Reinier Gerritsen 2020/12/07 18:03
I do think the bridge is the main problem, not the resistors but the
balun that converts the differential bridge voltage to a single ended
signal. Also the mixer may need to be replaced. It is specified to 3.8 GHz.
Reinier
Op 7-12-2020 om 16:53 schreef Jim Lux:
> On 12/7/20 7:34 AM, Kadir Mariño Abreu wrote:
>> It would be great to be able to work with more than 4Ghz, mainly in
>> the 5Ghz band, although it would be a bit difficult to build the SWR
>> bridge at such a high frequency, if a bridge with minimal
>> requirements is not achieved, at least one solution would be to
>> program in the firmware up to a certain frequency where said bridge
>> works acceptably, and the remainder of the bandwidth of the Max2870 /
>> 71 would be used for the measurement of the different band filters,
>> is my humble opinion.
>> Let's see if someone else can comment on this issue in more depth, in
>> my opinion it would be great, I reiterate since for lovers of the
>> 5Ghz band and Wi-Fi experimenters in that band, an instrument of this
>> type would be very useful, thank you.
>> _.
>
>
> It's not the bridge that's the hard part - most modern VNAs just use a
> resistor network of some sort. It's all the other pieces, oscillators,
> amplifiers, and detectors.
>
> The NanoVNA and NanoVNA2 both make clever use of very few inexpensive
> components. The Maxim parts you mention solve only part of the problem.
>
> If you don't need low frequencies, then one of the new parts like the
> AD9361, which goes up to 6GHz, but only goes down to around 100 MHz
> would work. You could probably use just that part and some sort of
> microcontroller since it includes the PLLs, the mixers, the
> amplifiers, and the ADCs. The problem is that those parts are pretty
> expensive - $175 in Qty 1000.
>
> I suspect that one could probably build a VNA using a couple of ADALM
> PLUTO modules (which use the one channel version of the AD9361) if you
> could sync them. But that's still no display or controller, and
> you've already spent $200 (if you get the discounted student price).
>
> To sell something for $100, the Bill of Materials cost needs to be
> less than $20. That's quite a challenge.