LMS7002 TX maximum band, TX frequency separation, I/Q DC calibration master

1

Hey!
I am evaluation LMS7002 for a project - here is some confusion after reading the data sheet.

  1. Our application would require 80M TX bandwidth in baseband. The base information is that 60M band is available, but many places in the data sheet mention 80M band (page 2 and 5 for example). So is 80M band possible?

  2. LMS7002 has 2 TX paths, but one mixer for both. I already found that it is possible to create some frequency separation between them, but what is the maximum separation possible? Could I start with TX2 where TX1 ends?

  3. Are DC correction and I/Q in-balance control values calculated by the embedded controller or is it external work? (data sheet notes that it is the job of baseband, but later introduces embedded controller “The on chip micro-controller unit (MCU) provides the option for independent control using code provided by Lime” )

Thank you for help :smile:

2

After another RTFM session i am able to elaborate my questions:

TX maximum band

Maximum TX band seems to be determined by the interpolation filter.

The filters are designed to provide a wide signal pass band from DC to
fp where:
fp = x * fclk / K .
Scaling factor x in the equation above, for K=2, 4, 8, 16, 32, should be
set to one of the following values:
x <= 0.27 for >= 108dB interpolation image suppression,
x <= 0.30 for >= 75dB interpolation image suppression,
x <= 0.32 for >= 60dB interpolation image suppression.
Obviously, x can be used to trade off interpolation image suppression
for the interpolation filter pass band.

fclk would be DAC sampling clock as i understand. Assuming sampling clock to be 640M and required image suppression 60 db minimum, we can calculate:

  1. K = 2 (interpolate by 2)
    Data rate = 320M
    Max bandwidth fp = 96M
  2. K = 4
    Data rate = 160M
    Max bandwidth fp = 48M
  3. K = 8
    Data rate = 80M
    Max bandwidth fp = 24M

For a classical FPGA i would go with 160M data rate max, that gives us 48M band.
Correct?

Maximum frequency separation using mixer

“TDD/FDD MODE ENHANCMENT OPTION” section in datasheet gives a formula for maximum frequency shift as:

mixMax = 0.6 * fdac / 2 (TX side)
"Note that the Nyquist frequency of the NCOs is scaled
by a factor of 0.6 to make space for TXLPF and RXLPF to operate. "

Maximum clock for DAC could be 640M, so maximum separation is 2 * mixMax = 384M (shift TX1 to left and TX2 right)
For ADC side maximum separation is 96M, because ADC clock is only 160M.

Calibration master

Generally the MCU inside LMS7002 is meant for handeling calibration tasks. It is noted that Lime provides this MCU code.

Contrast this with the LMS7002M, where the microcontroller can complete the full calibration. As I understand it, Lime has been tuning the calibration algorithms for some significant time. These algorithms will be published early in the second calendar quarter of 2015 – so watch out for a posting on this site. Customers can take these algorithms and use them to program either the on-chip 8051 or an external processor if they prefer. Lime expects to have optimized 8051 code ready for customers around a calendar quarter after the algorithms are frozen. (http://www.limemicro.com/blog-2/the-lowly-8051-proves-worth-its-weight-in-gold)

Is this code available? In software packages i can only find firmware for USB MCU.

MCU Firmware           - USB microcontroller related   
         |- LMS7002EVBv2.hex   - Firmware for UNITE7002 and LMS7002EVB USB microcontroller    Atmel Control center utility to program AT90USB162-16AU USB microcontroller can be downloaded from: http://www.atmel.com/tools/flip.aspx

Any comments?