|
Newsletter
- Edition Six
|
October
15, 2008
|
|
|
|
|
SFN 2008 - Washington, D.C. - From
November 15th - 19th, 2008 Neuralynx will be attending the annual
Society for Neuroscience meeting. Our Booth Number is #533
and we have a new exciting look. There will be many
representatives from our company, we'd love for you to drop by and say
"hi"!
Bozeman, MT - October 2008
- Please be sure to update both billing/shipping addresses within your
system. All phone numbers and email contact addresses remain the
same. Our new address is: 105 Commercial Dr. Bozeman,
MT 59715
|
|
|
TECHNICAL TIP OF THE
DAY - Digital Filtering in Cheetah
by: Rob Van
den Berg
The Cheetah DAS utilizes two types of digital filters for online signal
processing of Digital Lynx data. A Finite Impulse Response (FIR)
filter is used for all high-cut filters and low-cut filters above
50Hz. For low-cut filters below 50Hz a DC Offset (DCO) filter is
implemented.
FIR filters implemented in the Cheetah DAS are designed to be linear
phase. This means that the output of the FIR is delayed from the
input, but the delay is equal for all frequencies so the phase is not
distorted. The number of FIR taps/coefficients determines the
roll-off of the filter and the delay -- more taps/coefficients result
in a steeper roll-off with the sacrifice of CPU power, memory, and a
longer delay. The delay can be calculated with the formula:
Delay(s) = (Taps - 1) / (Freq(Hz) * 2)
Since the filtering is done prior to sub-sampling, the frequency at
which the data is filtered is always 32,556Hz. Therefore, the
delay equation becomes:
Delay(s) = (Taps - 1) / 65112
The FIR filter taps/coefficients offered in the Cheetah DAS are chosen
to keep CPU usage low and minimize delay for real-time feedback to
neural signals.
The DCO filter implemented at lower frequencies is a basic
sliding-window average in which the window length is determined by the
cutoff frequency. FIR filters are not used for lower frequencies
because a very large number of coefficients are required to obtain
satisfactory results when the desired cutoff frequency is a small
fraction of the sampling frequency. For online processing this
would result in significant latency.
It is important to have the delay (number of taps) of all spike
channels be consistent throughout your setup in order to keep timing
between spike channels consistent. If millisecond scale timing
relationships between CSC and spike channels are necessary then all CSC
and spike channels must have the same number of taps in the filters.
If you have questions on this system feature feel free to contact
Technical Support at Support@Neuralynx.com or give us a call.
|
|
TRACKING
THE STATUS OF YOUR ORDER
For
ordering, checking up on an order's status, or shipping details, please
be sure to use our sales@neuralynx.com
email address.
|
|
TECH
SUPPORT ISSUES
For
tech support questions, please be sure to use our support@neuralynx.com
email address.
|
|
Receiving
Emails/Updates/Newsletters
If you
do not wish to receive the newsletters, but do wish to
receive only our product updates, please email daphne@neuralynx.com and put in the Subject
line "Only product updates".
If you do not wish to receive any of our updates/newsletters please use
the "unsubscribe" option listed at the bottom of this
newsletter.
If you wish to add a member of your team to our newsletter/updates,
please simply forward this email and they can add themselves with the
"Join Our Mailing List" icon.
|
|
|
|
THE
NEURALYNX MISSION STATEMENT
"We
are the preferred provider of high quality electrophysiology hardware
and software solutions for the neuroscience research community and the
specific markets of epilepsy research and multi-unit neurosurgery
support."
|
|
©
Copyright 2008, Neuralynx,Inc., All Rights Reserved.
105
Commercial Dr., Bozeman, MT 59715
Phone:
(406) 585-4542 Fax: (406) 585-9034
sales@neuralynx.com
|
|
