Gain Through The Bypass Rf Conversion Path; Applying Calibration - SIGNALCORE SC5312A User Manual

10 SC5312A & SC5313A Hardware Manual
•
IF3_Filter2 setting is 0, 1500 MHz LPF is selected
•
IF3 bypass conversion is 0, RF is converted to by mixer 3
•
IF frequency is set at 150 MHz
•
RF is tuned from 100 MHz to 6200 MHz in 100 MHz steps
The gain of the device in this state is measured at different frequencies in the range of 100 MHz to 6.2
GHz. This set of measurements is the RF absolute gain stored at starting address 0x19F0 of the calibration
EEPROM. All other measurements taken as deviations from this reference setting are relative.

Gain Through the Bypass RF Conversion Path

The absolute gain through the bypass path is stored beginning at address 0x82C. The absolute gain
measurement is made every 50 MHz, between 50 MHz and 500 MHz.

Applying Calibration

The gain and attenuator values are relative measurements from the absolute reference values made over
various RF frequencies. These relative values are either subtracted (attenuation) or added (gain) to the
absolute gain value to determine the gain of the relative configuration. For example, assume the
RF_ATTEN#1 is at 20 dB, IF3_ATTEN#1 is at 10 dB, IF2_Filter bank is set to select the 80 MHz filter, IF3
frequency is set to 140 MHz, and the RF frequency is set to 1.550 GHz. A possible systematic approach
would be:
1. Compute the relative RF Atten#1 value by interpolation because there is no measurement value
at 1.55 GHz. A simple linear interpolation between the measured 1.5 GHz and 1.6 GHz values
would provide a good estimate. A local spline interpolation over 5-6 surrounding points would
provide better accuracy. Let us call this value ����_����������1.
2. The IF3 Atten#1 attenuation value is read directly from memory; however, it must be corrected
for frequency offset from 150 MHz. There are offset gain response values measured at 125 MHz
and 150 MHz, so a simple linear interpolation between 2 points should be sufficient. Let us call
this correct attenuation value ����3_����������1.
3. The IF2 filter gain is read directly from memory, which we shall call ����2_������������.
4. The absolute gain at the frequency can be determined using interpolation between 2 absolute
gain points, which we shall call ��_������.
5. The gain for this configuration is calculated using:
�� = �� + ����
������
If the current device temperature is different from the calibration temperature, the gain
correction due to temperature difference is computed using
∆�� = ��(��1)
��������
∆�� is the gain correction, ��(��1)
��������
gain coefficients respectively for RF band 1, and �� and ��
Rev 2.1 | SC5312A & SC5313A
− ���� − ����3
������������ ����������1 ����������1
( )
�� − �� + ��(��1) (�� − ��
0
1 2
and ��(��1)
1
User Manual
2
)
.
0
are the first and second order temperature
2
are the current temperature and
0
SignalCore, Inc.