GTA04 hardware suggestion and discussions
zbynecek at volny.cz
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.
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
> 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.
> Matrix (2D) barcodes:
> PCB-antennas (small):
> An antenna that can be sized for 100MHz reception
> around the perimeter of the PCB? Use two loops so
> ground is not needed:
> Also for 100MHz:
> (T2FD -- The Forgotten Antenna:
> 1/3/2003 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)..."
> 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
> 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.
> 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:
> "Sum" uses sum of ear-wires - and third-wire.
> "Difference" to some extent uses only ear-wires.
> Pattern Diversity:
> 90 degree hybrid:
> "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.
> Quote: "...
> Simultaneous Equalization and Rx Diversity on all
> bands (Advance Receiver Type 3i), except for
> Primary, diversity and GPS antenna contact pads
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