Anritsu Rubidium MG362 1A Series, Maintenance Manual

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Calibration 3-11 FM and Phase Modulation Calibration
MG362x1A MM PN: 10370-10386 Rev. B 3-33
LNFM Tune Gain for YIG High Band
This cal assumes “FM Tune Gain and FM Delay for YIG Low Band” has been completed. Connect equipment as
shown in
Figure 3-11 .
1. Set Mod mode = 2 (Low Noise FM), Mod Source = 0 (Internal), FM Mod rate = 200 kHz, FM Polarity = 1
(Positive), FM HPF = 0 (DC coupled), GFM_1 = 1.00, DFM = 20. Set FM deviation = 20 kHz, FM_Mute =
0 (unmuted). Set carrier frequency = 5 GHz.
2. Check FM PLL lock detector: Set SYN_SHIFT_REG_CR bits 14, 15, 16 (DOUTA, DOUTB, DOUTC) = 0,
1, 0 to connect FM lock detect to SYNTH_GP_MUX. Indication: 1 = Locked, 0 = Unlocked.
If the PLL is locked, then proceed. Otherwise, troubleshoot the lock error and go back to step 1.
3. Set SYN_SHIFT_REG_CR bits 14, 15, 16 (DOUTA, DOUTB, DOUTC) = 0, 1, 1 to connect the Synth
module’s U93 ADC “YL_MON_OUT” to SYNTH_MISO. Set SYN_SHIFT_REG_CR bit 30
(PHASE_MON_EN) = 1) so U93 will monitor FM PLL PFD phase deviation. Use YLMON_CS and SCLK
to clock out the YLMON ADC data. The ADC is an LTC2365: After ~CS falling edge, the ADC puts out
16 serial bits comprised of 2 leading zeros, then 12 bits of data (MSB first) then two trailing zeros.
Observe the 12-bit ADC output to get an indication of phase error across the FM PLL PFD. Initial
YL_MON output for 200 kHz mod rate and 20 kHz deviation should be near 0.
4. Mute FM. Set FM dev = 1.25 MHz. Unmute FM.
5. Adjust FM Tune Gain DAC (within a range of 1310 to 2048) to minimize YL_MON ADC output.
6. Calculate to 3 decimal places: GFM_1H = 1638/(Tune Gain DAC value)
7. Save the calculated result for GFM_1H to GFM_0H, GFM_1H, GFM_2H, GFM_3H in the FM cal table.
(Cells EF13 to EF16 in MG362x1A Freq-FM-Spurs Calc 3P2-20.xlsx).
8. Adjust FMdelay (within a range of 15 to 25) to minimize YL_MON ADC output. FMdelay is typically
19-21 at minimum YL_MON.
9. Save FMdelay value “DFM_H” to the FM cal table (Cell EF19 in MG362x1A Freq-FM-Spurs
Calc 3P2 20.xlsx).