RF chip that can demodulate/separate (multiple) orthogonal signals ?

Hi 

Thanks a lot for the response.

We checked the data sheet you mentioned, yes it is very helpful.

TWO Further detail questions:

1, From which PINs can we get the raw I/Q data ?

2, Is the I/Q raw data digital data or analog data ?

There are LPF0 and LPF1 PINs, and they should be Low Pass Filter output PINs. From the diagram on Page20, the two PINs are before the ADC. 

So I guess, if these two PINs are the only PINs that can output raw I/Q data, they output analog data. Right ?

Are there some PINs right after the ADC, to output digital raw I/Q data ? 

Thank you very much 

Kind regards

Bob

Hi

Thanks a lot.

I've checked the user guide "swru295.pdf" very carefuly, and yes the Table 8 describes GPIO.

However, it does not assure that the output of of GPIO is "the I/Q raw data" "after ADC".

In Table 8, it describes the GPIOx_CFG 0, that :

Associated to the RX FIFO: Asserts when RX FIFO is filled above 

FIFO_CFG.FIFO_THR. De-asserts when RX FIFO is drained below/equal 

to FIFO_THR.  

Best Regards

Hi

Thanks again for your response.

So these are probably the last questions:

Does CC1101 support this function of outputing soft values ? (Cause we already bought CC1101, that is, actually, CC430)

Does this kit http://www.ti.com/tool/cc1120dk give soft values output of CC1120?  (Yes we checked the datasheets and userguides of the kits, but still need to double-check. Thanks for your help) Or any other kit for CC1120 you may recommend ?

Kind regards

Bob

Hi

Thank you very much for your former responses.

Some more questions below .......

1st, We've bought the TrxEB (CC1120 DK) and did some tests. From the GPIO0 and GPIO2, some wave is output, and it looks like digital 0 or 1 signals. However, we do not know how to recover the original raw I Q data from these 0 or 1 sequence. We guess: the output is the coded 01 sequence of  the ADC output. For example, if the original analog signal is pi, while the sample is 3.1415926,  the ADC quantizes it into 3.14 (get rid of  the rest part, 0.0015925), and then encode this 3.14 in to some 01 sequence -- this encoded 01 sequence is the output of the GPIO0 and GPIO2. So, if our guess is right, how do we recover the value 3.14 from the observed 01 sequence output from GPIO0&2. 

2nd, Where may we find the brochure of this ADC, and detailed explaining of the CC1120 chip ?

3rd, Where may we find the detailed information of the other blocks besides ADC of CC1120 ?

The user guide and datasheet of CC1120 is not detailed enough, for example, there is no information about each block,

--e.g., the ADC: how many bits this ADC is ? what encoding scheme this ADC use ? Is there a preamble or synch word at the start of each encoded symbol ? and so on.

--e.g, the channel filter : is this a low-pass channel filter ? Or Is this a match filter to do equalization ? and so on.

and the other blocks

It is limited how much information we give on the external building blocks.

The ADC is a single bit sigma delta so a bit stream represent a symbol. For test purpose you should take the stream into Matlab and low pass filter it there to recover the original data. Start by applying a sine wave and see if you can recover that from the ADC data.

If you use the ADC data those are output before the channelfilter.

Hi 

Thank you very much again, for your answer and patience.

We still have some questions ....  :

Can you please let us know what is function of the channel filter, and that of the Cordic (we have knowledge about these though. But the questions still have to be asked because in some scenarios people refer to different concepts by the same terminology) ?  In other words, what kind of signal is output from the channel filter and Cordic ?

-- If there is some detailed documents we can read about those blocks of CC1120, that is the best.

I guess what we need may be as simple as: the output of the channel filter (if the channel filter functions just as a low pass filter) ; or may be the output of the Cordic.

Thanks

Bo

Hi

Thank you very much for your former responses and your help. We really appreciate.

Now The problem is like this: we always get the same output from the receiver, regardless the transmitter is on or off. 

The image from Oscilloscope. The transmitter is on, this image shows what the receiver get from its ADC output.

The image from Oscilloscope. The transmitter is off, this image shows what the receiver get from its ADC output .

Hi

Thanks for your former response. May I have more questions please 

1st --- 

We tried all the three modes "continuous Rx", "package Rx"  and "RF Device Commands" , but the output of GPIO0 and GPIO2 are all the same for these three modes.

Regardless the transmitter is on or off, the receiver always get the same thing from GPIO0 and GPIO2 for these three modes. (as the pictures of yesterday, from oscilloscope)

2nd --

Should the IOCFG to be configured as "2E" (to make GPIO output the raw ADC data) ? -- as the powerpoint file uploaded yesterday ?

3rd --

Does SmartRF NOT support CC1120 ? Should we strap some signals manually before using SmartRF with CC1120 ? (as follows, the Page 21 of swru294)

Best regards

Bo

Hi

Thanks for your former response. May I have more questions please 

1st --- 

We tried all the three modes "continuous Rx", "package Rx"  and "RF Device Commands" , but the output of GPIO0 and GPIO2 are all the same for these three modes.

Regardless the transmitter is on or off, the receiver always get the same thing from GPIO0 and GPIO2 for these three modes. (as the pictures of yesterday, from oscilloscope)

2nd --

Should the IOCFG to be configured as "2E" (to make GPIO output the raw ADC data) ? -- as the powerpoint file uploaded yesterday ?

3rd --

Does SmartRF NOT support CC1120 ? Should we strap some signals manually before using SmartRF with CC1120 ? (as follows, the Page 21 of swru294)

Best regards

Bo

Hi TER

Before we redo the experiments very carefully again (and we will try every possible ways we can think about to get the right result), I must say "thank you very much", for taking this seriously and helping us with so many efforts. Your efforts and testings have shown that at least our group is following the right way ( going the right direction ).

This really means a lot to us. Our project may turn out to be a big deal, and we may use large number of TI CC1120 chips in near future if we can make our project which is a 1-3 years project that is expected to lead to products commercialization. 

Kind regards

Bo and our group

Hi

Thanks for your former responses.

We carefully repeated the same testing, and get the same result as yours, that is: GPIO does output nothing when STX is strobed. The GPIO does output something when SRX is strobed and it outputs different waves each time. 

However, the wave it outputs are actually the same type regardless the transmitter is on or off, when SRX is strobed. We expected to get some signal from receiver's GPIO when transmitter is on, and no signal (or another totally different type of signal) from receiver's GPIO when transmitter is off. But regardless the transmitter is on or off, the output of GPIO is still the same "type". That is, from the output of GPIO (the oscilloscope), people cannot tell whether transmitter is on or off. -- This can not be right.

Please see the output of GPIO as the pictures below:

This above picture is the output of GPIO/oscilloscope when transmitter is off, SRX is strobed on the receiver.

This above picture is the output of GPIO/oscilloscope when transmitter is on , SRX is strobed on the receiver.

(we used a very good signal generator as the transmitter, and when the signal generator is on, the RSSI jumps up on the receiver which means the configuration of the signal generator is right.)

This above picture is the output of GPIO/oscilloscope when STX is strobed on the receiver.

Is it possible to probe before ADC ?  (That would be really helpful)

Thanks

Hi

Thank you for the response again. Still more questions .... 

ADC has three blocks: sample, quantization, coding. Let say an input analog signal is pi, then after sample it is 3.14159, after quantization it is 3.14, then after coding it is 1000100... (n bits), which is a 0/1 bit stream. I trust this 0/1 bit stream is the output of the output of GPIO or ADC. 

1, Now that we can trust the output of GPIO is the ADC output of the raw data, which is a 0/1 bit stream, how to decode this bit stream ? Information about the ADC is needed. For example, this is n-bits ADC, then how large is this n ? What is the sample rate ? How to find the start of each sample (suppose each sample is quantized into n bits.) ?

2, How to lowpass filter the output of ADC ? I mean, do we input the bit stream into a low pass filter ? Or do we first decode the bit stream (decode it back to a sample of the transmitted MSK symbol) and then input the decoded sample stream into a lowpass filter ? -- Another expression of this question could be : how does the channel filter in CC1120 work ? 

3, Similar as question 2, I tried directly perform FFT on the output of GPIO, but this seems not make sense, since this output of GPIO is not the sample of some signal. It is a 0/1 bit stream which comes from of the quantization of the sample of TX signal. The 0/1 bit stream is not supposed to be directly done by FFT (The figures below:)

The above figure is the output of GPIO 0 (Transmitter ON and OFF)

The above figure is the FFT of the output of GPIO 0 (Transmitter ON and OFF -- they are the same ?!)

---------------

If there are some manuals regarding the ADC , the channel filter, the cordic, the demodulator, that would be most helpful.

Best regards

Bo

Hi 

Thanks a lot for all the former responses. We have been always watching the responses and thinking/doing_testings accordingly.

Our target is to utilize the output of ADC "raw data" to recover the input of ADC (and do some DSP by MATLAB), so besides learning thoroughly this sigma-delta ADC thing (we are learning it and we realized that we must learn it seriously so as to make good use of the output of the ADC of CC1120), I guess we also need some more information or parameters:

1, what is the IF frequency ? (say, 1MHz, or 100KHz ?)

2, Sampling rate of the sigma-delta ADC

3, the center frequency of the channel filter

In short, is it possible to have the datasheet/user_guide of each block ( or,  at least the datasheet/user_guide of this ADC) of the CC1120 ? Cause the datasheet/user_guide of CC1120 itself (i.e., swru295   and http://www.ti.com/lit/ds/symlink/cc1120.pdf) does not provide much information regarding the ADC.

Hi 

On the CC1120DK (TRxEB),

is there some PIN to get the output of the channel filter ? (In CC1120 block diagram, its channel filter is after ADC) 

I suspect the channel filter of CC1120 functions as the filter&decimator as depicted in the dash line box below:

Thanks

1, what is the IF frequency ? (say, 1MHz, or 100KHz ?)

See 9.2 in the UserGuide.

2, Sampling rate of the sigma-delta ADC

See my previous post.

3, the center frequency of the channel filter

The center is the IF frequency

We don't have a supported way to output data after the channelfilter on a GPIO

Hi

Is it possible to make CC1120 send QPSK or BPSK signal ?

--Though according to the userguide and datasheet, the only available signal, which is close to QPSK, is MSK.

Thanks

Hi 

Thanks for your former responses.

We have problem in filtering the output of ADC (that is, the output of GPIO).

Is there anyway to get/buy this digital bandpass channel filter , such as from TI ?

Thanks a lot

No,

you have to use a MCU, FPGA or DSP with suffisient processing power and implement the filter in software.

Hi TER,

     More queston abot I/Q output: 

      Q1: Can I have I/Q data reading out from the CHFILT_Ix ( x= 0,1,2) and CHFILT_Qx (x= 0,1,2) registers instead of from GPIO0/GPIO2 ?  What clock rate for these registers is running on? What is maximum data rate for reading these registers out?

     Q2: Is it posible routing out the CHFILT_Ix ( x= 0,1,2) and CHFILT_Qx (x= 0,1,2) registers contents to output pin in CC1120?

     Q3: What is difference between ZERO-IF and LOW-IF ?

Robert Lin

1) Yes, the registers are updated with a rate of 4*RXFIlterBandwidth. Note that it is possible to have a signal out on GPIO that strobes when valid data is in the registers, see table 10 in the userguide.

2) Only if you use the LVDS interface

3) Low IF is used for low datarates and zero IF is used for high datarates.

Hi TER,

         Thank you for answer. Next step, we are going to use CC1120 I/Q output to ingreate with our exsiting baseband board for verification.So we need to you help to clarify how to use them. As you answer, "it is possible to have a signal out on GPIO that strobes when valid data is in the registers, see table 10 in the userguide."

           Here are the questions:

           Q1: What configuration that is need to configure for strobes signal to output from GPIO ? (Strobe by falling or raising edge) 

                  Is it CLKEN_SOFT[IOCFGx.GPIOx_CFG = 29] , SOFT_TX_DATA_CLK [ IOCFGx.GPIOx_CFG = 30], or other ?

           Q2: Where is the LVDS interface in CC1120 ?

Thanks,

Robert Lin

Hi Robert

Send me an email if you are interested to discuss/talk with me. I can send you my tel number through email.

had been working on the I/Q ouput (i.e., GPIO) for months when I was making my prototype using CC1120 board.

Maybe I can help you a little bit.

integrghb@gmail.com

Bob Guo

Robert Lin2 said:

Hi TER,

         Thank you for answer. Next step, we are going to use CC1120 I/Q output to ingreate with our exsiting baseband board for verification.So we need to you help to clarify how to use them. As you answer, "it is possible to have a signal out on GPIO that strobes when valid data is in the registers, see table 10 in the userguide."

           Here are the questions:

           Q1: What configuration that is need to configure for strobes signal to output from GPIO ? (Strobe by falling or raising edge) 

                  Is it CLKEN_SOFT[IOCFGx.GPIOx_CFG = 29] , SOFT_TX_DATA_CLK [ IOCFGx.GPIOx_CFG = 30], or other ?

           Q2: Where is the LVDS interface in CC1120 ?

Thanks,

Robert Lin

Hi Bob,

            Thank you . I will sent  my email address to yout

Robert Lin