Patent Publication Number: US-6707356-B2

Title: Method of constructing a relay

Description:
This is a Divisional of copending application Ser. No. 09/841,928, filed on Apr. 24, 2001, now U.S. Pat. No. 6,621,391 the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention pertains to electro-mechanical relays of the type which alternately allow current to flow through one of two or more circuits. 
     BACKGROUND OF THE INVENTION 
     One way to close a circuit connection is by way of an electro-mechanical relay. In its simplest form, a relay merely makes or breaks a single circuit connection (i.e., it opens or closes a path through which current may flow). Depending on the relay&#39;s intended use, a biased conductor which makes the circuit connection is biased so that the connection is “normally open” or “normally closed”. An armature which is movable between first and second positions then presses on the biased conductor when the armature is moved to one of its positions, and the pressing on the biased conductor causes the biased conductor to move from its biased state. In this manner, a normally open connection may be closed, and a normally closed connection may be opened. Movement of the armature is controlled by an electro-magnetic actuator assembly. Typically, the actuator assembly will comprise a magnetic core encircled by an electric coil. The ends of the coil are coupled to a control circuit. When the control circuit is closed, current flows through the coil and causes the magnetic core to exert an attractive or repelling force which causes a relay&#39;s armature to move out of its biased position. When the control circuit is opened, current ceases to flow through the coil and the magnetic force exerted by the core ceases to exist. Opening the control circuit therefore allows a relay&#39;s armature to return to its biased position. While the movement of an armature is typically rotational (e.g., the armature is mounted within a relay using pins which lie on the armature&#39;s rotational axis), the movement of an armature is sometimes translational (e.g., the armature is mounted so that it travels along a track). 
     While some simple relays comprise only a single circuit, and therefore a single current path which may be opened or closed, other relays comprise two or more circuits through which current may alternately flow, depending on which of the two or more circuits is currently closed. In some relays, two alternate circuit paths will comprise a pass-through circuit path and an attenuated circuit path. The pass-through circuit path simply allows electrical signals to flow through the relay without attenuation. On the other hand, and as its name implies, the attenuated circuit path attenuates electrical signals which flow through the relay. 
     With advances in manufacturing technology, electronic devices have become increasingly smaller. As a result, the size of electro-mechanical relays has decreased. However, as pass-through and attenuator circuits are mounted in closer proximity of one another, there is a greater chance that the two circuits will interfere with one another. For example, an electrical signal flowing through an attenuator circuit may receive unwanted attenuation from an open pass-through circuit or vice versa. The open circuit acts as an antenna which receives stray electrical signals and then capacitively transfers the stray signals to the closed circuit. Because this interference may increase as the distance separating the relevant circuits decreases, reducing this interference to a manageable level has become an increasingly important design criterion for miniature relays. 
     An example of a typical electro-mechanical relay comprising pass-through and attenuator circuits, which is hereby incorporated by reference for all that it discloses, is disclosed in the U.S. Patent of Blair et al. entitled “Attenuator Relay” (U.S. Pat. No. 5,315,273). The relay disclosed by Blair et al. is intended to be housed in a cannister having a volume of approximately 0.05 cubic inches. While such a miniature relay is adequate for some applications, the close proximity of its pass-through and attenuator circuits results in too much noise in other applications. 
     Consequently, a need exists for an electro-mechanical relay that is capable of alternately opening and closing two or more circuits (e.g., pass-through and attenuator circuits) such that an open one of the circuits does not impart noise to a closed one of the circuits. 
     SUMMARY OF THE INVENTION 
     In achievement of the foregoing need, the inventor has devised a new electro-mechanical relay. 
     In one embodiment of the invention, a relay comprises a substrate, a first circuit mounted on a first face of the substrate, a second circuit mounted on a second face of the substrate, an electro-magnetic actuator assembly, and an armature assembly which is movable between first and second positions with respect to the substrate. Movement of the armature assembly is controlled by the electro-magnetic actuator assembly, and when the armature assembly is moved to its first position, current is allowed to flow through the first circuit. When the armature assembly is moved to its second position, current is allowed to flow through the second circuit. Use of the substrate to separate the two circuits ensures that interference between the two circuits is kept below an adequate level. 
     The armature assembly can open and close the two circuits in a number of ways. In one relay which is described herein, an armature assembly comprises a number of actuator arms, some of which pass through the substrate. Actuator arms which do and do not pass through the substrate press on a number of spring clips and/or other biased conductors to open and/or close circuits. In another relay described herein, an armature assembly is mounted so that it presses on at least one biased conductor which abuts a substrate. The biased conductor comprises contacts which are suspended both above and below the substrate such that movement of the biased conductor enables it to alternately make contact with a circuit mounted on either of two faces of a substrate. 
     In some embodiments of the invention, a relay&#39;s armature assembly is provided with actuator arms which are used to couple a circuit which is not in use to ground. In this manner, it is even more unlikely that a relay&#39;s open circuit(s) will interfere with a relay&#39;s closed circuit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Illustrative and presently preferred embodiments of the invention are shown in the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a first relay embodiment; 
     FIG. 2 is a plan view of the armature assembly, substrate and header of the FIG. 1 relay; 
     FIG. 3 is an elevational view of the internal components of the FIG. 1 relay; 
     FIG. 4 is a plan view of the main body of the FIG. 1 armature assembly; 
     FIG. 5 is a plan view of the actuator arms of the FIG. 1 armature assembly; 
     FIG. 6 is a plan view of the first face of the FIG. 1 substrate; 
     FIG. 7 is a perspective view of the first face of the FIG. 1 substrate; 
     FIG. 8 is a plan view of the second face of the FIG. 1 substrate; 
     FIG. 9 is a perspective view of the second face of the FIG. 1 substrate; 
     FIG. 10 is an exemplary schematic of the attenuator circuit illustrated in FIGS. 8 &amp; 9; 
     FIG. 11 is a perspective view of a second relay embodiment; 
     FIG. 12 is an elevational view of the internal components of the FIG. 11 relay; 
     FIG. 13 is an enlarged view of a portion of FIG. 12; 
     FIG. 14 is a plan view of the first face of the FIG. 11 substrate; and 
     FIG. 15 is a plan view of the second face of the FIG. 11 substrate. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     1. In General 
     FIGS. 1 and 11 respectively illustrate first and second embodiments  100 ,  1100  of a relay. Common to both embodiments  100 ,  1100  is an armature assembly  102 ,  1102  which is movable between first and second positions with respect to a substrate  104 ,  1104  on which first  602 ,  1402  and second  802 ,  1502  circuits are mounted. In each embodiment  100 ,  1100 , the first circuit  602 ,  1402  is mounted on a first face  600 ,  1400  (FIGS. 6,  14 ) of the substrate  104 ,  1104 , and the second circuit  802 ,  1502  (FIGS. 8,  15 ) is mounted on a second face  800 ,  1500  of the substrate  104 ,  1104 . By way of example, each embodiment  100 ,  1100  1) shows the first  602 ,  1402  and second  802 ,  1502  circuits to be mounted on opposite faces of a substrate  104 ,  1104 , 2) shows the first circuit  602 ,  1402  to be a pass-through circuit, and 3) shows the second circuit  802 ,  1502  to be an attenuator circuit. 
     When the armature assembly  102 ,  1102  of one of the relays is moved to its first position, current is allowed to flow through the relay&#39;s first circuit  602 ,  1402 . Likewise, when the armature assembly  102 ,  1102  of one of the relays is moved to its second position, current is allowed to flow through the relay&#39;s second circuit  802 ,  1502 . 
     A relay&#39;s armature assembly  102 ,  1102  may be mounted for either rotational (pivotal) or translational (up/down or side/side) movement. However, by way of example, the armature assemblies in FIGS. 1 and 11 are shown to be mounted for rotational movement. 
     In each of FIGS. 1 and 11, an electromagnetic actuator assembly  106 ,  108 ,  110 ,  112  provides the force or forces which are needed to move an armature assembly  102 ,  1102  between its first and second positions. The electro-magnetic actuator assembly  106 - 112  may be more or less integrated with the structure of an armature assembly  102 ,  1102 , and FIGS. 1 and 11 only show one preferred embodiment of an electro-magnetic actuator assembly  106 - 112 . In the preferred embodiment of the electro-magnetic actuator assembly  106 - 112 , the assembly&#39;s application or withdrawal of a single, attractive magnetic force provides for armature assembly movement. For example, refer to FIG. 1 wherein the electro-magnetic actuator assembly  106 - 112  comprises a core  110  and coil  108  which are mounted between two magnetic poles  106 ,  112 . When a voltage is applied to the ends  107 ,  109  of the coil  108 , the core  110  causes a magnetic field to be formed between the two magnetic poles  106 ,  112 , and thereby causes an attractive magnetic force to be exerted on one end of the armature assembly  102 , thereby causing the armature assembly  102  to rotate in a first direction  114  (i.e., counter-clockwise in FIG.  1 ). When the voltage is withdrawn from the coil  108 , the magnetic field formed between the two magnetic poles  106 ,  112  dissipates, and a biasing spring  118  returns the armature assembly to its first position (i.e., the armature assembly  102  moves in direction  116 ). 
     Other means of moving an armature assembly  102  will be readily apparent to those skilled in the art. For example, an electro-magnetic actuator assembly could be designed to alternately attract and repel one end of an armature assembly  102  (e.g., in response to two different voltages which are applied to the electro-magnetic actuator assembly). An electro-magnetic actuator assembly could also take the form of a solenoid, wherein a plunger pushes and/or pulls one end of an armature assembly  102 . 
     Having briefly discussed some of the features which are common to the relay embodiments  100 ,  1100  illustrated in FIGS. 1 and 11, each of the relays  100 ,  1100  will now be described in greater detail. 
     2. A First Relay Embodiment 
     FIG. 1 illustrates a first embodiment  100  of a relay. The relay  100  is housed within a metallic structure comprising a base plate  120  and a cover  122 . Protruding through the base plate  120  are first and second pairs of conductive terminals  124 / 126 ,  128 / 130 , each pair of which is insulated from the metallic base plate  120 . The conductive terminals  124 ,  126  of the first pair are signal terminals, and are alternately coupled to one another via one of two circuits  602 ,  802  (FIGS. 6,  8 ) which are housed within the relay  100 . The conductive terminals  128 ,  130  of the second pair are control terminals, and are provided for the purpose of controlling an electro-magnetic actuator assembly  106 - 112  which is housed within the relay  100 . The presence of a voltage on the control terminals  128 ,  130  determines the state of the electro-magnetic actuator assembly  106 - 112 , which in turn determines which of the two circuits  602 ,  802  mounted within the relay  100  will be connected between the signal terminals  124 ,  126 . 
     A header  132  is mounted (e.g., welded) within the relay housing  120 ,  122  on top of the base plate  120 . The header  132  serves to give the relay  100  more rigidity, and is preferably formed of a metallic material which is grounded to the relay housing  120 ,  122 . By way of example, the header  132  may comprise gold plated Kovar. 
     The four conductive terminals  124 - 130  protrude through the header  132 , and into the interior of the relay housing  120 ,  122 . The terminals  124 - 130  are insulated from the header  132 , preferably by glass beads which form a glass to metal seal between each terminal  124 - 130  and the Kovar header  132 . 
     A ground terminal  134  is coupled to the header  132  and protrudes into the interior of the relay housing  120 ,  122 . 
     A substrate  104  (such as a lapped alumina (Al 2 O 3 ) ceramic substrate) is suspended above the header  132  (FIGS. 2,  3 ). Preferably, the substrate  104  is suspended above the header  132  by means of the signal terminals  124 ,  126  and the ground terminal  134 , each of which may protrude through, and be welded to, gold plated holes in the substrate  104 . 
     A pass-through circuit  602  (FIGS. 6,  7 ) is mounted to the bottom face  600  of the substrate  104 , and an attenuator circuit  802  (FIGS. 8,  9 ) is mounted to the top face  800  of the substrate  104 . Various metallic spring clips  604 ,  606 ,  812 ,  814  (or other biased conductors) and metallic pads  620 ,  622 ,  626 ,  628 ,  816 ,  818  mounted on the top and bottom surfaces  600 ,  800  of the substrate  104  serve to alternately couple the pass-through and attenuator circuits  602 ,  802  between the two signal terminals  124 ,  126 . Additional spring clips  608 ,  610  mounted on the bottom surface  600  of the substrate  104  serve to ground the attenuator circuit  802  when it is not in use. The various circuits  602 ,  802 , spring clips  604 ,  606 ,  608 ,  610 ,  812 ,  814  and metallic pads  620 ,  622 ,  626 ,  628 ,  816 ,  818  which are mounted on the substrate  104  will be described in greater detail later in this description. 
     The electro-magnetic actuator assembly  106 - 112  which is mounted within the relay housing  120 ,  122  comprises two magnetic poles  106 ,  112 , a coil  108 , and a core  110 . The coil  108  is slipped over the core  110 , and the core  110  and coil  108  are then mounted between the two magnetic poles  106 ,  112 . The first magnetic pole  106  is then used to mount the electro-magnetic actuator assembly  106 - 112  to the header  132  such that the second magnetic pole  112  is suspended over the header  132  and in back of the afore-mentioned substrate  104  (which is also suspended over the header  132 ; see FIG.  3 ). The two  107 ,  109  ends of the coil  108  are respectively and electrically coupled to the relay&#39;s control terminals  128 ,  130 . When a voltage is applied to the control terminals  128 ,  130 , current flows through the coil  108  and an electromagnetic force flows through the core  110 . The electromagnetic force in turn polarizes the two magnetic poles  106 ,  112  and causes the lower portion of the first magnetic pole to exert an attractive magnetic force on one end of the relay&#39;s armature assembly  102 . 
     The armature assembly  102  comprises a main body  148  (FIGS. 1,  4 ) and number of actuator arms  136  (FIGS. 1,  5 ). The main body is an essentially flat metallic structure to which the number of actuator arms  136  and two pivot pins  138 ,  140  are attached. The actuator arms  136  are preferably formed of a strong, non-conductive material such as plastic. The pivot pins  138 ,  140  may fit into indents  142 ,  144 , holes or crevices formed in the underside of the second magnetic pole  112 . A biasing spring  118  which is mounted on the header  132  applies pressure to the underside of the armature assembly  102  so that the armature assembly  102  assumes its first position when the electro-magnetic actuator assembly  106 - 112  is not energized. A stop  146  mounted on the header  132  prevents the spring  118  from over-biasing the armature assembly  102 . Other means of biasing the armature assembly  102  are contemplated, but not preferred. For example, the electro-magnetic actuator assembly  106 - 112  could bias the armature assembly  102  to its first position by repelling it, and then move the armature assembly  102  to its second position by attracting it. Or for example, the armature assembly  102  could be biased to its first position via an unequal weight distribution. 
     The actuator arms  136  which extend from the armature assembly  102  are positioned over various spring clips  604 ,  606 ,  608 ,  610 ,  812 ,  814  which are mounted on the substrate  104 . First and second pairs of actuator arms  502 / 504 ,  506 / 508  (FIG. 5) are positioned over holes  804 ,  806 ,  808 ,  810  (FIGS. 8 &amp; 9) in the substrate  104 , and when the armature assembly  102  is moved to its second position by the electro-magnetic actuator assembly  106 - 112 , the actuator arms  502 - 508  extend through the substrate  104  to press on spring clips  604 ,  606 ,  608 ,  610  (FIGS. 6 &amp; 7) which are mounted on the underside  600  of the substrate  104 . 
     When the armature assembly  102  is moved to its second position, the actuator arms  136  perform the following functions: 
     The first pair of actuator arms  502 ,  504  press on spring clips  604 ,  606  which are 1) coupled to the pass-through circuit  602 , and 2) biased to make contact with conductors  612 ,  614  which are coupled to the relay&#39;s signal terminals  124 ,  126  (i.e., when the armature assembly  102  assumes its first position, the spring clips  604 ,  606  couple the pass-through circuit  602  between the relay&#39;s signal terminals  124 ,  126 , and when the first pair of actuator arms  502 ,  504  press on the spring clips  604 ,  606 , their contact with the conductors  612 ,  614  which are coupled to the relay&#39;s signal terminals  124 ,  126  is broken). Note that when the spring clips  604 ,  606  are depressed, they may be designed to make contact with the header  132  so as to ground the pass-through circuit  602 . See FIGS. 3,  6  &amp;  7 . 
     The second pair of actuator arms  506 ,  508  press on spring clips  608 ,  610  which are normally biased to contact and ground the attenuator circuit  802  (i.e., when the armature assembly  102  assumes its first position, the spring clips  608 ,  610  ground the attenuator circuit  802 , and when the second pair of actuator arms  506 ,  508  press on the spring clips  608 ,  610 , their contact with the attenuator circuit  802  is broken). When the spring clips  608 ,  610  assume their normally biased positions, they make contact with the attenuator circuit  802  by means of conductive vias  630 ,  632  which pass through the substrate  104 . The spring clips  608 ,  610  are welded to a ground plane  624  which preferably covers most of the substrate&#39;s bottom face  600 . See FIGS. 3,  6  &amp;  7 . 
     The third pair of actuator arms  510 ,  512  press on spring clips  812 ,  814  which are normally biased to an open position. As a result, downward movement  114  of the third pair of actuator arms  510 ,  512  serves to connect the attenuator circuit  802  between the relay&#39;s signal terminals  124 ,  126  (i.e., when the armature assembly  102  assumes its first position, no current flows through the spring clips  812 ,  814 , and when the third pair of actuator arms  510 ,  512  press on the spring clips  812 ,  814 , the attenuator circuit  802  is coupled between the relay&#39;s signal terminals  124 ,  126  so that current flows therethrough). Note that the third pair of actuator arms  510 ,  512  do not pass through the substrate  104 . Also note that the weld pads  616 ,  618  found on the top face  800  of the substrate  104  are coupled to the relay&#39;s signal terminals  124 ,  126  by means of conductive vias  616 ,  618  which pass through the substrate  104  and couple the weld pads  616 ,  618  to conductors  612 ,  614 . See FIGS.  3  &amp;  6 - 9 . 
     As previously mentioned, a pass-through circuit  602 , an attenuator circuit  802 , a number of spring clips  604 ,  606 ,  608 ,  610 ,  812 ,  814 , and a number of conductive pads  620 ,  622 ,  626 ,  628 ,  816 ,  818  are mounted on the substrate  104 . FIGS. 6-9 illustrate these elements in greater detail. FIGS. 8 and 9 illustrate the elements which are mounted to the top face  800  of the substrate  104 , and FIGS. 6 and 7 illustrate the elements which are mounted to the bottom face  600  of the substrate  104 . 
     For ease of understanding, the elements which are mounted to the bottom face  600  of the substrate  104  will be described first. A first of the elements is a pair of conductors  612 ,  614 . Each of these conductors  612 ,  614  is preferably formed as a stripline or micro-strip which is electrically coupled between one of the relay&#39;s signal terminals  124 ,  126 , and one of a pair of conductive vias  616 ,  618  which extends through to the top surface  800  of the substrate  104 . Another element which is mounted to the bottom surface  600  of the substrate  104  is the pass-through circuit  602 . The pass-through circuit  602  is also preferably formed as a stripline or micro-strip. Each end of the pass-through circuit  602  terminates in a pad  620 ,  622  to which a spring clip  604 ,  606  is welded. Each spring clip  604 ,  606  is positioned and biased so as to make electrical contact with a conductor  612 ,  614  which is coupled to one of the relay&#39;s signal terminals  124 ,  126 . Each spring clip  604 ,  606  is also positioned so that it passes under one of the holes  804 ,  806  through which the first pair of actuator arms  502 ,  504  pass. In this manner, movement of the armature assembly  102  to its second position causes the first pair of actuator arms  502 ,  504  to break the connections between the pass-through circuit spring clips  604 ,  606  and the relay&#39;s signal terminals  124 ,  126 . 
     The pass-through circuit  602  and conductors  612 ,  614  are preferably formed as striplines or micro-strips so that each behaves as a transmission line. To this end, most of the substrate&#39;s bottom surface  600  is covered by a ground plane  624  which is coupled to the ground post  134 . Narrow gaps  634 ,  636 ,  638  separate the ground plane from the pass-through circuit  602  and other conductors  612 ,  614  which are applied to the bottom surface  600  of the substrate  104 . The ground plane  624  is preferably formed of gold. 
     The ground plane  624  comprises two weld areas  626 ,  628  to which two additional spring clips  608 ,  610  are coupled. These two additional spring clips  608 ,  610  are positioned and biased so as to make contact with a second pair of conductive vias  630 ,  632  which extend through to the top surface  800  of the substrate  104 . The second pair of conductive vias  630 ,  632  are coupled to the attenuator circuit  802 . The additional spring clips  608 ,  610  which are mounted to the underside  600  of the substrate  104  therefore serve to ground the attenuator circuit  802  when the armature assembly  102  is in its first position. Note that the additional spring clips  608 ,  610  are positioned so that they pass under the holes  808 ,  810  through which the second pair of actuator arms  506 ,  508  extend. In this manner, movement of the armature assembly  102  to its second position causes the second pair of actuator arms  506 ,  508  to break the connections between the attenuator circuit  802  and the additional spring clips  608 ,  610  (which connections would otherwise ground the attenuator circuit  802 ). 
     The pass-through circuit  602  and conductors  612 ,  614  referenced in the preceding paragraphs may be, for example, 50 ohm lines with Ni/Co/Au plated ends (e.g., hard gold&gt;=225 knoop hardness). The spring clips  604 ,  606 ,  608 ,  610  may be made of, for example, BeCu, and then plated with a NiPd Au flash. The weld pads  620 ,  622 ,  626 ,  628  may be formed, for example, via a plating process using NiPd with a Au flash, or hard Au (e.g., Ni/Co/Au≧225 knoop hardness). The pass-through circuit  602 , conductors  612 ,  614  and pads  620 ,  622 ,  626 ,  628  which are mounted to the substrate  104  may be mounted by gluing, masking, and/or other means (e.g., etching or plating). 
     It is generally preferred that the electrical lengths of corresponding contacts in contact pairs be equal, and that spring clip and pad sizes be kept at a minimum to reduce or eliminate problems associated with signal reflection. It is also preferable that conductor stubs be kept to minimum (e.g., when coupling a circuit between the relay&#39;s signal terminals  124 ,  126  and/or when coupling an inactive circuit to ground). In this manner, conductor stubs will not behave as RF antennas. 
     As previously mentioned, the attenuator circuit  802  is mounted to the top surface  800  of the substrate  104 . Also mounted to the top surface of the substrate is a pair of welding pads  816 ,  818 . First ends of the welding pads  816 ,  818  are electrically coupled to the conductive vias  616 ,  618  which pass through the substrate  104  and connect to the conductors  612 ,  614  which contact the relay&#39;s signal terminals  124 ,  126 . Second ends of the welding pads  816 ,  818  provide a place to weld a third pair of spring clips  812 ,  814 . This third pair of spring clips  812 ,  814  is biased to a disconnect state, with each spring clip  812 ,  814  being positioned over one end of the attenuator circuit  802 . When the armature assembly  102  is moved to its second position, the third pair of actuator arms  510 ,  512  on the armature assembly  102  press the third pair of spring clips  812 ,  814  against their corresponding contact pads of the attenuator circuit  802 , thereby causing the attenuator circuit  802  to be coupled between the relay&#39;s signal terminals  124 ,  126 . 
     Preferably, the top surface  800  of the substrate  104  also comprises a ground plane  820 . The ground plane preferably covers most of the top surface  800  and is coupled to the ground post  134 . 
     The attenuator circuit  802  may assume any of a number of configurations (e.g., a “T” network, a “Π” network, or an “L” network). Precise values and types of components which form a part of the attenuator circuit are beyond the scope of this disclosure, and may be chosen to suit a particular application. However, an exemplary attenuator circuit configuration is illustrated in FIG.  10 . Note that the exemplary configuration is a “Π” configuration comprising resistors R 1 , R 2  and R 3 . The attenuator circuit  802  may comprise either a lumped resistance network or distributed resistance network, as application merit. However, a distributed resistance is preferred in that it provides a better field distribution and results in smaller signal reflections. 
     For better RF performance, the propagation delays through the relay&#39;s alternate circuit paths  602 ,  802  should be equal. Therefore, it is generally preferred that 1) the electrical length of the circuit comprising the pass-through circuit  602  (including associated spring clips  604 ,  606  and weld pads  620 ,  622 ), and 2) the electrical length of the circuit comprising the attenuator circuit  802  (including associated vias  616 ,  618 , weld pads  816 ,  818 , and spring clips  812 ,  814 ), be equal, although such is not required. Also, equal length circuit paths makes it easier to place the relay  100  in a circuit design. 
     One advantage of the relay  100  shown in FIG. 1 is that by mounting the pass-through and attenuator circuits  602 ,  802  on different faces  600 ,  800  of the substrate  104  (e.g., opposite faces), the insulating nature of the substrate  104  helps to keep interference between the two circuits  602 ,  802  below a manageable level. A problem with past relays having two circuit paths is that the unused circuit tended to act as an antenna for noise, which noise was then imparted to the circuit path which was in use. The FIG. 1 relay  100  eliminates or at least significantly reduces this phenomenon. 
     Another advantage of a relay  100  such as that which is shown in FIG. 1 is that grounding the pass-through and attenuator circuits  602 ,  802  while they are not in use further helps to reduce the noise which the unused circuit can transfer to the circuit which is in use. If the ground planes are the same voltage potential, the RF signal should see&gt;100 dB isolation, and operation of the relay  100  should be effective up to 5-7 GHz. Effective grounding also helps to maintain a uniform characteristic impedance of all conductors  602 ,  612 ,  614 ,  802 ,  616 ,  618  which are mounted on the substrate  104 . To improve grounding even more, conductive vias joining the ground planes  624 ,  820  on the substrate&#39;s top and bottom surfaces  600 ,  800  may be placed at various points throughout the substrate  104 . The edges of the substrate  104  may also be metallized so as to join the two ground planes  624 ,  820  and improve the uniformity of the ground. 
     3. A Second Relay Embodiment 
     FIG. 11 illustrates a second embodiment of a relay  1100 . Like the first relay  100 , the second relay  1100  is housed within a metallic structure comprising a base plate  120  and a cover  122 . Protruding through the base plate  120  are signal and control terminals  124 / 126 ,  128 / 130 , each pair of which is insulated from the metallic base plate  120 . The signal terminals  124 ,  126  are alternately coupled to one another via one of two circuits  1402  (FIG.  14 ),  1502  (FIG. 15) which are housed within the relay  1100 . The control terminals  128 ,  130  are provided for the purpose of controlling an electro-magnetic actuator assembly  106 - 112  which is housed within the relay  1100 . The presence of a voltage on the control terminals  128 ,  130  determines the state of the electro-magnetic actuator assembly  106 - 112 , which in turn determines which of the two circuits  1402 ,  1502  mounted within the relay  1100  will be connected between the signal terminals  124 ,  126 . 
     A header  132  is mounted within the relay housing  120 ,  122  on top of the base plate  120 . The header  132  serves to give the relay  100  more rigidity, and is preferably formed of a metallic material which is grounded to the relay housing  120 ,  122 . By way of example, the header  132  may comprise gold plated Kovar. 
     The signal and control terminals  124 - 130  are insulated from the header  132  and protrude through the header  132  into the interior of the relay housing  120 ,  122 . Four ground posts  1112 ,  1114 ,  1116 ,  134  are preferably welded to the header  132  and protrude into the interior of the relay housing  120 ,  122 . A substrate  1104  (and preferably a lapped alumina ceramic substrate) is suspended above the header  132 . Preferably, the substrate  1104  is suspended above the header  132  by attaching it to the upper portions of three of the ground posts  1112 - 1116 . 
     A pass-through circuit  1402  is mounted to the bottom face  1400  of the substrate  1104 , and an attenuator circuit  1502  is mounted to the top face  1500  of the substrate  1104 . See FIGS. 14 and 15. 
     The electro-magnetic actuator assembly  106 - 112  which is mounted within the relay housing  120 ,  122  comprises two magnetic poles  106 ,  112 , a coil  108 , and a core  110 . The coil  108  is slipped over the core  110 , and the core  110  and coil  108  are then mounted between the two magnetic poles  106 ,  112 . The first magnetic pole  106  is then used to mount the electro-magnetic actuator assembly  106 - 112  to the header  132  such that the second magnetic pole  112  is suspended over the header  132  in back of the afore-mentioned substrate  1104  (which is also suspended over the header  132 ). The two ends  107 ,  109  of the coil  108  are respectively and electrically coupled to the relay&#39;s control terminals  128 ,  130 . When a voltage is applied to the control terminals  128 ,  130 , current flows through the coil  108  and an electromagnetic force flows through the core  110 . The electromagnetic force in turn polarizes the two magnetic poles  106 ,  112  and causes the lower portion of the first magnetic pole  106  to exert an attractive magnetic force on one end of an armature assembly  1102 . See FIG.  12 . 
     The armature assembly  1102  comprises a main body  148  and number of actuator arms  1101 ,  1103 ,  1105 . The main body is an essentially flat metallic structure to which the number of actuator arms  1101 ,  1103 ,  1105  and two pivot pins  138 ,  140  are attached. The actuator arms  1101 ,  1103 ,  1105  are preferably formed of a strong, non-conductive material such as plastic. The pivot pins  138 ,  140  fit in indents  142 ,  144 , holes or crevices formed in the underside of the second magnetic pole  112 . A biasing spring  118  which is mounted on the header  132  applies pressure to the underside of the armature assembly  1102  so that the armature assembly  1102  assumes its first position when the electro-magnetic actuator assembly  106 - 112  is not energized. A stop  146  mounted on the header  132  prevents the spring  118  from over-biasing the armature assembly  1102 . 
     Two of the actuator arms  1101 ,  1103  which extend from the armature assembly  1102  are positioned over biased leaf springs  1106 ,  1108  which are respectively and electrically coupled to the relay&#39;s signal terminals  124 ,  126  (see especially FIG.  13 ). The ends of the leaf springs  1106 ,  1108  which are not coupled to the signal terminals  124 ,  126  are bifurcated such that a contact on each leaf spring is provided above the substrate  1104 . The leaf springs  1106 ,  1108  are biased so that the lower contacts of each leaf spring  1106 ,  1108  make contact with ends  1404 ,  1406  (FIG. 14) of the pass-through circuit  1402  which is mounted to the underside  1400  of the substrate  1104 . Thus, when the armature assembly  1102  is in its first position, current flows through the pass-through circuit  1402 . When the armature assembly  1102  moves to its second position, a pair of actuator arms  1101 ,  1103  on the armature assembly  1102  press the leaf springs  1106 ,  1108  downward so that the upper contacts of the leaf springs  1106 ,  1108  make contact with ends  1504 ,  1506  (FIG. 15) of the attenuator circuit  1502  which is mounted on top  1500  of the substrate  1104 . As a result, movement of the armature assembly  1102  to its second position causes current to flow through the attenuator circuit  1502 . 
     The armature assembly  1102  may also comprise a third actuator arm  1105  for alternately grounding the pass-through and attenuator circuits  1402 ,  1502  when they are not being used. As shown in FIG. 13, a grounding member  1118 ,  1120  may extend from each of the pass-through and attenuator circuits  1402 ,  1502  such that it overhangs one edge of the substrate  1104 . A leaf spring  1110  which is electrically coupled to a grounding post  134  is then mounted such that it may alternately make contact with one or the other of the grounding members  1118 ,  1120 . For example, if the leaf spring  1110  is biased to contact the grounding member  1118  attached to the attenuator circuit  1502  when the armature assembly  1102  is at rest, then movement of the armature assembly  1102  to its second position can 1) cause the leaf spring  1110  to break its contact with the grounding member  1118  which is coupled to the attenuator circuit  1502 , and 2) alternately ground the pass-through circuit  1402  (i.e., via contact between the leaf spring  1110  and the pass-through circuit&#39;s ground member  1120 ). 
     As in the first relay  100 , the attenuator circuit  1502  may assume any of a number of configurations (e.g., a “T” network, a “Π” network, or an “L” network), and precise values and types of components which form a part of the attenuator circuit  1502  are beyond the scope of this disclosure. 
     4. Alternate Relay Embodiments 
     The relays disclosed in FIGS. 1 and 11 may be alternately embodied and constructed, without departing from the principles disclosed herein. 
     For example, each of their armature assemblies  102 ,  1102  may comprise more or fewer actuator arms  502 - 512 ,  1101 ,  1103 ,  1105 . As is known in the art, a circuit needs only one break to prevent current flow therethrough. Each pair of actuator arms  502 / 504 ,  506 / 508 ,  510 / 512 ,  1101 / 1103  discussed above may therefore be replaced with a single actuator arm. However, noise reduction may be greatly improved by wholly decoupling an unused circuit from a relay&#39;s signal terminals  124 ,  126  when the circuit is not in use. Furthermore, the grounding of a circuit as shown and described is not possible when a circuit is only disconnected from one or the other of a relay&#39;s signal terminals  124 ,  126 . 
     As previously mentioned, an armature assembly  102 ,  1102  need not move in a pivotal fashion, and could alternately move in a translational fashion. 
     An alternate embodiment of the electro-mechanical relay that is not shown may include an armature assembly wherein circuit paths are routed over (or through) the armature assembly itself. Thus, in lieu of an armature assembly comprising actuator arms which press on contacts, contacts and circuit paths could be formed directly on an armature assembly. 
     Also, the first and second circuits  602 / 802 ,  1402 / 1502  of each relay  100 ,  1100  need not be mounted on opposite faces  600 / 800 ,  1400 / 1500  of a substrate  104 ,  1104 . For example, first and second circuits could alternately be mounted to adjacent faces of a wedge-shaped substrate. 
     Furthermore, the first and second circuits need not be pass-through and attenuator circuits. Any combination of two circuits which one might alternately desire to couple into a circuit path could benefit from the principles disclosed herein. 
     To maintain good characteristic impedance and effective isolation between pass-through and attenuator circuits  602 / 802 ,  1402 / 1502 , it is generally preferred, but not required, that either the pass-through or attenuator circuit be grounded when it is not in use. However, such a grounding is not required. 
     While preferred materials of construction have been disclosed in some instances, a variety of insulating and conductive materials may be used to form the various components of the relays illustrated in FIGS. 1 and 11. 
     While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.