Bit of IQ

Jan Panteltje · 2019-05-30T13:27:19+00:00

There is a very old way to generate SSB using 90 degrees phase shifted audio and 90 degrees phase shifted RF. Found old circuit on the web for 90 degrees audio phase shift, modified it a bit: 1% capacitors, and 1% resistors made with trimpots: Stereo or mono in, + and - 45 phase shifted audio out. I like to build things in little modules so I can just connect things together for experiments, just like using pipes in Unix / Linux. It is working, still a bit of crud in the audio, laptop output audio is not so clear, ground loops, whatever, no screening whatsoever. The 90 degrees shifted audio signal goes into my DVB-S modulator: All controlled by a Raspberry Pi computer that is again controlled by the laptop via ssh. Will need to make a switch or break it up into more modules, so now I can select between DVB-S TV and SSB audio transmit mode. You can select double sideband suppressed carrier by using in phase audio signals (short the inputs): or SSB:

May 30, 2019 23 Replies

Rate this thread:

Allan Herriman 7 years ago

The '7007s is actually the same die as the (nominally larger) '7010. They use fuses to disable one of the ARM cores, and it's only possible to access about 70% of the FPGA fabric. This limitation is actually enforced by the development software; the chip has 100% of the FPGA fabric present (and tested). The FPGA bitstream header contains an identifying code though, which stops you from building a binary for the '7010 and loading it into the '7007s. The upside is that you can fully utilise "100%" of the '7007s fabric without running into problems (as "100%" is really only about 70% of the fabric, which is a fairly modest utilisation).

Other Xilinx Zynq-7 chips nobbled this way: '7020 => '7014S '7015 => '7012S

More recent families (e.g. Ultrascale Plus) do a similar thing, e.g. XCVU5P and XCVU7P have the same pair of dies but very different prices.

Regards, Allan

Vote

John Larkin 7 years ago

It is nice to be able to drop the bigger part onto the PC board, even if we have to pay more.

One 700 MHz ARM core is usually overkill, especially with an FPGA attached.

We have used some Altera chips with different specified numbers of CLBs and different prices that turn out to be identical; either runs the bit stream compiled for the other. Ditto speed and temperature grades, apparently.

John Larkin Highland Technology, Inc lunatic fringe electronics

Vote

Phil Hobbs 7 years ago

Of course that might not continue to be the case, especially if there's some yield problem in future--the mfr is within its rights to exceed specs if it likes. ;)

Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com

Vote

Lasse Langwadt Christensen 7 years ago

ohn

-45

and

but

wn a

wice

ux.

a place I worked eons ago used a cheaper reduced memory version of a DSP, someone had made a mistake in a linker file so few bytes of the memory that wasn't supposed to be there was used, it worked just fine because it was th e same die as the bigger chip. Until, the volume got so high the manufactur e made a new die that actually had less memory and the production ground to h alt with everything failing and much panic

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required