국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Generating Ka-Band Signals Using an X-Band Vector Modulator
저자	Smith, Scott;; Mysoor, Narayan;; Lux, James;; Cook, Brian;; Shah, Biren
Keyword	BANDWIDTH;; VOLTAGE CONTROLLED OSCILLATORS;; RADIO COMMUNICATION;; QUADRATURE AMPLITUDE MODULATION;; PHASE MODULATION;; EXTREMELY HIGH FREQUENCIES;; FREQUENCY MULTIPLIERS;; COMMUNICATION NETWORKS;; UP-CONVERTERS;; RATES (PER TIME); PROTOTYPES;;
URL	http://hdl.handle.net/2060/20090008408
보고서번호	NPO-42995
발행년도	2009
출처	NTRS (NASA Technical Report Server)
ABSTRACT	A breadboard version of a transmitter for radio communication at a carrier frequency of 32 GHz (which is in the Ka band) utilizes a vector modulator operating at a carrier frequency of 8 GHz (the low end of the X band) to generate any of a number of advanced modulations that could include amplitude and/or phase modulation components. The 8-GHz modulated signal is mixed with a 24-GHz signal generated by an upconverter to obtain the desired 32-GHz modulated output. The transmitter is being developed as a prototype of downlink transmitters for transmission of data from spacecraft to Earth at high rates (>100 Mb/s). The transmitter design could also be adapted to terrestrial and Earth/satellite communication links. The advanced modulations (which can include M-ary phase-shift keying (M-PSK), offset phase-shift keying (OPSK), and M-ary quadrature amplitude modulation (M-QAM). These modulations are needed because for a given amount of signal bandwidth, they enable transmission of data at rates greater than those of older, simpler modulation schemes. The transmitter architecture (see figure) was chosen not only to enable generation of the required modulations at 32 GHz but also to reduce the number of components needed to implement the transmitter. Instead of incorporating an 8-GHz signal source, the transmitter utilizes an 8-GHz signal generated by a voltage-controlled oscillator that is part of an X-band transponder with which the fully developed version of this transmitter would be used in the original intended spacecraft application. The oscillator power is divided onto two paths, one of which goes through the vector modulator, the other through amplifiers and a 3 frequency multiplier. Band-pass filters are included downstream of the frequency multiplier to suppress unwanted harmonics.