XB300 issues

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Guillaume
Posts: 2
Joined: Mon Jul 31, 2017 7:22 am

XB300 issues

Post by Guillaume » Mon Jul 31, 2017 8:11 am

Hi,

I own a blade 115K + XB300 with a 3A external power supply.

Does someone knows if PA amp output power from XB300 can be controlled?
It seems that PA can only be on or off (like LNA)
How to know the output power? - xb 300 pwr command fail with "device busy" while operating... and when I execute the command after I stop transmission the output show +4 dBm... that's the output of bladRF mother board NOT XB300 output!

I assume that out of the box XB300 has no MIMO capabilities... which resistors values on R8, R9, R10, R11, R12, R23 should I populate for Trx_Rx can swith between Tx and Rx? (with xb 300 trx rx command)
After re-engineering the board and for protecting the input Rx while transmitting at 4dBm, does the LNA bypass automatically enabled when configure Trx_rx as Tx? (xb 300 trx tx) - does we need to power off the LNA in order to protect the 23dBm max input Rx interface?
NUAND stated "In case the bladeRF is transmitting at +4dBm the bypass path should be engaged to protect the RF frontend." without further explanations.

What happen if we configure Trx_rx as Rx while transmitting? it seems that the signal stop in the SKY13446-374LF switch...

Last but not least, I've made some measures of a signal (sinusoid) receive power (with gnuradio blocks) and for the followings parameters I get a power of -12.4 dBm max when was expected ~ +4.5 dBm. It seems that xb300 power output is not 30 dB :o does someone can explain these values?

Thank you for any help!
Guillaume

From Friis equation;

F 1 Ghz
Gt 2 dBi
Gr 12 dBi
L 1 dB (feeder loss)
R 2 meters
(FSPL 24.4 dB)
Pt 30 dBm
Pr ~ +4.5 dBm
NF 1.4

bglod
Posts: 45
Joined: Thu Jun 18, 2015 6:10 pm

Re: XB300 issues

Post by bglod » Tue Aug 01, 2017 3:34 pm

Guillaume wrote:
Mon Jul 31, 2017 8:11 am
Hi,

I own a blade 115K + XB300 with a 3A external power supply.

Does someone knows if PA amp output power from XB300 can be controlled?
It seems that PA can only be on or off (like LNA)
That is correct.
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
How to know the output power? - xb 300 pwr command fail with "device busy" while operating... and when I execute the command after I stop transmission the output show +4 dBm... that's the output of bladRF mother board NOT XB300 output!
I see the timeout as well. I am not sure if that is intended or not. It may be a limitation in the software or HDL during sample streaming. Feel free to create an issue in the issue tracker on GitHub so we can address it.

The +4-5 dBm reading is expected; it is coming from the MAX11664AUB+ ADC, which is reading the VDET output voltage of the PA. For me, that is 0.320 V, which corresponds to +5dBm in the PA datasheet.

If I run the following, I see 1.037 V on the VDET test point (TP1) of the XB-300, and my signal analyzer shows +23.86 dBm output power from the TRX ANT port of the XB-300.

Code: Select all

echo "2047, 2047" > cw.csv
bladeRF-cli -l /path/to/fpga.rbf -i
set frequency tx 2.45G
set samplerate 40M
tx config file=/path/to/cw.csv format=csv repeat=0 delay=0
set txvga1 -4
set txvga2 25
xb 300 enable
xb 300 pa on
tx start
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
I assume that out of the box XB300 has no MIMO capabilities... which resistors values on R8, R9, R10, R11, R12, R23 should I populate for Trx_Rx can swith between Tx and Rx? (with xb 300 trx rx command)
I did not design the XB-300, but it would appear to me that you'd want to depopulate R23 and populate R10?
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
After re-engineering the board and for protecting the input Rx while transmitting at 4dBm, does the LNA bypass automatically enabled when configure Trx_rx as Tx? (xb 300 trx tx) - does we need to power off the LNA in order to protect the 23dBm max input Rx interface?
NUAND stated "In case the bladeRF is transmitting at +4dBm the bypass path should be engaged to protect the RF frontend." without further explanations.

What happen if we configure Trx_rx as Rx while transmitting? it seems that the signal stop in the SKY13446-374LF switch...
I believe you are correct. The SKY13446-374LF switch has about 38 dB of isolation between the RX and TX ports, which is more than what the PA amplifies the TX signal, so there should be minimal (if any) risk of the amplified TX signal feeding back into the RX LNA at dangerous levels. However, when RX'ing, the PA is not turned off automatically. If you want to be completely safe, turn off the PA before switching to TRX_RX mode.
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
Last but not least, I've made some measures of a signal (sinusoid) receive power (with gnuradio blocks) and for the followings parameters I get a power of -12.4 dBm max when was expected ~ +4.5 dBm. It seems that xb300 power output is not 30 dB :o does someone can explain these values?
What are your TXVGA1 and TXVGA2 amplifier stages set to? The "30 dB gain" of the SE2605L PA is relative to whatever the input signal is. When TXVGA1 and TXVGA2 are maxed out, the output power is +23 dBm in my setup.

Guillaume
Posts: 2
Joined: Mon Jul 31, 2017 7:22 am

Re: XB300 issues

Post by Guillaume » Wed Aug 02, 2017 8:16 am

Guillaume wrote:
Mon Jul 31, 2017 8:11 am
Hi,

I own a blade 115K + XB300 with a 3A external power supply.

Does someone knows if PA amp output power from XB300 can be controlled?
It seems that PA can only be on or off (like LNA)
That is correct.
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
How to know the output power? - xb 300 pwr command fail with "device busy" while operating... and when I execute the command after I stop transmission the output show +4 dBm... that's the output of bladRF mother board NOT XB300 output!
I see the timeout as well. I am not sure if that is intended or not. It may be a limitation in the software or HDL during sample streaming. Feel free to create an issue in the issue tracker on GitHub so we can address it.
I will.
The +4-5 dBm reading is expected; it is coming from the MAX11664AUB+ ADC, which is reading the VDET output voltage of the PA. For me, that is 0.320 V, which corresponds to +5dBm in the PA datasheet.
If I run your code (with TXVGA1=-4 TXVGA2=25) and then stop it xb 300 pwr show +4.647034 dBm (as I explained, I cannot run xb 300 pwr while transmitting)
Does it mean
- output power of bladerRF
- output power of XB 300 while not transmitting
- output power of XB 300 when it will transmit

bladeRF & XB 300 are enclosed so I cannot easily measure VDET (I'll if there is no other way to measure the output power of the unit)
If I run the following, I see 1.037 V on the VDET test point (TP1) of the XB-300, and my signal analyzer shows +23.86 dBm output power from the TRX ANT port of the XB-300.

Code: Select all

echo "2047, 2047" > cw.csv
bladeRF-cli -l /path/to/fpga.rbf -i
set frequency tx 2.45G
set samplerate 40M
tx config file=/path/to/cw.csv format=csv repeat=0 delay=0
set txvga1 -4
set txvga2 25
xb 300 enable
xb 300 pa on
tx start
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
I assume that out of the box XB300 has no MIMO capabilities... which resistors values on R8, R9, R10, R11, R12, R23 should I populate for Trx_Rx can swith between Tx and Rx? (with xb 300 trx rx command)
I did not design the XB-300, but it would appear to me that you'd want to depopulate R23 and populate R10?
Yes you right, depopulate r23 and populate r8, r10. But I don't know the values...
And it seem that there is also something to do with r9, r11, r12? (r9, r12 are DNP on the schematic)
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
After re-engineering the board and for protecting the input Rx while transmitting at 4dBm, does the LNA bypass automatically enabled when configure Trx_rx as Tx? (xb 300 trx tx) - does we need to power off the LNA in order to protect the 23dBm max input Rx interface?
NUAND stated "In case the bladeRF is transmitting at +4dBm the bypass path should be engaged to protect the RF frontend." without further explanations.

What happen if we configure Trx_rx as Rx while transmitting? it seems that the signal stop in the SKY13446-374LF switch...
I believe you are correct. The SKY13446-374LF switch has about 38 dB of isolation between the RX and TX ports, which is more than what the PA amplifies the TX signal, so there should be minimal (if any) risk of the amplified TX signal feeding back into the RX LNA at dangerous levels. However, when RX'ing, the PA is not turned off automatically. If you want to be completely safe, turn off the PA before switching to TRX_RX mode.
I mean on the schematic we can see two switchs ; one for RXTX antenna and the other for LNA bypass... my question was "does xb 300 tx_rx tx switchs LNA bypass switch together with TXRX switch"?
Guillaume wrote:
Mon Jul 31, 2017 8:11 am
Last but not least, I've made some measures of a signal (sinusoid) receive power (with gnuradio blocks) and for the followings parameters I get a power of -12.4 dBm max when was expected ~ +4.5 dBm. It seems that xb300 power output is not 30 dB :o does someone can explain these values?
What are your TXVGA1 and TXVGA2 amplifier stages set to? The "30 dB gain" of the SE2605L PA is relative to whatever the input signal is. When TXVGA1 and TXVGA2 are maxed out, the output power is +23 dBm in my setup.
I'll do some measures at the output of Tx with a power meter.
Thank you for your help.
Guillaume

bglod
Posts: 45
Joined: Thu Jun 18, 2015 6:10 pm

Re: XB300 issues

Post by bglod » Fri Aug 11, 2017 12:13 pm

Guillaume wrote:
Wed Aug 02, 2017 8:16 am
Does it mean
- output power of bladerRF
- output power of XB 300 while not transmitting
- output power of XB 300 when it will transmit

bladeRF & XB 300 are enclosed so I cannot easily measure VDET (I'll if there is no other way to measure the output power of the unit)
The host can't send the command to read the power during transmission. I suspect the TX sample stream is preventing the command from going through, hence the timeout error you see. When you run the command "xb 300 pwr" it is always the output power of the PA. Keep in mind it is uncalibrated, so it will not be exact. If you want exact, you'll need test equipment and build a cal table. There is no other way to read the output power using the bladeRF itself.

Don't put much faith in the value returned by "xb 300 pwr" just yet. It appears to be incorrect, and we can't even read it while transmitting anyway. Submit that issue to the bladeRF GitHub repo so we will remember to take a look at it.
Guillaume wrote:
Wed Aug 02, 2017 8:16 am
Yes you right, depopulate r23 and populate r8, r10. But I don't know the values...
And it seem that there is also something to do with r9, r11, r12? (r9, r12 are DNP on the schematic)
You'd depopulate R23 and populate R8 and R10 with 0-ohm resistors. Leave R9, R11, R12 alone. J5 antenna may be used for diversity.
Guillaume wrote:
Wed Aug 02, 2017 8:16 am
I mean on the schematic we can see two switchs ; one for RXTX antenna and the other for LNA bypass... my question was "does xb 300 tx_rx tx switchs LNA bypass switch together with TXRX switch"?
They do not switch in tandem. You would be responsible for setting both. Feel free to change the host code and submit a pull request if you'd like to see this feature mainlined.

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