Narayan R. Mysoor

An X-band spacecraft transponder for deep space applications-design concepts and breadboard performance

The design concepts and measured performance characteristics of an X-band breadboard deep-space transponder (DST) for future spacecraft applications are summarized. The DST consists of a double-conversion, superheterodyne, automatic phase tracking receiver, and an X-band exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X-band uplink carrier signal. The exciter phase modulates the X-band downlink signal with composite telemetry and ranging signals. The measured tracking threshold, automatic gain control (AGC), static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB. >

An analog MMIC phase modulator for X-band satellite transponder applications

The design and measured performance of a GaAs MMIC (monolithic microwave integrated circuit) analog linear phase modulator for the next-generation space-borne communications systems are presented. The analog phase shifter is based on the reflection-type hybrid coupled approach and uses a novel lumped quadrature hybrid and MESFET varactors as a building block. Three cascaded sections (with tapered varactor sizes) of this building block along with two high-isolation amplifiers have been realized in a single chip (96 mils*36 mils). This MMIC provides an X-band (8415+or-50-MHz) phase modulation with +or-2.6 radians (300 degrees ) of peak phase deviation, +or-2% of phase deviation linearity, 1.5-dB insertion loss, and better than 12-dB input and output return loss performance.<<ETX>>

An electronically tuned, stable 8415 MHz dielectric resonator FET oscillator for space applications

A voltage-controlled 8415-MHz FET oscillator stabilized by a dielectric resonator is described. The oscillator provides over 3.2-MHz linear electronic tuning range with a flat power output equal to +1.8 dBm (27 degrees C, nominal), a single-sideband noise-to-carrier ratio of -68 dBc/Hz at 1 kHz off carrier, and a frequency-temperature coefficient of 0.54 parts per million/ degrees C over a -24 degrees C to 75 degrees C range. The oscillator withstood 150 Krads (Si) of gamma radiation with no significant performance degradation. The overall performance of the FET oscillator is far superior in many ways to that of an equivalent bipolar oscillator for space applications. For space applications, the FET dielectric resonator oscillator (DRO) is preferred over bipolar DRO because of its lower DC power consumption, better thermal frequency stability, linear electronic tunability. and higher RF output power capability.<<ETX>>

Performance of a Ka-band transponder breadboard for deep space applications

This article summarizes the design concepts and implementation of an advanced Ka-band (34.4 GHz/32 GHz) transponder breadboard for the next generation of space communications systems applications. The selected architecture upgrades the X-band (7.2 GHz/8.4 GHz) deep space transponder (DST) to provide Ka-band up/Ka- and X-band down capability. In addition, it can also be configured to provide X-band up/Ka- and X-band down. The Ka-band Transponder breadboard incorporates state-of-the-art components including sampling mixers, Ka-band dielectric resonator oscillator, and microwave monolithic integrated circuits (MMICs). The MMICs that were tested in the breadboard include upconverters, downconverters, automatic gain control circuits, mixers, phase modulators, and amplifiers. The measured receiver dynamic range, tracking range, acquisition rate, static phase error, and phase jitter characteristics of the Ka-band breadboard interfaced to the advanced engineering model X-band DST are in good agreement with the expected performance. The results show a receiver tracking threshold of -149 dBm with a dynamic range of 80 dB, and a downlink phase jitter of 7/spl deg/ rms. The analytical results of phase noise and Allan standard deviation are in good agreement with the experimental results.

Performance results of a 300 degrees linear phase modulator for spaceborne communications applications

A phase modulator capable of large linear phase deviation, low loss, and wideband operation with good thermal stability is described. The phase modulator was developed for deep space spacecraft transponder (DST) applications at X-band (8.415 GHz) and Ka-band (32 GHz) downlinks. The design uses a two-stage circulator-coupled reflection phase shifter with constant gamma hyperabrupt varactors and an efficient modulator driver circuit to obtain a phase deviation of +or-2.5 rad with better than 8% linearity. The measured insertion loss is 6.6 dB+or-0.35 dB at 8415 MHz. It is shown that measured carrier and relative sideband amplitudes resulting from phase modulation by sinewave and square modulating functions agree well with the predicted results.<<ETX>>

Development of linear phase modulator for spacecraft transponding modem

A new Spacecraft Transponding Modem (STM) is being developed for deep space communication applications. The STM receives an X-band (7.17 GHz) uplink signal and generates an X-band (8.4 GHz) and a Ka-band (32.0 GHz) coherent or noncoherent downlink signals. The STM architecture incorporates two miniature linear phase modulators. These modulators are used to modulate the X-band and Ka-band downlink frequencies with the downlink telemetry, turnaround ranging, or regenerative PN-ranging signals. The linear phase modulators are designed with custom developed MMIC chips. The phase modulator MMICs, the amplifiers, and driver circuits are laid out on drop-in alumina substrates. These modulator designs meet the following requirements: phase deviation range of /spl plusmn/140 degrees at X-band and Ka-band downlink carrier frequencies, phase linearity of less than 8%, phase modulation input bandwidth of greater than 100 MHz, and differential input with sinewave or squarewave modulating format.

Performance of dielectric resonator oscillator for spacecraft transponding modem

A new Spacecraft Transponding Modem (STM) is being developed for deep space communication applications. The STM receives an X-band (7.17 GHz) uplink signal and generates an X-band (8.4 GHz) and a Ka-band (32.0 GHz) coherent or noncoherent downlink signals. The STM architecture incorporates three miniature dielectric-resonator-oscillators (DRO). These DROs are used in receiver and exciter frequency synthesis phase-locked loops (PLL) in the STM. The DROs are designed with custom developed monolithic microwave integrated circuit (MMIC) negative resistance oscillator chips. DROs are laid out on alumina substrates in RF cavity fixtures of 18 mm/spl times/18 mm/spl times/8 mm. The receiver and the exciter DRO designs meet the following requirements: frequency stability of /spl plusmn/2 ppm//spl deg/C, the free running single-sideband phase noise of -50 dBc at 1-kHz offset frequency, tuning linearity of /spl plusmn/10% over the /spl plusmn/1.75-MHz locking range, and output power of +10 dBm/spl plusmn/1 dB over a design temperature range of -55/spl deg/C to +85/spl deg/C. The phase-locked loop DRO frequency synthesizers are designed using sampling downconverter and phase detector MMIC chips. These PLL frequency synthesizers meet the following requirements: pull-in range of /spl plusmn/1.75 MHz, loop noise bandwidth of 100 kHz, and a single-sideband phase noise of -144 dBc at 1-kHz offset frequency.

Miniature X-band GaAs MMIC analog and bi-phase modulators for spaceborne communications applications

The design concepts, analyses, and the development of GaAs monolithic microwave integrated circuit (MMIC) linear-phase and digital modulators for the next generation of spaceborne communications systems are summarized. The design approach uses a very compact lumped-element, quadrature hybrid, and MESFET-varactors to provide low-loss and well-controlled phase performance for deep-space transponder (DST) applications. The measured results of the MESFET-diode show a capacitance range of 2:1 under reverse bias, and a Q of 38 at 10 GHz. Three cascaded sections of hybrid-coupled reflection phase shifters have been modeled and simulations performed to provide an X-band (8415+or-50 MHz) DST phase modulator with +or-2.5 radians of peak phase deviation.<<ETX>>

Design concepts and performance of NASA X-band transponder (DST) for deep space spacecraft applications

The authors summarize the design concepts and measured performance characteristics of an X-breadboard deep space transponder (DST) for future spacecraft applications, with the first use scheduled for the CRAF and Cassini missions (1995 and 1996). The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X-band exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase-tracks the modulated or unmodulated X-band uplink carrier signal. The exciter phase, modulates the X-band downlink signal with composite telemetry and ranging signals. The receiver-measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.<<ETX>>

Design and analysis of low-loss linear analog phase modulator for deep space spacecraft X-band transponder (DST) application

The authors summarize the design concepts, analyses, and development of an X-band transponder low-loss linear phase modulator for deep space spacecraft applications. A single-section breadboard circulator-coupled reflection phase modulator has been analyzed, fabricated, and evaluated. A linear phase deviation of 92 degrees with a linearity tolerance of +or-8% was measured for this modulator from 8257 MHz to 8634 MHz over the temperature range -20 degrees C to +75 degrees C. The measured insertion loss and the static delay variation with temperature were 2+or-0.3 dB and 0.16 ps/ degrees C, respectively. Based on this design, two and three cascaded sections have been modeled and simulations performed to provide an X-band DST phase modulator with +or-2.5 rad (+or-143 degrees ) of peak phase deviation to accommodate downlink signal modulation with composite telemetry data and ranging with a deviation linearity tolerance of +or-8% and insertion loss of less than 10+or-0.5 dB. A two-section phase modulator using constant gamma hyperabrupt varactors and an efficient modulator driver circuit was breadboarded. The measured results satisfy the DST phase modulator requirements, and show excellent agreement with the predicted results.<<ETX>>