AFE7071: Design Inquiry

JH:  Please see below.  --RJH

1. Can the user adjust the RF output of the AFE7071? If yes, what is the output range?

RJH>> The AFE707x incorporates a DAC + quadrature modulator.  The modulator requires an external LO source to convert to the desired range.  The AFE device supports an RF output frequency to 2.7 GHz.  You can pair the LMX2572 synthesizer with the AFE707x as a good LO source that provides programmable option to hit any band up to 2.7 GHz.

Note, the AFE707x also incorporates a numerically controlled oscillator (NCO).  This allows programmable option to adjust RF frequency up to +/- the BB LPF frequency.  In essence, this gives you adjustability of the signal up to +/- 10 MHz + LO.

2. There is no EVM for the AFE7071, but the AFE7070EVM is. Is it possible to operate the AFE7070EVM alone without an FPGA board?

RJH>>  You can use the AFE7070 EVM to evaluate the performance of the AFE7071.  You can operate the AFE7070x EVM without the EVM.  The AFE device has a constant output feature plus the aforementioned NCO.  With that, you can generate a constant input that is translated to a single CW tone at the NCO frequency and then upconverted to the RF band by the LO frequency.  This is a common way that I evaluate the function of the device.

3. Is it possible to check and simulate register settings with only GUI without EVM? If so, please provide the GUI.

RJH>>  The GUI is available for download here: https://www.ti.com/lit/zip/sloc289.  Yes, you can use the GUI to check/create register settings.

JH:

Yes, there are a couple of options that you can use to adjust the output control; however, you need to use these carefully because it will adjust the I/Q balance in the part and result in degradation in the sideband suppression and carrier suppression from an optimized configuration.

One option is to use the QMC gain setting.  This is a digital gain setting normally centered at 1024.  This parameter is intended to provide fine tune the gain to amplitude balance the I/Q paths.  If you move QMC Gain A and B simultaneously, it will behave like a digital attenuator.  This value can go down to 0.  It can also go higher, but that is not recommended.  As you increase the value, you have a higher probability of digitally clipping the DAC which will cause poor spurious performance.

The second option is to adjust the DAC current control.  The nominal setting is 15.  This value can be decreased which reduces the output current and attenuates the signal.  Optimum setting is between 10 to 15.  This value can go down to 0.  

Both options will distort the amplitude balance and the DC Offset balance.  In other words, if you adjust the parameters to null the lower sideband and the carrier and then decide to attenuate the signal using one of the above methods, the correction factors will not hold and the sideband and carrier will increase and require a new adjustment loop.

--RJH