I have made a chirp signal generator which should sweep from 10GHz to 14GHz based on HMC733 and HMC702. The schematic of HMC702 evaluation board was used as a reference. My issue is the board can only lock at the frequency band higher than 11GHz. At the band lower than 11GHz, HMC702 can not lock and the status of LD_SDO pin is LOW.
Should I adjust the Lock Detect Register or other Registers to make it working? Or should I adjust the loop filter circuit? Please find my values for all the registers. What should I measure to find the issue?@
BTW, AD797 is used for OpAmp Loop Filter. CVHD-950 is used for reference signal and Sine Reference Input has been selected.
If I try to write any read-only register, is there any potential issue?
Thank you very much.
Reg 01h Enable & Reset Register: 0xFF5B
Reg 02h Serial Data Out Force Register: 0x03
Reg 03h Reference Path Register: 0x18001
Reg 04h Prescaler Duty Cycle Register: 0x00
Reg 05h Phase Freq Detector Register: 0x07
Reg 06h Phase Freq Detector Delay Register: 0x01
Reg 07h Charge Pump UP/DN Control Register: 0x3FF
Reg 08h Charge Pump Trim & Offset Register: 0x2f000
Reg 09h Charge Pump EN Register; 0x00
Reg 0Fh Integer Division Register; 0x6e
Reg 10h Fractional Division Register: 0x01
Reg 11h Seed Register: 0x3A1953
Reg 12h Delta Sigma Modulator Register: 0x30F82
Reg 14h CW Sweep Control Register: 0xE2
Reg 15h CW Sweep Ramp Step Register: 0x66666
Reg 16h CW Sweep Ramp Step Number Register: 0x400
Reg 17h CW Sweep Dwell Time Register: 0xC34E
Reg 18h Auxiliary Oscillator Register 1: 0xA0
Reg 19h Auxiliary Oscillator Register 2: 0x0F
Reg 1Ah Lock Detect Register: 0x1040
Reg 1Bh GPO Control Register: 0x00
Reg 1Ch Phase Detector CSP Register: 0x20
Reg 1Eh Temperature Sensor Register: 0x00