Switched mode RF amplifiers

[amal banerjee]

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to
accurately sample the signal to be amplified. So, if
the input signal has frequency of e.g., 500 MHz, the
sampling frequency must be atleast 2x or 1 GHz, to
curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

 

On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
<dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to
accurately sample the signal to be amplified. So, if
the input signal has frequency of e.g., 500 MHz, the
sampling frequency must be atleast 2x or 1 GHz, to
curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Tauno Voipio]

On 9.10.19 17:51, Jeroen Belleman wrote:

jlarkin@highlandsniptechnology.com wrote:
On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to accurately
sample the signal to be amplified. So, if the input signal has
frequency of e.g., 500 MHz, the sampling frequency must be atleast 2x
or 1 GHz, to curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.


In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

I'm not sure what the OP is trying to do.

Jeroen Belleman

A normal Class C RF amolifier kicks the output tuned circuit
once per cycle, just at the output frequency rate.

The trick is that the amplifier does not attempt to preserve
the incoming waveform, only just the frequency.

--

-TV

 

[Jeroen Belleman]

jlarkin@highlandsniptechnology.com wrote:

On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to
accurately sample the signal to be amplified. So, if
the input signal has frequency of e.g., 500 MHz, the
sampling frequency must be atleast 2x or 1 GHz, to
curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.

In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

I'm not sure what the OP is trying to do.

Jeroen Belleman

 

[Rob]

Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:

On 9.10.19 17:51, Jeroen Belleman wrote:
jlarkin@highlandsniptechnology.com wrote:
On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to accurately
sample the signal to be amplified. So, if the input signal has
frequency of e.g., 500 MHz, the sampling frequency must be atleast 2x
or 1 GHz, to curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.


In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

I'm not sure what the OP is trying to do.

Jeroen Belleman


A normal Class C RF amolifier kicks the output tuned circuit
once per cycle, just at the output frequency rate.

The trick is that the amplifier does not attempt to preserve
the incoming waveform, only just the frequency.

But that works (without additional tricks) only for signals with
a constant amplitude, like FM.

For use with AM, RF amplifiers that use higher sampling frequencies
are used.

 

[Tauno Voipio]

On 9.10.19 19:29, Rob wrote:

Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:
On 9.10.19 17:51, Jeroen Belleman wrote:
jlarkin@highlandsniptechnology.com wrote:
On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to accurately
sample the signal to be amplified. So, if the input signal has
frequency of e.g., 500 MHz, the sampling frequency must be atleast 2x
or 1 GHz, to curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.


In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

I'm not sure what the OP is trying to do.

Jeroen Belleman


A normal Class C RF amolifier kicks the output tuned circuit
once per cycle, just at the output frequency rate.

The trick is that the amplifier does not attempt to preserve
the incoming waveform, only just the frequency.

But that works (without additional tricks) only for signals with
a constant amplitude, like FM.

For use with AM, RF amplifiers that use higher sampling frequencies
are used.

Linear amplification is a different beast.
For linear amplification, simple RF amplifiers need
to run Class B, AB or A.

There are ways to run a switching amplifier (Class C,
Class E and friends) on all kinds of higher modulations,
above AM. Google for EER amplifier (Envelope Erasure and
Restoration). The requirement is to control the supply
feed with the desird output envelope.

--

-TV

 

[Phil Allison]

Jeroen Belleman wrote:

-----------------------

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.


In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

** Think Jeroen just proved that chalk and cheese are the same.

Anyone wanna Chalk Burger ?


...... Phil

 

[Rob]

Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:

On 9.10.19 19:29, Rob wrote:
Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:
On 9.10.19 17:51, Jeroen Belleman wrote:
jlarkin@highlandsniptechnology.com wrote:
On Wed, 9 Oct 2019 02:40:00 -0700 (PDT), amal banerjee
dakupoto@gmail.com> wrote:

Could some electronics guru here clarify this a bit ?
A switched mode amplifier requires a sampling signal to accurately
sample the signal to be amplified. So, if the input signal has
frequency of e.g., 500 MHz, the sampling frequency must be atleast 2x
or 1 GHz, to curb aliasing. So, as the input signal frequency goes
up, so should the sampling frequencies.

If the output is a passive tuned network, the switching element can
just go hard on/off at the RF input rate, namely make a square wave,
so no sampling is involved.


In a way, that *is* sampling at twice the RF rate. It's
just that each sample lasts half an RF period.

I'm not sure what the OP is trying to do.

Jeroen Belleman


A normal Class C RF amolifier kicks the output tuned circuit
once per cycle, just at the output frequency rate.

The trick is that the amplifier does not attempt to preserve
the incoming waveform, only just the frequency.

But that works (without additional tricks) only for signals with
a constant amplitude, like FM.

For use with AM, RF amplifiers that use higher sampling frequencies
are used.


Linear amplification is a different beast.
For linear amplification, simple RF amplifiers need
to run Class B, AB or A.

There are ways to run a switching amplifier (Class C,
Class E and friends) on all kinds of higher modulations,
above AM. Google for EER amplifier (Envelope Erasure and
Restoration). The requirement is to control the supply
feed with the desird output envelope.

That is what I mean with "additional tricks". Things like HELAPS.