Quadrature Modulator
CMX993/CMX993W
Gain Control Register b6-b3: Modulator Attenuation
b6
F4
b5
F3
b4
F2
b3
F1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
0
1
0
30dB Attenuation
27.5dB Attenuation
25dB Attenuation
22.5dB Attenuation
20dB Attenuation
17.5dB Attenuation
15dB Attenuation
12.5dB Attenuation
10dB Attenuation
7.5dB Attenuation
5dB Attenuation
2.5dB Attenuation
0dB Attenuation (Max Gain)
Gain Control Register b7: Reserved for Modulator Attenuation, set to '0'.
6.4
Frequency Control Register: C-BUS address $08
8-bit write-only
Bit:
7
0
6
0
5
0
4
3
0
2
0
1
0
DIV
F2
F1
Frequency Control Register b7-5 and b3-2: Reserved for future use, set to '0'.
Frequency Control Register b4: Local Oscillator Divider Control
Writing ‘b4’ = 1 will enable "divide the local oscillator by 4" mode, writing ‘b4’ = 0 will enable the
"divide the local oscillator by 2" mode.
NOTE: Divide by 4 mode is not recommended for operation below 200MHz LO frequency (50MHz
RF output). For output frequencies below 50MHz the divide by 2 mode is recommended.
Frequency Control Register b1-b0
Controls the operating frequency band.
b1 b0
F2 F1
0
0
1
1
0
1
0
1
Operation below 500MHz
Operation above 500MHz
reserved
reserved
Note: Frequencies are the operating frequency, not the
local oscillator input frequency.
2013 CML Microsystems Plc
15
D/993/10
CMLMICRO [ CML MICROCIRCUITS ]
