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HMC1197 input (applying I+-/Q+- )

Question asked by jay1 on Oct 20, 2015
Latest reply on Oct 21, 2015 by stanis

the HMC1197-evaluation board as an image rejection IQ up converter. Before doing PCB work, we've tested the evaluation board with conditions below

 

 

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Conditions

1. signal generaton : FPGA -> DAC 

2. I/Q is made with the hybrid coupler.

3.the center taped transformer is used for making the I+- / Q+- signal,

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under those condition, we measured the output frequency spectrum.

but the results showed us the real, imag and  LO leakage.

i think that i've made some wrong while testing

so i wants to ask you  the proper ways to used the HMC1197

 

 

 

first,

when i check the datasheet of the HMC1197,

The table 8 (page 13 of the datasheet of HMC1197), it was written as we need to bias the offset voltage to the I/Q (positive and negative) signals,

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table 8

11,12 : QN,QP

Q channel differential baseband input.These are high impedance ports. The nominal recommended

bias voltage is 0.45V (0.4V-0.5V)[1].The nominal recommended baseband input AC voltage is 1.3V

peak-to-peak differential.By adjusting the DC offsets on ports QN & QP , the Carrier Suppression of the

device can be optimized for a specific frequency band and LO power level. The typical offset voltege for

optimization is less than 15 mV.

The amplitude and phase difference between The I and Q inputs can be adjusted in order to optimize the

Sideband Suppression for a specific frequency band and LO power level

 

25, 26 : ON,IP

I channel differential baseband input. These are high impedance ports. The nominal recommended bias

voltage is 0.45V (0.4V-0.5V). The nominal recommended baseband input AC voltage is 1.3V peak-topeak

differential.By adjusting the DC offsets on ports IN & IP , the Carrier Suppression of the device can

be optimized for a specific frequency band and LO power level. The typical offset voltege for optimization

is less than 15 mV.

The amplitude and phase difference between The I and Q inputs can be adjusted in order to optimize the

Sideband Suppression for a specific frequency band and LO power level

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when it comes to the differencial signal, we have used the center taped transformer. and connected the center tap to a ground to make positive and negative signal.

firstly we have thought biasing the DC offset at the center tap of the transformer, but I cannot expect the result that the product will operate properly.

is there recommended ways to applying the signal to the HMC1197

I want some reference circuit references of I+-/Q+- signal applying part, with the voltage biasing.

 

 

 

 

2nd problem is about the Carrier feedthorugh calibration.

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Carrier feedthrough is related to the DC offsets at the differential baseband inputs of the modulator. If

exactly the same DC common-mode voltage is applied to each of the baseband inputs, and there were

no DC offsets at the differential baseband inputs, the LO leakage at the RF output would be perfectly

suppressed.

By adding small DC offset voltages at the differential baseband inputs, the carrier feedthrough can be

optimized for a specific frequency band and LO power level. The carrier feedthrough can not be calibrated

by the DC common-mode level at the I and Q baseband inputs. DC offsets at the differential I and Q

baseband inputs should be iteratively adjusted until a minimum carrier feedthrough level is obtained.

Externally available offset voltage step resolution and the modulator’s noise floor limit the minimum

achievable calibrated carrier feedthrough level. The typical offset voltages for optimization are less than

15mV. Figure 47 illustrates the typical calibrated carrier feedthrough performance of the HMC1197LP7FE. In

this characterization of the HMC1197LP7FE, carrier feedthrough was calibrated with 500MHz LO frequency

steps at 25C and external offset voltage settings were held constant during tests over temperature.

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this problem is somewhat similar to the upper one.I've already read the datasheet and cannot understand the exact ways to calibrate the mixer. i wants to know the detailed procedure or ask some example of the calibration procedure.

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