LMS6002 EVB - Loopback and Tx Harmonics

[Tomás Franzosi]

Hello everyone,

I'm trying to perform some testing on the EVB6002. I was able to send some data to TX, but just notice some interesting harmonics (2nd and 3rd in particular), is this ok? which levels should I be expecting?

Another issue came when I configure the chip to make a RF Loopback, setting the Tx PLL 3 MHz higher than the Rx PLL. I can't see anything from Analog Rx Out Pins, neither single end ones, or differentials. Here is the steps I follow to complete this task:

0 - Set TxPLL 3MHz Higher than RxPLL

1 - 0x75[5:4] (LNASEL_RXFE) = 1   //Select LNA1 Path

2 - 0x7D[0] (PD_LNA_RXFE) = 1   //Turn off LNA

3 - 0x70[1] (DECODE) = 1   //PD take effect

4 - 0x08[3-0] (LBRFEN[3:0]) = 1   //Send RF Loopback to LNA1 Path

5 - 0x0B[0] (PD[0]) = 0   // Power up RF Switch

6 - 0x05[7] (DECODE) = 1   //LBRFEN take effect

7 - 0x25[1:0] (SELOUT) = 1   //Send RxPLL to LNA1 Path

8 - 0x44[2] (PA_EN[0]) = 0   //Turn on AUXPA

9 - 0x05[3] (STXEN) = 1  //Start sending

10 - 0x05[2] (SRXEN) = 1  //Start receiving

Pins 18, 19 and 20 from J3 are connected to and osciloscope. I even try doing this from the GUI, but having the exact same result, NO result.

Thanks in advance,

Tomas Franzosi

[Ricardas Vadoklis]

Hello Tomas,

Please find my comments below.

Best Regards,
Ricardas Vadoklis,
Senior System and Test Engineer,
Lime microsystems, 
r.vad...@limemicro.com
+44 0 1483 685 065

On 2/12/2016 6:03 PM, Tomás Franzosi wrote:

Hello everyone,

I'm trying to perform some testing on the EVB6002. I was able to send some data to TX, but just notice some interesting harmonics (2nd and 3rd in particular), is this ok? which levels should I be expecting?

Can you try to power down RXVGA2 and RXLPF DC calibration comparators after calibration. To do that:

1. Set 0x6E[7:6] = "11", power down RXVGA2 DC comparators
2. Set 0x5F[7] = "1", power down RXLPF DC comparator
   

Please note, auto DC offset calibration has to be executed before comparators are powered down.

Another issue came when I configure the chip to make a RF Loopback, setting the Tx PLL 3 MHz higher than the Rx PLL. I can't see anything from Analog Rx Out Pins, neither single end ones, or differentials. Here is the steps I follow to complete this task:

0 - Set TxPLL 3MHz Higher than RxPLL

1 - 0x75[5:4] (LNASEL_RXFE) = 1   //Select LNA1 Path

2 - 0x7D[0] (PD_LNA_RXFE) = 1   //Turn off LNA

3 - 0x70[1] (DECODE) = 1   //PD take effect

4 - 0x08[3-0] (LBRFEN[3:0]) = 1   //Send RF Loopback to LNA1 Path

5 - 0x0B[0] (PD[0]) = 0   // Power up RF Switch

6 - 0x05[7] (DECODE) = 1   //LBRFEN take effect

7 - 0x25[1:0] (SELOUT) = 1   //Send RxPLL to LNA1 Path

8 - 0x44[2] (PA_EN[0]) = 0   //Turn on AUXPA

9 - 0x05[3] (STXEN) = 1  //Start sending

10 - 0x05[2] (SRXEN) = 1  //Start receiving

Pins 18, 19 and 20 from J3 are connected to and osciloscope. I even try doing this from the GUI, but having the exact same result, NO result.

To see signal on analog output, you have to enable the RxOut switch: Register 0x09[7] set to '1'.

Thanks in advance,

Tomas Franzosi

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[Tomás Franzosi]

Hello Ricardas,

Regarding Tx Harmonics, I power down both RxVGA2(A and B) and RxLPF DC calibration comparators, and still have those harmonics (btw, it were 2nd and 4th). Just to verify, I will send a screenshot of the SA screen.

Speaking of the Loopback issue, I forgot to mention that RxOut switches have been powered up and RXVGA2 and ADC Disabled. I power down RXVGA2 because in the Datasheet it said so). Still trying to figure out what am I doing wrong.

Best Regards,
Tomas

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[Radio_Man]

hi Ricardas

powerd up or powerd down of DC comparator via 0x6E and 0x5F registers did they have an effect when 0x64 and 0x54 set to decode signal ???

because in 6002Dr.exe application those icon are enabled only when 0x64 and 0x54 set to direct signal

best regards