fc-rfcal-tools: doc/Tx-cal-theory annotate

annotate doc/Tx-cal-theory @ 107:8205ce02eb44

txlevels/fcom1-1900: we are now able to get the full 30 dBm

author	Mychaela Falconia <falcon@freecalypso.org>
date	Tue, 13 Feb 2018 00:30:35 +0000
parents	16aab86384a7
children	7bcbbba94c41

rev	line source
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	1 The Tx power levels put out by a GSM mobile station are subject to strict
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	2 specifications, and on the Calypso+Iota+Rita chipset they are produced by
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	3 writing different values into the APC DAC register. But what value should be
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	4 written into the APC DAC in order to produce a given Tx power level in dBm?
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	5 The answer varies from one produced device unit to the next, and even more from
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	6 one board design to the next, hence these APC values need to be calibrated.
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	7
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	8 The general procedure for calibrating Tx power levels is described in both Sara
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	9 and LoCosto calibration documents (see TI-docs), but the LoCosto document adds
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	10 one crucial detail which the Sara one fails to describe. The instructions given
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	11 in the Sara document appear to be perfectly intuitive at first: go through all
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	12 power levels in turn (PL numbers 5-19 for EGSM and GSM850 or 0-15 for DCS and
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	13 PCS), and for each power level command the DUT to transmit at that level,
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	14 measure the actual Tx output power with the CMU200 or other RF test equipment,
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	15 and adjust the APC DAC value up or down to make the output power match the spec.
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	16
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	17 The problem is with the very last part: the output power you get with the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	18 compiled-in APC DAC value is one number, the spec-defined target power is a
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	19 different number, exactly how do you adjust the APC DAC value to hit the target
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	20 power level?
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	21
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	22 The LoCosto document gives the answer which was not at all obvious to me at
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	23 first. I draw the reader's attention to section A.3.1 on page 43 of that
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	24 document. The trick is as follows: the relation between the APC DAC value and
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	25 the resulting Tx output power (or rather the equivalent in terms of voltage) is
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	26 modeled as a piecewise linear function, and this piecewise linear function is
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	27 constructed from a preliminary set of output power measurements with a fixed
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	28 set of APC DAC values.
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	29
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	30 We also have a strong piece of evidence that the Tx power level calibration
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	31 procedure performed by Openmoko at their factory was based on the same principle
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	32 as the LoCosto document version. If you look at the /gsm/rf/tx/levels.900 table
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	33 in Om-calibrated GTA02 units and compare it against the firmware's compiled-in
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	34 version, you will see that the APC DAC values for power levels 5-19 have been
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	35 replaced with calibrated ones as expected, but there is also this oddity: the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	36 APC DAC value for power level 0 (not a valid number for this band) has been
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	37 replaced with 600. Always 600, a perfect round number, on every unit.
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	38
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	39 Having understood the calibration method described in the LoCosto document, the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	40 mystery of this fixed number 600 becomes clear: the calibration program
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	41 establishes the basis for the calibration by temporarily overwriting the APC DAC
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	42 value in the power level 0 slot with a series of fixed values, 600 being the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	43 last of them. It constructs the piecewise linear model for the APC from power
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	44 measurements made with these fixed DAC values, and uses this model to compute
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	45 the DAC value for each target power level. The latter DAC values are then
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	46 written into Tx levels table slots 5-19 for EGSM and GSM850, or 0-15 for DCS
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	47 and PCS. In the case of DCS and PCS no visible artifacts remain from the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	48 calibration basis run (because slot 0 is a valid power level for these bands),
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	49 but an artifact remains in the levels.900 table in the unused slot 0.
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	50
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	51 Target power level numbers
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	52 ==========================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	53
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	54 Ideally the power level numbers to be used as the targets for the calibration
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	55 process would be the levels given in the GSM 05.05 spec: from 33 dBm down to
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	56 5 dBm for the EGSM and GSM850 bands or from 30 dBm down to 0 dBm for DCS and
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	57 PCS, in 2 dBm steps in each case. However, the evidence from TI's calibration
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	58 documents (both Sara and LoCosto) is that some devices are not able to produce
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	59 the very highest and sometimes the very lowest power levels given in the spec,
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	60 and getting a successful calibration requires setting the calibration targets
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	61 to slightly shifted numbers, although still within the tolerances allowed by
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	62 the GSM 05.05 spec. The table in TI's Sara calibration document (page 26) has
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	63 the highest power level reduced by 1.2 relative to the spec, the next highest
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	64 by 0.5, whereas the lowest 4 (EGSM) or 6 (DCS) levels are raised and compacted
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	65 together. The table in the LoCosto document (page 44) has the highest power
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	66 level for each band reduced by 0.8, making it 32.2 dBm for EGSM and GSM850 and
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	67 29.2 dBm for DCS and PCS, while all other levels are set to the spec numbers.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	68
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	69 In my own experience with getting the Tx power levels calibrated on our current
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	70 FCDEV3B boards, our hardware is able to hit all of the lowest spec power levels
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	71 with good margin (the APC DAC value never goes below the 60-70 range), hence
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	72 the low targets did not need to be shifted, but the highest spec power level
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	73 could not be achieved in every band. Following TI's practice with LoCosto, I
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	74 set the highest power level target to 32.2 dBm for the EGSM band and to 29.2 dBm
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	75 for PCS, but I was consistently able to get the full 30 dBm out in the DCS band,
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	76 hence I set the DCS band highest power level target to the official number of
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	77 30 dBm. It needs to be emphasized, however, that these results are quite
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	78 specific to our current flock of FCDEV3B hardware, and your results will most
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	79 likely be different if you are working with a different hw design such as a
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	80 non-FreeCalypso derivative of Openmoko's GTA02 design.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	81
103 16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	82 Update: the above calibration observations for the FCDEV3B should be held
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	83 doubly in doubt because the calibration status of my CMU200 itself is in
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	84 question, i.e., it is not currently known if the measurements it reports are
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	85 really trustworthy. After the above paragraph was written, I replaced the
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	86 Rx/Tx module inside my CMU (the original one was good for Rx, but the Tx side
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	87 was dead), and after this internal module replacement the power measurements
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	88 reported by the instrument are 0.5 dB less than what it reported before. Which
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	89 raises the questions: are the new measurements low by 0.5 dB relative to the
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	90 real truth, or were the old ones high by 0.5 dB relative to the real truth? Or
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	91 is the real truth something else altogether? Until we raise a LOT more money
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	92 to get this CMU200 properly calibrated, we are limited to guesswork and the
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	93 true transmitter behaviour of our FCDEV3B hardware remains unknown.
16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	94
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	95 Profiles for Tx levels calibration
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	96 ==================================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	97
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	98 Our fc-rfcal-txband program that performs the actual per-unit calibration of Tx
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	99 power levels for each band requires a preconfigured txlevels calibration profile
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	100 for each band as one of its inputs; if you are performing calibration on
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	101 individual units of a board design for which the correct profiles have already
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	102 been crafted, you simply use those given profiles (fcom1 for our current flock
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	103 of FCDEV3B boards), but if you are doing Tx power level calibration on a new
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	104 board design for the first time, you first need to characterize the Tx output
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	105 level behaviour of your new board design and craft the appropriate set of
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	106 profiles.
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	107
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	108 The profiles for txlevels calibration reside in /opt/freecalypso/rfcal/txlevels;
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	109 each per-band profile is sought in a file named profile_name-band_number, where
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	110 profile_name is the profile name argument given to fc-rfcal-txband and
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	111 band_number is one of 850, 900, 1800 or 1900. For example, the profile set for
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	112 our current FCDEV3B hardware is named fcom1 ("FreeCalypso hardware, Openmoko-
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	113 based, version 1"), this hw platform is 900/1800/1900 MHz triband, and the
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	114 individual profile config files are fcom1-900, fcom1-1800 and fcom1-1900.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	115
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	116 Each profile provides two key pieces of data: the list of fixed APC DAC values
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	117 to be used as the basis set for constructing the piecewise linear model, and
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	118 the list of power levels in dBm that will be the targets for the calibration.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	119
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	120 Crafting the txlevels calibration profiles for a new board design
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	121 =================================================================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	122
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	123 If you are working with a new (or new-to-you) board design with no previous Tx
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	124 levels calibration experience, you need to begin by characterizing its Tx
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	125 output level behaviour so you can determine what APC values are appropriate for
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	126 the basis set, whether or not you need to shift the highest and/or lowest
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	127 target levels from their nominal spec values, and if some target shifting is
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	128 needed, which levels need to be shifted and by how much.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	129
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	130 The tool you will need for this investigation is fc-rfcal-txbasis. It requires
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	131 fc-cmu200d and rvinterf to be running, talking to the CMU200 and to the DUT,
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	132 respectively, and it takes the band number (850/900/1800/1900) and a set of
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	133 APC DAC values on the command line; no pre-existing txlevels profile is needed.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	134 It commands the DUT to transmit at each of the specified APC DAC values in turn
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	135 and reports the power output levels measured by the CMU200.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	136
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	137 VERY IMPORTANT: You need to be very sure that your CMU200 or other measuring
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	138 instrument is itself in good calibration standing, i.e., that the measurements
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	139 it reports are trustworthy, and that the insertion loss in your cabling setup
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	140 (all the way from the actual DUT's antenna connector or RF test port to your
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	141 CMU200) really matches the numbers you have put in your cable configuration file
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	142 (see Cable-config-howto). If you fail to ensure these prerequisites, your
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	143 fc-rfcal-txbasis observations will be meaningless, as the cable insertion losses
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	144 are typically of the same order of magnitude as the transmitter differences you
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	145 are trying to determine.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	146
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	147 You will need to run fc-rfcal-txbasis with a guesstimated set of APC DAC values,
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	148 to be revised iteratively, and get a feel for what your DUT is putting out.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	149 Are you able to hit the lowest spec power level consistently while the APC DAC
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	150 value remains well above zero? Are you able to hit the highest spec power level
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	151 as well, or does the measured power output fall short of this target no matter
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	152 how high you crank the APC DAC? These observations will tell you whether or not
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	153 you need to shift the highest and/or lowest target power levels in your new
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	154 txlevels calibration profile.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	155
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	156 Regular calibration runs
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	157 ========================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	158
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	159 Once you have a good set of profiles for the type of Calypso GSM device you are
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	160 calibrating, just run fc-rfcal-txband with the band number and the name of your
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	161 profile.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	162
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	163 Checking existing calibration
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	164 =============================
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	165
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	166 fc-rfcal-txcheck is a completely non-invasive program (does not make any writes
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	167 to any L1 RF tables or to FFS) that steps through all power levels for the
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	168 specified band (5-19 for EGSM or GSM850, or 0-15 for DCS or PCS), performs a
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	169 power measurement at each level, and displays the measured result.

FreeCalypso > hg > fc-rfcal-tools

annotate doc/Tx-cal-theory @ 107:8205ce02eb44