  92  which are not typically electrically coupled to enclosure  90  by assembly, and both of which are coupled to a shield of a coaxial cable (not shown) by which they are coupled to reference potential of external circuitry, or are mounted to an equipment chassis or frame which is maintained at an electrical reference potential, or the like. Attenuator  10 , along with the attached pins  84 ,  86  and spring strip  88  are inserted into the interior  91  of the fixed pad enclosure  90 . BNC jack  82  and BNC plug  92  are then attached to the enclosure  90  by screwing the jack  82  and plug  92  onto the enclosure  90 . The assembled BNC connector  80  with integrated attenuator  10  is illustrated in FIG.  12 . 
   Illustrative resistor values for resistors  18 - 1 ,  18 - 2  and  18 - 3  for attenuators  10 - 1 ,  10 - 2 ,  10 - 3 ,  10 - 6  and  10 - 10  follow. 
   
     
       
         
             
             
             
             
           
             
                 
             
             
               Attenuation in 
               Value of resistor 
               Value of resistor 
               Value of resistor 
             
             
               dB 
               18-1 in ohms (Ω) 
               18-2 in Ω 
               18-3 in Ω 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
             
          
             
               1 
               866 
               5.23 
               866 
             
             
               2 
               432 
               11.5 
               432 
             
             
               3 
               294 
               17.8 
               294 
             
             
               6 
               150 
               37.4 
               150 
             
             
               10 
               95.3 
               71.5 
               95.3 
             
             
                 
             
          
         
       
     
   
   Attenuator  10 - 20  illustrated in  FIGS. 8   a-b  may be thought of as two attenuators of the type illustrated in  FIGS. 4   a-b ,  5   a-b ,  6   a-b  and  7   a-b  in series. Illustrative resistance values for an attenuator  10 - 20  providing 20 dB of attenuation include: resistor  18 - 1 , 97.6 Ω; resistor  18 - 2 , 71.5 Ω; resistor  18 - 3 , 95.3 Ω; resistor  18 - 4 , 95.3 Ω; resistor  18 - 5 , 71.5 Ω; and resistor  18 - 6 , 97.6 Ω. 
   The performance of attenuator  10  of the type described, in microstrip configurations, and housed in SMA-type connectors  50  is illustrated in  FIGS. 13   a-d ,  14   a-d ,  15   a-d ,  16   a-d ,  17   a-d  and  18   a-d .  FIG. 13   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 1  configured as a microstrip attenuator and designed to provide attenuation of 1 dB. S 21  is the forward gain of the attenuator  10 - 1 , which it is desired be constant at −1 dB over the frequency of interest. At 30 KHz, S 21 =−1.0728 dB. At 1 GHz, S 21 =−0.99320 dB. At 2 GHz, S 21 =−1.0527 dB. At 3 GHz, S 21 =−1.1155 dB. Finally, at 4GHz, S 21 =−1.0852 dB. 
     FIG. 13   b  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 1  configured as a microstrip attenuator and designed to provide attenuation of 1 dB. S 12  is the reverse gain of the attenuator  10 - 1 . At 30 KHz, S 12 =−0.9968 dB. At 1 GHz, S 12 =−0.982 dB. At 2GHz, S 12 =−1.0289 dB. At 3 GHz, S 12 =−1.0833 dB. Finally, at 4 GHz, S 12 =−1.1142 dB. 
     FIG. 13   c  illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 1  configured as a microstrip attenuator and designed to provide attenuation of 1 dB. S 11  is the input reflection coefficient of the attenuator  10 - 1 . At 30 KHz, S 11 =−50.356 dB. At 1 GHz, S 11 =−27.443 dB. At 2 GHz, S 11 =−25.384 dB. At 3 GHz, S 11 =−31.125 dB. Finally, at 4 GHz, S 11 =−26.655 dB. 
     FIG. 13   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency) of an attenuator  10 - 1  configured as a microstrip attenuator and designed to provide attenuation of 1 dB. S 22  is the output reflection coefficient of the attenuator  10 - 1 . At 30 KHz, S 22 =&lt;45.390 dB. At 1 GHz, S 22 =−28.493 dB. At 2 GHz, S 22 =−26.044 dB. At 3 GHz, S 22 =−25.271 dB. Finally, at 4 GHz, S 22 =−23.982 dB. 
     FIG. 14   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 2  configured as a microstrip attenuator and designed to provide attenuation of 2 dB. S 21  is the forward gain of the attenuator  10 - 2 , which it is desired be constant at −2 dB over the frequency of interest. At 30 KHz, S 21 =−2.1361 dB. At 1 GHz, S 21 =−2.0143 dB. At 2 GHz, S 21 =−2.0728 dB. At 3GHz, S 21 =−2.1286 dB. Finally, at 4 GHz, S 21 =−2.0475 dB. 
     FIG. 14   b  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 2  configured as a microstrip attenuator and designed to provide attenuation of 2 dB. At 30 KHz, S 12 =−2.0409 dB. At 1 GHz, S 12 =−1.9974 dB. At 2 GHz, S 12 =−2.0416 dB. At 3 GHz, S 12 =−2.0913 dB. Finally, at 4 GHz, S 12 =−2.0968 dB. 
     FIG. 14   c illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 2  configured as a microstrip attenuator and designed to provide attenuation of 2 dB. At 30 KHz, S 11 =−45.915 dB. At 1 GHz, S 11 =−24.657 dB. At 2 GHz, S 11 =−22.368 dB. At 3 GHz, S 11 =−28.841 dB. Finally, at 4 GHz, S 11 =−23.143 dB. 
     FIG. 14   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency) of an attenuator  10 - 2  configured as a microstrip attenuator and designed to provide attenuation of 2 dB. At 30 KHz, S 22 =−42.066 dB. At 1 GHz, S 22 =−24.799 dB. At 2 GHz, S 22 =−21.652 dB. At 3 GHz, S 22 =−22.309 dB. Finally, at 4 GHz, S 22 =−25.987 dB. 
     FIG. 15   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 3  configured as a microstrip attenuator and designed to provide attenuation of 3 dB. S 21  is the forward gain of the attenuator  10 - 3 , which is desired be constant at −3 dB over the frequency of interest. At 30 KHz, S 21 =−3.0803 dB. At 1 GHz, S 21 =−3.0121 dB. At 2 GHz, S 21 =−3.047 dB. At 3 GHz, S 21 =−3.0517 dB. Finally, at 4GHz, S 21 =−2.9244 dB. 
     FIG. 15   b  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 3  configured as a microstrip attenuator and designed to provide attenuation of 3 dB. At 30 KHz, S 12 =−3.0707 dB. At 1 GHz, S 12 =−2.9875 dB. At 2 GHz, S 12 =−3.0131 dB. At 3 GHz, S 12 =−3.0224 dB. Finally, at 4GHz, S 12 =−2.9451 dB. 
     FIG. 15   c  illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 3  configured as a microstrip attenuator and designed to provide attenuation of 3 dB. At 30 KHz, S 11 =−42.671 dB. At 1 GHz, S 11 =−23.601 dB. At 2 GHz, S 11 =−21 dB. At 3 GHz, S 11 =−25.147 dB. Finally, at 4 GHz, S 11 =−27.713 dB. 
     FIG. 15   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency) of an attenuator  10 - 3  configured as a microstrip attenuator and designed to provide attenuation of 3 dB. At 30 GHz, S 22 =−39.628 dB. At 1 GHz, S 22 =−24.398 dB. At 2 GHz, S 22 =−22.320 dB. At 3 GHz, S 22 =−26.147 dB. Finally, at 4 GHz, S 22 =−23.213 dB. 
     FIG. 16   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 6  configured as a microstrip attenuator designed to provide attenuation of 6 dB. S 21  is the forward gain of the attenuator  10 - 6 , which it is desired be constant at −6 dB over the frequency of interest. At 30 KHz, S 21 =−6.0879 dB. At 1 GHz, S 21  =−5.981 dB. At 2 GHz, S 21 =−6.049 dB. At 3 GHz, S 21 =−6.1303 dB. Finally, at 4 GHz, S 21 =−6.0615 dB. 
     FIG. 16   b  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 6  configured as a microstrip attenuator and designed to provide attenuation of 6 dB. At 30KHz, S 12 =−6.0747 dB. At 1GHz, S 12 =−5.9462 dB. At 2 GHz, S 12 =−6.0136 dB. At 3 GHz, S 12 =−6.1061 dB. Finally, at 4 GHz, S 12 =−6.0883 dB. 
     FIG. 16   c  illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 6  configured as a microstrip attenuator and designed to provide attenuation of 6 dB. At 30 KHz, S 11 =−45.340 dB. At 1GHz, S 11 =−26.116 dB. At 2 GHz, S 11 =−23.422 dB. At 3GHz, S 11 =−26.823 dB. Finally, at 4GHz, S 11 =−27.080 dB. 
     FIG. 16   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency) of an attenuator  10 - 6  configured as a microstrip attenuator and designed to provide attenuation of 6 dB. At 30 KHz, S 22 =−42.377 dB. At 1 GHz, S 22 =−25.656 dB. At 2 GHz, S 22 =−22.797 dB. At 3 GHz, S 22 =−25.085 dB. Finally, at 4 GHz, S 22 =−26.811 dB. 
     FIG. 17   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 10  configured as a microstrip attenuator and designed to provide attenuation of 10 dB. S 21  is the forward gain of the attenuator  10 - 10 , which it is desired to be constant at −10 dB over the frequency of interest. At 30 KHz, S 21 =−10.184 dB. At 1 GHz, S 21 =−9.9918 dB. At 2 GHz, S 21 =−9.9729 dB. At 3 GHz, S 21 =−10.003 dB. Finally, at 4 GHz, S 21 =−9.9386 dB. 
     FIG. 17   d  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 10  configured as a microstrip attenuator and designed to provide attenuation of 10 dB. At 30 KHz, S 12 =−10.172 dB. At 1 GHz, S 12 =−9.9506 dB. At 2 GHz, S 12 =−9.9415 dB. At 3 GHz, S 12 =−9.9895 dB. Finally, at 4 GHz, S 12 =−9.966 dB. 
     FIG. 17   c  illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 10  configured as a microstrip attenuator and designed to provide attenuation of 10 dB. At 30KHz, S 11 =−49.642 dB. At 1 GHz, S 11 =−33.254 dB. At 2 GHz, S 11 =−30.684 dB. At 3 GHz, S 11 =−36.066 dB. Finally, at 4 GHz, S 11 =−33.742 db. 
     FIG. 17   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency)of an attenuator  10 - 10  configured as a microstrip attenuator and designed to provide attenuation of 10 dB. At 30KHz, S 22 =−46.615 dB. At 1GHz, S 22 =−31.574 dB. At 2 GHz, S 22 =−29.108 dB. At 3 GHz, S 22 =−33.744 dB. Finally, at 4 GHz, S 22 =−36.513 dB. 
     FIG. 18   a  illustrates a plot of S 21  (in dB) versus log 10 (frequency) of an attenuator  10 - 20  configured as a microstrip attenuator and designed to provide attenuation of 20 dB. S 21  is the forward gain of the attenuator  10 - 20 , which it is desired be constant at −20 dB over the frequency of interest. At 30 KHz, S 21 =−20.48 dB. At 1 GHz, S 21 =−20.041 dB. At 2 GHz, S 21 =−19.988 dB. At 3 GHz, S 21 =−19.966 dB. Finally, at 4 GHz, S 21 =−19.832 dB. 
     FIG. 18   b  illustrates a plot of S 12  (in dB) versus log 10 (frequency) of an attenuator  10 - 20  configured as a microstrip attenuator and designed to provide attenuation of 20 dB. At 30 KHz, S 12 =−20.265 dB. At 1 GHz, S 12 =−19.996 dB. At 2 GHz, S 12 =−19.953 dB. At 3 GHz, S 12 =−19.945 dB. Finally, at 4GHz, S 12 =−19.864 dB. 
     FIG. 18   c  illustrates a plot of S 11  (in dB) versus log 10 (frequency) of an attenuator  10 - 20  configured as a microstrip attenuator and designed to provide attenuation of 20 dB. At 30 KHz, S 11 =−48.33 dB. At 1GHz, S 11 =−28.27 dB. At 2 GHz, S 11 =−25.756 dB. At 3GHz, S 11 =−28.999 dB. Finally, at 4 GHz, S 11 =−36.378 dB. 
     FIG. 18   d  illustrates a plot of S 22  (in dB) versus log 10 (frequency) of an attenuator  10 - 20  configured as a microstrip attenuator and designed to provide attenuation of 20 dB. At 30 KHz, S 22 =−47.129 dB. At 1 GHz, S 22 =−28.377 dB. At 2 GHz, S 22 =−25.855 dB. At 3 GHz, S 22 =−29.264 dB. Finally, at 4 GHz, S 22 =−36.111 dB. 
   In the illustrated embodiments, the substrates  12  are constructed from, for example, hot air solder leveling (hereinafter sometimes HASL) plated GML 2000 laminate 0.031 inch (about 0.79 mm) thick, coated with copper to a uniform thickness providing 1 oz. (about 28.4 g) of copper on each side of an 18 inch (about 45.7 cm) by 24 inch (about 61 cm) sheet (about 102 g/m 2 ) of GML 2000 laminate. GML 2000 laminate is available form GIL Technologies, 175 Commerce Rd. Collierville, Tenn. 38017. The substrate  12  may also be constructed from, for example, HASL plated 25N laminate 0.030 inch (about 0.76 mm) thick, coated with copper to a uniform thickness providing 1 oz. (about 28.4 g) of copper on each side of an 18 inch (about 45.7 cm) by 24 inch (about 61 cm) sheet (about 102 g/m 2 ) of 25N laminate. 25N laminate is available from Arlon Corporation, 199 Amaral Street, East Providence, R.I. 02915