multiband / multimode radio - virginia...
Post on 25-Aug-2020
0 Views
Preview:
TRANSCRIPT
Multiband/Multimode RadioEllingson – Feb 27, 2008
Multiband / Multimode Radio
Steve Ellingson (ellingson@vt.edu)
February 27, 2008
Multiband/Multimode RadioEllingson – Feb 27, 2008
Aud
io S
witc
h /
IP R
oute
r
Selected VoiceChannels
Selected Data Channel
Combine Many Radios into One*At least 13 bands relevant to Public Safety
x Many channels per band = A lot of radios!(*Above figure is just a functional description.)
Frequency Bands:VHF (138-174 MHz)220 MHzUHF (406-512 MHz)700 MHz P.S.800 MHz P.S.Cellular & PCS2.4 GHz ISM4.9 GHz P.S.
Problem Statement
Developing a prototype radio capable of operation over a large range of frequency bands now in use for public safety applications.
Goal: Seamless Interoperability
Multiband/Multimode RadioEllingson – Feb 27, 2008
I.M. M
UX
138-174
220-222
406-512
764-862
4.9 GHz Down
UHF
VHF
4.9 GHz Up
~ 10 dB
(BPF)
LO
ShortWhip
Ext.Ant.
~ 30 dB
A/D
A/D
D/A
D/A
FPGA
µP e
mul
atio
n
EmbeddedAntennas
800 MHz / PCS Cellular Chipset
2.4 GHz WLAN Cellular Chipset
CO
DEC
Oth
er I/
O
Touc
hscr
een
Knob
s
PTT
SPKRMIC
Design Concept
Motorola Direct Conv. RFIC100-2500 MHz
RF Multiplexer(Simultaneous access to all bands/channels through a single existing antenna)
4 MSPS Baseband ADC/DAC(~4 MHz instantaneous bandwidth)
SoPC/FPGA-centric approach; Currently100% Verilog HDL
Multiband/Multimode RadioEllingson – Feb 27, 2008
Fall 2007 Prototype
RF Mux& R/T
RFIC4DemoBoard
ADC/DACBoard
Altera EP2S60 FPGA Board
PowerTI AIC32CODEC(under board)
138-174 MHz 220-222 MHz406-512 MHz764-900 MHz
Analog FM mode(so far)
SoPC approach:No µP; Instead completely implemented in FPGA
7 x 20 in. as shown here
Ethernet
Multiband/Multimode RadioEllingson – Feb 27, 2008
RF CMOS Transceiver ICs• Dense integration achieved using same inexpensive process used for
high-speed digital circuitry
• Traditional objection: CMOS is fiendishly difficult to use for RF due to process variations and inaccurate design models
• These problems can now be largely mitigated by:• Implementing design to be robust to variations• Exploiting availability of nearby logic to enable radio to tweak chip
as needed
• Dense (90 nm!): Can put many copies of an RF path on a single chip
• RF and baseband can go on the same chip, if you are very careful about mitigating digital noise in the RF sections
Multiband/Multimode RadioEllingson – Feb 27, 2008
Motorola Direct Conversion RFIC
SPI
FREF
FEXT
RXBB_IP
RX1P
LLOP_B
TX1P
AOC_TXRF
GND
VDD1_2
VDD2_5
1 GHz ReferencePLL / VCO
1 GHzReference
1 GHzReference
AGC_RX
Tx FEEDBACKQuIET
++
++
++
SUB
Chop Clock
RECEIVEQuIET
1 GHzReference
DYNAMIC MATCHING
Chop Clock
DYNAMIC MATCHING
Chop Clock
TxQuIET
QuIETDM
1 GHzReference
RX_QGEN_LOQuadGen
QuadGen
QuadGen
TX_QGEN_FWD_ LO
TX_QGEN_FB_LO
RxMixers
TxMixersTx FBMixers
Chop
Chop
1.2 V
1.2 V
1.2 V
2.5 V
2.5 V
RF_FB_INP
CP_PLL
TANKN
Multiple pads
Multiple pads
Mux
Mux
To Rx B B I
To Rx BB Q
Tx ReverseBB I Channel
Tx ReverseBB Q Channel
SPIControlledFuntions
RX1N
RX2PRX2N
RX3PRX3N
RX4PRX4N
RX5PRX5N
TX1N
TX2PTX2N
TX3PTX3N
LLON_B
RF_FB_INN
TX_BB_QNTX_BB_QP
TX_BB_INTX_BB_IP
RESETMISOMOSI
SPI_CLKCSEL
RXBB_IN
RXBB_QPRXBB_QN
TANKP
Multiple pads
DM
DM
DM
5 RX Paths (1 output) 90 nm CMOS 3 TX Paths (1 input) No inductorsRX F ~ 5 dB QFP-128RX IIP2 ~ +60 dB < 400 mA @ 2.5V (RX+TX)RX IIP3 ~ – 5 dBm
Tunes 100 - 2500 MHz (continuous) BW: 6.25 kHz – 10 MHz (many steps)Sideband Rejection ~ 40 dB, up to 60 dBInternal DDSs for LO generationExcellent mitigation of 1/f noise
Specs (Verified by VT in Independent Testing)
G. Cafaro et al., “A 100 MHz – 2.5 GHz Direct Conversion CMOSTransceiver for SDR Applications,” 2007 IEEE RFIC Symp., June 2007.
Multiband/Multimode RadioEllingson – Feb 27, 2008
VT Implementation of Motorola SDR RFIC (V4)
40 mA (RX) + 40-90 mA (TX) + 80 mA/DDS @ 9V< 25 cm2 to implement on a 4-layer PCBAbout $100 in parts to implement, excluding PCB.
Technical Memo 22
Multiband/Multimode RadioEllingson – Feb 27, 2008
Advantages of RFIC-Based Direct Conversion in this Project
• Scalable – Same architecture works for reduced or increased number of simultaneous channels/bands (just add/remove chips)
• Reduced power (extended battery life) – lower power/channel and unneeded RFICs (or RFIC sections) can be shut down.
• Increased number of channels can be monitored simultaneously, even across bands: Scanner-like capability, “White space” seeker(s) for frequency-agile cognitive radio
• Con: Optimization requires calibration and tweaking of many parameters (over a low-bandwidth serial port)
Multiband/Multimode RadioEllingson – Feb 27, 2008
Antenna-Transceiver Integration• Meeting selectivity specs is
one of the big challenges once a direct conversion approach is chosen
• Our approach: RF multiplexer optimized to antenna impedance
• No antenna tuning! • Simultaneous
access to all bands / channels
“Transducer power gain” for RF multiplexer optimized for a 20 cm long monopole antenna
“External noise dominance” inVHF-High and 220 MHz bands
Technical Memo 25
Multiband/Multimode RadioEllingson – Feb 27, 2008
SDR Baseband Processing• Virtually all modern radios are “software defined” in the sense that
some functionality is implemented in software on a µP
• Modern notion of SDR emphasizes reconfigurability – achieving this in software requires large memory spaces, cache, etc.
• For an all-mode radio, SDR is useful primarily in that it may simplify the design by reducing the number of independent basebandsections, but it is not clear that it is better in any other sense (cost, size, weight, power). Truth here is somewhat application-specific.
• µP-based SDR makes sense if implementation in procedural languages or conformance to an existing architecture/paradigm isrequired. Not clear this makes sense for a “new start” radio which is not so contrained, however.
Multiband/Multimode RadioEllingson – Feb 27, 2008
Alternative SoPC Strategy• SoPC – “System on a Programmable Chip”. Typically refers to use of a
single Field Programmable Gate Array (FPGA) to perform all computing in an embedded system
• Key idea: Dedicated microprocessors are overkill for many applications, whereas FPGAs are often essential for other reasons and can take on many functions traditionally assigned to microprocessors through “soft core” implementation.
• In an SoPC system, compute functions are assigned either to FPGA LEs(via HDL-derived firmware) or software (via a soft-core processor), and the previously awkward partition between FPGA firmware and microprocessor software is eliminated.
• Now relatively simple to implement “soft core” processing on an FPGA (Altera: Nios II, Xilinx: MicroBlaze)
Multiband/Multimode RadioEllingson – Feb 27, 2008
SoPC in Contrast to SDR• In some sense, an SoPC-based radio is the opposite of SDR – we want to
implement as much as we can in efficient firmware (HDL), and strip the (inefficient) µP down to the minimum acceptable functionality
• In another sense, SoPC subsumes SDR, since we are talking about implementing software-defined functionality on firmware-defined processors!
• Potential advantages include cost, power, speed -- because only the functionality which is needed is implemented
• Explicit concurrency (huge advantage over traditional SDR)
Multiband/Multimode RadioEllingson – Feb 27, 2008
Major Challenges Remaining• “RF multiplexer” strategy for antenna integration is quite
practical for receive, but transmit requires better efficiency. Antenna tuning is a possibility, but looking into “Non-Foster” technology to avoid this
• Power amplifiers: Not scary; broadband (100-1000 MHz) ~1W solutions exist. However order of magnitude improvement desirable
• New operational/security/training issues to manage
Multiband/Multimode RadioEllingson – Feb 27, 2008
Thanks!
Web Sites:http://www.ece.vt.edu/swe/chamrad/http://www.ece.vt.edu/swe/http://wireless.vt.edu/
U.S. Dept. of JusticeNational Institute of Justice
Grant 2005-IJ-CX-K018
Acknowledgements:S.M. Shajedul Hasan (Ph.D. Student)Mahmud Harun (Ph.D. Student)Motorola: G. Cafaro, B. Stengle, N. Correal
Capstone Demo:Wireless @ Virginia Tech Annual Symposium and Summer SchoolJune 4-6, 2008
top related