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US 10,374,852 B1Granted
Ka-band modulator and transmitter
AssigneeUnited States of America as represented by the Administrator of NASA
InventorsWei-Chung Huang, Jeffrey M. Jaso
Life of this patent
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Abstract
The present invention relates to a high data rate Ka-band modulator and transmitter for space applications that functions on the entire NASA Space Network Return Link band of 25.25-27.75 GHz. The modulator is capable of quadrature phase-shift keying (QPSK) modulation and 8-PSK modulation. The transmitter can be designed to provide an adjustable drive to a traveling-wave tube amplifier (TWTA) or transmit power.
Claims20
A Ka-band transmitter, comprising:
- a first modulator including a field programmable gate array (FPGA), said FPGA including:
- a serializer/deserializer (SerDes), which receives data in a data stream;
- a buffer which buffers said data in said data stream from the serializer/deserializer;
- a low-density parity check (LDPC) encoder which encodes said data in said data stream from the buffer with a 7/8 LDPC error-correcting code to result in a data stream of encoded symbols;
- a randomizer which randomizes said encoded symbols in said data stream;
- an in-phase/quadrature (I/Q) splitter which splits said randomized encoded symbols in said data stream into an I channel data stream and a Q channel data stream;
- and
- a plurality of pulse shapers for each of said I channel data stream and said Q channel data stream, such that rates of said I channel data stream and said Q channel data stream of said encoded symbols below 400 Msps are digitally filtered with a root-raised cosine filter;
- wherein resulting digitally filtered encoded symbols in said I channel data stream and said Q channel data stream are parallelized into 12-bit words which are each clocked exiting said FPGA;
- a plurality of digital-to-analog converters (DACs) which receive said 12-bit words from said FPGA to form an I analog baseband signal and a Q analog baseband signal;
- a tunable filter bank including a plurality of low-pass analog filters which filter said I analog baseband signal and said Q analog baseband signal;
- a second harmonic vector modulator which receives said I analog baseband signal and said Q analog baseband signal from said tunable filter bank;
- and
- a synthesizer including a local oscillator which pumps said second harmonic vector modulator to output a radio frequency (RF) signal;
- wherein said RF signal is an Offset Quadrature Phase Shift Keying (OQPSK) modulated signal at a center frequency equal to:
- 2*fLo+fIF, where fIF is a total encoded symbol rate and fLo is a local oscillator frequency;
- and
- wherein said RF signal is in a Ka-band frequency range including inside a Ka-band return link range of 25.25-27.75 GHz.
15 more elements
A method of providing a high data rate Ka-band modulator and transmitter for space applications, comprising:
- receiving data in a data stream into a serializer/deserializer (SerDes) of a field programmable gate array (FPGA) of a first modulator;
- buffering said data from said serializer/deserializer (SerDes);
- encoding said buffered data in said serial data stream using a low-density parity check (LDPC) encoder with a 7/8 LDPC error-correcting code to result in a data stream of encoded symbols;
- randomizing said encoded symbols in said data stream;
- splitting said randomized encoded symbols in said serial data stream into an I channel data stream and a Q channel data stream;
- digitally filtering each of said I channel data stream and said Q channel data stream, such that rates of said I channel data stream and said Q channel data stream of said encoded symbols below 400 Msps are digitally filtered with a root-raised cosine filter;
- parallelizing resulting digitally filtered encoded symbols in said I channel data stream and said Q channel data stream into 12-bit words which are each clocked exiting said FPGA;
- receiving said 12-bit words from said FPGA into a plurality of digital-to-analog converters (DACs) to form an I analog baseband signal and a Q analog baseband signal;
- filtering said I analog baseband signal and said Q analog baseband signal using a tunable filter bank having a plurality of low-pass analog filters;
- receiving said filtered I analog baseband signal and said Q analog baseband signal into a second harmonic vector modulator;
- pumping said second harmonic vector modulator using a synthesizer having a local oscillator to output a radio frequency (RF) signal;
- wherein said RF signal is an Offset Quadrature Phase Shift Keying (OQPSK) modulated signal at a center frequency equal to:
- where fIF is a total encoded symbol rate and fLo is a local oscillator frequency;
- and
- wherein said RF signal is in a Ka-band frequency range including inside a Ka-band return link range of 25.25-27.75 GHz.
12 more elements
Dependencies are inferred from the claim text.