Saturday, December 19, 2009

The UNDP-1 Gobi 1000 Part III

I'm going to start this entry with a run down of the IC's used in the UNDP-1 Gobi 1000 module. They managed to cram an amazing amount of power and circuitry in a small package, 20 years ago a device with this power (if it could even be done) would probably be bigger than the average netbook or even a notebook. Starting from the antenna inputs (top) down:

Top middle - CXM3519 - antenna switch

The next section below it has 4 IC's

Left - TQS7M5008 - Quad band GSM RF power amp
The next 3 IC's are 'house marked' but they consist of:
850 Mhz CDMA/EV-DO RF power amp
1900 Mhz CDMA/EV-DO RF power amp
WCDMA/HSPA Dual band RF power amp

The two IC's in the bottom section:
Left - MDM1000 - GOBI 1000 baseband processor
Right - M58WR032 - 2Mb x 16 burst flash memory

Now on to the backside

Top left - RTR6500 - CDMA2k/EV-DO Transceiver with GPS

Top Right - RTR6285 - GSM/HSDPA Transceiver with GPS

Bottom Left - USB3316 - Hi-speed USB Transceiver

Bottom Right - PM6653 - Power Management

A couple of things to note that aren't usually mentioned. Receive diversity only works on the 3G bands, 2G bands only use the Main antenna. Also receiver diversity is disabled whenever the GPS is enabled. Since I'm on a 2G Edge (technically 2.75G) network it's not a sacrifice to give the GPS the Aux antenna exclusively but 3G users should take note that they will not get the diversity enhanced performance boost when GPS is enabled. Although no details on operation of the UNDP-1 are available I suspect that because there are 2 transceiver IC's with GPS and you only use one transceiver at a time, the unused transceiver IC provides the GPS. It's also entirely possible that some manufacturers intentionally sacrifice the GPS to keep receive diversity and the internal antennas aren't optimized for the GPS band (1500 Mhz). This also isn't a big deal to me, I plan on disconnecting the internal WWAN antennas and running them to SMA jacks, one for Wireless Internet, the other for GPS. I made a couple of colinear style omni-directional antennas last year and they made a huge difference over the stock internal antennas on my external EDGE wireless modem. The fun part will be finding a place to mount the two jacks, I'm hoping to get enough room by removing the VGA connector which I've never used anyway on any of the other 3 laptops I've owned.

I haven't decided the topic of my next post yet so keep your lines tight and your hooks baited ......

1 comment:

RS said...

Hi, I read your post and it's great, probably the best explanation on the web for the Gobi 1000. I was wondering if I could get in touch with you somehow. I'd have a specific question to which you may know an answer.