21 days, lotsa smiles, and heaping gobs of dynamic range

[Carl]

There are several things that limit the amount of time I can spend on metal detector circuits. For the past 3 weeks, it's been my project at work, a radio receiver chip design. After a busted wafer lot that put us wayyy behind, we got silicon on Oct. 2, with the first sample due a key customer on Oct. 23.

So, for 21 days I (and several others) have been working days, nights, and weekends trying to get everything on the chip working. And with no time to spare, we succeeded and mailed the first sample out yesterday.

Most of my chip design work centers around ADCs. My last project was a 14-bit 100MHz wideband ADC, which achieved 90dB of dynamic range. This latest design uses a wideband ADC in a narrowband system, with AGC and digital filtering. The plot above shows the output of the ADC in 500kHz, with an input signal level of -110dB full scale. It's still 20dB or so above the noise floor, suggesting a dynamic range of 130dB. And it looks even more impressive at the output of the digital filters.

This would make a heckuva IB receiver chip, if something could be done to actually null out the ground signal.

- Carl

[Randy Seden]

Re: 21 days, lotsa smiles, and heaping gobs of dynamic range

Congratulations Carl on the Receiver Chip design! What a great feeling and relief!

Hey I really like your suggestion for using it for a metal detector design. From what I've seen in past designs, the practice of using a low noise amp. on the front end to establish a good S/N ratio has been forgotten. Would be kinda neat to use that on a PI as well.

Randy Seden

[Russ_NY]

Congratulations Carl

Well Done Carl
Having worked in commercial and consumer electronics product development for the majority of my 30 years in the business I can certainly appreciate your situation with the long days as the deadline approaches, and the relief of getting the project finished. Been there quite a few times myself. A backpacking trip sounds like just the thing to let you wind down from the stress of the job. Taking a detector along might also provide an interesting diversion. I haven't had any time to work on the detector myself. Doing a transmission replacement in the daughters car. Hope you enjoy your weekend.
Russ_NY

[Robert Hoolko]

Re: 21 days, lotsa smiles, and heaping gobs of dynamic range

When will I be able to afford one for my detector?

Robert