Electromagnetic transducer system with integrated circuit card adapter

An apparatus according to various aspects of the present invention is configured to collect and/or emit electromagnetic waves, particularly microwaves. In one embodiment, a transducer system includes an integrated waveguide, transducer, and processing circuit. The processing circuit is disposed between two plates which also serve to define the waveguide. The transducer, such as an E-field probe, is disposed in the waveguide to collect or emit electromagnetic waves such as microwaves. The transducer is directly connected to the processing circuit within the integrated unit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to electromagnetic transmission and detection, and 
more particularly, to waveguides and sensors for electromagnetic wave 
transmission and reception. 
2. Description of the Related Art 
Microwave technology has long been known to be useful in telecommunications 
and radar systems. With the proliferation of low-cost microwave 
semiconductor technology, however, old applications are being revisited to 
take advantage of the advances and new applications are being developed. 
In telecommunications, microwaves carry information, such as for telephone 
and television systems. Microwaves, which have a higher frequency than 
ordinary radio waves, can carry more information. In addition, because of 
their high frequency, microwaves can be accurately focused in a narrow 
beam from a transmitting antenna to a receiving antenna. Similarly, the 
high frequency of microwaves makes them suitable for focused radar 
applications. 
Microwaves, like other electromagnetic radiation, may propagate through 
space, but may also be directed or guided. Microwaves are typically 
generated by an emitter and coupled to a waveguide, and are similarly 
received by a sensor, such as an E-field probe, coupled to a waveguide. 
The received signals are then directed to appropriate instruments for 
further processing. 
Conventionally, signals corresponding to microwaves are transmitted to and 
from the processing circuitry via a coaxial cable system, which is 
connected to an assembly which matches the wave to the waveguide mode and 
impedance. For example, referring to FIG. 4, microwave energy is collected 
(or excited) in a conventional launch by an electric field (E-field) 
coupling probe (or emitter) 400 disposed in a waveguide 402 (or 
resonator), such as a circular or rectangular waveguide. The E-field probe 
400 or emitter is attached to a coaxial connector 404. A non-waveguide 
coaxial cable is then suitably connected to the connector 404 to transmit 
the signals to and from the processing circuitry. Thus, the launch is 
configured to provide a transition between the waveguide 402 and other 
transmission systems. 
Preferably, the launch matches the waveguide's 402 wave orientation, field 
type, mode, and impedance to and from the processing circuit. The probe 
400 exchanges energy between the transmission line and the waveguide 402. 
The E-field probe 400 is typically configured as a linear, open-ended 
antenna which is positioned near the maximum magnitude of the electric 
field in the waveguide 404 and oriented so that its length is parallel to 
the electric field vector in the waveguide 402. Properly configured, the 
launch may minimize the RF power loss and maximize the power delivered to 
and from the processing circuit. 
Although this configuration may be effective in some applications, the 
assembly includes several inherent drawbacks. For example, the 
configuration is costly, partly due to the number of components and the 
close tolerances for properly assembling the launch and waveguide. In 
addition, conventional launches or adapters require intermediate 
connection between the waveguide and the processing circuit. Consequently, 
additional connectors and cable are necessary to transmit or receive 
signals in conjunction with an actual processing circuit, such as a 
microstrip circuit board. These components not only add cost, but tend to 
degrade the performance and reliability of the launch. 
SUMMARY OF THE INVENTION 
An electromagnetic transducer system according to various aspects of the 
present invention includes an integrated waveguide or resonator, 
transducer, and processing circuitry. The transducer is disposed in the 
waveguide/resonator to detect or transmit electromagnetic waves, such as 
microwaves. The transducer is directly connected to the processing circuit 
within the integrated unit. 
Accordingly, an electromagnetic transducer system according to various 
aspects of the present invention does not suffer many of the disadvantages 
associated with conventional systems. The integration of the components 
tends to reduce the cost and size of the assembly, as several components 
of the conventional assembly are eliminated from the present 
configuration. In addition, the present system provides improved 
performance by eliminating components which tend to degrade the 
performance and reliability of the system. The present system further 
provides for simpler manufacturing and reliability.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS 
Referring now to FIG. 1, an electromagnetic wave transducer system 100 is 
suitably configured for exciting and/or collecting electromagnetic waves, 
particularly microwave radiation. For example, a microwave receiver 
according to various aspects of the present invention may be configured 
for use in conjunction with an airborne weather radar system. In general, 
a transducer system according to various aspects of the present invention 
suitably comprises: a front plate 102; a back plate 106; and a central 
section 104 disposed between the front plate 102 and the back plate 106. 
The central section 104 is suitably sandwiched or enclosed between the 
front plate 102 and the back plate 106. The front plate 102, central 
section 104, and back plate 106 are suitably assembled into a single unit, 
for example using fasteners, such as bolts (not shown), passed through 
axially aligned apertures formed through the various components. 
The transducer system 100 of the present embodiment is configured as a 
receiver, for example for use in conjunction with a weather radar system. 
It should be noted, however, that the present embodiment is provided 
solely for illustrative purposes, and that various aspects and principles 
used in accordance with the present embodiment may be applied to other 
configurations, such as transmitters, resonators, and the like. 
The front plate 102 suitably forms a portion of a waveguide or resonator 
for transmitting electromagnetic waves. The front plate 102 preferably 
provides physical and high frequency electromagnetic shielding for the 
central section 104. For example, the front plate 102 suitably includes a 
body portion 108 having a first waveguide aperture 110; at least one 
connection aperture 112; and a plurality of fastener apertures 114. The 
body portion 108 is suitably comprised of an electromagnetically 
reflective material, such as aluminum, to shield the central section 104 
from electromagnetic interference. Alternatively, the front plate 102 may 
be made of, for example, brass or copper, and may be plated, suitably with 
an electromagnetically reflective material such as cadmium, nickel, gold, 
or silver. 
The body portion 108 is suitably configured to conform to the shape and 
size of the central section 104. For example, the front plate 102 may be 
slightly larger than the central section 104 and include a peripheral rim 
116. The rim 116 of the front plate 102 suitably mates with a rim 118 of 
the back plate 106 to enclose the central section 104 within a cavity 
formed between the front plate 102 and the back plate 106. Alternatively, 
the rim 116 of the front plate 102 suitably engages an outer perimeter 120 
of the central section 104 so that the outer perimeter 120 of the central 
section 104 is sandwiched between the rim 116 of the front plate 102 and a 
corresponding rim 118 of the back plate 106. The front plate 102 may be 
created and formed in any suitable manner, such as by casting, machining, 
or forming. 
To transmit waves into the transducer system 100, the first waveguide 
aperture 110 is suitably formed through the front plate 102. The first 
waveguide aperture 110 is suitably configured to transmit waves of a 
selected mode and within a selected range of frequencies toward the 
central section 104. For example, to transmit TE.sub.10 signals having a 
center frequency of 9.5 GHz, the first waveguide aperture 110 suitably has 
a length of 0.9 inches and a width of 0.4 inches. 
The first waveguide aperture 110 is suitably surrounded by a groove 122 
formed in the front face 124 of the front plate 102 opposite the central 
section 104. The groove 122 is suitably configured to receive an 
additional waveguide or other attachment fixed to the front face of the 
front plate 102. For example, a resilient weather sealing gasket may be 
seated in the groove 122 and fixed between an external waveguide and the 
transducer system 100. 
As is described below, the first waveguide aperture 110, a second waveguide 
aperture 126 associated with the central section, and the back plate 
waveguide cavity 128 cooperate to define at least a portion of a waveguide 
or resonator in which a transducer 130 is disposed. In the present 
embodiment, the waveguide is configured as a sensor for the dominant 
(TE.sub.10) rectangular waveguide mode. It should be noted, however, that 
the waveguide is not confined to the configuration shown and discussed, 
but may suitably comprise any sort of waveguide, conventional or 
otherwise, for directing or controlling the propagation of the relevant 
waves. For example, the waveguide suitably comprises a rectangular 
waveguide as shown, or alternatively, may comprise a circular waveguide. 
The configuration, size, and shape of the waveguide may be adjusted 
according to the particular application and to accommodate the desired 
wavelength and mode of the relevant signal. 
The connection aperture 112 suitably provides access to electrical 
connections within the interior of the transducer system 100, such as 
connectors mounted on the central section 104, for example to read or 
provide data or apply power to the system 100. For example, a transducer 
system 100 according to various aspects of the present invention includes 
at least two connection apertures 112 including an SMA interface aperture 
112 and a multiprong connector aperture (not shown). The SMA interface 
aperture 112 suitably provides access to an SMA connector mounted on the 
central section 104 of the transducer system 100, such as for transferring 
raw data from the system 100 to external devices. Similarly, the 
multiprong connector aperture provides access to a multiprong connector 
connected to the central section 104. Any suitable number of connection 
apertures 112 may be formed in the front plate 102 to facilitate access to 
the interior of the transducer system 100. Alteratively, other connection 
mechanisms, such as through the back plate 106, along the side of the 
central section 104, through the rim of the front plate 102 or back plate 
106, and the like may be provided as desired. 
The back side of the front plate 102 (i.e., the side of the front plate 102 
facing the central section 104) is suitably contoured to accommodate 
components or other variations in a front face of the central section 104. 
Portions of the front plate 102 accommodating fastener apertures 114, 
however, are suitably substantially flush with the rim of the front plate 
102 to provide support for the fasteners and electrical connections 
between the front plate 102, central section 104, and back plate 106 where 
desired. In addition, the fastener apertures 114 are suitably lined with a 
conductive material. 
The back side of the front plate 102 also suitably includes at least two 
mating pin cavities (not shown) for receiving mating pins. As described 
below, the mating pins protrude from the front side of the back plate 106, 
through the mating pin apertures in the central section 104, and into the 
mating pin cavities. Alignment of the mating pins into the appropriate 
holes and cavities assures proper assembly and alignment of the front 
plate 102, back plate 106, and central section 104. 
The back plate 106 suitably includes a body portion 136 having a waveguide 
cavity 128, a plurality of fastener apertures 114, and a transducer 
connection channel 138. The back plate body portion 136 is suitably 
comprised of an electromagnetically reflective material, such as aluminum, 
to shield the central section 104 from high frequency electromagnetic 
interference. The body portion 136 is also suitably configured to conform 
to the shape and size of the central section 104 and the front plate 102. 
For example, like the front plate 102, the back plate 106 may be slightly 
larger than the central section 104 and include a peripheral rim 118. The 
rim 118 of the back plate 106 suitably mates with the rim 116 of the front 
plate 102 to enclose the central section 104 between the front plate 102 
and the back plate 106. Alternatively, the rim 118 of the back plate 106 
suitably engages an outer perimeter 120 of the central section 104 so that 
the outer perimeter 120 of the central section 104 is sandwiched between 
the rim 116 of the front plate 102 and the rim 118 of the back plate 106. 
The back plate 106 may be created in any suitable manner, such as by 
casting, machining, or forming. 
The back surface of the back plate 106 may include a series of vanes (not 
shown), for example integrally formed into the back surface. Such vanes 
are suitably configured to operate as a heat sink to transfer heat away 
from the central section 104 during operation. 
The waveguide cavity 128 is suitably configured to transmit waves of a 
selected frequency through the first waveguide aperture 110, past the 
central section 104, and to a rear wall 140 of the cavity. The remaining 
walls of the waveguide cavity 128 are preferably coplanar with the walls 
defining the first waveguide aperture 110. The rear wall 140 of the 
waveguide cavity 128, on the other hand, is preferably configured to 
reflect a maximum amount of the electromagnetic energy back into the 
waveguide cavity 128 and to the transducer 130. For example, the rear wall 
140 of the waveguide cavity 128 is suitably comprised of or coated with an 
electromagnetically reflective material to reflect incident 
electromagnetic energy. In the present embodiment, the waveguide cavity 
128 is configured to have a depth of one quarter of the wavelength of the 
relevant waves to generate constructive interference and maximize the 
amplitude of the field at the transducer 130. For optimum efficiency, the 
depth should be within 5-10 mils of the desired depth for a transducer 
system configured for an approximately 10 GHz frequency. As the relevant 
frequency increases, the tolerances of the depth of the waveguide cavity 
128 become more restrictive. 
The front side 142 of the back plate 106 (i.e., the side of the back plate 
106 facing the central section 104) is suitably contoured to accommodate 
components or other variations in a back face of the central section 104. 
Portions of the back plate 106 accommodating fastener apertures 114, 
however, are suitably flush with the rim 118 of the back plate 106 to 
provide support for the fasteners and electrical connections between the 
front plate 102, central section 104, and back plate 106 where desired. In 
addition, the fastener apertures 114 are suitably lined with conductive 
material. The front side 142 of the back plate 106 suitably includes at 
least two mating pins (not shown) to assure the proper alignment of the 
back plate 106 with the front plate 102 and central section 104. The 
mating pins are suitably rigidly formed in the material of the back plate 
106. 
The transducer connection channel 138 is suitably formed in a portion of 
the front face 142 of the back plate 106 adjacent the waveguide cavity 
128. In particular, the transducer connection channel 138 is configured to 
provide a cavity between the front face 142 of the back plate 106 and the 
back face of the central section 104 through which a transducer disposed 
in the waveguide may be connected to other components, such as on a 
printed wiring board included in the central section 104 as described 
below. It should be noted that the transducer connection channel 138 may 
alternatively be formed on the back face of the front plate 102, or on 
either face of the central section 104. In addition, the transducer 
connection channel 138 may be enclosed, for example by a strip of 
insulative material or the like, to create a transducer connection 
"tunnel". Regardless of its configuration or location, the transducer 
connection channel 138 provides a route through which a transducer 130 in 
the waveguide may be connected to components relatively remote from the 
waveguide without electrically contacting the front plate 102, back plate 
106, or other grounded or otherwise inappropriate parts of the transducer 
system 100. 
Referring now to FIGS. 1 and 2, the central section 104 suitably includes a 
central board 150, a second waveguide aperture 126, a transducer 130, a 
circuitry interface 152. The central board 150 is suitably formed 
according to the size, shape, and configuration of the front plate 102 and 
the back plate 106. The depth of the central board 150 may be varied 
according to the density and amount of circuitry to be placed on and 
within the printed wiring board, as described below. 
The central board 150 of the present transducer system 100 according to 
various aspects of the present invention includes a conventional printed 
wiring board 154, for example a laminated or monolithic wiring board for 
use in conjunction with microstrip wiring, of substantially identical 
width and length as the front plate 102 and back plate 106. The central 
board 150 suitably includes a plurality of fastener apertures 114 and 
mating pin apertures (not shown). The fastener apertures 114 suitably 
correspond to the fastener apertures 114 formed in the front plate 102 and 
back plate 106, and are configured to received bolts or an analogous 
fastening mechanism to fix the components together into a single unit. 
Similarly, the mating pin apertures are suitably configured to correspond 
to the mating pins protruding from the front face of the back plate 106. 
The mating pins suitably pass through the apertures and are received in 
the mating pin cavities defined in the back surface of the front plate 
102. 
The second waveguide aperture 126 is suitably formed through the central 
board 150. The second waveguide aperture 126 suitably corresponds to the 
first waveguide aperture 110 of the front plate 102 and the waveguide 
cavity 128 of the back plate 106 such that the edges of the second 
waveguide aperture 126 are coplanar with the corresponding walls of the 
first waveguide aperture 110 and the back plate waveguide cavity 128. 
The printed wiring board 154 is suitably configured to receive a plurality 
of discrete components 155 mounted on one or both of its faces. The 
printed wiring board 154 is suitably constructed according to techniques, 
materials, and structures disclosed in U.S. Pat. No. 5,311,406. In 
addition, the printed wiring board 154 is configured to include a 
plurality of conductive connections 157 routed between the various 
components 155 on the surfaces of the printed wiring board 154 and among 
the various layers in between the two exposed faces of the printed wiring 
board 154. The connections 157 are suitably formed in accordance with 
conventional techniques, such as those associated with microstrip routing. 
Thus, the pattern of the routing and coverage of the conductor material on 
the surface of the printed wiring board 154 is controlled, for example, by 
the mask artwork used to define the pattern on the printed wiring board 
154. 
In addition to the wiring 157 connecting the various components 155, the 
central section 104 further suitably includes a flange 160 formed around 
the perimeter of the second waveguide aperture 126 to form an electrical 
contact with the front plate 102 and the back plate 106. The flange 160 is 
suitably formed of an electrically conductive material, such as aluminum 
or copper. For example, the flange 160 may be formed using the same method 
and materials for defining the connections 157 on the printed wiring board 
154. The flange 160 further suitably extends over a portion of the printed 
wiring board 154, for example to surround and line the fastener apertures 
114 formed in the central board 150. The flange 160 suitably is formed on 
both faces of the central board 150. 
In addition, the fastener apertures 114 and mating pin apertures are 
similarly surrounded and lined with conductive material. The conductive 
material surrounding and lining the fastener apertures 114, mating pin 
apertures, and the second waveguide aperture 126 are suitably connected 
together, for example via wiring printed on the printed wiring board 154. 
Also, both sides of the electrical conductor of the flange 160 are 
connected with a wrap around conductor extending around the circumference 
of the second waveguide aperture 126. The flange 160 is further suitably 
configured to contact the portions of the back face of the front plate 102 
that are flush with the rim 116 of the front plate 102, and similarly, 
with the portions of the front face of the back plate 106 that are flush 
with the rim 118 of the back plate 106. Consequently, the front plate 102, 
back plate 106, the flange 160, and the fasteners apertures 114 are all 
suitably connected to a single electrical potential. 
The transducer 130 is suitably configured in the present embodiment to 
sense electromagnetic waves traveling in the second waveguide aperture 126 
and waveguide cavity 128 and generate corresponding electrical signals, 
which are suitably transmitted to components 155 mounted on the printed 
wiring board 154. Alternatively, the transducer 130 may be configured as 
an emitter to generate electromagnetic waves in response to electric 
signals and transmit them via the waveguide. The transducer 130 is 
suitably connected to the components 155 on the printed wiring board 154 
to provide or receive signals. 
In the present embodiment, the transducer 130 comprises an E-field probe 
configured to detect E-field signals of electromagnetic waves traveling 
through the waveguide. The transducer 130 is suitably disposed in the 
second waveguide aperture 126 or waveguide cavity 128. Preferably, the 
transducer 130 is positioned about a quarter of a wavelength away from the 
rear wall of the waveguide cavity 128 to maximize the constructive 
interference effects of signals reflecting from the rear wall towards the 
transducer 130. For example, for microwave frequencies of 9.5 GHz, the 
transducer 130 is suitably positioned about 205 mils from the rear wall of 
the waveguide cavity 128. 
For example, the transducer 130 suitably comprises a conductive material 
disposed on, around, or in a cross member 162 extending across the second 
waveguide aperture 126 formed in the central board 150. For example, the 
conductive material may be formed on the cross member 162 using the same 
process for generating the connections 157 and the flange 160 on the 
printed wiring board. Referring now to FIGS. 3A-B, to create a transducer 
130, the conductive material is disposed on the cross member 162. A 
portion of the conductive material is removed from the area between the 
transducer 130 and the flange 160 and the edge of the second waveguide 
aperture 126 to electrically isolate the transducer 130 from the flange 
160 material surrounding the perimeter of the second waveguide aperture 
126. 
In one embodiment, the transducer 130 is suitably formed only on one side 
of the cross member. To increase the bandwidth of the transducer 130, 
however, the transducer may be thickened. For example, to provide greater 
thickness to the transducer 130, conductive material may be wrapped around 
the cross member 162 so that the conductive material encircles a portion 
of the cross member 162. For example, conductive material may be wrapped 
around the cross member by plating after an etching process. In addition, 
the conductive material is removed from the remaining part of the cross 
member 162 from which the transducer 130 is absent. Further, the 
transducer 130 suitably includes a plurality of small, plated-through 
holes 166 to reduce the effects of radial currents induced in the 
transducer 130 by the electromagnetic waves. 
It should be noted that it is possible to locate the cross member 162 and 
the transducer 130 on the front plate 102 or the back plate 106. In the 
present embodiment, the cross member 162 is comprised of the same material 
as the printed wiring board 154. In particular, the second waveguide 
aperture 126 according to various aspects of the present invention 
suitably comprises two separate apertures, separated by the cross member 
162. 
It should be noted that although the present embodiment illustrates only 
one potential configuration of the transducer 130, the transducer 130 may 
be positioned or formed in any manner. For example, the cross member 162 
may be replaced with a single protrusion from the side of the second 
waveguide aperture 126 on which the transducer 130 is formed. In addition, 
the transducer 130 suitably comprises a solid metal transducer 130 or 
other type of probe. The orientation and position of the transducer 130 
may also be adjusted according to the desired mode or other 
characteristics of the electromagnetic waves or the system 100. Also, 
multiple transducers 130 may be provided for sensing multiple wavelengths 
or higher order modes. 
By mounting the transducer 130 on the cross member, the lateral position of 
the transducer with respect to the wave propagation direction is 
determined according to the process used to create the transducer 130, 
such as a conventional circuit printing process. Because such techniques 
are typically highly precise, the position of the transducer 130 may be 
selected with great precision. Further, the position of the transducer 130 
with respect to the rear wall of the waveguide cavity 128 is determined 
according to the depth of the waveguide cavity 128. Modern machining tools 
are capable of easily providing a precise depth of the waveguide cavity 
128. Consequently, the position of the transducer 130 in the waveguide 
cavity may be easily fixed with high accuracy and precision. 
The transducer 130 is suitably connected to the components 155 of the 
printed wiring board 154 via the circuitry interface 152, such as an 
electrical connection, formed on one of the faces of the central board 150 
and through the transducer connection channel 138. In particular, the 
flange 160 material is suitably removed from the central board 150 in an 
area adjacent the transducer 130 and cross member 162. The printed wiring 
on the printed wiring board 154 suitably includes an electrically 
conductive connection 152 along the transducer connection channel 138 
between the transducer 130 and the relevant components 155 and through the 
area from which the flange 160 material is removed. Consequently, the 
transducer 130 may be connected to the relevant components without 
electrically contacting the flange 160, the front plate 102, or the back 
plate 106. In addition, the connector 152 may be selected to match the 
impedance of the relevant components 155. 
The front plate 102, central section 104, and back plate 106 are suitably 
fastened together to form a single unit. For example, a bolt may be 
received through each of said fastener apertures 114 formed in the front 
plate 102, central section 104, and back plate 106. The fastener apertures 
114 are suitably threaded to engage threads formed on the bolts. 
Alternatively, the bolt threads suitably engage corresponding nuts on the 
opposite side of the transducer system 100, for example on the back face 
of the back plate 106. The bolts may be electrically conductive to further 
maintain electrical communication between the front plate 102, back plate 
106, and grounded portions of the central section 104. 
In operation, the transducer system 100 according to the present embodiment 
emits or collects electromagnetic waves (or components of electromagnetic 
waves) and transmits corresponding signals to or from the electrical 
components on the printed wiring board 154. As electromagnetic waves 
propagate towards the front plate 102 of the system 100, a portion of the 
wave enters the first waveguide aperture 110 of the front plate 102 and 
propagates past the transducer 130 disposed in the second waveguide 
aperture 126 of the central board 150. As the waves intercept the 
transducer 130, current is generated in the transducer 130, which creates 
a voltage in the transducer connector 152. The voltage is suitably sensed 
by the electrical components and processed conventionally. Meanwhile, 
portions of the electromagnetic waves that do not enter the first 
waveguide aperture 110 are reflected by the front plate 102 and back plate 
106, thus reducing electrical interference. 
Thus, an electromagnetic transducer system 100 according to various aspects 
of the present invention may comprise a more cost effective and reliable 
transducer system having improved performance. In particular, a transducer 
system 100 according to various aspects of the present invention may be 
manufactured using industry standard processes without the need for 
specialized machinery or tools. In addition, factory adjustments are not 
required. The location of the transducer element 130 with respect to the 
rear wall of the waveguide cavity is easily maintained by properly 
machining the back plate 106, and the lateral position of the transducer 
130 element is determined according to the artwork used in the printing 
process. 
Further, the absence of the coaxial connections required by the prior art 
further reduce the size of the transducer system 100, which is crucial in 
many applications such as avionics. Also, increasing the thickness of the 
transducer, for example by wrapping conductor around the cross member, 
provides superior bandwidth to the transducer 130. 
While the principles of the invention have now been made clear in 
illustrative embodiments, it will be immediately obvious to many skilled 
in the art that many modifications of structure, arrangements, 
proportions, the elements, materials and components, used in the practice 
of the invention which are particularly adapted for a specific environment 
and operating requirements may be made without departing from those 
principles.