MODS & DEMODULATORS - SMT
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v03.0812
WIDEBAND DIRECT QUADRATURE
MODULATOR, 100 - 6000 MHz
HMC1097LP4E
with LO input power.
The LO input impedance is set by the LO quadrature phase splitter. The LO port can be driven differentially with 100
Ω differential input impedance or single ended through LON input with 50Ω input impedance while the unused LOP
input should be terminated to GND through 50Ω. The LO port requires -6 to +6 dBm input power in either differential
or single-ended mode and does not require DC blocking capacitors.
I/Q Modulator
The differential baseband inputs (QP, QN, IP, and IN) present a high impedance. The DC common-mode voltage
at the baseband inputs sets the currents in the I and Q double-balanced mixers. The nominal baseband input DC
common-mode voltage used in the characterization of the HMC1097LP4E is 0.45V, which should be externally applied.
The baseband input DC common-mode voltage can be varied between 0.4V and 0.5V to optimize overall modulator
performance. It is not recommended to leave the baseband inputs oating which generates excessive current ow that
may cause damage to the IC. The baseband inputs should be pulled down to GND in shutdown mode. The nominal
baseband input AC Voltage used in the characterization of the HMC1097LP4E is 1.3Vpp differential. The baseband
input AC voltage can be varied to optimize overall modulator performance.
It is recommended to drive the baseband inputs differentially to reduce even-order distortion products and also use
reconstruction lters at the baseband inputs to avoid aliasing
After upconversion, the outputs of the I and Q mixers are summed together differentially and converted to single-
ended RF output. The single-ended RF output port is internally matched to 50 Ohms and does not require any
external matching components. Only a standard DC-blocking capacitor is required at this interface.
Bias and Enable/Disable Circuits
A bandgap reference circuit generates the reference currents used by the different sections. The part requires a single
supply voltage of +5V to operate.
The EN pin can be used to disable the bandgap reference circuit. Disabling the bias circuit will also disable the
reference currents to the LO limiting ampliers,I and Q mixers and the output stage. If the EN pin is connected
to ground or left oating, the part operates normally. If the EN pin is connected to the +5V VCC, the LO limiting
ampliers, I and Q mixers and the output stage are disabled and the LO leakage is also reduced. The LO signal itself
is suppressed approximately by 57.1 dB at 2.1GHz when the EN pin is connected to the +5V VCC. The enable and
disable settling times are approximately 400 ns.
Carrier Feedthrough Calibration
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 specic 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 steps and the
modulator’s noise oor limit the minimum achievable calibrated carrier feedthrough level. The typical offset voltages
for optimization are less than 15mV. Figure 2 illustrates the typical calibrated carrier feedthrough performance of the
HMC1097LP4E. In this characterization of the HMC1097LP4E, carrier feedthrough was calibrated with 500MHz LO
frequency steps at 25C and external offset voltage settings were held constant during tests over temperature. For
instance, the required the Q channel offset is 2mV and the I channel offset is -3mV at 2.5GHz.