Any low power low frequency quadrature receivers?

[Joerg]

While looking at a single sideband receiver project that may be coming
up I checked the usual suspects for quadrature demodulators. Many won't
(technically ...) go much below 100MHz. Some do and I need to be more in
the 5-10MHz region. But they are massive guzzlers when it comes to
draining the battery. Like this one which slurps a whole watt (!):

http://cds.linear.com/docs/Datasheet/5584f.pdf

Isn't there anything better out there that hasn't been discontinued? Or
do I have to roll my own again?

 

[Tim Williams]

Hell... these days, it's more like... ADC, Hilbert transform, lowpass
filter. And it'd probably come out way less than a watt. That's kind of
sad.

Tim

 

[miso]

Hell... these days, it's more like... ADC, Hilbert transform, lowpass
filter. And it'd probably come out way less than a watt. That's kind of
sad.

Tim

If you have access to the clock, actually 4x the clock, the demod can be
quite simple. Split the sample stream in half, then with those two
streams, alternately multiply by -1. Then you have I and Q channels.

 

[Joerg]

something like this?: http://www.analog.com/en/rfif-components/modulatorsdemodulators/ad8333/products/product.html

Yes, something like but just not at so much power consumption. This one
is especially archaic. Needs a negative supply which nowadays hardly any
device has (ok, I can make that) and then almost 200mW. They state it
"per channel", probably so it looks better

 

[Joerg]

Hell... these days, it's more like... ADC, Hilbert transform, lowpass
filter. And it'd probably come out way less than a watt. That's kind
of sad.

That's going to consume lots of real estate and power. I have a spectrum
analyzer that works in a similar way but still needs 2W (which, of
course, is much less then the 200-300W of a big boat anchor). The PC
digs all the signals back out but after a few minutes the fans come on
and stay on ...

 

[Joerg]

If you have access to the clock, actually 4x the clock, the demod can be
quite simple. Split the sample stream in half, then with those two
streams, alternately multiply by -1. Then you have I and Q channels.

I know, I've done it many times that way using discrete parts. Since the
late 80's, pretty much. But that consumes lots of real estate and power.
This time I don't have either.

 

[miso]

I know, I've done it many times that way using discrete parts. Since the
late 80's, pretty much. But that consumes lots of real estate and power.
This time I don't have either.

Lots of patents on that scheme. It is really a pity since the scheme is
totally obvious to those skilled in the art.

 

[Joerg]

Come to think of it, I've done this using CMOS switches as the "mixer" --
but that was in a spot that could stand being low dynamic range, and it
was at audio-ish frequencies.

Either method is the classical one, with lots of parts and lots of rea
estate. Nowadays one can get many chips in TSSOP but not all of them. A
SO-package would be like a Mack truck on this board.

 

[Joerg]

Lots of patents on that scheme. It is really a pity since the scheme is
totally obvious to those skilled in the art.

If such silly patents haven't run out all it takes is proof that you
dunnit 25 years ago and ... poof ... blows it out the water.

 

[Les Cargill]

So, are the semiconductor manufacturers really missing the boat on this,
or is there really not a big market outside of a few old ex ham radio
guys?

I'd guess the latter. Lots of 900MHz, lots of 2.4, not a lot
else...

Because there does seem to be a big gap (from about 0Hz to 100MHz, in
fact) for a nice, modern, small, low-power implementation of this.

Maybe all that most of the engineering world knows how to do is copy
their competitor's designs, or go straight to digital.

I think the salient question is: will it end up on a box
in a Frys? Even then, you're gambling the NRE...

 

[Joerg]

dual flipflop and dual dpdt switch?

Sure, that's the usual way because the SA612 and others cannot be had in
TSSOP whereas some CMOS muxes can. But that leaves a ton of other
circuitry such as amps and such to be added.

I am just surprised that when it comes to complete quadrature
demodulators on a single chip there's on Goliaths out there.

 

[Joerg]

So, are the semiconductor manufacturers really missing the boat on this,
or is there really not a big market outside of a few old ex ham radio
guys?

They are missing the whole medical and NDT market. Ok, those aren't big
but very profitable. Because there you can easily sell a chip at five
bucks that costs 10c in production and is simply a stripped-down version
of a big one.

Because there does seem to be a big gap (from about 0Hz to 100MHz, in
fact) for a nice, modern, small, low-power implementation of this.

Maybe all that most of the engineering world knows how to do is copy
their competitor's designs, or go straight to digital.

Often that is the case, they follow each other and sometimes blindly.
There are many things in the world of ICs that IC designers or their
managers fail to see. Another classic one: Switcher chips that support
higher voltage designs often have an on-chip LDO that supplies the gate
driver with a fixed 7V or so. Yet anyone in the trade who has designed
switchers a lot knows that most FETs above 100V are not spec'd at any
Vgs under 10V. So _every_ time I design such a switcher I have to
backfeed the LDO output. Chips that don't have that piped out or have a
shunt regulator at less than 10V are useless for such designs.

 

[John S]

While looking at a single sideband receiver project that may be coming
up I checked the usual suspects for quadrature demodulators. Many won't
(technically ...) go much below 100MHz. Some do and I need to be more in
the 5-10MHz region. But they are massive guzzlers when it comes to
draining the battery. Like this one which slurps a whole watt (!):

http://cds.linear.com/docs/Datasheet/5584f.pdf

Isn't there anything better out there that hasn't been discontinued? Or
do I have to roll my own again?

Would this do you any good?....

http://www.silabs.com/products/audiovideo/amfmreceivers/Pages/Si4840-44.aspx

Mind the wrap.

 

[Joerg]

Would this do you any good?....

http://www.silabs.com/products/audiovideo/amfmreceivers/Pages/Si4840-44.aspx


Mind the wrap.

Almost ... but: According to the datasheet its DSP is limited to a
cast-in-concrete command set. It doesn't allow piping I and Q straight
through but does AM detection. No independent sideband processing :-(

 

[John S]

Almost ... but: According to the datasheet its DSP is limited to a
cast-in-concrete command set. It doesn't allow piping I and Q straight
through but does AM detection. No independent sideband processing :-(

Well, then, how about the AD8339?

 

[Glenn]

While looking at a single sideband receiver project that may be coming
up I checked the usual suspects for quadrature demodulators. Many won't
(technically ...) go much below 100MHz. Some do and I need to be more in
the 5-10MHz region. But they are massive guzzlers when it comes to
draining the battery. Like this one which slurps a whole watt (!):

http://cds.linear.com/docs/Datasheet/5584f.pdf

Isn't there anything better out there that hasn't been discontinued? Or
do I have to roll my own again?

How about this one?:

12V 50mA (74HC4052 based):

Direct Conversion HF Receiver with DDS VFO, OH2NLT and OH7SV:
http://www.nikkemedia.fi/juma-rx1/index-en.html

-

12V 11mA:

Very High Performance Image Rejecting Direct Conversion Receivers
Or how can an 11 ma receiver out perform the world’s best ham transceivers?:
http://www.norcalqrp.org/files/AustinNC2030Presentation.pdf

-

144MHz All Mode Transceiver:
http://www.qsl.net/va3iul/144MHz All Mode Transceiver/2m_allmode.html

MC1496:
http://www.onsemi.com/PowerSolutions/product.do?id=MC1496

-

More here:
http://home.pages.at/chirt/Projects/HDR2005/ref/ref.htm

Glenn

 

[Joerg]

How about this one?:

12V 50mA (74HC4052 based):

Direct Conversion HF Receiver with DDS VFO, OH2NLT and OH7SV:
http://www.nikkemedia.fi/juma-rx1/index-en.html

That's the good old classical way with a very "busy" schematic:

http://www.nikkemedia.fi/juma-rx1/juma-rx1-main-SCH-Rev-E.pdf

-

12V 11mA:

Very High Performance Image Rejecting Direct Conversion Receivers
Or how can an 11 ma receiver out perform the world’s best ham
transceivers?:
http://www.norcalqrp.org/files/AustinNC2030Presentation.pdf

Almost the same.

-

144MHz All Mode Transceiver:
http://www.qsl.net/va3iul/144MHz All Mode Transceiver/2m_allmode.html

Yikes! Somebody must have been vey patient at the soldering station

MC1496:
http://www.onsemi.com/PowerSolutions/product.do?id=MC1496

You get one lone mixer in a fairly big package, like with the SA612.
After it's all said and done you've got a whole big circuit board full
of stuff. I just won't have that much space in this case.

-

More here:
http://home.pages.at/chirt/Projects/HDR2005/ref/ref.htm

Thanks, Glenn. Unfortunately none of the authors seems to have found a
more integrated solution than the usual concoction of single-part mixers
and logic chips. If I absolutely have to I'll probably use logic chips,
the main reason being that those can now be bought in TSSOP packages
whereas mixers can't be.

 

[Joerg]

Why not use a cheap microcontroller, low current like the Cortex M0
NXP series.

Simple analog bandpass filter of the incoming signal, syncronize a ADC
from a PWM Local Osc generated by the micro, use a low frequency FIR
filter to regenerate the shifted down signal from the undersampled
output of the ADC.

The ADC needs to be triggered with low jitter, but that should be
simple.

The Cortex M0 can run at full speed below 1mA, add another 1mA for a
1MSa/s ADC. A number of other microcontrollers can do the same, the
Cortex is just a very nice part.

First we'd have to mix it down for that because my signal will be at
5-10MHz carrier frequency. Can also be undersampled, of course, but
that'll cost a little SNR. Which would probably be ok in this
application, we don't need to be able to hear the grass grow.

Initially I thought about using a PSoC because it already has digital
blocks for the quadrature oscillator generation. Also switched-capacitor
blocks which I should be able to "mis-use" as mixers, and then opamps
for some gain. But I am not a programmer whizkid. Once we get into a
higher volume project I'll revisit that, possibly a PSoC-3 is the ticket
here if I disable the uC in there. The on-board ADC capabilities are a
bit paltry though.

 

[Joerg]

If you feel you need to do direct conversion or analog I/Q (Ahem, I
hope not!) ...

Unfortunately, yes, that's exactly what I need to do.

... Heyward's "Solid State Design for the Radio Amateur" is
loaded with QRP direct conversion and many simple quadrature IF
schemes.

I hope you find a AM/ssb chip.

My hope in that respect has dwindled quite a bit. There used to be a
TDA-something chip but NXP has discontinued a lot of chips. Anything
else I've seen falls more under the energy guzzler class where you
pretty much can't operate it unless there is a wall outlet, and in this
case there isn't.

 

[Joerg]

AFAIC the psoc1 max mixer freq is in tens of kHz whereas the psoc3 can
handle up to 1 MHz. You may be able to use the psoc1 internal analog
bus as a integrated S/H, but I don't think the specs are to your
liking.

Yes, specs are the other reason why I didn't pursue this further right
now. Last time I looked at the opamp data I was not too thrilled. It's
ok for mundane stuff such as control gear but for sensitive RF
processing maybe not. The PSoC-3 has nice digital fliter blocks though,
it may be much better than the old ones.