On 01/16/2018 07:29 AM, prog wrote:
On Sun, Jan 14, 2018 at 10:41 pm, drew231955 wrote:
The main break through with the HF+ is the Polyphase
harmonic rejection mixer. As best I can work out, when
converting to base-band, it is an effective filter for the
desired signal and rejects even strong signals close by with
virtually no filtering ahead of the mixer.
It uses multiple phases of the local oscillator to use phasing
to reject its harmonics, but at the same time, and because it is
to a 200 kHz base-band, it rejects everything else too.
The big advantage is not needing a large number of band pass
filters like a direct sampling SDR; the IC-7300 has 15!
The best explanation I have found is a slide show; http://icd.ewi.utwente.nl/temp_files/158b39412cff88a4181bfec0f4449c24.pdf.
It is also subject to patent; https://www.google.ch/patents/US20110298521?hl=de.
One of the authors wrote the slide show.
There is something wrong with this url. I think it's the second /
What should the character be?
You can see it as a "super Tayloe mixer". The problem with the
original Tayloe Mixer is the harmonic responses at multiples of
the LO frequency. The fix is to mathematically suppress these
responses by adding more phases. The LO will no longer look like a
square wave, but rather like a quantized sine wave. Basically, the
more phases you add, the more harmonics you cancel.
Presumably the mixer is a CMOS device, but I have not found one.
And the RF cover on the HF+ is too hard to remove!
Any thoughts on this very novel approach?
Regards Drew VK4ZXI
This method is combined with narrow band filtering at the mixer
itself. There is a switched-capacitor N-Path filter built into the
mixer that is tuned using the same LO phases, which provides
When you see it, all the ingredients required to implement this
architecture can be implemented using CMOS silicon, and have a
very good "horizontal" and "vertical" scalability: Horizontal with
more phases (hence, less harmonics); Vertical with better fab
processes (better linearity and NF).
The icing on the cake: This same technology can also work for TX.
The future looks bright!