GTA04 hardware suggestion and discussions

Thu Feb 3 23:09:21 CET 2011

I would appreciate two little improvements/changes.

- 3.5mm 3 way jack instead of 2.5mm 4 way.

- LEDs driven by external ICs, so they would be able to lit eve if FR is
in suspend. I"m planning (-> which means that it may not even
happen :-) ) to drive LEDs by I2C drivers, or to add some latch between
the LED and FR's processor.

Zb.

Glenn píše v So 22. 01. 2011 v 23:22 +0100:
> Hi All!
> 
> Here are some hardware suggestion for discussion:
> 
> 
> 1) Possibility of IR RC5 receiver/transmitter
> 
> 
> 2) Possibility of IRDA transceiver
> 
> 
> 3) Possibility of a "video-link"? Use 
> touch-screen as a color matrix (2D) barcode video 
> transmitter - and the camera as a receiver (half 
> or full duplex). Let the link automatically adapt 
> to to half duplex, if you need to turn your 
> smartphone to establish the other half duplex 
> connection. The link should also adapt frame rate 
> and if the camera and/or screen is dirty - or the 
> link is through a dirty window. I have no idea 
> how fast the link can be as a function of 
> distance. The link should automatically adapt if 
> the video color matrix (2D) barcode is mirrored 
> in any way - or "played" backwards.
> 
> 
> 4) Antenna diversity of (preferably pattern, 
> space - or polarisation diversity):
> 
> * GSM/UMTS? (receive diversity incl. external antenna).
> 
> * 802.11(a)bg(n) (diversity) (W2CBW009Di: "For 
> Dual Antenna application") Almost every laptop 
> has diversity.
> 
> * FM-receiver (receive diversity requires 
> 2*Si4721 - uC selects the best signal (listen to 
> one - let the other turn on and scan when the 
> listen-signal has to low S/N ratio) - or you can 
> listen to one and record another).
> 
> * GPS? (receive diversity including external antenna).
> 
> For FM-diversity you can use a 180 degree hybrid 
> (two loaded LC-circuits?) to separate common-mode 
> and differential-mode - for diversity - if three 
> space divided poles are available. I know that 
> there is a capacitance between ear-wires and 
> their ground, so I do not know, how well it will 
> work. Note that some impedance matching might be 
> needed.
> 
> For VHF/FM the head-phone cable might be used. 
> The diversity might be implemented isolating 
> ground by a adequate inductor (100MHz parallel 
> LC-circuit) - and two high-pass filter from left 
> and right earphone non-ground wires - and the 
> GTA04 itself as a kind of "ground"/third-wire.
> 
> -
> 
> Links:
> 
> Matrix (2D) barcodes:
> http://en.wikipedia.org/wiki/Barcode#Matrix_.282D.29_barcodes
> 
> PCB-antennas (small):
> http://www.numatechnologies.com/pdf/foilantennas.pdf
> 
> An antenna that can be sized for 100MHz reception 
> around the perimeter of the PCB? Use two loops so 
> ground is not needed:
> http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/k9ay_orig.pdf
> http://www.hard-core-dx.com/nordicdx/antenna/loop/k9ay/index.html
> 
> Also for 100MHz:
> (T2FD -- The Forgotten Antenna: 
> http://www.hard-core-dx.com/nordicdx/antenna/wire/t2fd.html 
> )
> 
> 
> 1/3/2003 Antenna Diversity Strengthens Wireless LANs:
> http://www.eetimes.com/design/communications-design/4008941/Antenna-Diversity-Strengthens-Wireless-LANs
> Quote: "...While detailed implementations of 
> dynamic diversity can vary widely, it's possible 
> to summarize the simulated performance of a 
> conceptually simple scheme relative to that of a 
> single-antenna mode, as well as full diversity 
> and selection diversity (Figure 6)..."
> 
> 
> http://en.wikipedia.org/wiki/Antenna_diversity
> Quote: "...
> Spatial diversity employs multiple antennas, 
> usually with the same characteristics, that are 
> physically separated from one another. Depending 
> upon the expected incidence of the incoming 
> signal, sometimes a space on the order of a 
> wavelength is sufficient.
> ...
> Pattern diversity consists of two or more 
> co-located antennas with different radiation 
> patterns.
> ...
> A polarisation difference of 90° will result in 
> an attenuation factor of up to 34dB in signal 
> strength. By pairing two complementary 
> polarizations, this scheme can immunize a system 
> from polarization mismatches that would otherwise 
> cause signal fade. Additionally, such diversity 
> has proven valuable at radio and mobile 
> communication base stations since it is less 
> susceptible to the near random orientations of 
> transmitting antennas.
> ..."
> 
> 
> http://web.archive.org/web/20060427002449/www.tvhandbook.com/support/pdf_files/Chapter17_7.pdf
> Quote: "...
> Diversity is only of value for the relatively 
> rapid fading caused by multipath. This kind of 
> fading is encountered extensively at HF and for 
> tropospheric and iono- spheric scatter 
> propagation at higher frequencies. Similarly, 
> mobile vehicles passing through a static 
> multipath field at VHF and UHF encounter such 
> fading as a result of their motion.
> ..."
> 
> 
> 180 degree hybrid:
> http://upload.wikimedia.org/wikipedia/commons/6/62/Combine2.svg
> "Sum" uses sum of ear-wires - and third-wire.
> "Difference" to some extent uses only ear-wires.
> 
> 
> Pattern Diversity:
> 90 degree hybrid:
> http://upload.wikimedia.org/wikipedia/commons/6/62/Combine2.svg
> "X" uses ear-wires in one direction.
> "Y" uses ear-wires in the other one direction.
> 
> 180 degree hybrid and 90 degree hybrid might be 
> combined. One 90 and two 180 degrees? Then you 
> have 4 receive pattern diversity output ports.
> 
> 
> http://www.option.com/en/products/products/embedded-mobile-broadband/lgamodulegtm601-609/specifications/#start
> Quote: "...
> Simultaneous Equalization and Rx Diversity on all 
> bands (Advance Receiver Type 3i), except for 
> GSM/GPRS/EDGE
> ...
> Primary, diversity and GPS antenna contact pads
> ..."
> 
> regards,
> 
> Glenn
> 
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