Radio frequency passband signal generation using photonics
Devices, methods and systems for generating wideband, high-fidelity arbitrary radio frequency (RF) passband signals are described. A voltage tunable optical filter for arbitrary RF passband signal generation includes a first input configured to receive a broadband optical pulse train, a second input configured to receive a first control voltage representative of an amplitude signal, an electrooptic modulator to receive the broadband optical pulse train and the first control voltage, to modulate the broadband optical pulse train in accordance with the amplitude signal, and to produce two complementary optical outputs that form two arms of an interferometer, an optical delay component to impart an optical path difference into one of the complementary outputs of the electrooptic modulator, and a combiner or a splitter to receive two complementary optical outputs of the electrooptic modulator after impartation of the optical path difference and to produce an output interference pattern of fringes.
1. An apparatus for generating an arbitrary radio frequency (RF) passband signal, comprising:
a plurality of cascaded electrooptic modulators; and
a plurality of digital-to-analog converters (DACs), each DAC configured to independently, from other DACs in the plurality of DACs, drive a corresponding one of the plurality of cascaded electrooptic modulators;
a first of the plurality of cascaded electrooptic modulators configured to receive an input optical pulse train and vary a phase of the input optical pulse train based on a voltage signal from a first DAC of the plurality of DACs, and
a second and subsequent of the plurality of cascaded electrooptic modulators configured to receive a modified optical pulse train from a previous of the plurality of cascaded electrooptic modulators and vary a phase or an amplitude of the received modified optical pulse train based on the voltage level from the second and subsequent DAC of the plurality of DACs,
wherein driving each of the plurality of cascaded electrooptic modulators independently using each of the plurality of DACs suppresses the thermal noise in generating the arbitrary RF passband signal, wherein each DAC in the plurality of DACs is configured to produce a corresponding voltage signal for driving a corresponding electrooptic modulator in a synchronized fashion with other DACs in the plurality of DACs.
2. The apparatus of claim 1 , wherein each of the plurality of DACs is configured to produce the same voltage level.
3. The apparatus of claim 1 , wherein the plurality of cascaded electrooptic modulators includes one or more electrooptic phase modulators.
4. The apparatus of claim 1 , wherein the plurality of cascaded electrooptic modulators includes one or more electrooptic amplitude modulators.
5. The apparatus of claim 1 , wherein the plurality of DACs includes more than two DACs and the plurality of cascaded electrooptic modulators includes more than two electrooptic modulators.
6. The apparatus of claim 1 , comprising N DACs and N electrooptic modulators, wherein N is greater than or equal to two, and wherein each of the electrooptic modulators is configured to be driven by a corresponding DAC, all DACs are configured to independently produce the same voltage level and drive a corresponding electrooptic modulator in synchronization to allow a voltage boost that scales with N and a noise boost that scales with square root of N.
7. An apparatus for generating an arbitrary radio frequency (RF) passband signal, comprising:
an electrooptic modulator having multiple sets of electrodes coupled to different sections of the electrooptic modulator; and
a plurality of digital-to-analog converters (DACs), each DAC driving a corresponding one the multiple sets of electrodes,
the electrooptic modulator configured to receive an input optical pulse train and vary a phase or an amplitude of the input optical pulse train based on a voltage signal from each of the plurality of DACs as the input optical pulse train propagates through the different sections of the electrooptic modulator, wherein each set of electrodes is driven by an independent DAC and all DACs are synchronized and are configured to produce the same voltage signal level.
8. The apparatus of claim 7 , wherein the electrooptic modulator is an electrooptic phase modulator.
9. The apparatus of claim 7 , wherein the electrooptic modulators is an electrooptic amplitude modulator.
10. The apparatus of claim 7 , wherein the independent, synchronized DACs are configured to alleviate a slew rate requirement for the voltage signal provided by each DAC.
11. The apparatus of claim 7 , wherein the plurality of DACs includes more than two DACs and the multiple sets of electrodes includes more than two sets of electrodes.
12. The apparatus of claim 7 , comprising N DACs and N sets of electrodes, wherein N is greater than or equal to two, and configured to produce a voltage boost that scales with N and a noise boost that scales with square root of N.