RF switches...

[John Larkin]

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Rich S]

On Saturday, February 26, 2022 at 12:03:45 AM UTC, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.


HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Well the HMC347B seems to be \"in production\"
https://www.analog.com/en/products/hmc347b.html#product-overview

and in stock
https://www.digikey.com/en/products/detail/analog-devices-inc./HMC347B/9484664?utm_source=505&utm_medium=supplier&utm_campaign=buynow
https://www.mouser.com/ProductDetail/Analog-Devices/HMC347B?qs=sGAEpiMZZMv0NwlthflBi%252BwqWTQIZySMXYxFWpKgzJk%3D

cheers, RS

 

[server]

On Fri, 25 Feb 2022 17:44:35 -0800 (PST), Rich S
<richsulinengineer@gmail.com> wrote:

On Saturday, February 26, 2022 at 12:03:45 AM UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.


HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Well the HMC347B seems to be \"in production\"
https://www.analog.com/en/products/hmc347b.html#product-overview

and in stock
https://www.digikey.com/en/products/detail/analog-devices-inc./HMC347B/9484664?utm_source=505&utm_medium=supplier&utm_campaign=buynow
https://www.mouser.com/ProductDetail/Analog-Devices/HMC347B?qs=sGAEpiMZZMv0NwlthflBi%252BwqWTQIZySMXYxFWpKgzJk%3D

cheers, RS

347B is a bare die. Mouser seems to have some of the only surviving
packaged part, HMC347ALP. We could scoop up a lifetime supply, for $70
each.

Thanks.



--

I yam what I yam - Popeye

 

[Clifford Heath]

On 26/2/22 11:03 am, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
<https://www.qorvo.com/products/switches/discrete-switches>
<https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7>

Clifford Heath

 

[John Walliker]

On Saturday, 26 February 2022 at 00:03:45 UTC, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

The data sheet does say:
\"All of the RF ports (RFC, RF1, and RF2) are dc-coupled to 0 V,
and no dc blocking is required at the RF ports when the RF line
potential is equal to 0 V.\"
There is a similar device, the ADRF5025 that goes down to 9kHz, but that has
much slower switching.
There must be resistive filtering on the gate drive and a resistive path from the
FET sources to ground to bias the FETs. The time constant must be such that
there is not enough time for the gate charge to leak away during each half-cycle of
the switched signal. If so, the tradeoff between minimum operating frequency
and switching time would make complete sense, as would the power derating
at low frequencies.
The data sheet also mentions that there are no low-frequency spurious signals, so
they are not using a charge pump for FET bias.

John

 

[server]

On Sat, 26 Feb 2022 03:22:53 -0800 (PST), John Walliker
<jrwalliker@gmail.com> wrote:

On Saturday, 26 February 2022 at 00:03:45 UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

The data sheet does say:
\"All of the RF ports (RFC, RF1, and RF2) are dc-coupled to 0 V,
and no dc blocking is required at the RF ports when the RF line
potential is equal to 0 V.\"
There is a similar device, the ADRF5025 that goes down to 9kHz, but that has
much slower switching.
There must be resistive filtering on the gate drive and a resistive path from the
FET sources to ground to bias the FETs. The time constant must be such that
there is not enough time for the gate charge to leak away during each half-cycle of
the switched signal. If so, the tradeoff between minimum operating frequency
and switching time would make complete sense, as would the power derating
at low frequencies.

Maybe. I suspect the gate drivers are slow to save power.

The data sheet also mentions that there are no low-frequency spurious signals, so
they are not using a charge pump for FET bias.

John

The RF people seem to pick some arbitrary low frequency limit on
parts, possibly based on the blocking caps on their eval board.

Some people apparently work with spectrum analyzers that commonly have
a 9 KHz low end, so spec their parts to 9 KHz.

I did once use a Hittite 8-to-1 RF mux that was spec\'d \"DC-to-12 GHz.\"
It didn\'t work right below about 50 MHz. I eventually got the chip
designer on the phone but he wouldn\'t explain it because it was
proprietary.

The RF world is weird.



--

I yam what I yam - Popeye

 

[server]

On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
<no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both. So I was thinking that a switch could
select the impulse and then immediately switch over to the arb. But
the customer wants at most 5 ns between the fid and the arb.

Maybe we\'ll tell them they have to wait longer. The 5 ns requirement
might not be absolute.

I could delay the fiducial some, to start it after we\'ve told the
pokey analog switch to go. Maybe.





--

I yam what I yam - Popeye

 

[Joe Gwinn]

On Fri, 25 Feb 2022 18:02:56 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 25 Feb 2022 17:44:35 -0800 (PST), Rich S
richsulinengineer@gmail.com> wrote:

On Saturday, February 26, 2022 at 12:03:45 AM UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.


HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Well the HMC347B seems to be \"in production\"
https://www.analog.com/en/products/hmc347b.html#product-overview

and in stock
https://www.digikey.com/en/products/detail/analog-devices-inc./HMC347B/9484664?utm_source=505&utm_medium=supplier&utm_campaign=buynow
https://www.mouser.com/ProductDetail/Analog-Devices/HMC347B?qs=sGAEpiMZZMv0NwlthflBi%252BwqWTQIZySMXYxFWpKgzJk%3D

cheers, RS

347B is a bare die. Mouser seems to have some of the only surviving
packaged part, HMC347ALP. We could scoop up a lifetime supply, for $70
each.

Probably why I mostly see PIN diodes used for such things.

Joe Gwinn

 

[John Larkin]

On Sat, 26 Feb 2022 13:20:54 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:

On Fri, 25 Feb 2022 18:02:56 -0800, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 25 Feb 2022 17:44:35 -0800 (PST), Rich S
richsulinengineer@gmail.com> wrote:

On Saturday, February 26, 2022 at 12:03:45 AM UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.


HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Well the HMC347B seems to be \"in production\"
https://www.analog.com/en/products/hmc347b.html#product-overview

and in stock
https://www.digikey.com/en/products/detail/analog-devices-inc./HMC347B/9484664?utm_source=505&utm_medium=supplier&utm_campaign=buynow
https://www.mouser.com/ProductDetail/Analog-Devices/HMC347B?qs=sGAEpiMZZMv0NwlthflBi%252BwqWTQIZySMXYxFWpKgzJk%3D

cheers, RS

347B is a bare die. Mouser seems to have some of the only surviving
packaged part, HMC347ALP. We could scoop up a lifetime supply, for $70
each.

Probably why I mostly see PIN diodes used for such things.

Joe Gwinn

PINs are cheap and can switch lots of power. They are terrible for
time domain signals. At really high frequencies, their off capacitance
can be a problem. 0.2 pF is about 50 ohms at 14 GHz.



--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[John Walliker]

On Saturday, 26 February 2022 at 15:08:14 UTC, jla...@highlandsniptechnology.com wrote:

On Sat, 26 Feb 2022 03:22:53 -0800 (PST), John Walliker
jrwal...@gmail.com> wrote:

On Saturday, 26 February 2022 at 00:03:45 UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

The data sheet does say:
\"All of the RF ports (RFC, RF1, and RF2) are dc-coupled to 0 V,
and no dc blocking is required at the RF ports when the RF line
potential is equal to 0 V.\"
There is a similar device, the ADRF5025 that goes down to 9kHz, but that has
much slower switching.
There must be resistive filtering on the gate drive and a resistive path from the
FET sources to ground to bias the FETs. The time constant must be such that
there is not enough time for the gate charge to leak away during each half-cycle of
the switched signal. If so, the tradeoff between minimum operating frequency
and switching time would make complete sense, as would the power derating
at low frequencies.
Maybe. I suspect the gate drivers are slow to save power.
The data sheet also mentions that there are no low-frequency spurious signals, so
they are not using a charge pump for FET bias.

John
The RF people seem to pick some arbitrary low frequency limit on
parts, possibly based on the blocking caps on their eval board.

Some people apparently work with spectrum analyzers that commonly have
a 9 KHz low end, so spec their parts to 9 KHz.

There are two almost identical parts (ADRF5024 and ADRF5025) with different
tradeoffs between switching speed and low-frequency cutoff. That isn\'t going
to be explained by limitations of the test gear or blocking caps on the eval
board - especially when the eval board doesn\'t even have any dc blocking caps on it!
The data sheet is quite specific that there is a dc path to ground on all the rf pins.
It is a real tradeoff and there is nothing arbitrary about it.

John

 

[Chris Jones]

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:

On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

 

[server]

On Sun, 27 Feb 2022 21:09:48 +1100, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

Amplitide. Neither the arb nor the fiducual generator can make over
about 0.75 volts peak, and the distributed amp needs all of that to
drive the modulator. DA\'s invert, so adding another $300 chip in the
signal chain creates new tangles.

The many available RF switches are various flavors of weird and all
are poorly spec\'d. I\'ve never seen any mention of the capacitance of
the mux control pins, for instance. Or of switching glitches. OIr,
heaven forbid, any actual waveforms. The really fast ones need a pair
of maybe-big poorly-specified negative switch control voltages.

Analog Devices acquired Hittite, which had the fastest RF switches.
\"Support\" is mostly now forums. Some issues that I care about are
asked about on the forum; some haven\'t been answered in four years.

TI had the same problem when they acquired Burr-Brown. Nobody knew
much about the parts.



--

I yam what I yam - Popeye

 

[Gerhard Hoffmann]

Am 27.02.22 um 16:35 schrieb jlarkin@highlandsniptechnology.com:

Analog Devices acquired Hittite, which had the fastest RF switches.
\"Support\" is mostly now forums. Some issues that I care about are
asked about on the forum; some haven\'t been answered in four years.

TI had the same problem when they acquired Burr-Brown. Nobody knew
much about the parts.

But this is not only for aquired products. My questions about
the bleeding controls in the ADF5356 synthesizer are unanswered,
too, after 2 years. Some 500 reads.

About as helpful as the Altium forum.

Gerhard

 

[server]

On Sun, 27 Feb 2022 18:15:57 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 27.02.22 um 16:35 schrieb jlarkin@highlandsniptechnology.com:

Analog Devices acquired Hittite, which had the fastest RF switches.
\"Support\" is mostly now forums. Some issues that I care about are
asked about on the forum; some haven\'t been answered in four years.

TI had the same problem when they acquired Burr-Brown. Nobody knew
much about the parts.

But this is not only for aquired products. My questions about
the bleeding controls in the ADF5356 synthesizer are unanswered,
too, after 2 years. Some 500 reads.

We had a lot of hassle using the LMX2571 synth, that TI made necessary
by being coy. Makes no sense.

About as helpful as the Altium forum.

Gerhard

It must be difficult to find and keep good application and support
engineers. They have a life that is, basically, continuous job
interviews. It\'s a great job for a recent grad.

I guess that the chip designers, if they are even still around, need
to be defended against customer questions, or they wouldn\'t get work
done.

We have to test a lot of parts ourselves to understand them.

We need a web site where we share insights, measurements, code, bugs.



--

I yam what I yam - Popeye

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Sat, 26 Feb 2022 03:22:53 -0800 (PST), John Walliker
jrwalliker@gmail.com> wrote:

On Saturday, 26 February 2022 at 00:03:45 UTC, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

The data sheet does say:
\"All of the RF ports (RFC, RF1, and RF2) are dc-coupled to 0 V,
and no dc blocking is required at the RF ports when the RF line
potential is equal to 0 V.\"
There is a similar device, the ADRF5025 that goes down to 9kHz, but that has
much slower switching.
There must be resistive filtering on the gate drive and a resistive path from the
FET sources to ground to bias the FETs. The time constant must be such that
there is not enough time for the gate charge to leak away during each half-cycle of
the switched signal. If so, the tradeoff between minimum operating frequency
and switching time would make complete sense, as would the power derating
at low frequencies.

Maybe. I suspect the gate drivers are slow to save power.

The data sheet also mentions that there are no low-frequency spurious signals, so
they are not using a charge pump for FET bias.

John

The RF people seem to pick some arbitrary low frequency limit on
parts, possibly based on the blocking caps on their eval board.

And the 1/f corner of the parts.

Some people apparently work with spectrum analyzers that commonly have
a 9 KHz low end, so spec their parts to 9 KHz.

HP 8566B, for instance. That isn\'t a coupling cap, it\'s just the wings
of the huge peak at DC. The HP 8568B has a coupling cap, which makes it
harder to blow up the first mixer.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Chris Jones]

On 28/02/2022 02:35, jlarkin@highlandsniptechnology.com wrote:

On Sun, 27 Feb 2022 21:09:48 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

Amplitide. Neither the arb nor the fiducual generator can make over
about 0.75 volts peak, and the distributed amp needs all of that to
drive the modulator.

Could you increase the output of the fiducial generator somehow? Then a
combiner with unequal resistors could have low loss for the arb.

If you don\'t care too much about the shape of the fiducial, there are
probably also some less-broadband-on-one-port combiners that could help
with lower loss for the arb.

If you can\'t increase the output voltage of the fiducial generator, it
may be sufficient to provide multiple outputs with the same voltage, or
a single, lower-impedance output driving a combiner designed for
different impedances.

Could you yank the arb output high just during the fiducial pulse, with
the emitter of a fast NPN? The impedance would not stay constant, but
that mightn\'t matter.

 

[server]

On Mon, 28 Feb 2022 11:20:28 +1100, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 28/02/2022 02:35, jlarkin@highlandsniptechnology.com wrote:
On Sun, 27 Feb 2022 21:09:48 +1100, Chris Jones
lugnut808@spam.yahoo.com> wrote:

On 27/02/2022 03:16, jlarkin@highlandsniptechnology.com wrote:
On Sat, 26 Feb 2022 13:08:15 +1100, Clifford Heath
no.spam@please.net> wrote:

On 26/2/22 11:03 am, John Larkin wrote:
Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

ADRF5024 is 100 MHz to 44 GHz, but switches in about 17 ns. The 100
MHz lower signal bw makes no sense.

HMC347 looked pretty good, DC-14 GHz and 10 ns typ, but it\'s gone
obsolete.

Who else makes parts like this?

We\'ve used Skyworks SKY13453 (2-way) and SKY13317 (3-way) but they\'re
only 6GHz. Check their other parts?

And Qorvo of course:
https://www.qorvo.com/products/switches/discrete-switches
https://store.qorvo.com/products/switches/rf-switch?att_4714=1&att_4719=6%2c7

Clifford Heath

Wow, a lot of near-misses.

I\'m amplifying an arbitrary waveform as the seed of a largish laser.
And I want to inject a 100 ps fiducial pulse. We can make a nice
programmable 100 ps gaussian pulse, but can\'t passively mix it with
the arb without wrecking both.

Why? Does each one produce interfering crud when it should produce
nothing, or are you just not able to tolerate the amplitude loss of a
passive resistive combiner?

Amplitide. Neither the arb nor the fiducual generator can make over
about 0.75 volts peak, and the distributed amp needs all of that to
drive the modulator.

Could you increase the output of the fiducial generator somehow? Then a
combiner with unequal resistors could have low loss for the arb.

We\'re using a Micrel laser driver chip, Sy88022. It makes 25 ps edges
and has beautiful linear amplitude control, but is intended to drive a
low impedance laser and won\'t swing even one volt.

Inspired by Leo Bodnar\'s pulse generator, which uses a similar Maxim
chip.

If you don\'t care too much about the shape of the fiducial, there are
probably also some less-broadband-on-one-port combiners that could help
with lower loss for the arb.

The shape really matters. It will be used to test the response of
laser bits downstream. The customer wants a 100 ps gaussian.

If you can\'t increase the output voltage of the fiducial generator, it
may be sufficient to provide multiple outputs with the same voltage, or
a single, lower-impedance output driving a combiner designed for
different impedances.

Could you yank the arb output high just during the fiducial pulse, with
the emitter of a fast NPN? The impedance would not stay constant, but
that mightn\'t matter.

It\'s hard enough to make a 100 ps programmable gaussian pulse. The
analog switch looks like the thing we need.

There are some amazing RF switches around. ADRF5025 is rated for 9 KHz
to 44 GHz. It switches slow so we\'d have to deal with that.

The fast switches all look like nightmares. Some need 7 volt (or 40
volt!) gate drives into unspecified capacitances.





--

I yam what I yam - Popeye

 

[Gerhard Hoffmann]

Am 26.02.22 um 16:07 schrieb jlarkin@highlandsniptechnology.com:

The RF people seem to pick some arbitrary low frequency limit on
parts, possibly based on the blocking caps on their eval board.

Some people apparently work with spectrum analyzers that commonly have
a 9 KHz low end, so spec their parts to 9 KHz.

The 9 KHz come from some EMC norms. If a lab wants to certify
compliance to these norms, they must measure to 9 KHz.
Everything better might cost one more synthesizer loop aka money
or lose dynamic range because of 1/f, filter bandwidth or
over all synthesizer quality.

I did once use a Hittite 8-to-1 RF mux that was spec\'d \"DC-to-12 GHz.\"
It didn\'t work right below about 50 MHz. I eventually got the chip
designer on the phone but he wouldn\'t explain it because it was
proprietary.

The 8720A network analyzer goes from 20 GHz down to 50 MHz.
They won\'t specify anything they cannot measure.
And 50 MHz is just nervous DC.

Many s-parameter files end at either 3 or 6 GHz because
the 8753 A/B/SE/WHATEVER ends at 3 or 6 GHz without/with
the option -6.

> The RF world is weird.

No, just costly.

And PINs will switch even slower.
They start to distort below a few MHz.

Maybe you can build something discrete with CEL 20 GHz GaAsFets.

< https://www.digikey.de/de/products/detail/cel/CE3520K3-C1/6165462 >

Cheers, Gerhard

 

[server]

On Mon, 28 Feb 2022 02:49:53 +0100, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

Am 26.02.22 um 16:07 schrieb jlarkin@highlandsniptechnology.com:

The RF people seem to pick some arbitrary low frequency limit on
parts, possibly based on the blocking caps on their eval board.

Some people apparently work with spectrum analyzers that commonly have
a 9 KHz low end, so spec their parts to 9 KHz.

The 9 KHz come from some EMC norms. If a lab wants to certify
compliance to these norms, they must measure to 9 KHz.
Everything better might cost one more synthesizer loop aka money
or lose dynamic range because of 1/f, filter bandwidth or
over all synthesizer quality.


I did once use a Hittite 8-to-1 RF mux that was spec\'d \"DC-to-12 GHz.\"
It didn\'t work right below about 50 MHz. I eventually got the chip
designer on the phone but he wouldn\'t explain it because it was
proprietary.

The 8720A network analyzer goes from 20 GHz down to 50 MHz.
They won\'t specify anything they cannot measure.
And 50 MHz is just nervous DC.

The Hittite mux thing was real. It is supposed to terminate the
unselected inputs with 50 ohms, but there is apparently a cap in
series with each terminator resistor. So much for \"DC.\"

Many s-parameter files end at either 3 or 6 GHz because
the 8753 A/B/SE/WHATEVER ends at 3 or 6 GHz without/with
the option -6.

The RF world is weird.

No, just costly.

And PINs will switch even slower.
They start to distort below a few MHz.

Maybe you can build something discrete with CEL 20 GHz GaAsFets.

https://www.digikey.de/de/products/detail/cel/CE3520K3-C1/6165462

We use a lot of MiniCircuits enhancement phemts, the SAV series. I
considered making my own RF switch from a couple of them, but it would
be risky. Gate drive would be interesting.

We did make a nice switchable attenuator with a SAV541.




--

I yam what I yam - Popeye

 

[John Miles, KE5FX]

On Friday, February 25, 2022 at 4:03:45 PM UTC-8, John Larkin wrote:

Question for the RF guys here.

We want a wideband RF switch IC that switches fast. Bandwidth lf to 10
GHz or better, switching in well under 10 ns.

PE42525, maybe. 9 kHz-60 GHz, SPDT, 8-12 ns switching time to
10%/90%, 48-60 ns settling time to 0.05 dB.

I\'d be surprised if you find anything faster than that. PSemi makes
fantastic stuff (at least, when you can buy it.)

-- john, KE5FX