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When
controlling the Companion with the Companion
Data Logger™
via PC, the user may perform an incremental scan which steps one-by-one
through the channels of the entire band.
-------------------------------Companion
1 SECOND REPORT-------------------------------
ITEM
/ DATE / GPS / MARKER / FREQ 1 / 64 MEASUREMENTS / FREQ 2 / 64 /
MEASUREMENTS
- Incremental
Scan (using PC software): steps channel-by-channel through
entire band
- Table
Scan (using PC or Companion keypad): scans through a list
of user-defined channels (80 channels per Rx)
-
- 40
Lambda Averaging in Chameleon CW
- In some
instances it is desirable to reduce the effect of fading in
the analysis of transmitted signal propagation. The 40 Lambda
averaging technique is a known scheme for accomplishing this
goal.
- Berkeley
Varitronics Systems, Inc. has support for this type of averaging
in ChameleonCW,
the universal data conversion tool, starting with version 1.53.
This tool converts data that has been collected using Berkeley's
CW line of receiver equipment. It has been concluded
that the sampling rate needed to suppress the Rayleigh fading
of a propagated signal is:
36-50 samples/ 40 wavelengths
- An explanation
of this theory can be found in the book titled "Mobile
Cellular Telecommunications Systems" by William C. Y. Lee.
Therefore, assuming that the sampling rate of the receiving
equipment is greater than the number of samples required by
the 40 Lambda theory, the samples maybe reduced to the needed
number of samples per second through averaging.
- Example:
Signal frequency = 800MHz.
Drive-study speed = 100KM/H.
l = Wavelength of signal
v = Velocity of signal
f = frequency of signal
- Therefore,
l=v/f. l=(300000000m/s)/(800000000/s).
- l = .375
meters
-
- Now,we
will take 40 samples per 40 wavelengths. Therefore, we need
the time duration for 1 wavelength.
T = time duration to drive 1 wavelength.
V = Velocity of vehicle.
- V = (100km/h)(1000m/km)/(3600s/h)
= 27.78 m/s
T = (l) / V = (.375m) / (27.78m/s)
T = .0135 seconds
- S = Sampling
rate needed.
- S = 1 /
.0135 s = 74.08 samples / second
-
-
- Chameleon
CW 40 Lambda Conversion
- The BVS
Chameleon CW data conversion tool has an option for averaging
based on the 40 Lambda theory. This option is available for
data collected via the BVS Panther 4-channel receiver.
- In the
FAST mode of each piece of equipment, 512 samples per second
are taken. The BVS Chameleon CW then reduces this data to the
appropriate amount of samples required by the 40 Lambda criteria.
The user only has to input the average drive speed of the vehicle.
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