COM-1002 BPSK/QPSK/OQPSK modulator 
-> COM-2001 Dual D/A converters 
-> COM-4001 dual-band 915MHz/2.4GHz quadrature modulator
-> 20 - 30 dB attenuator 
-> COM-3001 dual-band 915 MHz / 2.4 GHz receiver 
-> COM-1001 BPSK/QPSK/OQPSK demodulator
-> COM-1005 BER measurement


Purpose:
Demonstrate the transmission of a 19.8 Mbit/s QPSK modulated data stream at 850 MHz.


(a) assemble the ComBlock modules listed above. 
Insert an RF attenuator (20 to 30 dB will work) between the transmitter assembly
and the receiver assembly.
Connect a serial link between a host PC and the COM-1002 module.
Connect an external 10 MHz frequency reference to the EXT_CLK port of the COM-4001 module.
Connect an external 10 MHz frequency reference to the EXT_CLK port of the COM-3001 module.
Power up the assemblies.
Using the ComBlock control center, enumerate the ComBlocks (2nd button to the left), 
then import (Menu File | Import) the transmitter settings file 1002_2001_4001_3001_1001_1005_tx.stn

(b) move the serial link to the COM-3001 module.
Using the ComBlock control center, enumerate the ComBlocks (2nd button to the left), 
then import (Menu File | Import) the receiver settings file 1002_2001_4001_3001_1001_1005_rx.stn
Both assemblies are now configured. Switch the power supply off then on again.


(c) verify that the RF frequency synthesizers are locked:
at the COM-4001 modulator: SYNC_LOCK is low, PLL_REF is a 10 MHz clock
at the COM-3001 receiver: PLL_LOC is low, PLL_REF is a 10 MHz clock.

(d) check the baseband signals using an oscilloscope. 
- At the COM-2001 dual D/A converter: probe at the capacitors C3 and C24 near the output SMA connectors.
  The signals should be 1Vpp, filtered (no sharp transition), bit streams. The I-channel is near C3, 
  the Q-channel at C24. 

- At the COM-3001 receiver. 
  The same baseband signals can be visualized at the COM-3001 receivers at test points
  TP1 (I-channel) and TP2 (Q-channel).
  When the receiver AGC is working properly, the received I and Q baseband signals should be
  1Vpp, filtered (no sharp transition) bit streams. Because of carrier phase offset between 
  transmitter and receiver, the received baseband signals are phase rotated versions of the
  transmitted baseband signals.

(e) Verify demodulator lock:
at the COM-1001 demodulator: 
  - TP1 is high when the carrier tracking loop is locked
at the COM-1005 BER measurement: 
  - TP1 is high when the module is synchronized with the PRBS-11
  - TP3 is low (no bit error)
pseudo-random bit stream