GC4016 - wideband mode - Decimation

Vinod Aduru

I have attached ultra wideband mode configuration file of GC4016. This configuration is working fine for Decimations 8,10 and 16 and not working for 9,11,12,13,14 and 15. Why it is behaving like that.

/* Wideband configuration file */

/* general modes register */
   global_reset 1
out_blk_reset 1
      pad_reset 1
resampler_reset 1
    edge_write 1
      ck_2x_en 0
    ck_2x_test 0
ck_loss_detect 0

/* general sync */
          lvds 0
4_bit_address 0
   output_sync 4
     diag_sync 7

/* count sync */
      one_shot 1
       os_mode 1
    count_test 0
counter_sync 7
   diag_source 0

/* terminal count */
           cnt 0

/* channel configurations */
       channel 0
         phase 0
          freq 0x4CCCCCCD
     cfir_coef ../Taps/cfir_150.taps
     pfir_coef ../Taps/pfir_150.taps
      ch_reset 0
     use_shift 1
         shift 4
     freq_sync 7
    phase_sync 7
   dither_sync 0 /* Original is 4 */
      nco_sync 4
       zpad_en 0
     zpad_sync 4
        nzeros 0
    flush_sync 4
      dec_sync 4
           dec 7
      gain_sync 7
        mix20b 1
     big_scale 7
         scale 5 /* Changed - ELSEC */
         qonly 0
         ionly 1
       splitiq 1
       neg_ctl 0
          test 0
        coarse 0
     idly_cfir 0
     qdly_cfir 0
   no_sym_cfir 0
   peak_select 0
     idly_pfir 0 /* Changed - ELSEC */
     qdly_pfir 1
   no_sym_pfir 0
       msb_pol 0
        in_fmt 0
        ab_sel 0
     input_sel 0
     peak_mode 0
peak_threshold 3
     peak_sync 5
     fine_gain 1070

       channel 1
/* copy_channel 0 same as 0 */
    /* ch_reset 1*/
         phase 0x4000
          freq 0x4CCCCCCD
     cfir_coef ../Taps/cfir_150.taps
     pfir_coef ../Taps/pfir_150.taps
      ch_reset 0
     use_shift 1
         shift 4
     freq_sync 7
    phase_sync 7
   dither_sync 0 /* Original is 4*/
      nco_sync 4
       zpad_en 0
     zpad_sync 4
        nzeros 0
    flush_sync 4
      dec_sync 4
           dec 7
      gain_sync 7
        mix20b 1
     big_scale 7
         scale 5 /* Changed - ELSEC */
         qonly 1
         ionly 0
       splitiq 1
       neg_ctl 0
          test 0
        coarse 0
     idly_cfir 0
     qdly_cfir 0
   no_sym_cfir 0
   peak_select 0
     idly_pfir 0 /* Changed - ELSEC */
     qdly_pfir 1
   no_sym_pfir 0
       msb_pol 0
        in_fmt 0
        ab_sel 0
     input_sel 0
     peak_mode 0
peak_threshold 3
     peak_sync 5
     fine_gain 1070

       channel 2
/*   copy_channel 0 same as 0 */
/*    ch_reset 1*/
       phase 0x0
          freq 0x4CCCCCCD
     cfir_coef ../Taps/cfir_150.taps
     pfir_coef ../Taps/pfir_150.taps
      ch_reset 0
     use_shift 1
         shift 4
     freq_sync 7
    phase_sync 7
   dither_sync 0 /* Original is 4*/
      nco_sync 4
       zpad_en 0
     zpad_sync 4
        nzeros 0
    flush_sync 4
      dec_sync 4
           dec 7
      gain_sync 7
        mix20b 1
     big_scale 7
         scale 5 /* Changed - ELSEC */
         qonly 0
         ionly 1
       splitiq 1
       neg_ctl 0
          test 0
        coarse 0
     idly_cfir 0
     qdly_cfir 0
   no_sym_cfir 0
   peak_select 0
     idly_pfir 0
     qdly_pfir 0
   no_sym_pfir 0
       msb_pol 0
        in_fmt 0
        ab_sel 0
     input_sel 0
     peak_mode 0
peak_threshold 3
     peak_sync 5
     fine_gain 1070


       channel 3
/*   copy_channel 0 same as 0 */
/*ch_reset 1*/
         phase 0x4000
          freq 0x4CCCCCCD
     cfir_coef ../Taps/cfir_150.taps
     pfir_coef ../Taps/pfir_150.taps
      ch_reset 0
     use_shift 1
         shift 4
     freq_sync 7
    phase_sync 7
   dither_sync 0 /*Original is 4*/
      nco_sync 4
       zpad_en 0
     zpad_sync 4
        nzeros 0
    flush_sync 4
      dec_sync 4
           dec 7
      gain_sync 7
        mix20b 1
     big_scale 7
         scale 5 /* Changed - ELSEC */
         qonly 1
         ionly 0
       splitiq 1
       neg_ctl 0
          test 0
        coarse 0
     idly_cfir 0
     qdly_cfir 0
   no_sym_cfir 0
   peak_select 0
     idly_pfir 0
     qdly_pfir 0
   no_sym_pfir 0
       msb_pol 0
        in_fmt 0
        ab_sel 0
     input_sel 0
     peak_mode 0
peak_threshold 3
     peak_sync 5
     fine_gain 1070

/* resampler parameters */
       ratio_0 0x04000000
       ratio_1 0x04000000
       ratio_2 0x04000000
       ratio_3 0x04000000
      res_coef 0 ../Taps/res_bypass_1024.taps
      res_sync 4
            nf 0
            nc 0
    no_sym_res 1
            nm 6
filter_sel_3 0
filter_sel_2 0
filter_sel_1 0
filter_sel_0 0
        tag_22 0
         round 3
   final_shift 4
    chan_map_d 0
    chan_map_c 0
    chan_map_b 0
    chan_map_a 0
    ratio_sync 7
    add_c_to_d 0
    add_b_to_c 0
    add_a_to_b 0
   res_clk_div 0
     ratio_map 0x00

/* output control */
        en_par 1
         en_p3 1
         en_p2 1
         en_p1 1
         en_p0 1
        en_sfs 1
        en_rdy 1
        en_sck 1

/* outsync */
out_blk_sync 2
     rdy_width 0
        tag_en 0
       inv_sfs 0
       inv_rdy 0
       inv_sck 0

/* out format */
    reverse_iq 0
   output_mode 3
     real_only 0
        master 1
      parallel 1
        nibble 0
          link 0

/* out frame length */
      sfs_mode 2
frame_length 0

/* out word size */
    block_size 0
bits_per_word 5
words_per_frame 0

/* out clock */
output_order 0
       nserial 0
      sck_rate 0

/* serial port selection */
        smux_3 3
        smux_2 2
        smux_1 1
        smux_0 0

/* tags */
        tag_ai 0
        tag_aq 1
        tag_bi 2
        tag_bq 3
        tag_ci 4
        tag_cq 5
        tag_di 6
        tag_dq 7

/* miscellaneous */
         en_so 1
       en_4_fs 0

over 14 years ago

0 Radio-Joe over 14 years ago

TI__Mastermind 37500 points

Hello,

The GC4016 in wideband downconvert mode uses a CIC in splitIQ mode, CFIR in splitIQ mode, and PFIR in a polyphase mode. In this case, the CFIR decimates by 2, the

CIC decimates by values from 4 to 1024. The two splitIQ channels in a polyphase mode, cause the PFIR to decimate by 1 between the two pairs of splitIQ channels.

This means that the decimation is based on CICdec * cfir_dec = (4 to 1024) * 2 * 1. The decimation range is 8 to 2048 in steps of 2. So decimation of 9, 11, 13, 15 are not

possible in the CIC, CFIR, PFIR structure. The values 8, 10, 12, 14, 16 are all possible.

Under the CIC programming description, the value for CIC is 2N-1 for splitIQ mode, so for a CIC decimation of 4, we put in a value of 7.

dec pgm value, desired CIC decimation, desired wideband decimation

7, 4, 8,

9, 5, 10,

11, 6, 12,

13, 7, 14,

15, 8, 16

When you change these decimations the CIC scaling parameters also need to be recomputed for BIG_SCALE and SCALE. The CFIR coefficients

have both a Low pass filter, and High pass CIC compensation. As you change the CIC decimation, the High pass CIC compensation can be recomputed to

generate a flatter passband response.

I have run the wideband decimations 8, 10, 12, 14, and 16 through the cmd4016 tool.

Regards,

Radio Joe

0 Hiren Patel over 14 years ago in reply to Radio-Joe

Prodigy 10 points

Hi,

I have attached my configuration for SPLIT I/Q mode configuration file of GC4016. I am trying to run this configuration for decimation rate of 2,6, and 12. It does not work for

decimation rate 6 and 12, but i get some result for 2. I am running the chip in Nibble Mode, with Output Order of 0, and the resampler is bypassed.

Channel Control

Dec :[0:7] = 7

SHIFT = 4

SCALE = 5

BIG_SCALE = 7

MIX20B = 1

Resampler Control Page (Pg 64)

NC = 1

NF = 0

FINAL_SHIFT = 5

ROUND = 1;

Output Control Page (98)

FRAME_LENGTH = 7;

WORDS_PER_FRAME = 7;

BITS_PER_WORD = 0;

BLOCK_SIZE = 2

NSERIAL = 0

OUTPUT_ORDER = 0;

GLOBAL REGISTERS
Address		0	1	2	3	4	5	6	7
		f8	0	0	0	0	2	cf	f2
PAGED REGISTERS
Address		16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
CHA	Pages 0,1	cFIR Coefficents
	Pages 2-5	pFIR Coefficents
	Page 6	0	0	FREQ				Unused
	Page 7	0c	44	4	0	22	7	70	7D	30	0	10	0	1c	0	e0	8
CHB	Pages 8,9	cFIR Coefficents
	Pages 10-13	pFIR Coefficents
	Page 14	0	40	FREQ				Unused
	Page 15	0c	44	4	0	22	7	70	7D	50	0	10	0	1c	0	e0	8
CHC	Pages 16,17	cFIR Coefficents
	Pages 18-21	pFIR Coefficents
	Page 22	0	0	FREQ				Unused
	Page 23	0c	44	4	0	22	7	70	7D	30	0	10	0	1c	0	e0	8
CHD	Pages 24,25	cFIR Coefficents
	Pages 26-29	pFIR Coefficents
	Page 30	0	40	FREQ				Unused
	Page 31	0c	44	4	0	22	7	70	7D	50	0	10	0	1c	0	e0	8
RES	Pages 32-63	By Pass Resampler
	Page 64	41	0e	0	15	50	70	0	0	Unused
	Page 65	0	0	0	4	0	0	0	4	0	0	0	4	0	0	0	4
OUT	Page 98	7d	41	ca	7	87	0	0	21	43	65	87	0	2	Unused

0 Radio-Joe over 14 years ago in reply to Hiren Patel

TI__Mastermind 37500 points

Hello

The GC4016 Wideband Downconvert mode, has a CIC that decimates from 4 - 1024, a CFIR that decimates by 2, and a PFIR that is polyphased to not decimate.

I have attached a decimate by 8 example, that has worked inthe past with the GC4016 tool. The allowable decimations would be 8 - 1024 as the CIC increases from 4 to 512.

In this mode two sets of splitIQ channels are combined.

I have attached the example configuration file, filter taps, and cmd4016 tool. This example is decimation of 8. The general cmd4016 tool is available on the TI website under the GC4016.

REgards,

Radio Joe

gc4016wideband_downconvert.zip

0 srilatha jasthi over 12 years ago in reply to Radio-Joe

Prodigy 30 points

Hello

In our application, we are operating at 100MHz input sampling frequency. We have chosen wideband mode of DDC and decimation factor set to 10.

With these settings we need a 8MHz filter bandwidth (160%) CFIR and PFIR fitler coefficients.

Could you please provide coefficients for the above requirement?

0 Radio-Joe over 12 years ago in reply to srilatha jasthi

TI__Mastermind 37500 points

Hello,

In the previous email, I sent an example for 8Mhz bandwidth with a decimation of 8. It was also stated that we don't normally provide the ultra wide mode custom coefficients, and the Matlab script was sent with the email.

I have attached a modified matlab script. You will need to characterize your filter requirements, passband and stopband, and use the matlab tool to adjust the filter. Along with the CFIR and PFIR filter design there is a CIC compensation for the droop of the CIC filter. This is a 3 tap High Pass filter, that can be adjusted for the passband flatness.

The Matlab script must have a destination folder, it is listed at the beginning of "C:\Temp" Line 11, it must be created before running the script.

Line 691 - adjust the desired bandwidth in %

Line 744 - adjust the CFIR 3 tap High Pass filter for system passband flatness,

When the system bandwidth is > 65% (130% for ultrawide mode), the stopband rejection of the channel is less. You would get better stopband rejection using the previous example, I sent last time, with a decimation of 8.

I have included the script, and the desired dec10, bandwidth setting of 160, depending on the actual filter characteristics (transition band) this is not the same as an 8Mhz passband filter, you will need to adjust 691 and 744 to meet your filter requirements.

Regards,

Radio Joe

cfirUW4016_160.taps

0 Radio-Joe over 12 years ago in reply to Radio-Joe

TI__Mastermind 37500 points

Here are both the PFIR, CFIR, and matlab script.

Regards,

Radio Joe

pfircfir_uw160.zip

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GC4016 - wideband mode - Decimation