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Discussion and technical support related to USRP, UHD, RFNoC
View all threadsUsable bandwidth of X300 USRP with UBX-160 daughterboard
Point taken. At this stage we are mainly interested in straight IQ
recording & playback with minimal processing. However, in the future it
would be desirable to be able to display a real-time spectrum trace &
waterfall plot during recording/playback, using GNU Radio or something like
it.
As you suggest, I am assuming our host machine will need a dual-10Gbe
adaptor card and a high-spec CPU, memory, SSD etc. This is a complex
procurement exercise all by itself.
On Wed, 19 Feb 2025 at 10:58, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 19:26, Brendan Horsfield wrote:
I thought your name sounded familiar! 🙂
Overall the X310+UBX-160 appears to be a good fit to our requirements. My
original question was really about ensuring that our host PC & network
interface have sufficient bandwidth to ingest the IQ data from a pair of
UBX-160s. It would be nice (although not essential) if we could run one
channel at 100 Msps, and the other at 200 Msps, to reduce the bandwidth
requirements on the backend hardware.
You'd need to have separate streamers to support two different sample
rates, and two 10Gbe interfaces.
But in terms of "what kind of PC hardware do I need?". There's no
closed-form answer to that question. There's no
handy-dandy "engineering worksheet" that tells you how much "grunt" you
need for different DSP "flows" at
a given sample-rate--so very much depends on what you're doing, and how
you're doing it. Generally, as you scale up
in sample-rate, you have to scale up in:
o CPU base clock rate
o Memory bandwidth
o Number of CPUs
On Wed, 19 Feb 2025 at 10:17, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 19:13, Brendan Horsfield wrote:
Thanks for the suggestion about the noise source -- that's what I would
normally do. Unfortunately I haven't actually purchased the hardware yet
-- I was hoping to clarify this issue before raising a purchase order.
Perhaps I should follow this up with one of the application engineers at
NI? They might have access to an X310+UBX-160 system that they can use to
answer my question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
I actually do work for NI on USRP devices (on a very very very part-time
basis). My X310 is currently elsewhere, and not populated
with a UBX-160.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is not clear from the
X300 documentation how sharp those filters are. Can you tell me how wide
the transition band is at the lower sample rates?
To give you some context, I would like to use an X300 (or X310) with a
UBX-160 daughterboard to digitise the entire 2.4 GHz Wi-Fi band, which is
83.5 MHz wide. Ideally I would like to use a sample rate of 100 Msps to
minimise the data rate between the USRP and the host PC. However, before I
do this I need to be certain that the usable bandwidth at this sample rate
will be greater than 83.5 MHz. Is this information documented somewhere?
It somewhat depends on the decimation. If the decimation has a factor
of two or 4, the edge roll-off is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a less-desirable
pass-band.
But I don't know, precisely, what the transition band is in the "nicer"
filter shapes.
If you have an X310+UBX-160, you can always just use a noise source, and
measure it yourself to see if it's appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech patchvonbraun@gmail.com
wrote:
There will always be some edge roll off. Decimation includes filtering
and those filters cannot be infinitely steep.
Sent from my iPhone
On Feb 18, 2025, at 2:12 AM, Brendan Horsfield <
brendan.horsfield@vectalabs.com> wrote:
Hi All,
I have a question about the usable bandwidth of the X300 USRP /
UBX-160 daughterboard combo at sampling rates below 200 Msps:
As I understand it, the UBX-160 receiver has an analog (hardware)
filter before the ADC that limits the usable bandwidth to 160 MHz, while
the ADC runs at 200 Msps. Therefore the usable bandwidth is around 80% of
the sample rate.
My question is: What is the usable bandwidth at lower sampling
rates? Does the 80% factor always apply?
For example, if I set the decimation factor to 4, so that my sampling
rate is 50 Msps, does this mean that the usable bandwidth will be 40 MHz?
Thanks & Regards,
Brendan.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
On 18/02/2025 21:45, Brendan Horsfield wrote:
Point taken. At this stage we are mainly interested in straight IQ
recording & playback with minimal processing. However, in the future
it would be desirable to be able to display a real-time spectrum trace
& waterfall plot during recording/playback, using GNU Radio or
something like it.
As you suggest, I am assuming our host machine will need a dual-10Gbe
adaptor card and a high-spec CPU, memory, SSD etc. This is a complex
procurement exercise all by itself.
My understanding (and I haven't played with them) is that NVME SSDs are
among the fastest. Performance up to a few GByte/Sec
on write is possible, although I don't know if it can be sustained
at those rates, or whether it's "bursty".
I've been able to produce "real-time" spectral displays on 10yo
dual-Xeon hardware at 100Msps, but only using the
kind of "stuttered" display approach that Gnu Radio FFT displays
often use, where most of the data is discarded. Often,
that's all that's needed to show a quick summary of the spectrum.
On your other question, about transition bandwidth, I don't have a
direct answer, but on an N310 I measured the roll-off
as a fraction of the overall bandwidth, and it is about 12.5%. That
doesn't necessarily translate to the X310, but the
DDC implementation is of the same generation.
On Wed, 19 Feb 2025 at 10:58, Marcus D. Leech
patchvonbraun@gmail.com wrote:
On 18/02/2025 19:26, Brendan Horsfield wrote:
I thought your name sounded familiar! 🙂
Overall the X310+UBX-160 appears to be a good fit to our
requirements. My original question was really about ensuring
that our host PC & network interface have sufficient bandwidth to
ingest the IQ data from a pair of UBX-160s. It would be nice
(although not essential) if we could run one channel at 100 Msps,
and the other at 200 Msps, to reduce the bandwidth requirements
on the backend hardware.
You'd need to have separate streamers to support two different
sample rates, and two 10Gbe interfaces.
But in terms of "what kind of PC hardware do I need?". There's no
closed-form answer to that question. There's no
handy-dandy "engineering worksheet" that tells you how much
"grunt" you need for different DSP "flows" at
a given sample-rate--so very much depends on what you're doing,
and how you're doing it. Generally, as you scale up
in sample-rate, you have to scale up in:
o CPU base clock rate
o Memory bandwidth
o Number of CPUs
On Wed, 19 Feb 2025 at 10:17, Marcus D. Leech
<patchvonbraun@gmail.com> wrote:
On 18/02/2025 19:13, Brendan Horsfield wrote:
Thanks for the suggestion about the noise source -- that's
what I would normally do. Unfortunately I haven't actually
purchased the hardware yet -- I was hoping to clarify this
issue before raising a purchase order.
Perhaps I should follow this up with one of the application
engineers at NI? They might have access to an X310+UBX-160
system that they can use to answer my question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
I actually do work for NI on USRP devices (on a very very
very part-time basis). My X310 is currently elsewhere, and
not populated
with a UBX-160.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech
<patchvonbraun@gmail.com> wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is not
clear from the X300 documentation how sharp those
filters are. Can you tell me how wide the transition
band is at the lower sample rates?
To give you some context, I would like to use an X300
(or X310) with a UBX-160 daughterboard to digitise the
entire 2.4 GHz Wi-Fi band, which is 83.5 MHz wide.
Ideally I would like to use a sample rate of 100 Msps
to minimise the data rate between the USRP and the host
PC. However, before I do this I need to be certain
that the usable bandwidth at this sample rate will be
greater than 83.5 MHz. Is this information documented
somewhere?
It somewhat depends on the decimation. If the
decimation has a factor of two or 4, the edge roll-off
is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a
less-desirable pass-band.
But I don't know, precisely, what the transition band is
in the "nicer" filter shapes.
If you have an X310+UBX-160, you can always just use a
noise source, and measure it yourself to see if it's
appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech
<patchvonbraun@gmail.com> wrote:
There will always be some edge roll off. Decimation
includes filtering and those filters cannot be
infinitely steep.
Sent from my iPhone
On Feb 18, 2025, at 2:12 AM, Brendan Horsfield
<brendan.horsfield@vectalabs.com> wrote:
Hi All,
I have a question about the usable bandwidth of
the X300 USRP / UBX-160 daughterboard combo at
sampling rates below 200 Msps:
As I understand it, the UBX-160 receiver has an
analog (hardware) filter before the ADC that limits
the usable bandwidth to 160 MHz, while the ADC runs
at 200 Msps. Therefore the usable bandwidth is
around 80% of the sample rate.
My question is: What is the usable bandwidth at
lower sampling rates? Does the 80% factor always
apply?
For example, if I set the decimation factor to 4,
so that my sampling rate is 50 Msps, does this mean
that the usable bandwidth will be 40 MHz?
Thanks & Regards,
Brendan.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to
usrp-users-leave@lists.ettus.com
Just to clarify one point: How do you define the start of the transition
region? Do you go from the 3 dB corner frequency, or something else, like
the equiripple bandwidth of the FIR filter?
On Wed, 19 Feb 2025 at 13:11, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 21:45, Brendan Horsfield wrote:
Point taken. At this stage we are mainly interested in straight IQ
recording & playback with minimal processing. However, in the future it
would be desirable to be able to display a real-time spectrum trace &
waterfall plot during recording/playback, using GNU Radio or something like
it.
As you suggest, I am assuming our host machine will need a dual-10Gbe
adaptor card and a high-spec CPU, memory, SSD etc. This is a complex
procurement exercise all by itself.
My understanding (and I haven't played with them) is that NVME SSDs are
among the fastest. Performance up to a few GByte/Sec
on write is possible, although I don't know if it can be sustained at
those rates, or whether it's "bursty".
I've been able to produce "real-time" spectral displays on 10yo dual-Xeon
hardware at 100Msps, but only using the
kind of "stuttered" display approach that Gnu Radio FFT displays often
use, where most of the data is discarded. Often,
that's all that's needed to show a quick summary of the spectrum.
On your other question, about transition bandwidth, I don't have a direct
answer, but on an N310 I measured the roll-off
as a fraction of the overall bandwidth, and it is about 12.5%. That
doesn't necessarily translate to the X310, but the
DDC implementation is of the same generation.
On Wed, 19 Feb 2025 at 10:58, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 19:26, Brendan Horsfield wrote:
I thought your name sounded familiar! 🙂
Overall the X310+UBX-160 appears to be a good fit to our requirements.
My original question was really about ensuring that our host PC & network
interface have sufficient bandwidth to ingest the IQ data from a pair of
UBX-160s. It would be nice (although not essential) if we could run one
channel at 100 Msps, and the other at 200 Msps, to reduce the bandwidth
requirements on the backend hardware.
You'd need to have separate streamers to support two different sample
rates, and two 10Gbe interfaces.
But in terms of "what kind of PC hardware do I need?". There's no
closed-form answer to that question. There's no
handy-dandy "engineering worksheet" that tells you how much "grunt" you
need for different DSP "flows" at
a given sample-rate--so very much depends on what you're doing, and how
you're doing it. Generally, as you scale up
in sample-rate, you have to scale up in:
o CPU base clock rate
o Memory bandwidth
o Number of CPUs
On Wed, 19 Feb 2025 at 10:17, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 19:13, Brendan Horsfield wrote:
Thanks for the suggestion about the noise source -- that's what I would
normally do. Unfortunately I haven't actually purchased the hardware yet
-- I was hoping to clarify this issue before raising a purchase order.
Perhaps I should follow this up with one of the application engineers at
NI? They might have access to an X310+UBX-160 system that they can use to
answer my question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
I actually do work for NI on USRP devices (on a very very very part-time
basis). My X310 is currently elsewhere, and not populated
with a UBX-160.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is not clear from the
X300 documentation how sharp those filters are. Can you tell me how wide
the transition band is at the lower sample rates?
To give you some context, I would like to use an X300 (or X310) with a
UBX-160 daughterboard to digitise the entire 2.4 GHz Wi-Fi band, which is
83.5 MHz wide. Ideally I would like to use a sample rate of 100 Msps to
minimise the data rate between the USRP and the host PC. However, before I
do this I need to be certain that the usable bandwidth at this sample rate
will be greater than 83.5 MHz. Is this information documented somewhere?
It somewhat depends on the decimation. If the decimation has a factor
of two or 4, the edge roll-off is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a less-desirable
pass-band.
But I don't know, precisely, what the transition band is in the "nicer"
filter shapes.
If you have an X310+UBX-160, you can always just use a noise source,
and measure it yourself to see if it's appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech patchvonbraun@gmail.com
wrote:
There will always be some edge roll off. Decimation includes filtering
and those filters cannot be infinitely steep.
Sent from my iPhone
On Feb 18, 2025, at 2:12 AM, Brendan Horsfield <
brendan.horsfield@vectalabs.com> wrote:
Hi All,
I have a question about the usable bandwidth of the X300 USRP /
UBX-160 daughterboard combo at sampling rates below 200 Msps:
As I understand it, the UBX-160 receiver has an analog (hardware)
filter before the ADC that limits the usable bandwidth to 160 MHz, while
the ADC runs at 200 Msps. Therefore the usable bandwidth is around 80% of
the sample rate.
My question is: What is the usable bandwidth at lower sampling
rates? Does the 80% factor always apply?
For example, if I set the decimation factor to 4, so that my
sampling rate is 50 Msps, does this mean that the usable bandwidth will be
40 MHz?
Thanks & Regards,
Brendan.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
Hi Brendan,
80% is an excellent rule of thumb for both the analog and digital filters.
If you use "odd" decimations (e.g., you try and capture at 66 Msps), then
the digital filter response is worse, but if you capture at say 50 Msps (at
a 200 Msps sampling rate) then you have two nice half-band filters doing
the resampling. The filter taps for those half-bands are in the code, if
you want the raw numbers without running UHD then we can pick them out for
you.
Also thanks to everyone here with your suggestions!
--M
On Wed, Feb 19, 2025 at 1:13 AM Brendan Horsfield <
brendan.horsfield@vectalabs.com> wrote:
Thanks for the suggestion about the noise source -- that's what I would
normally do. Unfortunately I haven't actually purchased the hardware yet
-- I was hoping to clarify this issue before raising a purchase order.
Perhaps I should follow this up with one of the application engineers at
NI? They might have access to an X310+UBX-160 system that they can use to
answer my question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech patchvonbraun@gmail.com
wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is not clear from the X300
documentation how sharp those filters are. Can you tell me how wide the
transition band is at the lower sample rates?
To give you some context, I would like to use an X300 (or X310) with a
UBX-160 daughterboard to digitise the entire 2.4 GHz Wi-Fi band, which is
83.5 MHz wide. Ideally I would like to use a sample rate of 100 Msps to
minimise the data rate between the USRP and the host PC. However, before I
do this I need to be certain that the usable bandwidth at this sample rate
will be greater than 83.5 MHz. Is this information documented somewhere?
It somewhat depends on the decimation. If the decimation has a factor of
two or 4, the edge roll-off is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a less-desirable
pass-band.
But I don't know, precisely, what the transition band is in the "nicer"
filter shapes.
If you have an X310+UBX-160, you can always just use a noise source, and
measure it yourself to see if it's appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech patchvonbraun@gmail.com
wrote:
There will always be some edge roll off. Decimation includes filtering
and those filters cannot be infinitely steep.
Sent from my iPhone
On Feb 18, 2025, at 2:12 AM, Brendan Horsfield <
brendan.horsfield@vectalabs.com> wrote:
Hi All,
I have a question about the usable bandwidth of the X300 USRP /
UBX-160 daughterboard combo at sampling rates below 200 Msps:
As I understand it, the UBX-160 receiver has an analog (hardware)
filter before the ADC that limits the usable bandwidth to 160 MHz, while
the ADC runs at 200 Msps. Therefore the usable bandwidth is around 80% of
the sample rate.
My question is: What is the usable bandwidth at lower sampling
rates? Does the 80% factor always apply?
For example, if I set the decimation factor to 4, so that my sampling
rate is 50 Msps, does this mean that the usable bandwidth will be 40 MHz?
Thanks & Regards,
Brendan.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
On 19/02/2025 02:22, Brendan Horsfield wrote:
Just to clarify one point: How do you define the start of the
transition region? Do you go from the 3 dB corner frequency, or
something else, like the equiripple bandwidth of the FIR filter?
I just did it visually on an FFT display from the 3dB corner.
On Wed, 19 Feb 2025 at 13:11, Marcus D. Leech
patchvonbraun@gmail.com wrote:
On 18/02/2025 21:45, Brendan Horsfield wrote:
Point taken. At this stage we are mainly interested in straight
IQ recording & playback with minimal processing. However, in the
future it would be desirable to be able to display a real-time
spectrum trace & waterfall plot during recording/playback, using
GNU Radio or something like it.
As you suggest, I am assuming our host machine will need a
dual-10Gbe adaptor card and a high-spec CPU, memory, SSD etc.
This is a complex procurement exercise all by itself.
My understanding (and I haven't played with them) is that NVME
SSDs are among the fastest. Performance up to a few GByte/Sec
on write is possible, although I don't know if it can be
sustained at those rates, or whether it's "bursty".
I've been able to produce "real-time" spectral displays on 10yo
dual-Xeon hardware at 100Msps, but only using the
kind of "stuttered" display approach that Gnu Radio FFT displays
often use, where most of the data is discarded. Often,
that's all that's needed to show a quick summary of the spectrum.
On your other question, about transition bandwidth, I don't have a
direct answer, but on an N310 I measured the roll-off
as a fraction of the overall bandwidth, and it is about 12.5%.
That doesn't necessarily translate to the X310, but the
DDC implementation is of the same generation.
On Wed, 19 Feb 2025 at 10:58, Marcus D. Leech
<patchvonbraun@gmail.com> wrote:
On 18/02/2025 19:26, Brendan Horsfield wrote:
I thought your name sounded familiar! 🙂
Overall the X310+UBX-160 appears to be a good fit to our
requirements. My original question was really about
ensuring that our host PC & network interface have
sufficient bandwidth to ingest the IQ data from a pair of
UBX-160s. It would be nice (although not essential) if we
could run one channel at 100 Msps, and the other at 200
Msps, to reduce the bandwidth requirements on the backend
hardware.
You'd need to have separate streamers to support two
different sample rates, and two 10Gbe interfaces.
But in terms of "what kind of PC hardware do I need?".
There's no closed-form answer to that question. There's no
handy-dandy "engineering worksheet" that tells you how much
"grunt" you need for different DSP "flows" at
a given sample-rate--so very much depends on what you're
doing, and how you're doing it. Generally, as you scale up
in sample-rate, you have to scale up in:
o CPU base clock rate
o Memory bandwidth
o Number of CPUs
On Wed, 19 Feb 2025 at 10:17, Marcus D. Leech
<patchvonbraun@gmail.com> wrote:
On 18/02/2025 19:13, Brendan Horsfield wrote:
Thanks for the suggestion about the noise source --
that's what I would normally do. Unfortunately I
haven't actually purchased the hardware yet -- I was
hoping to clarify this issue before raising a purchase
order.
Perhaps I should follow this up with one of the
application engineers at NI? They might have access to
an X310+UBX-160 system that they can use to answer my
question directly.
Thanks again for your help in this matter.
Regards,
Brendan.
I actually do work for NI on USRP devices (on a very
very very part-time basis). My X310 is currently
elsewhere, and not populated
with a UBX-160.
On Wed, 19 Feb 2025 at 09:55, Marcus D. Leech
<patchvonbraun@gmail.com> wrote:
On 18/02/2025 18:45, Brendan Horsfield wrote:
Yes, I assumed that was the case. However, it is
not clear from the X300 documentation how sharp
those filters are. Can you tell me how wide the
transition band is at the lower sample rates?
To give you some context, I would like to use an
X300 (or X310) with a UBX-160 daughterboard to
digitise the entire 2.4 GHz Wi-Fi band, which is
83.5 MHz wide. Ideally I would like to use a
sample rate of 100 Msps to minimise the data rate
between the USRP and the host PC. However, before
I do this I need to be certain that the usable
bandwidth at this sample rate will be greater than
83.5 MHz. Is this information documented somewhere?
It somewhat depends on the decimation. If the
decimation has a factor of two or 4, the edge
roll-off is fairly sharp. Otherwise,
there's a half-band filter in-place that causes a
less-desirable pass-band.
But I don't know, precisely, what the transition
band is in the "nicer" filter shapes.
If you have an X310+UBX-160, you can always just
use a noise source, and measure it yourself to see
if it's appropriate for
your application.
On Tue, 18 Feb 2025 at 23:11, Marcus D Leech
<patchvonbraun@gmail.com> wrote:
There will always be some edge roll off.
Decimation includes filtering and those
filters cannot be infinitely steep.
Sent from my iPhone
On Feb 18, 2025, at 2:12 AM, Brendan
Horsfield <brendan.horsfield@vectalabs.com> wrote:
Hi All,
I have a question about the usable bandwidth
of the X300 USRP / UBX-160 daughterboard combo
at sampling rates below 200 Msps:
As I understand it, the UBX-160 receiver has
an analog (hardware) filter before the ADC
that limits the usable bandwidth to 160 MHz,
while the ADC runs at 200 Msps. Therefore the
usable bandwidth is around 80% of the sample rate.
My question is: What is the usable
bandwidth at lower sampling rates? Does the
80% factor always apply?
For example, if I set the decimation factor
to 4, so that my sampling rate is 50 Msps,
does this mean that the usable bandwidth will
be 40 MHz?
Thanks & Regards,
Brendan.
USRP-users mailing list --
usrp-users@lists.ettus.com
To unsubscribe send an email to
usrp-users-leave@lists.ettus.com
Hi Martin,
Thanks for your kind offer. I would be very interested in obtaining the taps for the half-band filters in the X300 series, if it’s not too much trouble.
Another contributor emailed me the taps for a USRP half-band filter yesterday, but they weren’t 100% sure if the taps were from the X300 series, or one of the older USRP models. Here is a link to the FPGA code on GitHub where the taps came from: https://github.com/EttusResearch/uhd/blob/master/fpga/usrp3/lib/dsp/hb_dec.v
Based on the taps in the above link, I was able to generate the filter response shown in the see attached PNG. From this I was able to extract the following table of “usable bandwidths” for different insertion loss specifications:
-
Max IL spec : Usable BW (as % of decimated sample rate)
-
0.00075 dB (passband equiripple limit) : 70%
-
0.5 dB: 83.5%
-
1 dB : 87%
-
3 dB : 94%
-
6 dB : 100%
Brendan.
