FreeCalypso > hg > freecalypso-docs

annotate Quadband-ideas @ 27:f7ed8c45a8ec

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
DUART-cable article written
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 14 Dec 2019 06:24:24 +0000
parents 00216b7cfc4d
children 3799892b1a79
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
24
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
1 Triband status quo
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
2 ==================
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
3
20
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
4 Our current Openmoko-based Calypso+RF modem core is very very good, but it has
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
5 one shortcoming compared to TI's Leonardo+ reference design: it is triband
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
6 rather than quadband. This triband restriction stems from OM's use of discrete
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
7 antenna switch and SAW filter components as opposed to an integrated FEM (front
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
8 end module) like on Leonardo+. In addition to the band restriction, our current
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
9 triband RF design suffers from one other very unpleasant problem: we have no
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
10 datasheet for the antenna switch component which we have to use. We know from
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
11 Openmoko's BOM data that the manufacturer is Darfon and that the part number for
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
12 this antenna switch component is ASM4532T0P06-1, we are able to buy this part
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
13 from our Chinese grey market suppliers, we build our boards with these parts and
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
14 our boards do work perfectly fine when we get a good batch, but we have to do
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
15 this entire process blindly, without any datasheet or other documentation for
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
16 this mystery part.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17
24
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
18 While we lack any official documentation for our triband ASM, we know its basic
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
19 logical function: it has two Tx inputs (low band and high band Tx coming from
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
20 the PA), 3 Rx outputs going to 3 separate SAW filters for the 3 supported bands,
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
21 and 3 switch control inputs. Two of these switch control inputs are Tx controls
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
22 (low band Tx enable and high band Tx enable) which appear to be the same across
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
23 all common RFFEs, whether they are 2-band (single region), triband or quadband.
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
24 The 3rd switch control input gets a logic high voltage applied to it during PCS
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
25 band Rx, thus it appears to be a switch that diverts the high band Rx path
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
26 between DCS and PCS SAW filters. The same arrangement is found in most other
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
27 triband phones and modems from that era, i.e., they also have two Tx switches
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
28 and one Rx path switch selecting between DCS and PCS, plus 3 discrete SAW
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
29 filter components (outside the ASM) for the 3 bands.
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
30
20
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
31 This article outlines some ideas for how we may be able to move from this RFFE
24
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
32 to a different one, replacing our current mystery ASM with something less
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
33 mysterious and better documented, and improving our radio capability from
20
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
34 triband to quadband at the same time.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
35
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
36 Epcos M034F
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
37 ===========
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
38
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
39 TI's Leonardo+ and E-Sample boards used a magic component made by Epcos (the
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
40 canonical SAW filter manufacturer during that era) called M034 or M034F (the
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
41 exact proper designation is unclear). It was an integrated quadband FEM,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
42 integrating the antenna switch and SAW filters in one component package, with a
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
43 special twist. The special twist is that even though there are 4 separate Rx
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
44 band SAW filters inside that M034 "chip" module, corresponding to its advertised
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
45 quadband capability, only 3 Rx signal path differential pairs come out of it,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
46 neatly corresponding to the 3 LNA inputs on TI's Rita transceiver. This twist
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
47 is important because even though the Rita transceiver itself is fully quadband
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
48 internally, it has only 3 LNA inputs, with GSM850 and EGSM bands sharing the
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
49 same LNA input while each of DCS and PCS get their own.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
50
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
51 We do have an M034F.pdf datasheet for this magic component (came along with
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
52 Calypso and Leonardo docs), and the block diagram on page 6 shows the magic
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
53 quite clearly: there is a baseband-controlled switch selecting between EGSM Rx
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
54 and GSM850 Rx (in addition to the two usual Tx switches), this switch directs
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
55 the low band Rx path toward one of two different SAW filters, and the outputs
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
56 of those two filters are then joined. The high band Rx path always goes to both
24
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
57 DCS and PCS band SAW filters, and each of those high band Rx SAW filters gets
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
58 its own output going to its own dedicated Rita LNA input. Note the lack of a
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
59 baseband-controlled switch between DCS and PCS in the high band Rx path: this
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
60 switch is present in all triband RFFE designs I have seen, thus a big question
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
61 is raised as to how this magic M034 component functions without one. I can
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
62 think of two possibilities:
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
63
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
64 Possibility 1: perhaps they do a 50/50 split of the total incoming energy
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
65 between DCS and PCS Rx paths, with each path suffering by 3 dB as a result.
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
66
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
67 Possibility 2: perhaps by virtue of integrating the ASM and the SAW filters
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
68 into a single monolithic FEM, Epcos found some way to have unswitched DCS and
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
69 PCS Rx without incurring that 3 dB penalty. Perhaps they successfully
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
70 implemented some form of frequency diplexer such that out of the total incoming
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
71 energy picked up by the wideband antenna, DCS downlink frequencies go through
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
72 the DCS Rx SAW filter, PCS downlink frequencies go through the PCS Rx SAW
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
73 filter, and no needless losses are incurred. This hypothesis is supported by
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
74 the observation that the available M034F.pdf document gives approximately the
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
75 same insertion loss numbers for all 4 Rx bands, i.e., the same between the
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
76 switched low bands and the unswitched high bands. Note that they could not
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
77 have similarly eliminated the GSM850 Rx switch: both EGSM Rx and GSM850 Rx need
00216b7cfc4d Quadband-ideas: better explanation of DCS/PCS switching or diplexing mystery
Mychaela Falconia <falcon@freecalypso.org>
parents: 20
diff changeset
78 to go to the same LNA on the transceiver, thus a switch is needed somewhere.
20
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
79
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
80 I (Mother Mychaela) would absolutely love to play with an M034-based quadband
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
81 Calypso+Iota+Rita board in my lab with the trusty CMU200 instrument, and to see
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
82 how well it actually performs, especially in comparison with our current
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
83 OM-based triband version. However, in all of my years of searching I have never
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
84 found a physical Leonardo board (any version), nor have we ever found any
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
85 Leonardo PCB layout files which would allow us to build a modern recreation -
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
86 thus the magic of M034 remains elusive.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
87
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
88 Unless a miracle happens and we are able to obtain either a physical Leonardo+
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
89 board or a PADS PCB file for one, there is no quick or low-effort way to "just
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
90 try" this M034 RFFE. Instead if we wish to build a FreeCalypso board with this
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
91 RFFE, it would have to be "the full 9 yards": a full-blown PCB design and layout
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
92 effort. There is no way to just "drop" the M034 into our existing PCB design
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
93 in the place of our current triband RFFE, it would have to be either a very
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
94 disruptive RF section layout change or an entirely new PCB layout, making this
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
95 idea very open-ended - an open-ended venture with quite uncertain outcome, but
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
96 with a high dollar cost attached to it. Given the massive effort required and
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
97 PCB layout labor costs, I currently have no active plans to pursue this idea
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
98 beyond hypothetical.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
99
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
100 Commissioning a new custom RF FEM
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
101 =================================
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
102
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
103 Here is a wild thought: what if instead of twisting over backwards trying to
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
104 hammer an existing RF FEM like M034F into our not-quite-fitting PCB design, we
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
105 were to get an entirely new FEM made specially for us, made exactly the way we
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
106 need it? If we were to venture that way, I would ask for a FEM very similar
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
107 conceptually to M034F, but with a few changes:
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
108
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
109 1) Instead of diplexing between DCS and PCS SAW filter inputs with a 50/50
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
110 energy split, implement another switch (just like the GSM850 Rx switch) for
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
111 PCS Rx, exactly the same way how it is done in classic triband designs like
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
112 our current OM-based one. This change should eliminate the extra 3 dB
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
113 penalty which I assume (for lack of experimental data) must happen with the
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
114 existing M034 FEM. Or as an alternative to making this change, if someone
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
115 who is more knowledgeable than me in this area can explain to me why it isn't
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
116 necessary, I would accept that option as well.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
117
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
118 2) I would ask for a rearranged pinout: the existing M034F pinout does not fit
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
119 at all into our OM-based PCB layout, but it would fit much better with some
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
120 rearrangement.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
121
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
122 3) The hypothetical M034-like FEM would fit into our OM-based PCB layout a lot
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
123 better if it were made a little smaller than the 8.2x5.5 mm size of M034F.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
124 Considering that the original M034F was created some 15-16 y ago, I assume
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
125 that it should be possible to make a smaller version in 2020 or 2021 or
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
126 whenever.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
127
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
128 Timeline sequentiality
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
129 ======================
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
130
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
131 All of the above ideas will be considered on a less hypothetical level after we
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
132 get our already-committed FCM40 product built. FCM40 will be a modem module in
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
133 the same 56.5x36 mm form factor as Huawei GTM900 (with a mostly-compatible FPC
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
134 interface with only a few changes), featuring the same OM-based triband modem
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
135 core as FCDEV3B V2. The reason for this sequencing is that our current FCDEV3B
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
136 suffers from a couple of issues which FCM40 is expected to solve:
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
137
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
138 1) FCDEV3B has a very tight PCB layout: not only do we have the tightly laid out
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
139 core from GTA02, but also the whole board is quite small for the implemented
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
140 peripheral complexity, imposing further constraints from all sides. This
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
141 tight and complex layout makes a poor choice of starting point for bold
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
142 experiments like RFFE changes.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
143
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
144 2) FCDEV3B is locked into Altium. Layout data migration from Altium to FOSS
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
145 appears to be much less feasible than migration from PADS to FOSS, thus
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
146 freeing our PCB layout from the clutches of proprietary software will most
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
147 likely require giving up (or rather setting aside) all of FCDEV3B new layout
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
148 and going back to the GTA02 starting point, which is in PADS format rather
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
149 than Altium. Redoing all of FCDEV3B anew does not sound appealing at all,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
150 but the much simpler FCM40 board offers a perfect opportunity for a fresh
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
151 start.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
152
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
153 FCM40 will have exactly the same OM-based triband RFFE as our current FCDEV3B,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
154 but it will be a much simpler board, and if we can get it done in FOSS instead
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
155 of continuing the Altium track, then we would have a very solid reference and a
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
156 good starting point for potential RFFE change experiments.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
157
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
158 Firmware compatibility
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
159 ======================
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
160
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
161 Our current FreeCalypso firmwares drive TSPACT RFFE control signals as follows
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
162 on FC hw family targets (CONFIG_TARGET_FCFAM):
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
163
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
164 TSPACT1 = Rx PCS band
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
165 TSPACT2 = Tx high bands
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
166 TSPACT4 = Tx low bands
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
167 TSPACT5 = Rx GSM850 band
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
168
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
169 The driving of TSPACT1, TSPACT2 and TSPACT4 matches the way these signals have
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
170 been assigned by Openmoko and thus the way they function on our current OM-based
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
171 triband RFFE, whereas TSPACT5 is a new signal which is not wired anywhere on
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
172 our current FCDEV3B. This signal driving arrangement is expected to be
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
173 compatible with all 3 RFFE hw possibilities under consideration:
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
174
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
175 * On our current OM-based triband RFFE it works as is.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
176
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
177 * If we use Epcos M034 or a semi-clone thereof that has the two Tx switches and
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
178 a GSM850 Rx switch but no PCS Rx switch, then we will need to connect TSPACT2,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
179 TSPACT4 and TSPACT5 per the table above, and leave TSPACT1 unconnected.
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
180
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
181 * If we get a new M034-like FEM custom-made with a full set of all 4 switches,
3fa4006696d0 Quadband-ideas article written
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
182 then all 4 TSPACT signals will need to be connected per the table above.