On Sun, 15 Feb 2004 23:48:47 +0000, Paul Burridge
wrote:

What's the maximum multiplication factor it's practical and sensible
to attempt to achieve in one single stage of multiplication? (Say from
a 7Mhz square wave source with 5nS rise/fall times.)

You ought to be able to answer that yourself... what's the spectral
roll-off of a square wave ??

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

I think it boils down to something very practical:

If you want good spectral purity, then you need to bandpass filter the
output of the multiplier. It becomes a matter of how close and how large the
undesired spectral components are compared to the desired spectral
components. After that, you can consult your filter design charts to
determine how complex a filter will be required and whether it's physically
realizable.

As an example, a x4 multiplier stage will have a desired output at Fin x 4,
and close-in undesired products at Fin x 3 and Fin x 5. This means the
output bandpass filter has to be able to attenuate signals at +/-25% of the
center frequency sufficiently to meet the desired spectral purity. In
practice with simple single-ended multiplier designs, a x4 multiplier is
approaching the threshold of realizability for high purity applications
(40-60 dB purity). It is possible to make push-pull and push-push
multipliers that have better output purity, but these techniques are seldom
used.

Joe
W3JDR



"Jim Thompson" wrote in message
...
On Sun, 15 Feb 2004 23:48:47 +0000, Paul Burridge
wrote:

What's the maximum multiplication factor it's practical and sensible
to attempt to achieve in one single stage of multiplication? (Say from
a 7Mhz square wave source with 5nS rise/fall times.)

You ought to be able to answer that yourself... what's the spectral
roll-off of a square wave ??

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:

I think it boils down to something very practical:

If you want good spectral purity, then you need to bandpass filter the
output of the multiplier. It becomes a matter of how close and how large the
undesired spectral components are compared to the desired spectral
components. After that, you can consult your filter design charts to
determine how complex a filter will be required and whether it's physically
realizable.

As an example, a x4 multiplier stage will have a desired output at Fin x 4,
and close-in undesired products at Fin x 3 and Fin x 5. This means the
output bandpass filter has to be able to attenuate signals at +/-25% of the
center frequency sufficiently to meet the desired spectral purity. In
practice with simple single-ended multiplier designs, a x4 multiplier is
approaching the threshold of realizability for high purity applications
(40-60 dB purity). It is possible to make push-pull and push-push
multipliers that have better output purity, but these techniques are seldom
used.

Joe
W3JDR


[snip]

I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)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 in message
...
On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:

I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |


One would think a "PE" could give the man a civil answer.

Pete

I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.

I guessed I missed Jim's comment in the earlier post, or I would have replied earlier.
Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it.

Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage.

In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined.

Joe
W3JDR

On Mon, 16 Feb 2004 17:02:20 GMT, "W3JDR" wrote:

I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.

I guessed I missed Jim's comment in the earlier post, or I would have replied earlier.
Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it.

Only mildly so, just "funning" you ;-)


Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage.

In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined.

Joe
W3JDR

It depends on what your are starting from. If it's a sine wave, yes
even harmonics can be made from diode non-linearities.

The OP has a inverter-style XTAL oscillator, output very nearly
square.

A square wave is rich in odd harmonics, a perfect square wave has NO
even harmonics.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

It depends on what your are starting from. If it's a sine wave, yes
even harmonics can be made from diode non-linearities.

The OP has a inverter-style XTAL oscillator, output very nearly
square.

A square wave is rich in odd harmonics, a perfect square wave has NO
even harmonics.



Oh! I see what you're talking about...
I presumed that he was starting with a single spectral component (sine wave) and wanted to end up with another single spectral component.


Joe
W3JDR

On Mon, 16 Feb 2004 10:19:49 -0700, Jim Thompson
wrote:


It depends on what your are starting from. If it's a sine wave, yes
even harmonics can be made from diode non-linearities.

The OP has a inverter-style XTAL oscillator, output very nearly
square.

A square wave is rich in odd harmonics, a perfect square wave has NO
even harmonics.

---
Starting with a perfect square wave at f1, bang the hell out of a diode
with it, and then bandpass it and the 3rd harmonic (f2) separately, then
mix them to get f1, f2, f1+f2, and f1-f2. Using a doubly balanced mixer
will get rid of f1 and f2, then notching out f1+f2 will leave f1-f2,
which will be 2f1, that non-existent second harmonic.

--
John Fields

It depends on what your are starting from. If it's a sine wave, yes
even harmonics can be made from diode non-linearities.

The OP has a inverter-style XTAL oscillator, output very nearly
square.

A square wave is rich in odd harmonics, a perfect square wave has NO
even harmonics.



Oh! I see what you're talking about...
I presumed that he was starting with a single spectral component (sine wave) and wanted to end up with another single spectral component.


Joe
W3JDR

On Mon, 16 Feb 2004 10:19:49 -0700, Jim Thompson
wrote:


It depends on what your are starting from. If it's a sine wave, yes
even harmonics can be made from diode non-linearities.

The OP has a inverter-style XTAL oscillator, output very nearly
square.

A square wave is rich in odd harmonics, a perfect square wave has NO
even harmonics.

---
Starting with a perfect square wave at f1, bang the hell out of a diode
with it, and then bandpass it and the 3rd harmonic (f2) separately, then
mix them to get f1, f2, f1+f2, and f1-f2. Using a doubly balanced mixer
will get rid of f1 and f2, then notching out f1+f2 will leave f1-f2,
which will be 2f1, that non-existent second harmonic.

--
John Fields