Myriad RF1 TX Test with external PLLCLK


#1

Hi guys,

I am working around LMS6002D reference kit, talking to my own microcontroller. I have so far able to configure its register via SPI, wrote and read it back correctly.

Currently I am doing LO leakage TX test as in the programming guide doc. Since I dont have the interface board, registers are set through my own microcontroller, and PLLCLK is supplied by function generator, running on 24MHz. One reason of not using default 30.72MHz PLLCLK is my function generator can only go up to 30MHz.

Tried to transmit on several frequencies such as 430MHz, 600MHz, 700MHz, 750MHz. Spectrum analyzer however shows transmitted frequencies to be offset around 60Mhz from ones I set.
Calculation of NINT, NFRAC, and VCO CAP are done using ctr_6002d.exe software, and I also tried NINT and NFRAC calculation by hand.

An example registers I set for transmission at 600MHz, PLLCLK of 24MHz as follows:

  1. top level page
    “tx dsm spi clock” buffer enable (addr 0x09, val 0x41)
    “soft tx enable” enable (addr 0x05, val 0x3a)

  2. tx lpf page
    “lpf bandwidth” = 14MHz (addr 0x34, val 0x02)

  3. tx rf page
    “vga1 gain” = -10 (addr 0x41, val 0x19)
    “vga2 gain” = 15 (addr x045, val 0x78)
    “pa1” selected (addr 0x44, val 0x0b)

  4. tx pll setup page

    Freq sel (addr 0x15, val 0xb9)
    CP Current 1200uA (addr 0x16, val 0x8c)
    CP Up offset 30uA (addr 0x17, val 0xe3)
    VCO capacitance 44 (addr 0x19, val 0xbd)
    N Integer: 200 (addr 0x10, val 0x64)
    N fractional: 0 (addr 0x11, val 0x0)
    (addr 0x12, val 0x0)
    (addr 0x13, val 0x0)

May I know which part went wrong? Please kindly advise.

Thanks,
Dareen


#2

Do you take a reference frequency change into account?


#3

Hi Zack,

Thanks for replying.

By reference frequency you mean the PLLCLK right?
Yes I do take that change into calculation.

One thing I am not sure is my supply to PLLCLK, I simply connected output of function generator to my X8 connector on Myriad board. Is it okay that way?

Thanks.


#4

Is R49 mounted? It is no fit by default, you have to solder it manually.


#5

Hi Zack,

Thanks.
Yes I soldered a wire in place of R49. I found out what was wrong, actually the way I was calculating my VCO cap was through this ctr6002_d software while I am using my own microcontroller to interface with MyriadRF, and just realized that way the VCO tuning won’t work since it needs to read VTUNE value during tuning.
So I made a VCO tuning using my microcontroller, and it transmitting in right frequency now.

One thing I realized is NINT needs to be an integer of two for the transmission frequency to be correct or else it will be offset by 1-4 MHz.


#6

Glad to hear you’ve sorted it out!


#7

Thanks Zack!

Yeah now I can tinker more with it :smiley:

Anyway thanks a lot for your help.