budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:



In RF circles, the 'normal' way to do this would be a simple Class C
amplifier with a collector load tuned to the fifth harmonic. In calls C,
conduction only occurs for a small fraction of a cycle which produces a
correspondingly higher proportion of higher harmonics than a square wave.

I've been waiting for someone to post this. I would only add "The drive level,
and the bais point, will vary the amount of fifth (or whichever) you will see."

It's as common as noses in RF, as Ian pointed out. Just look at the average
two-way radio prior to frequency synthesisers. Crystal freqs were multiplied
this way in transmitter chains and for receive injection, although use of fifth
wasn't especially common because you normally had enough design control to use
the more efficient *2, *3 or *4.

'Tune for smoke' isn't an option for most new products, which have to
be manufactured without hands.

Better to pick a suitable duty cycle (or more likely a conduction time
period in a digital circuit), that has an efficient 5th harmonic
component, including delays, at low power levels.

http://www.wenzel.com/pdffiles/choose.pdf

RL

Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output
level you like.

Whatever you do don't go for phase locked loops.

Junk your Spice. It tells you nothing you didn't already ought to know. If
you don't know it then you shouldn't be doing the job anyway.

You must have plenty of room on the PCB. But why don't you invest in a 17.2
MHz quartz crystal. They're cheap enough. You've already spent more time
and trouble on research and investigation. Cut your losses.

Redundency is a serious crime. It degrades reliabilty. Reliability is
Quality versus Time. Every individual component must serve a recognisable,
readily understandable purpose. If it's not understood then it shouldn't be
there.

High Quality is adherence to the specified intended purpose.

Now I suppose some bright spark will say deliberate redundency can improve
reliability. But ONLY when all else has failed.
----
Reg.


"Paul Burridge" wrote in message
...
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it
will
drop fairly quickly as the sides of the input square wave deviate from
vertical.

Does the 3.44MHz have a 50% duty cycle?

Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif

This other trace was snapped at the base of the transistor stage that
does the multiplying. All there is (circuitry-wise) between this trace
and the last one is a 330 ohm series resistor and a 47pF cap. I'd have
expected to see some clamping action due to the b/e junction, but the
waveshape seems very odd - but does concur with the Spice simulation.
Is there anything amiss, here? (Setting here is 0.5V/div)

http://www.burridge8333.fsbusiness.co.uk/trace2.gif

Still not a sniff of a fifth! :-(
Currently building Reg's 17.2Mhz BPF to see if that can expose it.
--

The BBC: Licensed at public expense to spread lies.

Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output
level you like.

Whatever you do don't go for phase locked loops.

Junk your Spice. It tells you nothing you didn't already ought to know. If
you don't know it then you shouldn't be doing the job anyway.

You must have plenty of room on the PCB. But why don't you invest in a 17.2
MHz quartz crystal. They're cheap enough. You've already spent more time
and trouble on research and investigation. Cut your losses.

Redundency is a serious crime. It degrades reliabilty. Reliability is
Quality versus Time. Every individual component must serve a recognisable,
readily understandable purpose. If it's not understood then it shouldn't be
there.

High Quality is adherence to the specified intended purpose.

Now I suppose some bright spark will say deliberate redundency can improve
reliability. But ONLY when all else has failed.
----
Reg.


"Paul Burridge" wrote in message
...
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it
will
drop fairly quickly as the sides of the input square wave deviate from
vertical.

Does the 3.44MHz have a 50% duty cycle?

Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif

This other trace was snapped at the base of the transistor stage that
does the multiplying. All there is (circuitry-wise) between this trace
and the last one is a 330 ohm series resistor and a 47pF cap. I'd have
expected to see some clamping action due to the b/e junction, but the
waveshape seems very odd - but does concur with the Spice simulation.
Is there anything amiss, here? (Setting here is 0.5V/div)

http://www.burridge8333.fsbusiness.co.uk/trace2.gif

Still not a sniff of a fifth! :-(
Currently building Reg's 17.2Mhz BPF to see if that can expose it.
--

The BBC: Licensed at public expense to spread lies.

On Fri, 12 Mar 2004 13:56:10 +0000, Paul Burridge
wrote:

Hi all,

Is there some black magic required to get higher order harmonics out
of an oscillator?
I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far
failing spectacularly. I've tried everything I can think of so far to
no avail. All I can get apart from the fundamental is a strong third
harmonic on 10.32Mhz, regardless of what I tune for. I've tried
passing the osc output through two successive inverter gates to
sharpen it up, but still nothing beyond the third appears after tuned
amplification for the fifth. I no longer have a spectrum analyser so
can't check for the presence of a decent comb of harmonics at the
input to the multiplier stage but can only assume the fifth is well
down in the mush for some reason. I could change the inverters for
schmitt triggers and gain a couple of nS but can't see that making
enough difference. What about sticking a varactor in there somewhere?
Would its non-linearity assist or are they only any good for even
order harmonics?
Any suggestions, please. I'm stumped!

Certain duty cycles contain better 5th harmonic component amplitudes.
A graph of fourier components is a useful guide -

http://www.wenzel.com/pdffiles/choose.pdf

One precaution; the chart in this article does not include phase
information - this can reverse - which may be important for timing.

RL

On Fri, 12 Mar 2004 13:56:10 +0000, Paul Burridge
wrote:

Hi all,

Is there some black magic required to get higher order harmonics out
of an oscillator?
I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far
failing spectacularly. I've tried everything I can think of so far to
no avail. All I can get apart from the fundamental is a strong third
harmonic on 10.32Mhz, regardless of what I tune for. I've tried
passing the osc output through two successive inverter gates to
sharpen it up, but still nothing beyond the third appears after tuned
amplification for the fifth. I no longer have a spectrum analyser so
can't check for the presence of a decent comb of harmonics at the
input to the multiplier stage but can only assume the fifth is well
down in the mush for some reason. I could change the inverters for
schmitt triggers and gain a couple of nS but can't see that making
enough difference. What about sticking a varactor in there somewhere?
Would its non-linearity assist or are they only any good for even
order harmonics?
Any suggestions, please. I'm stumped!

Certain duty cycles contain better 5th harmonic component amplitudes.
A graph of fourier components is a useful guide -

http://www.wenzel.com/pdffiles/choose.pdf

One precaution; the chart in this article does not include phase
information - this can reverse - which may be important for timing.

RL

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:


Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif



That waveform *has* bunches of 5th harmonic. All you need is a
properly functioning bandpass filter to pluck it out.

John

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:


Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif



That waveform *has* bunches of 5th harmonic. All you need is a
properly functioning bandpass filter to pluck it out.

John

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:

On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it will
drop fairly quickly as the sides of the input square wave deviate from vertical.

Does the 3.44MHz have a 50% duty cycle?

Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif

---
That's close enough to 50% that you should have no problem generating
and extracting a fifth harmonic.
---

This other trace was snapped at the base of the transistor stage that
does the multiplying. All there is (circuitry-wise) between this trace
and the last one is a 330 ohm series resistor and a 47pF cap. I'd have
expected to see some clamping action due to the b/e junction, but the
waveshape seems very odd - but does concur with the Spice simulation.
Is there anything amiss, here? (Setting here is 0.5V/div)

http://www.burridge8333.fsbusiness.co.uk/trace2.gif

---
If you've got the cap and resistor in series with the base, and no other
circuitry in there, then what you're doing is half-wave rectifying the
square wave in the base-to-emitter diode, and that's what you're seeing,
along with what looks like some AC at the fundamental riding on the
falling peaks and rising valleys of the square wave. The reason you
can't see the fifth harmonic is because it's far enough down that
everything else is so much higher in voltage that it's essentially down
in the mud. If you want the fifth out, you'll have to extract it using
a filter of some sort, the easiest being a series tuned trap or a
parallel tuned tank.

Why don't you post your schematic so we can see exactly what you're
doing?
---

Still not a sniff of a fifth! :-(
Currently building Reg's 17.2Mhz BPF to see if that can expose it.

---
That'll probably do it, but it needs to go on the output of the
multiplier, not between the square wave generator and the input, I
think.

Again, why don't you post a schematic of what you're up to? Please?-)

--
John Fields

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:

On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it will
drop fairly quickly as the sides of the input square wave deviate from vertical.

Does the 3.44MHz have a 50% duty cycle?

Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif

---
That's close enough to 50% that you should have no problem generating
and extracting a fifth harmonic.
---

This other trace was snapped at the base of the transistor stage that
does the multiplying. All there is (circuitry-wise) between this trace
and the last one is a 330 ohm series resistor and a 47pF cap. I'd have
expected to see some clamping action due to the b/e junction, but the
waveshape seems very odd - but does concur with the Spice simulation.
Is there anything amiss, here? (Setting here is 0.5V/div)

http://www.burridge8333.fsbusiness.co.uk/trace2.gif

---
If you've got the cap and resistor in series with the base, and no other
circuitry in there, then what you're doing is half-wave rectifying the
square wave in the base-to-emitter diode, and that's what you're seeing,
along with what looks like some AC at the fundamental riding on the
falling peaks and rising valleys of the square wave. The reason you
can't see the fifth harmonic is because it's far enough down that
everything else is so much higher in voltage that it's essentially down
in the mud. If you want the fifth out, you'll have to extract it using
a filter of some sort, the easiest being a series tuned trap or a
parallel tuned tank.

Why don't you post your schematic so we can see exactly what you're
doing?
---

Still not a sniff of a fifth! :-(
Currently building Reg's 17.2Mhz BPF to see if that can expose it.

---
That'll probably do it, but it needs to go on the output of the
multiplier, not between the square wave generator and the input, I
think.

Again, why don't you post a schematic of what you're up to? Please?-)

--
John Fields

In article , Paul Burridge
writes:

On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa)
wrote:

Fifth harmonic frequency multipliers do exist, but it's usually much
easier to double and triple your way to the final frequency if possible.
(You just discovered this, I think!)

Yeah, but trying to get the 5th is hardly asking for the moon...

In a way, it IS. Fifth harmonic of an infinitely sharp transition
rectangular waveform is still low in energy compared to the
fundamental. Chances are that a single stage using an active
device as a quintupler will NOT be successful, transistor or tube
(valve).

Let's get to some specifics on this problem -

1. Let us know what you are using to determine whether or not
a 5th harmonic exists. The lack of indication may be due to
whatever it is (not a spectrum analyzer) being used.
2. Describe the multiplier stage in more detail and include an
approximate level and impedance/admittance of the RF
source. That would include supply rails and biasing.
3. Describe whatever is being used to select the 5th harmonic
and inhibit the fundamental and other harmonics. There's
lots of energy at many different frequencies floating around
there and you only want one frequency.
4. Review again with us the output drive level requirements so
we can get a handle on that.
5. If you are using an oscilloscope to measure the fundamental
waveform, estimate the actual risetime/falltime based on the
rise/fall times limits of the oscilloscope. That yields some
basic data that can be applied to a Fourier series to determine
the level of 5th harmonic energy you have to work with. [that
will also reveal the approximate frequency limits of the scope]

The lack of even harmonics is typical of push-pull stages ... if you
are messing around with CMOS gates, you might try using a TTL gate
(which pulls low much stronger than it pulls high) or an open collector
TTL gate, both with smmallish (100-200 ohm) pull-up resistors for
doubling.

I've a reasonably fast Schmitt I'm going to stick in there in place of
the 74HC04 before I resort to anything fancy (same pin-out).

Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz?

Because I don't have a rock lying about for that fundamental!

Hint: A mixed 2x and 3x = 5x out if filtered to pass that. No lying-
around rock needed. [not an optimum solution]

Note: As already pointed out, a single PLL IC can do the job in the
same PCB footprint.

When frustration hits a peak, it's time to sit back away from the
problem and do an objective review of what is the overall task and
what you've accomplished so far and what you know about certain
circuits fundamentals. General problem descriptions only result in
general solutions without quantitative values needed for a specific
application.

I've found that NON-linear circuits (a multiplier stage is definietly
in the non-linear category) take rather more development time
than a linear circuit. There's lots of different things going on in a
multiplier circuit and those have to be considered for the whole.

Hopefully some supreme being here will spot a problem with the traces
I've now posted...

Try as we might in the depths of our frustrations, supreme beings
tend not to intervene in us humans' petty affairs. :-)

Len Anderson
retired (from regular hours) electronic engineer person