notes about gps antenna choices, more futzing

[hw/telemega] / Notebook

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                                                                i2c2
                                                bootloader intf usart1
                                                                usart2
+To Do
+
+- tweak up the paste mask dimensions and so forth on BMA250.py, which is sort
+  of crude at the moment .. see page 68 of the BMA250 data sheet
+
+2011.11.29
+- Eleazar Zuniga <ezuniga@taoglas.com> says in email of 28 Nov 2011 that we 
+  should be able to use any of the pin or SMT patches other than the 35mm ones,
+  as long as we have ground plane under the patch itself that's as large as the
+  patch or bigger.  I'm not sure I believe that, but adding an 0402 site to 
+  ground for a tuning cap ala what the chip antenna docs call for might be a
+  reasonable thing to try?
+
+  pinned versions
+
+    GP.1575.12.4.A.02
+       12x12x4 mm, pin plus adhesive
+       gain towards zenith -0.5 dBic
+
+    GP.1575.15.4.B.02
+       15x15x4 mm, pin plus adhesive
+       1.0 dBic at zenith
+
+    GP.1575.18.2.A.02
+       18x18x2 mm, pin plus adhesive
+       gain towards zenith -0.5 dBic
+
+    GP.1575.18.4.A.02
+       18x18x4 mm, pin plus adhesive
+       gain towards zenith +3.5 dBic
+       $4.13 at q100                           *** 50% the mass of 25mm
+
+    GP.1575.25.2.A.02
+       25x25x2 mm, pin plus adhesive
+       +2.0 dBic gain at zenith
+
+    GP.1575.25.4.A.02
+       25x25x4 mm, pin plus adhesive
+       gain towards zenith +3.5 dBic
+       $4.05 at q100
+
+  surface-mount versions
+
+    SGP.1575.12.4.A.02
+       12x12x4.5 mm
+       -2.0 dBic at zenith, 4dB axial ratio, 6Mhz bandwidth
+
+    SGP.1575.15.4.A.02
+       15x15x4.5 mm
+       +1.0 dBic at zenith, 3dB axial ratio, 6Mhz bandwidth
+
+    SGP.1575.18.4.C.02
+       18x18x4.5 mm
+       +1.0 dBic at zenith, 4dB axial ratio, 5Mhz bandwidth
+       $4.94 at q100
+
+    SGP.1575.25.4.C.02
+       25x25x4.5 mm
+       +2.0 dBic at zenith, 3dB axial ratio, 5Mhz bandwidth
+
+  By comparison the data on the chip antenna from Pulse Engineering we're
+  trying out on TeleTerra is:
+
+    W3011A
+       required PCB surface around around 6x8 mm on a board edge
+       +1.0 dBic peak
+       $1.28 at q100
+
+  From all of this, GP.1575.18.4.A.02 would seem to be the clear winner.  It
+  has 2.5 dB more gain than the chip antenna at the expense of a bit more 
+  mass.  However, if the chip antenna performance is "adequate", it saves
+  surface area, mass, and BOM cost.