1 Abstract—A UHF half-duplex micro-transceiver for future Mars exploration missions is described. The transceiver target specifications include a volume of less than 1 cm 3 , mass of less than 10 grams, and power consumption of <40 mW on receive and 50mW, 300mW, or 3W on transmit. It is compatible with a subset of Prox-1 protocols and supports transmission rates from 1 to 4096 ksps, depending on RF link parameters, in BPSK or QPSK format. Command and control instructions can be received at 1 or 8 ksps. In addition to its low mass/power features, temperature compensation to –100 C and radiation tolerance to 100 krad allow operation outside of large, thermally controlled, shielded enclosures, further reducing the mass and complexity of exploration vehicles. Although designed around Mars missions and environmental constraints, the transceiver is expected to be useful as well in other proximity links where a small/low-power radio compatible with Prox-1 protocols is desired. 1. INTRODUCTION During the early decades of the twenty-first century, a series of robotic missions will be launched to support the exploration of Mars. Miniaturized, lightweight, and low-power telecommunications systems are among the needed technologies. Existing radio transceivers typically measure as large as 5000 cm 3 , weigh up to 5 kg, and consume more than 50 W on transmit and 10 W on receive. A transceiver measuring in the 1 cm 3 range and operating at fractions of a Watt will enable the design of new types of Mars exploration craft ranging from low-cost, low-mass, networked ground sensors/rovers to airplanes or balloons. The micro-transceiver will communicate collected scientific results to earth by relaying data through Mars orbiters already under development as well as support surface-to-surface links for geographically extended local exploration. The top-level design and specifications are described in this paper, with emphasis on the analog/RF integrated circuit portion of the micro-transceiver. The development effort targets operation in the Mars temperature and radiation environment using a rad-hard Silicon-on-Sapphire (SOS) IC process [1-2], and leverages recent advancements in on-chip 1 0-7803-9546-8/06/$20.00© 2006 IEEE power amplifier design techniques, resonant TR switch circuits, and the specific requirements of the Mars telecommunications environment. A companion paper [3] presents data on designing for the Mars environment temperature range of –100 C to +25 C. 2. SYSTEM ARCHITECTURE A top-level block diagram illustrating the micro-transceiver in relation to a host vehicle is shown in Figure 1. The transceiver interfaces to a microprocessor on-board a scout craft and transmits collected data to an orbiter using the Microtransceiver Electronics through a suitable external antenna (nominally a low-mass wire monopole or dipole). TCXO Digital Modem / Control Circuits RF Transceiver Circuits Antenna Microprocessor / Memory Sensors / Actuators Small/low-mass (E.g. 7 - 20 cm whip) Control/Sleep Data Scout Science Electronics Microtransceiver Electronics Figure 1. Top-level diagram of micro-transceiver and external interfaces. Frequencies of operation and data formatting are a subset of those specified in the Proximity-1 Space Link Protocol recommendations [4]. The nominal uplink (micro-transceiver to Orbiter) frequency is 400 MHz, and the nominal downlink frequency is 440 MHz. Transmit power levels are selectable from 10 mW to 1 W to suit particular mission requirements. Data transmission is via suppressed or residual carrier BPSK modulation or via QPSK modulation at rates up to 256 ksps. Higher rates are supportable for local links [5]. The micro- transceiver also receives command and control data from the orbiter/relay. Command reception is limited to rates up to 8 ksps to reduce size and power consumption of digital circuits. Total power consumption on transmit can be as low as 50 mW William Kuhn 1 , Norman Lay 2 , Edwin Grigorian 2 wkuhn@ksu.edu, norman.e.lay@jpl.nasa.gov, edwin.r.grigorian@jpl.nasa.gov 1 Kansas State University 2 Jet Propulsion Laboratory, California Institute of Technology A UHF Proximity Micro-Transceiver for Mars Exploration