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

annotate doc/Tx-cal-theory @ 128:623340e2c475

LICENSE: update for copyright registration completed

author	Mychaela Falconia <falcon@freecalypso.org>
date	Wed, 25 Dec 2019 05:27:25 +0000
parents	aa2533be2ec1
children

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
120 32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	28 set of APC DAC values. Looking at the Vout/LSB slope in each segment of this
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	29 constructed piecewise linear function, one can see that the relation stays
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	30 mostly linear throughout most of the RF PA's valid control range, and at least
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	31 in the case of GSM MS devices made by Openmoko, the factory-calibrated power
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	32 levels all fall into this "good" range in which the PA's response to the APC DAC
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	33 control value is mostly linear.
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	34
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	35 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	36 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	37 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	38 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	39 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	40 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	41 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	42 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	43
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	44 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	45 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	46 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	47 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	48 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	49 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	50 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	51 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	52 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	53 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	54 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	55
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	56 Target power level numbers
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	57 ==========================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	58
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	59 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	60 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	61 5 dBm for the EGSM and GSM850 bands or from 30 dBm down to 0 dBm for DCS and
120 32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	62 PCS, in 2 dB steps in each case. However, the evidence from TI's calibration
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	63 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	64 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	65 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	66 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	67 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	68 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	69 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	70 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	71 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	72 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	73
111 7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	74 The calibration that was performed by Openmoko's factory (FIC?) on their GTA02
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	75 units is similar to what the old Sara document calls for: the highest power
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	76 level is set to 31.8 dBm for EGSM or GSM850 and to 28.8 dBm for DCS and PCS,
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	77 the next one down is 30.5/27.5 dBm instead of 05.05-spec-given 31/28 dBm, and
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	78 for the lowest 4 (EGSM or GSM850) or 6 (DCS and PCS) power levels the decrement
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	79 between levels is 1.5 instead of 2, putting the lowest EGSM or GSM850 power
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	80 level at 7 dBm instead of 5 dBm, and the lowest DCS and PCS power levels at
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	81 3 dBm instead of 0 dBm.
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	82
120 32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	83 When it comes to the highest power levels, my (Mychaela's) first thought was
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	84 that OM's calibration had them reduced to 31.8/28.8 dBm for no good reason other
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	85 than OM/FIC mindlessly using some TI-provided calibration software that had
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	86 those settings by default, as a leftover from some much older hw platform that
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	87 was poorer in this department than OM's GTA0x hardware. As a matter of fact,
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	88 it is possible to make an Openmoko-made GTA02 device put out the full 33 dBm
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	89 in the EGSM band and the full 30 dBm in the DCS and PCS bands by setting the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	90 APC DAC to higher values than those used by OM's factory calibration. However,
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	91 a closer look reveals that those higher-than-OM's APC DAC values which produce
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	92 the full 33/30 dBm output put the PA outside of its linear range, i.e., the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	93 relation between the APC DAC control value and the resulting RF Vout no longer
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	94 has the same linearity as is maintained at the lower power levels. In our own
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	95 FreeCalypso calibration, we used to set the higher 32.2/29.2 or even the full
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	96 33/30 dBm targets for the highest power levels prior to the discovery of the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	97 linearity issue, but our current rf3166 profile set (see below) uses the same
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	98 conversative upper-end targets as OM's original: 31.8/28.8 dBm for the highest
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	99 power level and 30.5/27.5 dBm for the next one down.
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	100
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	101 When it comes to the lowest power levels, the empirical observation is that the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	102 official spec bottom power levels of 5 dBm for the low bands and 0 dBm for the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	103 high bands are perfectly attainable both on Openmoko-made units and on our own
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	104 FCDEV3B, with APC DAC values that are only a tiny bit lower than the lowest
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	105 values in OM's calibration. We currently use 70 as the lowest basis point in
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	106 the EGSM and GSM850 bands and 60 as the lowest basis point for DCS and PCS,
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	107 following the LoCosto document; we are consistently able to get 5 dBm for the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	108 low bands or 0 dBm for the high bands within our basis range, and examination
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	109 of the piecewise Vout/LSB slopes shows that the PA appears to be happily linear
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	110 in this range. Therefore, we use the official spec numbers for the lowest
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	111 power level targets in our current rf3166 profile set, not the raised target
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	112 numbers from TI's older platforms.
103 16aab86384a7 doc/Tx-cal-theory: update regarding our current FCDEV3B calibration Mychaela Falconia <falcon@freecalypso.org> parents: 98 diff changeset	113
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	114 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	115 ==================================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	116
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	117 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	118 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	119 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	120 individual units of a board design for which the correct profiles have already
120 32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	121 been crafted, you simply use those given profiles (rf3166 for Openmoko and
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	122 OM-based FreeCalypso hardware), but if you are doing Tx power level calibration
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	123 on a new board design for the first time, you first need to characterize the Tx
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	124 output level behaviour of your new board design and craft the appropriate set
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	125 of profiles.
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	126
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	127 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	128 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	129 profile_name is the profile name argument given to fc-rfcal-txband and
111 7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	130 band_number is one of 850, 900, 1800 or 1900. For example, if you are using
120 32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	131 the rf3166 profile set (appropriate for recalibrating Openmoko GTA02 devices
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	132 and for factory production of new FreeCalypso devices with the same RF PA), the
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	133 individual profile config files are rf3166-900, rf3166-1800 and rf3166-1900 for
32bf19fb8a2a doc/Tx-cal-theory: update for the new conservative rf3166 profile set Mychaela Falconia <falcon@freecalypso.org> parents: 111 diff changeset	134 the tri900 band configuration.
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	135
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	136 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	137 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	138 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	139
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	140 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	141 =================================================================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	142
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	143 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	144 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	145 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	146 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	147 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	148 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	149
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	150 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	151 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	152 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	153 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	154 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	155 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	156
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	157 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	158 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	159 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	160 (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	161 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	162 (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	163 fc-rfcal-txbasis observations will be meaningless, as the cable insertion losses
111 7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	164 and instrument errors are typically of the same order of magnitude as the
7bcbbba94c41 doc/Tx-cal-theory: update with properly calibrated CMU200 and cabling setup Mychaela Falconia <falcon@freecalypso.org> parents: 103 diff changeset	165 transmitter differences you are trying to determine.
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	166
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	167 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	168 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	169 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	170 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	171 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	172 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	173 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	174 txlevels calibration profile.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	175
121 76faa4f52a4d doc/Tx-cal-theory: fc-rfcal-txbasis -l option documented Mychaela Falconia <falcon@freecalypso.org> parents: 120 diff changeset	176 2018-02 addition: fc-rfcal-txbasis takes a new command line option -l; this
76faa4f52a4d doc/Tx-cal-theory: fc-rfcal-txbasis -l option documented Mychaela Falconia <falcon@freecalypso.org> parents: 120 diff changeset	177 option causes it to compute and print the Vout/LSB slope after the second and
76faa4f52a4d doc/Tx-cal-theory: fc-rfcal-txbasis -l option documented Mychaela Falconia <falcon@freecalypso.org> parents: 120 diff changeset	178 subsequent basis points; this option is useful for studying the linearity of
76faa4f52a4d doc/Tx-cal-theory: fc-rfcal-txbasis -l option documented Mychaela Falconia <falcon@freecalypso.org> parents: 120 diff changeset	179 the RF PA's response to APC DAC control values.
76faa4f52a4d doc/Tx-cal-theory: fc-rfcal-txbasis -l option documented Mychaela Falconia <falcon@freecalypso.org> parents: 120 diff changeset	180
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	181 Regular calibration runs
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	182 ========================
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	183
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	184 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	185 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	186 profile.
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	187
122 aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	188 Channel correction calibration
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	189 ==============================
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	190
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	191 The APC DAC values given in the levels tables apply directly only to the
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	192 channels in the centre of each band. The transfer function from APC DAC control
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	193 values to power output levels in dBm depends on the frequency, and the APC DAC
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	194 values need to be adjusted for different subbands within each band in order to
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	195 produce the correct output power levels for all channels. TI's RF driver code
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	196 and calibration data structures provide for a Tx channel calibration, and all
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	197 historical commercial manufacturers of Calypso GSM devices that are known to us
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	198 have performed this Tx channel calibration on a per-unit basis on their
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	199 production lines.
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	200
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	201 Our fc-rfcal-txband calibration tool implements Tx channel correction
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	202 calibration as of 2018-02, and we do it a little better than the way it was done
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	203 by the big folks Back In The Day. TI's RF data structures allow for up to 4
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	204 channel calibration tables, to be used for different power levels, but
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	205 Openmoko's factory only did one channel calibration set (calibrated at the
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	206 highest power level for each band), using only one table out of the possible 4,
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	207 and this one table (calibrated at the highest power level) is then used for all
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	208 power levels. As far as we can tell, other Calypso GSM device manufacturers
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	209 have done likewise.
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	210
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	211 Our Tx calibration implementation makes use of all 4 available channel
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	212 correction table slots. We divide the 15 power levels of EGSM and GSM850 bands
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	213 or the 16 power levels of DCS and PCS into 4 groups (5-7, 8-11, 12-15, 16-19
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	214 for EGSM and GSM850; 0-3, 4-7, 8-11, 12-15 for DCS and PCS), perform channel
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	215 calibration at the highest power level in each group, and set the resulting
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	216 channel calibration table to be used for all 3 or 4 power levels in that group.
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	217 Our procedure produces Tx behaviour that is identical to Openmoko's for the
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	218 highest 3 or 4 power levels, but the lower power levels run with channel
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	219 calibration that was made closer to them, as opposed to the very highest power
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	220 level. The price of our approach is more time spent in RF calibration for each
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	221 unit on the production line, but our approach is perfectly suited for low volume
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	222 production and aftermarket recalibration services.
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	223
98 615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	224 Checking existing calibration
615df2fb1ec3 doc/Tx-cal-theory: update with both theory and practice Mychaela Falconia <falcon@freecalypso.org> parents: 66 diff changeset	225 =============================
66 8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	226
8e675142cca7 doc/Tx-cal-theory written Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	227 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	228 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	229 specified band (5-19 for EGSM or GSM850, or 0-15 for DCS or PCS), performs a
122 aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	230 power measurement at each level, and displays the measured result. By default
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	231 the test is performed at the centre frequency of the specified band, but the
aa2533be2ec1 doc/Tx-cal-theory: channel calibration documented Mychaela Falconia <falcon@freecalypso.org> parents: 121 diff changeset	232 ARFCN to be used can also be specified on the command line.

FreeCalypso > hg > fc-rfcal-tools

annotate doc/Tx-cal-theory @ 128:623340e2c475