| Optimization routines are typically developed in-house, allowing
MEI to perform beyond the use of canned, off-the-shelf programs widely used by
others. A rudimentary, but colorful example of a manual antenna optimization
chart for a similar 3 element PCS array can be found below. This is actually an
intermediate output of an MEI generated optimizing program, used to verify the
final computer output (computers are wonderful machines that will always give
you an answer, no matter how meaningful or meaningless it is. Thus, it is
always prudent to commit such results to the scrutiny of experience, intuition
and common sense.) In the chart, warmer colors represent stronger signals, the
Y-axis represents the elevation angle (nadir at bottom) and the X-axis is the
parameter being optimized (in the case below, element spacing.)
Once an Antenna is electrically designed and optimized, its
mechanical design is reviewed, changed and documented accordingly. Prototypes
are then created against drawings. Below is a an example of a PCS antenna
drawing and the actual prototype. All parts and labor comprising the prototype,
except for the type-N connector and the black anodized flange finish, were
produced at MEI.
After prototypes are made, MEI is adequately equipped for
testing almost any antenna parameter, within the spectrum of 90 MHz to 26 GHz.
More information about antenna testing capabilities at MEI exists on this site,
click here (Anechoic
Chamber page.)
2) Radios & RF
Electronics:
MEI's strengths in Antenna design and development capabilities
extend well into active and passive RF & Microwave circuits, subsystems and
full systems. Armed with vast experience and know-how (approx. 50 years between
the 2 key young RF Engineers alone), linear and non-linear computer simulators,
the ability to develop in-house custom simulation and optimization software,
and a well equipped laboratory, it can develop almost any wireless device or
system. This, coupled with its Signal Processing capabilities, affords MEI
unique means to create over-the-air data out to data in links and
sub-systems.
Below are screen captures of four simulation projects shown
above:
In order to make sure that a design is stable enough for high
yield production, MEI commits all of its designs to a stability test. A widely
used test technique in circuit designs is the Montecarlo method, in which
selected component values (tolerance) and paramemters (transmission line
lengths, temperature, etc.) are allowed to vary, subject to a set of
statistical constraints (Gaussian distribution, etc.), while monitoring yield.
For example, consider the Nominal response of a
Notch Filter design. The design performed very well in a production run of 1000
pieces with the chosen components as seen in the Montecarlo results. In addition to the Montecarlo
method, MEI submits most of its designs to parametrical checks using in-house
generated codes. This practice reduces both Engineer and Client risks. At
Microwave frequencies, typically, concepts are verified by in-house prototyping
of the key circuits at the design level. Below is a picture of a machined part
actually used in an MEI microwave prototype.
As a sample of prior work, you may see copyright pictures and
basic specifications of an UHF transmitter and
receiver and an S-band IEEE-802.11 compliant Spread
Spectrum Transceiver/MODEM.
Passive networks often designed include: impedance matchers,
hybrid couplers, directional couplers, filters, phasing couplers and power
splitters and combiners.
3) Wireless Communications
Systems:
The unique strengths outlined above integrate to offer
formidable System Design and Support. Regularly, client firms request
assistance from MEI in the overall engineering of an RF Link or Wireless
Network. For example, the analysis in the two pictures below showed that an
existing Transmitter-Receiver pair failed to reliably maintain communications
in more than 70% of its range (in the lower chart, the darkened areas mean that
the link is successful; the colors in the upper graph reveal the magnitude of
the success or failure.) To view full screen images of these charts, right
click on the chart of interest and left click on "View Image" in the menu, or
just click on the image.
The parameters swept by MEI in the generation of the above
pictures were distance (X-axis) and central site height (Y-axis.) In the next 2
images, similar charts were created for a link fixed at its maximum range
(distance), while both devices were rotated, producing all possible
combinations of antenna interactions, for a given orientation of the wireless
units. In the lower graph, blue means success and red means failure to
communicate reliably.
A more familiar example may be found in the picture below, where
MEI's Smooth Earth model was used to evaluate a low power radio data link, with
a receiver sensitivity corresponding to fixed threshold 4-FSK demodulation
(this is actually a made-up example based on a different real-life problem.)
The red and blue solid traces correspond to antenna full height and half
heights respectively. The system has a range of about 350 meters, but it can be
seen that "more height" is not necessarily best within the range of 125 to 250
m. To view a full screen image of this chart, right click on the chart and left
click on "View Image" in the menu, or just click in the image.
Oftentimes, the experience, specialized knowledge and tools of a
professional results in a significant project savings for problems involving
Wireless Communications Systems. Use of canned software and traditional Rules
of Thumb is prevalent in the field. Examples above show significant failures
resulting from the misuse of theoretical models and computer programs.
Fortunately, the field enjoys the participation of a number of qualified and
reputable Professionals who can aide you in your current and upcoming projects.
MEI would be happy to review such requirements and problems, and offer its
support to your programs.
Furthermore, MEI can improve or even double the range of a
low-power communications system. To learn how MEI can expand your wireless
product's capabilities, click here
(Wireless OEMs only).
MEI is also competent in the development of Software and Firmware for Signal
Processing, Real-Time, Embedded, Metrology and other Scientific Applications. For
more information, visit this site's Software Page.
If radio
traffic is your concern, MEI has developed software to simulate the
transient and steady state performance of a communications system under
adjustable loading conditions. With the above, the effect of predicted traffic
can be studied over a number of hours, days or even weeks (data resolution is
one minute.) Using its software and knowledge of your wireless network's
operating rules, MEI can help you determine your communications system
breakdown, performance contours and which network rule changes would extend the
capacity or reliability of your system. |
