Post on 11-Jun-2022
www.idetic.eu
Seminar in
Broadband HF transceiverdesign experiences
Speaker: Baltasar Pérez Díaz <bperez@idetic.eu>
Author: Baltasar Pérez Díaz
Multimedia Room, Polivalente II, 2nd floor
Campus de Tafira, Las Palmas 16th May, 2014
Broadband HF transceiver design experiences
BACKGROUND INFORMATION
Broadband digital HF transceiver
Wattmeter
Driver
BroadbandTransceiver
1KW Poweramplifier
DUC/DDC multichannel
(FPGA)
More than 15 years developing HF modem (software) (IDeTIC+UPM)Last 10 years hardware development HFDVL (High Frequency Data+Voice Link) architecture1MHz bandwidth (not signal) = +300 times conventional radio (3KHz)
16th May IDeTIC Seminar 2
Broadband HF transceiver design experiences
PRESENTATION INDEX
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
16th May 3IDeTIC Seminar
Broadband HF transceiver design experiences
BROADBAND DIGITAL HF TRANSCEIVER INTRODUCTION
Digitalreceiver (DDC)
Receiverantenna
RF receiver(analog)
AUDIO
D/AConverter
STATION
A/DConverter
IF to bedigitized
Signalprocessing
Digitalreceiver (DDC)
Receiverantenna
RF receiver(analog)
AUDIO
D/AConverter
STATION
A/DConverter
IF to bedigitized
A/DConverter
IF to bedigitized
Signalprocessing
Signalprocessing
• RF-Front end moves 1MHz to IF (10.7MHz). Implements a double conversionsuperheterodyne architecture based on DDS
• A/D D/A converters and DDC/DUC : Altera FPGA (Cyclone II EP2C70)
• Signal processing: Fixed point DSP (TMS32C6416) and software runningon a GNU/Linux PC.
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Receving section block diagram
16th May IDeTIC Seminar 4
Broadband HF transceiver design experiences
BROADBAND DIGITAL HF TRANSCEIVER INTRODUCTION
RF Front-end and FPGA setupINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
FPGA
RF Front-end
16th May IDeTIC Seminar 5
Broadband HF transceiver design experiences
BROADBAND DIGITAL HF TRANSCEIVER INTRODUCTION
RF Front-end block diagramINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Antenna
Relay
Receiver
Transmitter
ControlUnitOscillators
To FPGA ADC
From FPGA DAC
Antenna
Relay
Receiver
Transmitter
ControlUnitOscillators
To FPGA ADC
From FPGA DAC
• Double conversion superheterodyne architecture• Half-duplex transceiver: two common blocks• Oscillators based on DDS (v0), later DDS+PLL (v1)• Control unit: manages front-end and interacts with operator using a PC
16th May IDeTIC Seminar 6
Broadband HF transceiver design experiences
BROADBAND DIGITAL HF TRANSCEIVER INTRODUCTION
Receiver block diagramINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
3-30 MHz ADC
BW = 1.0 MHz112 MHz
122.7 MHz
82-109 MHz
BW 1 MHz10.7 MHz
Image-rejection Filter 3-30MHz
Band Pass Filters 3-30MHz RF Amp
≤ 20 dB
DDS
Low Pass10.7 MHz
AGC
≤ 75 dB
RS232
Antenna
µControllerCARDS12
3-30 MHz ADC
BW = 1.0 MHz112 MHz
BW = 1.0 MHz112 MHz
122.7 MHz
82-109 MHz
BW 1 MHz10.7 MHzBW 1 MHz10.7 MHz
Image-rejection Filter 3-30MHzImage-rejection Filter 3-30MHz
Band Pass Filters 3-30MHz
Band Pass Filters 3-30MHz RF Amp
≤ 20 dB≤ 20 dB
DDS
Low Pass10.7 MHz
AGC
≤ 75 dB
RS232
Antenna
µControllerCARDS12
• Double conversion superheterodyne (up-mixing).• 1st IF: 112MHz and 2nd IF: 10.7MHz.• Frequency step: 1Hz.• Sensitivity (@1MHz): -70dBm.• Microcontroller-based RX, TX, AGC and ALC control.• Modular assembly.• TX output power +20dBm.• External power amplifier (linear class A) 5W.
16th May IDeTIC Seminar 7
Broadband HF transceiver design experiences
BROADBAND DIGITAL HF TRANSCEIVER INTRODUCTION
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
TXRX OL
ANT
Control
PS
19’’ subrack 3U form board (100x160mm) with connector DIN41612Rear: digital signalsFront: analog signalsPower Supply: 220VAC and 12VDC
16th May IDeTIC Seminar 8
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
16th May IDeTIC Seminar 9
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS• DDS (Direct Digital Synthesis) ⇒ is a method of producing an analog
waveform,usually a sine wave,• by generating a time-varying signal in digital form
• converted into analog signals using a DAC
• DDS is a standard in radio equipment oscillator.
• NCO (Numeric Controlled Oscillator) ⇒ also called
• Advantages
• Capable of generating a variety of waveforms (sine, triangle, square)• Preferred form of signal generation nowadays• Fast switching capability (freq. hopping systems (phase-continuous))• High precision ⇒ sub Hz (mHz) and sub degree phase tuning• Digital circuitry
• Small size (single chip) ⇒ fraction of analog synthesizer size• Fewer components per system - low cost• Small low-powered devices – portability• Easy implementation (no Barkhaussen criterion, PLL (LPF design))• Fewer assembly operations / reduced product reject rates
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
16th May IDeTIC Seminar 10
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Typical DDS ArchitectureINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1/1/ffoutout1/1/ffoutout
1/1/ffclkclk
1/1/ffoutout
1/1/ffclkclk
1/1/ffoutout
1/1/ffclkclk
ffoutout==ffclkclkFFrr
22NNAccumAccum--ulatorulator
NN24 to24 to48bits48bits
WW14 to14 to16bits16bits
SineSineLookupLookupTableTable
RR10 to10 to14bits14bits
LowLowPassPassFilterFilter
SineSineWaveWave
FFrr
Digital CircuitsDigital Circuits
DD--toto--AAConv.Conv.
• Sampling theory (sinc(x)) • Nyquist: Fundamental signal <= Fclk/2 (1/3 better)• Filter required to eliminate unwanted products
16th May IDeTIC Seminar 11
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Broadband Transceiver oscillator board (v0)INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
TXRX OL
ANT
Control
PS
DDS 1
DDS 2
OL 2
OL 1
Clock
DDS 1
DDS 2
OL 2
OL 1
Clock
DDS 1
DDS 2
OL 2
OL 1
Clock
16th May IDeTIC Seminar 12
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Spurs !!! Worst problem in DDSINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
13IDeTIC Seminar
• AD9835 (fclk=50MHz)• Spurs situation and quantity depend on output frequency (become birdies)• Mix up AGC
16th May
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Spurs !!! Worst problem in DDSINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
14IDeTIC Seminar
• AD9835 (fclk=50MHz)• Spurs situation and quantity depend on output frequency (become birdies)• Mix up AGC
16th May
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Another problem: Clock reference purityINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Comparison: frequency output purity 400MHz Clock vs Agilent Generator
16th May IDeTIC Seminar 15
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Another problem: Clock reference purityINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Comparison: frequency output purity 400MHz Clock vs Agilent Generator
16th May IDeTIC Seminar 16
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Spurs sourcesINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• A DDS have four principal sources of spurs. Most of them are predictable.• Reference clock: highest purity and freq. possible. Spurs next to carrier.
Must have constant amplitude to avoid spurs.16th May IDeTIC Seminar 17
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONSAnalog Devices solution:
SpurKiller Technology: The Results on a DDS Output SpurINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
AFTERBEFORE
500 kHz / DIVISION500 kHz / DIVISION
OUTPUT FREQUENCY = 166 MHzFclk = 500 MSPS
16th May IDeTIC Seminar 18
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Analog Devices solution:
SpurKiller Technology
• Use an auxiliary DDS channel to add in a signal at the same frequency andamplitude as the spur, but 180° out of phase with the highest spur…
AD9911 DDS core
Σ Σ COS(X)
FTW
FrequencyAccumulator
PhaseOffset
143216 10
DAC
DDS Channelfor spur reduction
DDS Channelfor amplitudemodulation
DDS Channelfor phase
modulationRegister Register Register
It’s all in the Digital Domain!
• Spurs are therefore predictable. • In addition, the relative phase of each spur does not change.
16th May IDeTIC Seminar 19
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Adopted solution was: Change synthesizer topologyINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
DDS Used as PLL Reference
20IDeTIC Seminar16th May
nref
2RFF FNM=
÷N
Loop Filter
Phase/ Frequency Detector VCO
RFDDSFref
M
Take advantage of PLL low phase noise and spurs, and DDS frequency resolution
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Broadband Transceiver oscillator board (v1)INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
PLL: NB4N441 DDS: AD9835
DDS
PLL TCXO: 50MHz
• DDS output: 10 to 13MHz
16th May IDeTIC Seminar 21
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Comparison: oscillator board v0 (green) vs v1 (blue)INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Phase noise improvement: 20dB
16th May IDeTIC Seminar 22
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
PLL output: ImprovesINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
16th May IDeTIC Seminar 23
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
16th May IDeTIC Seminar 24
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Measurement SAW Filter bandwidth
• Limited filters with 1MHz bandwidth• Only found TFS112 (fc=112.32MHz, BW(3dB)=1.1MHz, L=12.5dB)• SAW (Surface Acoustic Wave) filter
• Low S11 (high mismatch) BRICK!! (Z=3.5Kohms)• High attenuation• 40dB band-stop• 2.55 form factor• Redesign TRX OLs
16th May IDeTIC Seminar 25
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
16th May IDeTIC Seminar 26
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Problem: Big/good ears in a noisy environment (HF band)• Point 1) AGC algorithm must keep constant 1MHz varying signals
power at ADC input (few bits left for weak signals)• Point 2) Narrow band interference (NBI) intentionally (jamming) or
unintentionally (Broadcast radio stations) within signal or BW
NBI demo video
Two HF broadband TCVR 10 meters apart tuned to 14MHz freq.Function generator as jammer (pure tone)Taking output at BaseBand (10.7MHz) RF Front-end receiverUsing a Agilent VSA (Vector Signals Analyzer) 89600SShowing 700KHz around 10.7MHz
Innovation #8 of the Top 10 Most Wanted Wireless Innovations(Interference Mitigation Techniques) Software Defined Radio andCognitive Radio (CR)
Source: Wireless Innovation forum
16th May IDeTIC Seminar 27
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
IDeTIC Seminar 2816th May
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Wireless Innovation Forum proposed solutions(They are already used in high-end systems but want lower cost and widespread)
Power control throughout the communications systemonly enough power to maintain communications at the minimum acceptable level.
Adaptive beam-forming to maximize antenna gain in the direction of thecommunication path and minimize gain in the interference direction.
Adaptable data rate to the minimum rate needed for the communication.
Adaptive frequency control to increase frequency separation of the interferencesources from the desired radio path.
Adaptive receive filtering to provide better rejection of the interference balancedagainst possible sensitivity loss.
Improved roaming algorithms(change sites or systems to one that has a better SINR).
Change channel coding algorithms to relax the required signal to interferenceplus noise ratio at the expense of more data overhead.
Some of them are difficult to implement at HF (heavier and larger antennas,noisy environment, worldwide coverage, propagation)
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Our proposed solution
Interference must be mitigated enough to let the ADC work under proper condx.Cancellation process after AD conversion (digital filtering)
Two phases: detection (SW) & mitigation (HW)
Detection: Zero crossing and Compressive Sensing (Random Demodulator)Mitigation: Variable notch filter (BW3dB 50KHz; BW50dB 25KHz; Tunable 10.2~11.2MHz)
Bandpass filtering (xtal), LPF+HPF (need Q > 200)technological challenge: low Q components (filters), diff. tunable and speed processing
16th May IDeTIC Seminar 29
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Our proposed solution (cont)
Desired response Low Pass Filter + High Pass Filter
Wien-Robinson active filter Sallen-Key 2nd order
A(dB)
50
3BW=50KHz
BW=10kHz
f(MHz)10
LPF
HPF
16th May IDeTIC Seminar 30
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Our proposed solution (end)Double T Band-reject LC filter
Schematic BW measurement
16th May IDeTIC Seminar 31
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
16th May IDeTIC Seminar 32
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
33IDeTIC Seminar16th May
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Problem: Broadband signals on nonlinear amplifier
OFDM Signal PAPR (~10dB)
- Peak to average power ratio (PAPR)is one major drawback of OFDM.
- Requires power amplifier (PA) to beoperated in the linear region, resultingin poor efficiency.
- 1KW PA operating at 100W
- Commercial power amplifiers (PA)have nonlinear characteristics andneed to be linearized.
Innovation #5 of the Top 10 Most Wanted Wireless Innovations(Techniques to minimize power amplifier spectral regrowth innon-continuous spectral environment)
Source: Wireless Innovation forum
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
34IDeTIC Seminar16th May
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Problem: Broadband signals on nonlinear amplifier (cont) Increasing gain (spectral regrowth)
16 tones 25KHz spaced (400KHz)
- Careful design to avoid intermodulationproducts (below 1dB compress point)
- Poor effiency- Dirty spectrum- Interference to other band users
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Problem: Broadband signals on nonlinear amplifier (cont)
SPE Expert 1K-FA E&I A1000800W 1000WAmateur equipment Professional EquipmentClass AB Class ASome segments in HF band 300KHz - 35MHz
low HD & IMD
16th May IDeTIC Seminar 35
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Problem: Broadband signals on nonlinear amplifier (end)
Some techniques to overcome distorsioned PA ouput:
PREDISTORSION
- adds harmonic content at phaseangles that cancel out the spursthat the nonlinear RF PA creates
- allows driving RF PA closer tosaturation, which improvespower efficiency.
PAPR REDUCTION TECHNIQUES
- Clipping and Filtering: Let the signal clip and filter out of band signal- Coding schemes: Try to avoid the case with all the subcarrier with same phase.- …
16th May IDeTIC Seminar 36
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
1. HF broadband digital transceiver introductiona. Block diagram and pics
2. Main problems and solutionsa. Local oscillator (DDS spurs, reference clock)b. Filter (low availability, limited)c. AGC (algorithm and narrow band interference)d. Amplifier (intermodulation products)e. Antenna (broadband antennas)
3. Summary
16th May IDeTIC Seminar 37
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Problem: Most of antennas have a very narrow bandwidth (10% fc)INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
27MHz (higher f more BW)
SWR CurvesTransmitting 1MHz BW signal at 10MHz (fc)
Filter behaviour (S11)
16th May IDeTIC Seminar 38
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
Solution: Fatter elements (CAGE DP), introduce losses (T2FD) orINDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
• Cage dipole• x2 broader BW compared to dipole
• T2FD (Tilted Terminated Folded Dipole)• 30% RF Power converted heat at resistor• -3 to +3dBi gain• Modest size and cost• No need electronic matching• Used by Army and Civil Guard
16th May IDeTIC Seminar 39
Broadband HF transceiver design experiences
MAIN PROBLEMS AND SOLUTIONS
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Solution (cont.): or Log Periodic antenna
• can operate on a wide frequency band (10:1)• has the ability to provide directivity and gain (4-8dBi)• radiation and impedance characteristics repeated as a logarithmic function of freq
• NBI: different polarization• R&S HE016 antenna
16th May IDeTIC Seminar 40
Broadband HF transceiver design experiences
SUMMARY
INDEX
INTRODUCTION
MAIN PROBLEMSAND SOLUTIONS
SUMMARY
Remember: Broadband system introduces a number of challenges
• It needs to coexist with traditional narrowband systems
• So need to tackle problems as sensitivity to strong narrow sigs (AGC mute)
• Take into account the low linearity of commercial PA (IMD and interferesother users).
• Necessary to have broadband antennas capable to work with these sigs.
Future Trends
• Harris 25KHz bandwidth
• New HF broadband SDR transceiver 25KHz with same form factor as HFDVL modem. TX using FPGA, RX analog front-end+FPGA
16th May IDeTIC Seminar 41
www.idetic.eu
Seminar in
Broadband HF transceiverdesign experiences
Thanks for your attention!!Any question?
Speaker: Baltasar Pérez-Díaz <bperez@idetic.eu>
Author: Baltasar Pérez Díaz
Multimedia Room, Polivalente II, 2nd floor
Campus de Tafira, Las Palmas 16th May, 2014