Need VCO for 14 MHz PLL

W

W Letendre

Guest
Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre
 
Hello W Letendre,

Look at digitally controlled oscillators (DCO). Analog Devices has lots
of these. You basically follow with a simple filter that cuts off above
your desired range, send it the frequency you want and that's it. I know
that this sounds like buying a pre-cooked pizza (which we'd never do...)
but if you want it done fast that may be the way to go.

Regards, Joerg

http://www.analogconsultants.com
 
On 17 Jul 2005 10:46:17 -0700, "W Letendre"
<wjlservo@worldnet.att.net> wrote:

Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre
Click to expand...
You could just buy a cheap commercial RF VCO from MiniCircuits or
Emhiser or somebody, and divide it down as necessary. The AD9901 is a
nice, very fast phase detector.

The 4x pll + divider is good, but you will get phase ambiguity that
you'll have to repair somehow.

John
 
On Sun, 17 Jul 2005 11:11:43 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On 17 Jul 2005 10:46:17 -0700, "W Letendre"
wjlservo@worldnet.att.net> wrote:

Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre

You could just buy a cheap commercial RF VCO from MiniCircuits or
Emhiser or somebody, and divide it down as necessary. The AD9901 is a
nice, very fast phase detector.

The 4x pll + divider is good, but you will get phase ambiguity that
you'll have to repair somehow.

John
Click to expand...
Naaah! It's trivial to make a quadrature divider that has no
ambiguity ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
John Larkin wrote:
On 17 Jul 2005 10:46:17 -0700, "W Letendre"
wjlservo@worldnet.att.net> wrote:

Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre

You could just buy a cheap commercial RF VCO from MiniCircuits or
Emhiser or somebody, and divide it down as necessary. The AD9901 is a
nice, very fast phase detector.

The 4x pll + divider is good, but you will get phase ambiguity that
you'll have to repair somehow.

John
Click to expand...
Fortunately, do not need to lock output signals "in phase" to input
reference; suffices for application that output in phase and quad
signals have exact 90deg phase match to each other.

Will check out MinCircuits; should have thought of those guys. They
make a ton of solder-in RF "gadgets" as I recall....

W Letendre
 
Fear that DCO would be too expensive for application. Will check
prices, though; they may have come down since last time I looked at
them.

W Letendre
 
On 17 Jul 2005 10:46:17 -0700, "W Letendre"
<wjlservo@worldnet.att.net> wrote:

Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?
Click to expand...
---
http://www.minicircuits.com/dg03-228.pdf

http://focus.ti.com/lit/ds/symlink/cd74hc4046a.pdf

http://www.standardics.philips.com/products/hc/pdf/74hc7046a.pdf
--
John Fields
Professional Circuit Designer
 
W Letendre wrote:

Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre

If "quite stable" means "crystal stable", and you don't need a large
Click to expand...
range, and you have the time for things to settle down, then take a look
at VXCO's -- they're available from many, if not most, of the crystal
oscillator folks. And they're nearly crystal stable themselves.

--
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
Hello W Letendre,

Fear that DCO would be too expensive for application. Will check
prices, though; they may have come down since last time I looked at
them.
Click to expand...
That is the downside of DDS chips. They are expensive and that is why I
dealt with them only once so far. You need one where the master clock is
about 3 times your frequency or higher. Maybe you could scrape by with
the AD9835 but that is still over $5:
http://www.analog.com/UploadedFiles/Data_Sheets/7569011AD9835_0.pdf

However, if you want 14MHz quad you'd need one with 200MHz clock or so,
to be able to divide down. Those will be more in the $10 range.

If it's very cost sensitive you'll have to do your own PLL.

Regards, Joerg

http://www.analogconsultants.com
 
Hello W Letendre,

Will check out MinCircuits; should have thought of those guys. They
make a ton of solder-in RF "gadgets" as I recall....
Click to expand...
I don't want to spoil the broth here but since you mentioned cost: These
are often well above the cost of a DDS chip.

Regards, Joerg

http://www.analogconsultants.com
 
On Sun, 17 Jul 2005 19:26:39 GMT, Joerg <notthisjoergsch@removethispacbell.net>
wrote:

Hello W Letendre,

Will check out MinCircuits; should have thought of those guys. They
make a ton of solder-in RF "gadgets" as I recall....

I don't want to spoil the broth here but since you mentioned cost: These
are often well above the cost of a DDS chip.

Regards, Joerg
Click to expand...
The DDS chip itself is cheap but you still need a reference frequency source
that adds to the overall cost.

The minicircuit vco is about $20, if that's still too expensive look into
designing your own vco.

Synergy Microwave has a few good references on vco design, if you want to take
that route...

http://www.synergymwave.com/Articles/Articles.htm
 
Hello John,

Had 15megs from a 4046 but it was pushing it. The X4 loop multiplier is
easily made by using (for example) 2 off, 4013 style, dual flip flops, wired
as a 'walking ring counter'. All four 0-90-180-270 phases, appear on the 'Q'
output pins.
Click to expand...
15MHz out of a 4046 is indeed pushing it. For the 4013 I'd use some
faster HC stuff for better 0-90 tolerance.

Regards, Joerg

http://www.analogconsultants.com
 
Hello Max,

The DDS chip itself is cheap but you still need a reference frequency source
that adds to the overall cost.
Click to expand...
Yes, but that boils down to a crystal and a fast unbuffered inverter.
Plus you can still rent out the remaining inverters from the six-pack.
Ok, if you need a really quiet clock source you'd have to throw in a
BFS17 but that won't set you back more than a dime.

The minicircuit vco is about $20, if that's still too expensive look into
designing your own vco.
Click to expand...
It's not me who needs this VCO. But if it was me and it had to be low
cost as the OP said I would certainly roll my own.

Synergy Microwave has a few good references on vco design, if you want to take
that route...

http://www.synergymwave.com/Articles/Articles.htm
Click to expand...
Thanks. Ulrich Rhode really knows his stuff. Got his Communication
Receivers book.

Regards, Joerg

http://www.analogconsultants.com
 
"W Letendre" <wjlservo@worldnet.att.net> wrote in message
news:1121622377.362880.149240@g14g2000cwa.googlegroups.com...
Need to generate in phase and quadrature digital signals, locked to
laser detector output at ~ 3.6 MHz (quite stable). Need reasonably high
precision 90deg shift and 50% duty fator +/- a percent or so. Thought
of building 4X multiplying PLL, followed by 2 bit quadrature divider.
So, looking for VCO that will run at 14.4 MHz.

Seem to find lots of chips for cell phone and other VHF/UHF/uWave apps,
and old standbys from 556 and 4046 family, but nothing that would work
at 14.4 MHz. Suppose I could make a Colpitts or Hartley circuit using
varactor diode for variable capacitance, but, hoping there is a chip
that will do this. Checked Maxim, National, Motorola, Linear
Technologies, Burr Brown, with no joy. Any other suggestions?

Thanks
W Letendre

Had 15megs from a 4046 but it was pushing it. The X4 loop multiplier is
Click to expand...
easily made by using (for example) 2 off, 4013 style, dual flip flops, wired
as a 'walking ring counter'. All four 0-90-180-270 phases, appear on the 'Q'
output pins.
regards
john
 
Hello John,

(CDxxxx's, as I'm stuck with balanced 6V supplies and signals)
Click to expand...
If you could run the logic just on the +6V side maybe HC would work.

Regards, Joerg

http://www.analogconsultants.com
 
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:MEzCe.231$Fk4.110@newssvr21.news.prodigy.com...
Hello John,

Had 15megs from a 4046 but it was pushing it. The X4 loop multiplier is
easily made by using (for example) 2 off, 4013 style, dual flip flops,
wired
as a 'walking ring counter'. All four 0-90-180-270 phases, appear on the
'Q'
output pins.

15MHz out of a 4046 is indeed pushing it. For the 4013 I'd use some
faster HC stuff for better 0-90 tolerance.

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
Yes, indeed.
74HC4046. F=15meg. Vcc=12V. IC=hot!. I've a 100kc-400kc setup using
CD4046/CD4013's running on the bench at the moment. Even at this relatively
low speed I've needed a small lead adding to back-off the loop delays.
(CDxxxx's, as I'm stuck with balanced 6V supplies and signals)
regards
john
 
On Sun, 17 Jul 2005 22:58:30 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello John,

(CDxxxx's, as I'm stuck with balanced 6V supplies and signals)

If you could run the logic just on the +6V side maybe HC would work.

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
HC will actually stand off about +7V, but the manufacturers won't tell
you that ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Hello Jim,

HC will actually stand off about +7V, but the manufacturers won't tell
you that ;-)
Click to expand...
Yes, I have read that somewhere. Some Asian mfgs have also allowed
operation down to 1.5V. But I work mostly in med and there everything
has to be cast in stone. IOW if it ain't in the data sheet you can't do it.

Did you get the kitchen drawers done?

Regards, Joerg

http://www.analogconsultants.com
 
On Sun, 17 Jul 2005 23:12:38 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

HC will actually stand off about +7V, but the manufacturers won't tell
you that ;-)

Yes, I have read that somewhere. Some Asian mfgs have also allowed
operation down to 1.5V. But I work mostly in med and there everything
has to be cast in stone. IOW if it ain't in the data sheet you can't do it.
Click to expand...
Ordinary 74HC... is optimized at +5V, will work reasonably well down
to +2.5V, but becomes like molasses at +1.5V

The I/C stuff I'm working on right now has 5V, 3.3V, 2.5V and 1.8V
devices on a single chip.

Did you get the kitchen drawers done?

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
Not yet. I'm installing wire baskets on ball-bearing glides in the
cabinets right now :-(

But it's giving me ideas for the drawers. These commercially-made
baskets have a cross piece in the back to maintain alignment of the
ball-bearing glides.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote...
The I/C stuff I'm working on right now has 5V, 3.3V, 2.5V and 1.8V
devices on a single chip.
Click to expand...
These days the multiplicity of supply-voltages is getting to be a
real pain for the designer. For example, modern 2.5 and 1.8V cPLDs
have a rather substantial power draw, and generally their supply is
not well-made using a linear regulator from +5V. One ends up with
multiple supply sources, often with special sequencing rules, and
perhaps with surprise interactions, like the difference frequency
between two switching regulators. A design I'm finishing now, a
five-channel DDS frequency generator, has seven supply voltages...
And it's meant to be well-behaved to the 10ppm level. What a pain!


--
Thanks,
- Win
 
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