EMRFD Message Archive 5171

Message Date From Subject
5171 2010-09-17 12:37:52 Chris Trask X-Mode Mixer (was: mixers: strong signal immunity)
>
> >
> > > I found it horrible how many tranformers/parts you typically used
before :-)
> > >
> >
> > Nah! Transformers are your friend. Once you understand how the
hybrid (or
> > bridge) transformer works, which is the same as a hybrid junction, you
can do
> > all sorts of wonderful signal processing things.
>
> T4 concerns me a bit in that IFs I've worked with range from high 144mhz,
to low
> .455mhz and more than a few audio baseband IQ DCRX. For most of the RF
range
> it's core selection and turns, for the very low end The transformer starts
with
> laminations (audio).
>
> Drive required?
> Lo to RF isolation?
>

Here's the numbers for the port-to-port isolation for this preliminary
prototype:

RF to IF -54dB
RF to LO -76dB
IF to RF -54dB
IF to LO -54dB
LO to RF -54dB
LO to IF -76dB

Not bad for parts pulled out of a jar.


Chris Trask
N7ZWY / WDX3HLB
Senior Member IEEE
http://www.home.earthlink.net/~christrask/
5172 2010-09-17 12:49:37 David Stone Re: X-Mode Mixer (was: mixers: strong signal immunity)
Chris, they are too good, are you measuring them while the mixer is working,
that is two sig gens and a network analyser or three and a spectrum analyser?
These sound awfully like the isolations of a set of switched off diodes

David




________________________________
5173 2010-09-17 13:30:52 Chris Trask Re: X-Mode Mixer (was: mixers: strong signal immunity)
>
> Chris, they are too good, are you measuring them while the mixer is
working,
> that is two sig gens and a network analyser or three and a spectrum
analyser?
> These sound awfully like the isolations of a set of switched off diodes
>
>
> Here's the numbers for the port-to-port isolation for this preliminary
> prototype:
>
> RF to IF -54dB
> RF to LO -76dB
> IF to RF -54dB
> IF to LO -54dB
> LO to RF -54dB
> LO to IF -76dB
>
> Not bad for parts pulled out of a jar.
>

Duh! I didn't have the LO turned on. Let me try that again with the
LO on this time:

RF to IF -40dB
IF to RF -38dB
LO to IF -47dB
LO to RF -57dB

I'd like to see how this improves when using four matched diodes, such
as the BAV70DW (silicon) or BAS40-05V (Schottky). But, I won't have any of
those in the near term.

Chris
5174 2010-09-17 17:37:13 kb1gmx Re: X-Mode Mixer (was: mixers: strong signal immunity)
5206 2010-09-19 13:19:20 Chris Trask Re: X-Mode Mixer (was: mixers: strong signal immunity)
Much to my surprise, my first batch of Schottky diodes arrived
yesterday, so now I can begin making some performace comparisons:

Diode BAV70 BAT54C
LO Level 2.0V 1.0V
Isolation RF to IF -40dB -47dB
IF to RF -38dB -47dB
LO to IF -47dB -59dB
LO to RF -57dB -67dB
OIP3 +22dBm +18dBm
Conversion Gain -5dB -4dB

I'm not surprised that the OIP3 is lower with the BAT54C diodes as the
LO level is much lower and therefore they will saturate earlier. Also,
these are 5nS recovery time diodes, and I'd really like to try something
faster.

I have other diodes on the way, but no BAS40-05 or BAS40-06 as of yet.
Those are much faster and should yield better OIP3 performance. Ultimately,
I'd like to try some HSMS-281x devices as they have a controlled dynamic
resistance. These diodes I'm using now are not exactly premium quality
mixer devices.


Chris Trask
N7ZWY / WDX3HLB
Senior Member IEEE
http://www.home.earthlink.net/~christrask/
5207 2010-09-19 14:55:58 ehydra Re: X-Mode Mixer
Looks good.

And the frequency is? Powered with your mentioned squarer circuit?

Where is the problem to sample BAS40-05 ? I googled and it is all over
alround there...
I'm not sure if all sources mean the same chip specs.
The quadruple is the BAS40-05V and BAS40XY. See:
http://www.nxp.com/documents/data_sheet/BAS40_1PSXXSB4X_SER.pdf

And for the HP devices:
http://www.avagotech.com/pages/en/rf_microwave/diodes/schottky/hsms-2805/
It is not possible to sample them? Maybe they are just to expensive to
be used final.

regards -
Henry


--
ehydra.dyndns.info


Chris Trask schrieb:
> Much to my surprise, my first batch of Schottky diodes arrived
> yesterday, so now I can begin making some performace comparisons:
>
> Diode BAV70 BAT54C
> LO Level 2.0V 1.0V
> Isolation RF to IF -40dB -47dB
> IF to RF -38dB -47dB
> LO to IF -47dB -59dB
> LO to RF -57dB -67dB
> OIP3 +22dBm +18dBm
> Conversion Gain -5dB -4dB
>
> I'm not surprised that the OIP3 is lower with the BAT54C diodes as the
> LO level is much lower and therefore they will saturate earlier. Also,
> these are 5nS recovery time diodes, and I'd really like to try something
> faster.
>
> I have other diodes on the way, but no BAS40-05 or BAS40-06 as of yet.
> Those are much faster and should yield better OIP3 performance. Ultimately,
> I'd like to try some HSMS-281x devices as they have a controlled dynamic
> resistance. These diodes I'm using now are not exactly premium quality
> mixer devices.
5235 2010-09-23 13:49:22 Chris Trask Re: X-Mode Mixer (was: mixers: strong signal immunity)
Yet another batch of Schottky diodes arrived this morning, these being
BAT54S devices, which is a pair of Schottky diodes connected in series.
Here are the performace comparisons:

Diode BAV70 BAT54C HSMS-2804 BAT54S
LO Level 2.0V 1.0V 1.0V 2.0V
Isolation RF to IF -40dB -47dB -46dB -45dB
IF to RF -38dB -47dB -47dB -45dB
LO to IF -47dB -59dB -60dB -60dB
LO to RF -57dB -67dB -90dB -63dB
OIP3 +22dBm +18dBm >+20dBm >+27dBm
Conversion Gain -5dB -4dB -6.5dB -6.5dB

This is getting more interesting by the moment. Seems that this X-Mode
mixer has the potential for getting 6dB or better OIP3 performance than a
comparable diode ring mixer (DRM). Looks like I'll have to add the
HSMS-2812 to my shopping list.


Chris Trask
N7ZWY / WDX3HLB
Senior Member IEEE
http://www.home.earthlink.net/~christrask/
5236 2010-09-23 16:20:27 ehydra Re: X-Mode Mixer (was: mixers: strong signal immunity)
This is a fine overview for rf parts:
http://www.rfmicrowave.it/catalogo/eng/catalogo.pdf

- Henry

--
ehydra.dyndns.info


Chris Trask schrieb:
> Yet another batch of Schottky diodes arrived this morning, these being
> BAT54S devices, which is a pair of Schottky diodes connected in series.
> Here are the performace comparisons:
>
> Diode BAV70 BAT54C HSMS-2804 BAT54S
> LO Level 2.0V 1.0V 1.0V 2.0V
> Isolation RF to IF -40dB -47dB -46dB -45dB
> IF to RF -38dB -47dB -47dB -45dB
> LO to IF -47dB -59dB -60dB -60dB
> LO to RF -57dB -67dB -90dB -63dB
> OIP3 +22dBm +18dBm >+20dBm >+27dBm
> Conversion Gain -5dB -4dB -6.5dB -6.5dB
>
> This is getting more interesting by the moment. Seems that this X-Mode
> mixer has the potential for getting 6dB or better OIP3 performance than a
> comparable diode ring mixer (DRM). Looks like I'll have to add the
> HSMS-2812 to my shopping list.