QPSK modulator COM-1002 -> Dual D/A converter COM-2001 -> Dual band 915 Hz - 2.4 GHz modulator COM-4001(option -C or -D)

Note: this script only works with COM-4001 option -C or -D.

This test setup demonstrates the ability to 
- tune to the extreme frequencies: 850 MHz, 1 GHz, 2.025 GHz, 2.5 GHz
- switch between internal and external 10 MHz frequency reference
The COM-1002 is only used as a digital sinewave generator. 

(a) connect a 10 MHz external frequency reference to the COM-4001 EXT_CLK port (J2). 
A convenient source for this signal is generally found at the back of spectrum analyzers or
RF signal generators.

(b) import the 1002_2001_4001cd.stn settings into the assembly. Power the assembly down, then up again.

(c) using an oscilloscope, probe the COM-2001 I and Q outputs. The capacitors C3 and C24
are convenient test points. The signals should be 39.062 KHz sinewaves, with amplitude
of 1Vpp.

(d) using a spectrum analyzer, check the COM-4001 output.
The output is an unmodulated carrier at 850 MHz. The level is -3 dBm or above.
LO leakage is -27 dBm typ.
Image rejection for the entire assembly is -40 dBc typ.

(e) Using the ComBlock Control Center, change the REG6 to the following values and observe
the following spectrum outputs:
REG6 = x25 selects RF frequency 1, 100 KHz steps. Output is -3 dBm (typ) @ 1 GHz - 39.062 KHz
REG6 = x45 selects RF frequency 2, 100 KHz steps. Output is -8 dBm (typ) @ 2.025 GHz - 39.062 KHz
REG6 = x65 selects RF frequency 3, 100 KHz steps. Output is -10 dBm (typ) @ 2.5 GHz - 39.062 KHz
For every frequency, check that the SYNC_LOCK test point is low, indicating frequency
synthesizer lock.

(f) Transmit level:
Set REG4/5 from FF 03 (maximum gain) to 00 00 (minimum gain)
Output level should be 15 dB lower @ 2.5 GHz. (goes down from -10 to -25 dBm @2.5 GHz).

(g) Modulator on/off:
Set REG6 bit 2 to 0. 
Output level should be below the spectrum analyzer noise floor.

(h) Internal frequency reference:
Switch to internal frequency reference by setting REG6 to 04
Remove the 10 MHz external frequency reference.
You may have to switch the assembly power off and then on again.
The center frequency may have moved by as much as 75 ppm (63.7 KHz)
Re-do step (d).