XB300 issues

[Guillaume]

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 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]

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.

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

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?

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.

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 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]

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.

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

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)

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"?

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 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]

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.

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.

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.

[Guillaume]

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.

I'll submit it as an issue on github.

I tested the output of the xb300 board with a calibrated RF power meter.

xb 300 on
xb 300 pa on
set frequency tx 1G
set samplerate tx 4M
tx config file=~/cw.csv format=csv repeat=0
set txvga1 -4
set txvga2 25
tx start

lead to +21.6 dBm
I'm a little bit disapointed, I expected ~+30 dBm
When you said "xb 300 pwr" it is always the output power of the PA" you mean PA on bladeRF main board, right?
because the value is never greater than a +4 dBm which is typically the output power of the bladeRF main board but NOT the output power of the xb300 board (~ +22 dBM max)

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.

Does J5 antenna the same that TxRx antenna?

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.

I'll have a look on it.
Thank you.

[bglod]

I tested the output of the xb300 board with a calibrated RF power meter.
<snip>
set frequency tx 1G
<snip>
lead to +21.6 dBm
I'm a little bit disapointed, I expected ~+30 dBm
When you said "xb 300 pwr" it is always the output power of the PA" you mean PA on bladeRF main board, right?
because the value is never greater than a +4 dBm which is typically the output power of the bladeRF main board but NOT the output power of the xb300 board (~ +22 dBM max)

It's the value returned by the ADC (U66) located on the XB-300 board. This ADC samples the voltage coming out of the DET pin of the PA (U4.7) on the XB-300 board. It is not the power output by the bladeRF itself (never has been, nor will be -- there is no way to measure the output power of the bladeRF itself without external test equipment). The fact that it's a similar reading when you're not transmitting, to the output power of the bladeRF by itself, is just coincidence.

When the PA is off, it is off, it is not in bypass; VDET will always read nearly 0 V due to the pull-down on VDET and the VDET circuitry being disabled within the PA. (Note that if you transmit into the disabled PA with the bladeRF at max power, you will see very weak RF coming out of the TX SMA port of the XB-300, it's simply leakage through the PA and is normal).

When the PA is powered on, but no signal is present on RF_IN (bladeRF not transmitting), the DET pin of the PA outputs a voltage that corresponds to +4-5 dBm. That's the minimum voltage (around 0.33 V) that the DET pin can output. It does not mean the PA is actually outputting +4 dBm (see datasheet Table 6). Perhaps we could come up with a reasonably generic correction table for the readout so it's not so misleading. Please feel free to make this an issue in the issue tracker.

When the PA is powered on and a CW at 2.45 GHz at max TX power of the bladeRF is provided, the DET voltage will read 1.037 V (per a previous post of mine). According to the datasheet, this corresponds to an output power of about +30 dBm from the PA with an accuracy of +/- 1.5 dB. However, with my test equipment, I read about +24 dBm of actual output power measured at the output spigot through about 3' of coax. So there's about 6 dB of loss somewhere, which I'd say is a lot for just cables and device variances.

I reviewed the product page and it does appear to be advertised as a 33 dB / +31 dBm amplifier. These numbers correspond to the 1 dB compression point of the PA itself, per its datasheet. While they have basis in reality, I would agree that the advertised amplification is a bit misleading -- it's not what the end customer will see in practice. I have informed the folks responsible for the product page so we can hopefully get that fixed up. Thanks for pointing this out.

One friendly reminder is that this PA is only spec'd for operation between 2.4 GHz to 2.5 GHz, so with your test tone transmitting at 1 GHz I'm surprised you were able to get as much as +21 dBm out of it!

Does J5 antenna the same that TxRx antenna?

It depends on what kind of diversity you're looking to achieve. If you don't care about diversity, I think you can just leave it open. If you terminate the input, I'd imagine it would reduce the SNR of the one antenna because you'd effectively be creating a 150-ohm path to ground.

[Guillaume]

It's the value returned by the ADC (U66) located on the XB-300 board. This ADC samples the voltage coming out of the DET pin of the PA (U4.7) on the XB-300 board. It is not the power output by the bladeRF itself (never has been, nor will be -- there is no way to measure the output power of the bladeRF itself without external test equipment). The fact that it's a similar reading when you're not transmitting, to the output power of the bladeRF by itself, is just coincidence.

When the PA is off, it is off, it is not in bypass; VDET will always read nearly 0 V due to the pull-down on VDET and the VDET circuitry being disabled within the PA. (Note that if you transmit into the disabled PA with the bladeRF at max power, you will see very weak RF coming out of the TX SMA port of the XB-300, it's simply leakage through the PA and is normal).

When the PA is powered on, but no signal is present on RF_IN (bladeRF not transmitting), the DET pin of the PA outputs a voltage that corresponds to +4-5 dBm. That's the minimum voltage (around 0.33 V) that the DET pin can output. It does not mean the PA is actually outputting +4 dBm (see datasheet Table 6). Perhaps we could come up with a reasonably generic correction table for the readout so it's not so misleading. Please feel free to make this an issue in the issue tracker.

I didn't realized that here dBm is mV related!
xb 300 pwr
PA output power: +5.615814 dBm
means VDET ~ 0.4268 V

What is really misleading is the wording... "PA output power: " shouldn't be better something like "PA Detector Voltage (dBmV):" ?

When the PA is powered on and a CW at 2.45 GHz at max TX power of the bladeRF is provided, the DET voltage will read 1.037 V (per a previous post of mine). According to the datasheet, this corresponds to an output power of about +30 dBm from the PA with an accuracy of +/- 1.5 dB. However, with my test equipment, I read about +24 dBm of actual output power measured at the output spigot through about 3' of coax. So there's about 6 dB of loss somewhere, which I'd say is a lot for just cables and device variances.

I reviewed the product page and it does appear to be advertised as a 33 dB / +31 dBm amplifier. These numbers correspond to the 1 dB compression point of the PA itself, per its datasheet. While they have basis in reality, I would agree that the advertised amplification is a bit misleading -- it's not what the end customer will see in practice. I have informed the folks responsible for the product page so we can hopefully get that fixed up. Thanks for pointing this out.

One friendly reminder is that this PA is only spec'd for operation between 2.4 GHz to 2.5 GHz, so with your test tone transmitting at 1 GHz I'm surprised you were able to get as much as +21 dBm out of it!

Thank you for these explanations. I replaced the two cables from bladeRF Tx/Rx to xb300 Tx IF / Rx IF and rechecked the output for a 2.45G signal and this time the result is MUCH better as you highlighted it! the board output at +31.87 dBm !
Thank you again for your time.
Guillaume

[bglod]

Oh wow! You got almost +32 dBm out, nice job! I was not able to do that; could be my setup or test equipment though.

Please remember to make those GitHub issues (feel free to reference this thread). We've got a lot on our plate right now, so it's helpful to have the "official" issue tracker to remind us of outstanding problems.

[Guillaume]

Yes ! I'm very happy with these results!
I'll post an issue on gihub referencing this topic about "xb 300 pwr" while transmitting and the used wording (dBmV) ...
Thank you a lot for your help on this matter!
Best regards,
Guillaume