[time-nuts] Advanced 5 to 10 MHz doubler

paul swed paulswedb at gmail.com
Tue Jun 14 20:11:57 UTC 2011


Wow those are good results.
I have to say the thread was one that motivated me to buy parts and then to
do something.
If Luciano will be writing this up, I look forward to it. Always a good read
with excellent pictures.
I do not have a particular need just wanted to see what the suggestions
would do.
I do have a question. The doubler really would work for anything as I
recall.
10 mc in 20 out etc. Certainly some output adjustments needed.

Other comment injection locking is always interesting to me because you can
inject at quite low frequencies. I would like to see some of the details
from Henry.
Regards
Paul
WB8TSL

On Tue, Jun 14, 2011 at 3:00 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz
> wrote:

> Luciano followed this up off list and found that the suggested improvements
> (and others) worked well.
> The performance now closely mimics that of the simulations.
> Final results:
>
> Input range +6 to +13 dBm
> Gain 0dB ± 1 dB on the input range.
> Output harmonics and subharmonics -60 dBc
>
> He intends to write an article on it.
>
> As yet he hasn't been able to measure the phase noise as this requires
> using a pair of doublers with their outputs in phase quadrature.
>
> Bruce
>
>
> paul swed wrote:
>
>> Lets see feb to june. Time to restart this thread.
>> I found this a very interesting thread and finally ordered the
>> transformers
>> from mini circuits. Needed some other parts and had enough of an order to
>> make sense.
>> I do plan to build the circuit and try some of the comments suggested to
>> see
>> what happens.
>> Though this may take a bit of time. Lots of other things to work on.
>> Regards
>> Paul
>> WB8TSL
>>
>> On Wed, Feb 16, 2011 at 9:11 AM, paul swed<paulswedb at gmail.com>  wrote:
>>
>>
>>
>>> This has been a great read.
>>> Though I don't have a need at the moment. I may assemble this with the
>>> various comments just to try it out. Dead bug style.
>>> Regards
>>>
>>>
>>> On Wed, Feb 16, 2011 at 8:46 AM, Paramithiotti, Luciano Paolo S<
>>> luciano.paramithiotti at hp.com>  wrote:
>>>
>>>
>>>
>>>> Bruce,
>>>> I have collected yours comments, I hope they will be usefull for my next
>>>> doubler version.
>>>> A question: do you have ever made a physical doubler like this? if so,
>>>> can
>>>> you show us the schematic, photos and results of measurements made?
>>>>
>>>> Luciano
>>>>
>>>> Luciano P. S. Paramithiotti
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>>> Behalf Of Bruce Griffiths
>>>> Sent: martedì 15 febbraio 2011 22.19
>>>> To: Discussion of precise time and frequency measurement
>>>> Subject: Re: [time-nuts] Advanced 5 to 10 MHz doubler
>>>>
>>>> Simulation using LTSpice confirms that the 2N3904's actually saturate in
>>>> this circuit.
>>>> The phase noise performance will be poor.
>>>> The transistor conduction angle is also poorly defined and significant
>>>> conduction overlap due to saturation may render the circuit ineffective
>>>> at
>>>> high frequencies.
>>>>
>>>> The attached circuit schematic using a 1:4 (impedance ratio) input
>>>> transformer will work much better and has a relatively well defined
>>>> large
>>>> signal input impedance.
>>>> The output filter can be elaborated by replacing the 80pF caps with a
>>>> combination of series tuned LC traps and a smaller shunt capacitance to
>>>> reduce the level unwanted components.
>>>> Suitable 100uH inductors (with SRF>  20MHz) are readily available from
>>>> Farnell/element14.
>>>> The output impedance is relatively low and a better match to 50 ohms may
>>>> be achieved by adding a suitable low phase noise output buffer amp
>>>> stage.
>>>> Alternatively a 4:1 impedance ratio transformer can be used at the
>>>> collector node with its primary shunted by a 200 ohm resistor.
>>>>
>>>> Any balancing circuitry (should this be necessary) should be implemented
>>>> at the BJT emitters as any attempt to do this at the collectors will be
>>>> ineffective.
>>>>
>>>> Bruce
>>>>
>>>> Bruce Griffiths wrote:
>>>>
>>>>
>>>>> Paramithiotti, Luciano Paolo S wrote:
>>>>>
>>>>>
>>>>>>    http://www.timeok.it/files/5_to10_mhz_advanced_doubler.pdf
>>>>>>
>>>>>>
>>>>>>
>>>>>>> This design appears to have gone somewhat astray.
>>>>>>> high impedance unless of course the transistors enter saturation in
>>>>>>> which case the phase noise performance will be severely degraded.
>>>>>>> The best place for a balance adjustment circuit is actually in the
>>>>>>> emitter circuit.
>>>>>>>
>>>>>>>
>>>>>> *The collector balancing work correctly and is more simple to
>>>>>>
>>>>>>
>>>>> implement.
>>>>
>>>>
>>>>>
>>>>>>
>>>>> I contend that the collector balancing technique you use only works
>>>>> because the doubler isn't operating correctly.
>>>>> With a high impedance collector output it would be relatively
>>>>> ineffective unless the balancing resistance is increased to a level
>>>>> that degrades the phase noise performance or saturation occurs.
>>>>>
>>>>>
>>>>>> The description of the biasing is misleading in that the actual bias
>>>>>>> level that sets the crossover current is determined by the signal
>>>>>>> dependent voltage>across the two 0.1uF capacitors in the emitter.
>>>>>>> With a 1:1 input transformer the quoted figure of 35 ohms for the
>>>>>>> input impedance seems excessive for large signal operation of the CB
>>>>>>> stages unless of>course they saturate.
>>>>>>>
>>>>>>>
>>>>>> *the input impedance is 35 Ohms @ 0dBm as measured with network
>>>>>> vector analyzer. It can be upgraded to 50 ohms adding resistance on
>>>>>> emitters, with some gain reduction and probably less phase noise. I
>>>>>> will do some modification in the next future, including an input 6
>>>>>> Mhz low pass filter. As you know, the input signal have to be pure
>>>>>> sinewave to avoid unsymmetrical positive and negative half wave and
>>>>>> obvious unbalaced output and high harmonics contens. I will test also
>>>>>> the common emitter configuration to better isolate the doubler from
>>>>>> the input impedance and level variations. Regarding the input level I
>>>>>> have setup it's range, as my personal standard,from +7 to +13 dBm.
>>>>>>
>>>>>>
>>>>>>
>>>>> I thought as much, the large signal input impedance (this is far more
>>>>> important than the small signal value) will be much lower.
>>>>> Since the bias shifts with input signal level the small signal input
>>>>> impedance that you measured is of little value.
>>>>>
>>>>>
>>>>>
>>>>>> It would also appear that the 20MHz tank 5.6uH + 12pF as drawn is
>>>>>>> inappropriate in that it inevitably leads to saturated operation.
>>>>>>> A series resonant 20MHz tank from the collector node to ground would
>>>>>>> be a better choice.
>>>>>>>
>>>>>>>
>>>>>> * The LC on collector is to adapt the impedance between the doubler
>>>>>> and the filter and to cut the higher harmonics. The filter itself
>>>>>> contain trap for 15 20 and 30 Mhz.
>>>>>>
>>>>>>
>>>>>>
>>>>> Maybe so, but the filter input topology adopted is inappropriate for
>>>>> low phase noise and avoiding saturation.
>>>>> Attempting to match the (poorly predictable and varying - with
>>>>> temperature and input signal level) collector output impedance to the
>>>>> filter input impedance is misguided, just treat the output as a high
>>>>> impedance source. The 4:1 (impedance ratio) output transformer should
>>>>> suffice, if necessary you can add a 200 ohm resistor in shunt from the
>>>>> collector node to Vcc if you need a 50 ohm output impedance. In
>>>>> practice it may be better to buffer the output with a series
>>>>> transformer feedback stage with well defined output impedance. Series
>>>>> resonant LC traps from the doubler collector node to ground should be
>>>>> more effective than parallel resonant series traps in that the high
>>>>> frequency component amplitudes at the doubler collector will be
>>>>> significantly reduced rather than enhanced by the filter.
>>>>>
>>>>>
>>>>>
>>>>>> A snapshot or even a sketch of the collector voltage waveforms would
>>>>>>> be useful in showing that the transistors saturate or not.
>>>>>>>
>>>>>>>
>>>>>> *Actually the prototype is gone to friend's home and I cannot do any
>>>>>> more measure on it. My next prototype's pubblication will be complete
>>>>>> of collector voltage waveform to better understand the working
>>>>>> condition of the doubler stage. I think the 2N3904 is not the best
>>>>>> solution, i will test some more devices and bias point.
>>>>>>
>>>>>>
>>>>>>
>>>>> At 10MHz you will find that most wideband transistors will be noisier.
>>>>> However using transistors with a lower base spreading resistance than
>>>>> the 2N3904 may be useful.
>>>>>
>>>>>
>>>>>> Thank you
>>>>>> Luciano
>>>>>>
>>>>>> note: I'm not a genius, I just try to enjoy myself. If someone follow
>>>>>> me, is at his own risk.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Luciano P. S. Paramithiotti
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>> Bruce
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>>
>>>>
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>>>
>>>
>>>
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