Any low power low frequency quadrature receivers?

On Fri, 04 May 2012 08:13:29 -0700, Joerg wrote:

> miso wrote:
>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>> 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.
>> 
>> 
> 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.

You could reduce power (maybe) by using NE612 parts -- but not space, I 
think.

-- 
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On 5/4/2012 8:13 AM, Joerg wrote:
> miso wrote:
>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>> 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.
>>
>
> 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.

On Fri, 04 May 2012 10:47:31 -0500, Tim Wescott wrote:

> On Fri, 04 May 2012 08:13:29 -0700, Joerg wrote:
> 
>> miso wrote:
>>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>>> 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.
>>> 
>>> 
>> 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.
> 
> You could reduce power (maybe) by using NE612 parts -- but not space, I
> think.

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.

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Thu, 03 May 2012 17:53:25 -0700, Joerg wrote:

> 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?

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?

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.

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On 4 Maj, 17:13, Joerg <inva...@invalid.invalid> wrote:
> miso wrote:
> > On 5/3/2012 7:38 PM, Tim Williams wrote:
> >> 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.
>
> 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.
>

dual flipflop and dual dpdt switch?


-Lasse

Tim Wescott wrote:
> On Fri, 04 May 2012 10:47:31 -0500, Tim Wescott wrote:
> 
>> On Fri, 04 May 2012 08:13:29 -0700, Joerg wrote:
>>
>>> miso wrote:
>>>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>>>> 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.
>>>>
>>>>
>>> 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.
>> You could reduce power (maybe) by using NE612 parts -- but not space, I
>> think.
> 
> 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.

-- 
Regards, Joerg

http://www.analogconsultants.com/

miso wrote:
> On 5/4/2012 8:13 AM, Joerg wrote:
>> miso wrote:
>>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>>> 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.
>>>
>>
>> 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.


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.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Tim Wescott wrote:
> On Thu, 03 May 2012 17:53:25 -0700, Joerg wrote:
>
>> 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?
>
> 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...

--
Les Cargill

langwadt@fonz.dk wrote:
> On 4 Maj, 17:13, Joerg <inva...@invalid.invalid> wrote:
>> miso wrote:
>>> On 5/3/2012 7:38 PM, Tim Williams wrote:
>>>> 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.
>> 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.
>>
> 
> 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.

-- 
Regards, Joerg

http://www.analogconsultants.com/

Tim Wescott wrote:
> On Thu, 03 May 2012 17:53:25 -0700, Joerg wrote:
> 
>> 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?
> 
> 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.

-- 
Regards, Joerg

http://www.analogconsultants.com/