A Microtransceiver for UHF Proximity Links Including Mars Surface-to-Orbit Applications
Kuhn, W., Lay, N. E.,Grigorian, E.; Nobbe, D.; Kuperman, I.; Jeon, J.; Wong, K.; Tugnawat, Y.; He, X.
Proceedings of the IEEE, Vol. 95, Issue 10, pp. 2019-2044, Oct 2007
A UHF Proximity Micro-Transceiver for Mars Exploration
Kuhn, W.; Lay, N.; Grigorian, E.
2006 IEEE Aerospace Conference, 4-11 March 2006
Low temperature performance of COTS electronic components for Martian surface applications
Tugnawat, Y. and Kuhn, W.
IEEE Aerospace Conference, 2006, 4-11 March 2006
A Low-Volume, Low-Mass, Low-Power UHF Proximity Micro-Transceiver for Mars Exploration
W. Kuhn; N. Lay; and E.Grigorian
12th NASA Symposium on VLSI Design, Oct 4-5, 2005
Low Temperature Performance of COTS Electronic Components for Future Mars Missions
Y. Tugnawat; and W. Kuhn
12th NASA Symposium on VLSI Design, Oct 4-5, 2005
Low Temperature Performance of Commerical-Off-The-Shelf (COTS) Electronic Components for Future Mars Missions
YOGESH TUGNAWAT M.S., Kansas State University, 2004
On June 9th, 2009, KSU electrical engineers were awarded with
NASA's Group Achievement Award for the development of a low-weight and
low-power transceiver, intended to be considered for future missions to
Mars for use on "scouts" and "rovers." This project is well
documented and may be found
The environment on Mars presents many challenges to communications
engineers, mainly due to the ultra-low temperatures and cosmic
radiation. Not only this, but the transceivers used on Mars rovers
weighed 2 kg and used up to 70 Watts of power, and so there was a need
to develop a transceiver unit that would not only weigh far less, but
would also use significantly less power. Through a grant from
NASA's "Mars Technology Program," students and professors embarked on an
effort to create this RFIC.
In order to design a chip that would work throughout a range of temperatures from +20 °C to -120 °C (average day and night temperatures on Mars, respectively), parametric drift had to be well understood. For this reason, extensive research was conducted at KSU in the field of cryogenic testing. One example of parametric drift is frequency vs. temperature drift. Basically, as the ambient temperatures change, physical properties of the TCXO change, which causes the frequency at which it oscillates to also change. If this drift isn't too significant, communications can still be transmitted and received without error. However, as drift continues to increase, the signals on transmit/receive will fall out of the intended signal bandwith, causing communication systems to fail.
Here on planet Earth, cosmic rays rarely interact with electronic components because most cosmic rays are deflected by the Earth's magnetic field. However, on Mars, that is not the case. Over time Mars' core has lost its magnetic properties, preventing Mars from being shielded by a uniform magnetic field. As a result of this, the prevalence of cosmic rays is significantly higher. The danger introduced by cosmic rays, as they pertain to electronics, is they are capable of hitting the device in a sensitive area and changing the voltage at that node, which may cause a circuit to operate incorrectly. Because of this, one aim of this project is to design the transceiver at Technology Readiness Level 5 - which would render it insensitive to radiation. To meet this goal, the IC was fabricated using Peregrine's Silicon-on-Sapphire technology, which is intrinsically radiation-hard.
A block diagram of the proposed IC can be seen below:
This design was to be used in conjunction with a digital-encoding IC developed by JPL (Jet Propulsion Laboratory) for PCB implementation according to the following block diagram:
Fabrication 1: RFIC Receiver Unit
The first fabrication produced an IC with just the receiver portion of the above block diagram. The layout and a photograph of the die can be seen below.
To test this IC, a corresponding PCB was designed and made:
The testing of this device included transmitting a signal to be received by the RFIC, which is then passed on to the digital encoder for BPSK analog-to-digital conversion. The following pictures were acquired during this verification process:
Upon confirming the operation of the receiver portion of the planned IC, the next step was to design the transmit portions of the IC.
Fabrication 2: RFIC Transmitter Unit
The intent of the transmitter-design process was to allow the microtransceiver to pass modulated I/Q outputs for BPSK, RC-BPSK, and QPSK encoding schemes. In addition to this, 10 mW and 100 mW amplifiers were also implemented on the IC. Lastly, the synthesizer was tweaked to provide for fractional-N digital tuning and the LNA was improved. Following are two images; the first shows the IC layout for fabrication 2, while the second is a photo of the actual IC die upon fabrication.
A separate test PCB was also made in order to check the behavior of the transmitter IC. A picture of this testboard can be seen here:
This board was tested to ensure correct operation when using BPSK and RC-BPSK encoding schemes, running at 1 kbps. The output of the testboard, when emitting a BPSK signal, is pictured here.
The output of the testboard, when emitting an RC-BPSK signal, is pictured here.
Fabrication 3: 1 Watt Power Amplifier
A 1 Watt power amplifier was also developed in order to provide higher data return rates from the microtransceiver. This PA itself was a separate IC, implemented so that the user may choose between higher and lower power operation modes on the Mars PCB. Below are images of its layout and die.
Fabrication 4: A Fully-Integrated Transceiver
By combining the designs in fabrications 1 and 2, a fully-integrated transceiver was implemented. Capable of low and medium output-power modes, this was the microtransceiver that led to NASA's recognition of K-State's work during the Mars PCB project. The layout and die for this RFIC are shown below.
Here is an image of the RFIC's output when operated in medium-power mode:
Microtransceiver PCB Implementations
This RFIC was the heart and soul of the Mars PCB mentioned above. The following photo is of the evaluation board, the final deliverable of the project:
Upon including the 1 Watt power amplifier from fabrication 3, the following demo PCB was made:
This, however, was not the final PCB implementation for the microtransceiver RFIC. During the entirety of the KSU/JPL Mars PCB program, only the RFIC portion of the board was pursued by K-State. The digital control and interfacing circuits were designed by JPL. The block diagram below displays the different compartments of the Mars PCB, the green and yellow lines outline what was developed at KSU; the blue line indicates what was designed by JPL.
After the completion of the project, a new PCB implementation was undertaken. The same RFIC microtransceiver was used, but this time K-State wrote the digital encoding algorithms, which were ran on a PIC microcontroller. Not only this, but the new board included an LCD screen and four buttons that allowed for quick and simple digital tuning. This final PCB is pictured below.
This photo displays the different functions possible on the board, as seen on the LCD screen:
The PCB itself is operated according to this block diagram:
Final Product Testing
Extensive testing was carried out in K-State's Communications Research Laboratory to ensure that the above PCB worked as expected. Operating at these high frequencies (e.g. ~433 MHz) requires sensitive laboratory equipment in order to take accurate measurements. The testing environment for this device can be seen below, along with a picture of the signal generator used to generate pager signals during the PCB demonstration.
Frequency Hopping measurements at 10 us dwell time were taken, which can be seen below:
Lastly, this photo shows the demo board receiving a 390 MHz communication stream at -110 dBm: