On Mon, 15 Dec 2003 06:59:30 GMT, said...
Paul Burridge wrote:

I'll add that my Optoelectronics handi-counter's fsm bargraph can detect
a few hundred milliwatts at several feet away.

I visualize a radio-field power density being grid-lines painted on a
balloon around a 1/2 wave dipole. As the balloon is blown up, the
grid-line expand, given by 4 pi r^2.

For some good app notes on designing electrically small antennas and
radio link calculations:

Goto -
http://www.rfm.com/corp/apnotes.htm

Checkout:
http://www.rfm.com/corp/appdata/antenna.pdf
http://www.rfm.com/products/tr_des24.pdf

HP (now Agilent) has some app-notes on designing diode detectors, and
has some utility programs that will help you design and calculate
performance. Some I think, in context of RFID reading devices. But they
point out you get a square-law for small signals, which gets nonlinear
for larger signal levels. And what bias the detector diode has on it.



Any particular search string to use for that Agilent stuff? They're
usually good for info on stuff like that.

Mike

Active8 wrote:

On Mon, 15 Dec 2003 06:59:30 GMT, said...

HP (now Agilent) has some app-notes on designing diode detectors

Any particular search string to use for that Agilent stuff? They're
usually good for info on stuff like that.

I though Agilent made you answer a bunch of questions before they would
let you at their stuff. Doing a web search on one of the app notes I
downloaded, I get:
http://rf.rfglobalnet.com/library/Ap...s/1/An1089.pdf

RF Globalnet's got lots of good stuff. Probably where I got the design
apps from too.

HP app notes I collected:

pin diode pi atten an1048
pin diode switch an1049
x-band mixer an1052
pin diode freq mult. an1054
(comb gen)
pin diode t/r switch an1067
schottkey diode apps an1069
schot. diode det - RFID an1089
atf-36163 10GHz LNA an1091
pin diode switch an957-1,2,3
z-mtchng for mix & dets an963
0-bias schotky diode an969
broadbnd mixers an976
square-law detectors an986
diode bias an987
zero-bias an988
harmonic mixing an991
shttky diode mixer an995
choke network design ana001
osc design ana008
vco design anm024
5ghz active mixer ans010
transistors primer1
noise and s-parms primer2
thermal primer3
thermal primer3a
gasfets primer4
HP product line quickguide

"Designing Detectors for RF/ID Tags Application Note 1089"

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

Active8 wrote:

On Mon, 15 Dec 2003 06:59:30 GMT, said...

HP (now Agilent) has some app-notes on designing diode detectors

Any particular search string to use for that Agilent stuff? They're
usually good for info on stuff like that.

I though Agilent made you answer a bunch of questions before they would
let you at their stuff. Doing a web search on one of the app notes I
downloaded, I get:
http://rf.rfglobalnet.com/library/Ap...s/1/An1089.pdf

RF Globalnet's got lots of good stuff. Probably where I got the design
apps from too.

HP app notes I collected:

pin diode pi atten an1048
pin diode switch an1049
x-band mixer an1052
pin diode freq mult. an1054
(comb gen)
pin diode t/r switch an1067
schottkey diode apps an1069
schot. diode det - RFID an1089
atf-36163 10GHz LNA an1091
pin diode switch an957-1,2,3
z-mtchng for mix & dets an963
0-bias schotky diode an969
broadbnd mixers an976
square-law detectors an986
diode bias an987
zero-bias an988
harmonic mixing an991
shttky diode mixer an995
choke network design ana001
osc design ana008
vco design anm024
5ghz active mixer ans010
transistors primer1
noise and s-parms primer2
thermal primer3
thermal primer3a
gasfets primer4
HP product line quickguide

"Designing Detectors for RF/ID Tags Application Note 1089"

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

On Tue, 16 Dec 2003 23:56:14 GMT, said...
Active8 wrote:

On Mon, 15 Dec 2003 06:59:30 GMT, said...

HP (now Agilent) has some app-notes on designing diode detectors

Any particular search string to use for that Agilent stuff? They're
usually good for info on stuff like that.

I though Agilent made you answer a bunch of questions before they would
let you at their stuff. Doing a web search on one of the app notes I
downloaded, I get:

I don't remember having to do that. I better get a sneakemail
(.com) addys ready for the next registration proceeses, though

http://rf.rfglobalnet.com/library/Ap...s/1/An1089.pdf

Ah. RFID. Big market in the works.

RF Globalnet's got lots of good stuff. Probably where I got the design
apps from too.

Thanks. You're right. I haven't had time to hit RF Globalnet in a
while. I used to get the news letter. Tnx for the reminder.

I wish I had more time. Maybe someone has the time to collect all
our app notes and get permission to organize them with
comprehensive synopses and mirror them on a free site. Maybe
qsl.net or something.



HP app notes I collected:

That's all? Oh, just from HP, ok.

Mike

pin diode pi atten an1048
pin diode switch an1049
x-band mixer an1052
pin diode freq mult. an1054
(comb gen)
pin diode t/r switch an1067
schottkey diode apps an1069
schot. diode det - RFID an1089
atf-36163 10GHz LNA an1091
pin diode switch an957-1,2,3
z-mtchng for mix & dets an963
0-bias schotky diode an969
broadbnd mixers an976
square-law detectors an986
diode bias an987
zero-bias an988
harmonic mixing an991
shttky diode mixer an995
choke network design ana001
osc design ana008
vco design anm024
5ghz active mixer ans010
transistors primer1
noise and s-parms primer2
thermal primer3
thermal primer3a
gasfets primer4
HP product line quickguide

"Designing Detectors for RF/ID Tags Application Note 1089"

On Tue, 16 Dec 2003 23:56:14 GMT, said...
Active8 wrote:

On Mon, 15 Dec 2003 06:59:30 GMT, said...

HP (now Agilent) has some app-notes on designing diode detectors

Any particular search string to use for that Agilent stuff? They're
usually good for info on stuff like that.

I though Agilent made you answer a bunch of questions before they would
let you at their stuff. Doing a web search on one of the app notes I
downloaded, I get:

I don't remember having to do that. I better get a sneakemail
(.com) addys ready for the next registration proceeses, though

http://rf.rfglobalnet.com/library/Ap...s/1/An1089.pdf

Ah. RFID. Big market in the works.

RF Globalnet's got lots of good stuff. Probably where I got the design
apps from too.

Thanks. You're right. I haven't had time to hit RF Globalnet in a
while. I used to get the news letter. Tnx for the reminder.

I wish I had more time. Maybe someone has the time to collect all
our app notes and get permission to organize them with
comprehensive synopses and mirror them on a free site. Maybe
qsl.net or something.



HP app notes I collected:

That's all? Oh, just from HP, ok.

Mike

pin diode pi atten an1048
pin diode switch an1049
x-band mixer an1052
pin diode freq mult. an1054
(comb gen)
pin diode t/r switch an1067
schottkey diode apps an1069
schot. diode det - RFID an1089
atf-36163 10GHz LNA an1091
pin diode switch an957-1,2,3
z-mtchng for mix & dets an963
0-bias schotky diode an969
broadbnd mixers an976
square-law detectors an986
diode bias an987
zero-bias an988
harmonic mixing an991
shttky diode mixer an995
choke network design ana001
osc design ana008
vco design anm024
5ghz active mixer ans010
transistors primer1
noise and s-parms primer2
thermal primer3
thermal primer3a
gasfets primer4
HP product line quickguide

"Designing Detectors for RF/ID Tags Application Note 1089"

Sorry for the slow response.

The voltage at the terminals of a short, lossless dipole of length l
which is perfectly terminated with the complex conjugate of its
feedpoint impedance is E * l / 2 where E is the impinging field in volts
per meter. Any mismatch lowers this value -- it's one of those valid and
useful applications of the concept of "mismatch loss", which can be used
to quantify the reduction when mismatched. It's one of the contributions
to the extensive variation with frequency of the "antenna factor"(*) of
test dipoles used in EMI work. (And careful measurement of this factor
is a large fraction of what you're paying for when you purchase one.)
Doesn't matter how wonderful your field strength meter is unless you
have a very good handle on the "antenna factor" of the test antenna.

In simple terms, the factor of 1/2 is the ratio of the average current
to the feedpoint current. The average current along a short dipole is
about 1/2 the current at the feedpoint. You could get a factor of 1 if
you used a short dipole with large end hats to make the current
distribution uniform. Kraus addresses this case in detail in _Antennas_.

And no, I don't mean "antenna to free space" match. I mean the match
between the antenna feedpoint as a source and the detector as a load.

(*) Ratio of output voltage when terminated in 50 ohms to the impinging
field in volts/meter.

Roy Lewallen, W7EL

Active8 wrote:
On Sat, 13 Dec 2003 17:39:27 -0800, said...

It's too bad it isn't that simple.

A 1V/m field doesn't result in one volt at the feedpoint of a perfectly
matched one meter dipole or monopole, and the value it does induce
depends on the quality of the impedance match


you mean antenna to free space, right?


as well as the fraction of
a wavelength the one meter antenna length represents.


amplify, very please. por favor. Refresh my ram.


| E(uV/m) |
V (dBmV) = 20log | --------- / 1000 |
| 0.021f(MHz) |

plus correction for distance (regulations for limits are for
specific measuring distances), etc. I'll mull the above eq over.
Gotta figure out where the .021 came from, but not now. My eyes are
getting fatigued from this 'puter.


And, if one volt
does appear at the feedpoint, it's very unlikely that a simple circuit
will measure it as one volt.


It would have to be calibrated to compensate for the circuit. Maybe
that's why it's called a "relative" field strength meter. Relative
to another signal or no signal


Probably best to stick with your $1.5 kilobuck meter if you really want
to measure field strength.


I don't. He does At least not tonight. But my SLM *will* measure
field strenth using a cheap ass dipole cut to the frequency of
interest with or without an external preamp and do it to the
satisfaction of the FCC, assuming it's calibrated. I even have a
near-field probe, not so cheap. It beats guess work.

I wouldn't expect his sniffer to be real accurate but he did ask
for guesstimates. Started off as "around 4 feet" for a half watter
now we're at 100mW - prob his reference Tx.

BRs,
Mike



Roy Lewallen, W7EL

Active8 wrote:

On 13 Dec 2003 03:50:41 -0800, said...


What you are descrbing is a "signal sniffer", not a signal strength meter.


Who are you replying to? Paul did not say Signal Stength Meter, but
the guy you replied to kinda hints at it when he mentions power
level.

I would have to say that my 1GHz Signal Level Meter, which cost
$1500 would be the better than a relative field strength meter, but
if he measures say, 1V with his Tx off and 2V with it on, then
that's 1V and if his Rx antenna is a 1m dipole, that's 1V/m.

Mike

Sorry for the slow response.

The voltage at the terminals of a short, lossless dipole of length l
which is perfectly terminated with the complex conjugate of its
feedpoint impedance is E * l / 2 where E is the impinging field in volts
per meter. Any mismatch lowers this value -- it's one of those valid and
useful applications of the concept of "mismatch loss", which can be used
to quantify the reduction when mismatched. It's one of the contributions
to the extensive variation with frequency of the "antenna factor"(*) of
test dipoles used in EMI work. (And careful measurement of this factor
is a large fraction of what you're paying for when you purchase one.)
Doesn't matter how wonderful your field strength meter is unless you
have a very good handle on the "antenna factor" of the test antenna.

In simple terms, the factor of 1/2 is the ratio of the average current
to the feedpoint current. The average current along a short dipole is
about 1/2 the current at the feedpoint. You could get a factor of 1 if
you used a short dipole with large end hats to make the current
distribution uniform. Kraus addresses this case in detail in _Antennas_.

And no, I don't mean "antenna to free space" match. I mean the match
between the antenna feedpoint as a source and the detector as a load.

(*) Ratio of output voltage when terminated in 50 ohms to the impinging
field in volts/meter.

Roy Lewallen, W7EL

Active8 wrote:
On Sat, 13 Dec 2003 17:39:27 -0800, said...

It's too bad it isn't that simple.

A 1V/m field doesn't result in one volt at the feedpoint of a perfectly
matched one meter dipole or monopole, and the value it does induce
depends on the quality of the impedance match


you mean antenna to free space, right?


as well as the fraction of
a wavelength the one meter antenna length represents.


amplify, very please. por favor. Refresh my ram.


| E(uV/m) |
V (dBmV) = 20log | --------- / 1000 |
| 0.021f(MHz) |

plus correction for distance (regulations for limits are for
specific measuring distances), etc. I'll mull the above eq over.
Gotta figure out where the .021 came from, but not now. My eyes are
getting fatigued from this 'puter.


And, if one volt
does appear at the feedpoint, it's very unlikely that a simple circuit
will measure it as one volt.


It would have to be calibrated to compensate for the circuit. Maybe
that's why it's called a "relative" field strength meter. Relative
to another signal or no signal


Probably best to stick with your $1.5 kilobuck meter if you really want
to measure field strength.


I don't. He does At least not tonight. But my SLM *will* measure
field strenth using a cheap ass dipole cut to the frequency of
interest with or without an external preamp and do it to the
satisfaction of the FCC, assuming it's calibrated. I even have a
near-field probe, not so cheap. It beats guess work.

I wouldn't expect his sniffer to be real accurate but he did ask
for guesstimates. Started off as "around 4 feet" for a half watter
now we're at 100mW - prob his reference Tx.

BRs,
Mike



Roy Lewallen, W7EL

Active8 wrote:

On 13 Dec 2003 03:50:41 -0800, said...


What you are descrbing is a "signal sniffer", not a signal strength meter.


Who are you replying to? Paul did not say Signal Stength Meter, but
the guy you replied to kinda hints at it when he mentions power
level.

I would have to say that my 1GHz Signal Level Meter, which cost
$1500 would be the better than a relative field strength meter, but
if he measures say, 1V with his Tx off and 2V with it on, then
that's 1V and if his Rx antenna is a 1m dipole, that's 1V/m.

Mike

On Tue, 16 Dec 2003 22:38:50 -0800, said...
Sorry for the slow response.

s'ok. but i don't think my stinkin' reader alerted me to the
response. or I missed it.

The voltage at the terminals of a short, lossless dipole of length l
which is perfectly terminated with the complex conjugate of its
feedpoint impedance is E * l / 2 where E is the impinging field in volts
per meter. Any mismatch lowers this value -- it's one of those valid and
useful applications of the concept of "mismatch loss", which can be used
to quantify the reduction when mismatched. It's one of the contributions
to the extensive variation with frequency of the "antenna factor"(*) of
test dipoles used in EMI work. (And careful measurement of this factor
is a large fraction of what you're paying for when you purchase one.)
Doesn't matter how wonderful your field strength meter is unless you
have a very good handle on the "antenna factor" of the test antenna.

I'll dig into the Antenna Engrs Handbook.

I guess we've been lucky. So far no FCC gigs on leakage. Haven't
heard about anyone failing a flyover either. Maybe the systems
consider the FCC spec and set their spec to account for cheap-assed
dipoles. If so, that's smart and I'd be surprised. Some day I'll
check that out.

In simple terms, the factor of 1/2 is the ratio of the average current
to the feedpoint current. The average current along a short dipole is
about 1/2 the current at the feedpoint. You could get a factor of 1 if
you used a short dipole with large end hats to make the current
distribution uniform. Kraus addresses this case in detail in _Antennas_.

And no, I don't mean "antenna to free space" match. I mean the match
between the antenna feedpoint as a source and the detector as a load.

That's a given. I figure Paul already knows that.

BRs,
Mike

(*) Ratio of output voltage when terminated in 50 ohms to the impinging
field in volts/meter.

Roy Lewallen, W7EL

Active8 wrote:
On Sat, 13 Dec 2003 17:39:27 -0800, said...

It's too bad it isn't that simple.

A 1V/m field doesn't result in one volt at the feedpoint of a perfectly
matched one meter dipole or monopole, and the value it does induce
depends on the quality of the impedance match


you mean antenna to free space, right?


as well as the fraction of
a wavelength the one meter antenna length represents.


amplify, very please. por favor. Refresh my ram.


| E(uV/m) |
V (dBmV) = 20log | --------- / 1000 |
| 0.021f(MHz) |

plus correction for distance (regulations for limits are for
specific measuring distances), etc. I'll mull the above eq over.
Gotta figure out where the .021 came from, but not now. My eyes are
getting fatigued from this 'puter.


And, if one volt
does appear at the feedpoint, it's very unlikely that a simple circuit
will measure it as one volt.


It would have to be calibrated to compensate for the circuit. Maybe
that's why it's called a "relative" field strength meter. Relative
to another signal or no signal


Probably best to stick with your $1.5 kilobuck meter if you really want
to measure field strength.


I don't. He does At least not tonight. But my SLM *will* measure
field strenth using a cheap ass dipole cut to the frequency of
interest with or without an external preamp and do it to the
satisfaction of the FCC, assuming it's calibrated. I even have a
near-field probe, not so cheap. It beats guess work.

I wouldn't expect his sniffer to be real accurate but he did ask
for guesstimates. Started off as "around 4 feet" for a half watter
now we're at 100mW - prob his reference Tx.

BRs,
Mike



Roy Lewallen, W7EL

Active8 wrote:

On 13 Dec 2003 03:50:41 -0800, said...


What you are descrbing is a "signal sniffer", not a signal strength meter.


Who are you replying to? Paul did not say Signal Stength Meter, but
the guy you replied to kinda hints at it when he mentions power
level.

I would have to say that my 1GHz Signal Level Meter, which cost
$1500 would be the better than a relative field strength meter, but
if he measures say, 1V with his Tx off and 2V with it on, then
that's 1V and if his Rx antenna is a 1m dipole, that's 1V/m.

Mike

On Tue, 16 Dec 2003 22:38:50 -0800, said...
Sorry for the slow response.

s'ok. but i don't think my stinkin' reader alerted me to the
response. or I missed it.

The voltage at the terminals of a short, lossless dipole of length l
which is perfectly terminated with the complex conjugate of its
feedpoint impedance is E * l / 2 where E is the impinging field in volts
per meter. Any mismatch lowers this value -- it's one of those valid and
useful applications of the concept of "mismatch loss", which can be used
to quantify the reduction when mismatched. It's one of the contributions
to the extensive variation with frequency of the "antenna factor"(*) of
test dipoles used in EMI work. (And careful measurement of this factor
is a large fraction of what you're paying for when you purchase one.)
Doesn't matter how wonderful your field strength meter is unless you
have a very good handle on the "antenna factor" of the test antenna.

I'll dig into the Antenna Engrs Handbook.

I guess we've been lucky. So far no FCC gigs on leakage. Haven't
heard about anyone failing a flyover either. Maybe the systems
consider the FCC spec and set their spec to account for cheap-assed
dipoles. If so, that's smart and I'd be surprised. Some day I'll
check that out.

In simple terms, the factor of 1/2 is the ratio of the average current
to the feedpoint current. The average current along a short dipole is
about 1/2 the current at the feedpoint. You could get a factor of 1 if
you used a short dipole with large end hats to make the current
distribution uniform. Kraus addresses this case in detail in _Antennas_.

And no, I don't mean "antenna to free space" match. I mean the match
between the antenna feedpoint as a source and the detector as a load.

That's a given. I figure Paul already knows that.

BRs,
Mike

(*) Ratio of output voltage when terminated in 50 ohms to the impinging
field in volts/meter.

Roy Lewallen, W7EL

Active8 wrote:
On Sat, 13 Dec 2003 17:39:27 -0800, said...

It's too bad it isn't that simple.

A 1V/m field doesn't result in one volt at the feedpoint of a perfectly
matched one meter dipole or monopole, and the value it does induce
depends on the quality of the impedance match


you mean antenna to free space, right?


as well as the fraction of
a wavelength the one meter antenna length represents.


amplify, very please. por favor. Refresh my ram.


| E(uV/m) |
V (dBmV) = 20log | --------- / 1000 |
| 0.021f(MHz) |

plus correction for distance (regulations for limits are for
specific measuring distances), etc. I'll mull the above eq over.
Gotta figure out where the .021 came from, but not now. My eyes are
getting fatigued from this 'puter.


And, if one volt
does appear at the feedpoint, it's very unlikely that a simple circuit
will measure it as one volt.


It would have to be calibrated to compensate for the circuit. Maybe
that's why it's called a "relative" field strength meter. Relative
to another signal or no signal


Probably best to stick with your $1.5 kilobuck meter if you really want
to measure field strength.


I don't. He does At least not tonight. But my SLM *will* measure
field strenth using a cheap ass dipole cut to the frequency of
interest with or without an external preamp and do it to the
satisfaction of the FCC, assuming it's calibrated. I even have a
near-field probe, not so cheap. It beats guess work.

I wouldn't expect his sniffer to be real accurate but he did ask
for guesstimates. Started off as "around 4 feet" for a half watter
now we're at 100mW - prob his reference Tx.

BRs,
Mike



Roy Lewallen, W7EL

Active8 wrote:

On 13 Dec 2003 03:50:41 -0800, said...


What you are descrbing is a "signal sniffer", not a signal strength meter.


Who are you replying to? Paul did not say Signal Stength Meter, but
the guy you replied to kinda hints at it when he mentions power
level.

I would have to say that my 1GHz Signal Level Meter, which cost
$1500 would be the better than a relative field strength meter, but
if he measures say, 1V with his Tx off and 2V with it on, then
that's 1V and if his Rx antenna is a 1m dipole, that's 1V/m.

Mike