maxim 2870
Moderators: adafruit_support_bill, adafruit

maxim 2870

by numbskull on Mon Feb 10, 2014 6:04 am

Can i use Maxim 2870 http://www.maximintegrated.com/datasheet/index.mvp/id/7691 as a replacement for ROS2700 and 1300 ??
numbskull
 
Posts: 3
Joined: Thu Dec 01, 2011 11:53 pm

Re: maxim 2870

by lightningserpent on Wed Feb 12, 2014 9:09 am

The short answer is no. The operating voltages are not compatible and the package footprint is different.

1)Depending on the WB you are building you either need 5v or 12v VCOs. The maxim chip uses ~3.3v
2)The VCO footprint for the WB is a 16 pin package where-as the maxim chip has 32.

Ultimately the maxim chip is fundamentally different and a significant number of changes would have to be made to the original design for it to operate. I imagine the firmware would also have to be modified for the maxim chip to tune properly.
lightningserpent
 
Posts: 50
Joined: Tue May 01, 2012 7:27 am

Re: maxim 2870

by TheFallen on Fri Feb 14, 2014 3:07 pm

Trying to use that chip would result in a jammer that would have no resemblance to a Wave Bubble. While that chip does generate frequencies between 23.5MHz and 6000MHz it does so with 4 separate VCOs each with 4 sub-bands for a total of 16 sub-bands that would need to be switched through using the SPI port. That's not to say it's impossible, just that it is NOT a replacement in any way for the Minicircuits VCOs currently in use.
TheFallen
 
Posts: 92
Joined: Mon Feb 08, 2010 1:28 pm
Location: UK

Re: maxim 2870

by numbskull on Tue Feb 18, 2014 12:26 pm

I dont mind a change in the circuit or the code. The question i wanted to ask was whether the chip can generate the frequencies that are needed for a jammer. Besides i find that the chip is cheaper. I understand that it is not a direct replacement, but wanted to know if i can build one with the same jamming capabilites of a Wavebubble.
numbskull
 
Posts: 3
Joined: Thu Dec 01, 2011 11:53 pm

Re: maxim 2870

by TheFallen on Sun Mar 02, 2014 10:40 am

It wouldn't just be changes to the code or schematics or PCB, it'd be a COMPLETE redesign and I doubt that it would have the same capabilities as the wavebubble.
TheFallen
 
Posts: 92
Joined: Mon Feb 08, 2010 1:28 pm
Location: UK

Re: maxim 2870

by numbskull on Mon Mar 03, 2014 11:15 am

Can you please elaborate on why it cant function with same ablilities of wavebubble.. Because i find that it can generate the same frequency range as the one used in wavebubble
numbskull
 
Posts: 3
Joined: Thu Dec 01, 2011 11:53 pm

Re: maxim 2870

by TheFallen on Sun Mar 09, 2014 3:30 am

Like the Wave Bubble's Voltage Controlled Oscillators (VCOs) the MAX2870 has a tuning voltage pin, varying the voltage supplied to this pin changes the frequency. However it only varies the frequency between the sub-band's frequency range.There are 64 sub-bands, selected by bits 31:26 in Register 3, and I *think* that each sub band is 40MHz wide. I calculated this from (6GHz - 3Ghz) / 64 ~ 45MHz. Another way of looking at it is if you were to have a single band the maximum control voltage would be +3.3V and you would get 1MHz of bandwidth for each millivolt on the tuning pin.

So in manual mode you'll need to figure out which sub-band to start in, then ramp the control voltage until max, then go to the next sub-band then ramp the control voltage until max until you get to your upper limit frequency. Luckily most signals seem to only require a bandwidth of 30MHz - 75MHz which would require up to 3 sub-band changes, of course if you wanted to cover multiple bands you'd need to increase that figure.

Another option is to use the auto select state machine to re-tune the VCO every time you hit the limits of the control voltage pin but I'm not sure how well that would work.

The Wave Bubble on the other hand is very simple, a 555 timer generates an continuously resetting ramp signal which is amplified so it can reach the max vtune voltage of +28V for the minicircuits VCOs. Then a digital pot limits the range of this ramp to match the max bandwidth required. A DC offset is added from the microcontrollers PWM pins to set the minimum frequency of the ramp. A PLL chip is used as a glorified frequency matcher to check that lower and upper limits are reached and it's assumed the band is swept by the ramp in between.

In short the MAX2870 cannot be controlled as easily as the Wave Bubble. It can be controlled but it would require a completely different circuit, completely new code and thus would no longer be a Wave Bubble. It also seems to be just as hard as the LMX2433/VCOs to purchase.
TheFallen
 
Posts: 92
Joined: Mon Feb 08, 2010 1:28 pm
Location: UK