Final Report Summary - PHODIR (PHOtonic-based full DIgital Radar)
The PHODIR goal was the study, design and realization of a technological demonstrator of a fully digital radar, based on photonics both for generating and receiving the Radio Frequency (RF) signal.
Next radar will need software-defined radio (SDR) paradigm to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today’s digital microwave components (synthesizers and analog-to-digital converters (ADCs)) suffer limited bandwidth with high noise at increasing frequencies, on the contrary, photonics has proved high precision and ultra-wide bandwidth, allowing the flexible generation of extremely stable radio-frequency (RF) signals with arbitrary waveforms up to the millimeter waves, and their detection and precise direct digitization without down-conversions. PHODIR has pioneered the fully photonics-based radar verifying for, the first time, photonic technologies in a radar system. The proposed architecture exploits a single pulsed mode locked laser (MLL) for both generating tunable radar signals and receiving their echoes, avoiding RF up-/down-conversions and guaranteeing software-defined approach and at the same time reducing the impact of photonics on the system costs. The flexible and high frequency photonic generation of RF signals is based on the extremely stable heterodyning of two spectral MLL lines in a photodiode. Two tunable optical filters select two modes from the spectrum of the MLL, one is modulated by the baseband radar pulse in a Mach-Zehnder modulator, whereas the other is shifted in frequency. The receiver exploits photonics for realizing an ADCs accepting input signals over several tens of GHz, with fast sampling rates. The train of short optical pulses provided by the MLL is directly modulated by the RF signal to be digitized. The modulated pulses are then serial-to-parallel converted to multiple lower-rate sample streams so that, after opto-electronic conversion, multiple electronic ADCs with low sampling frequency and high precision can be used to digitize the pulse peak power carrying the sample information. The parallel digital samples are then interleaved at the digital signal processor to reconstruct the original signal. A frequency shift is added in the transmitter stage the carrier frequency different from a multiple of the sampling rate.
The precision of photonics can be particularly appreciated in coherent radars, for this reason the PHODIR transceiver also generates the reference signal.
The test of the PHODIR transceiver demonstrates its performance exceeding the state-of-the-art electronics at carrier frequencies above 2GHz. It enables radars with unprecedented frequency flexibility and signal quality, and with a record receiver resolution at high carrier frequency. It has been tested producing and receiving signals with carriers up to 40GHz. At the transmitter it has a signal-to-noise ratio>73dB/MHz and a spurious-free dynamic range >70dBc and at the receiver an effective number of bit >7 up to 40 GHz. Performance improvements can be obtained exploiting photonic integration techniques.
The PHODIR transceiver has been tested in radar field-trials working at 10GHz. To this extent, a RF front-end has been designed and developed. The cooperation with local traffic Authorities (Livorno port and Pisa airport) allowed to consider naval and aerial traffic in both long and short distance scenarios, detecting non-cooperating targets. The PHODIR results have been compared and validated with official data provided by the involved Authorities. The PHODIR outcomes have been selected to be divulged through an official video by ERC and they have been accepted for publication on NATURE. Moreover the PHODIR project produced 1 Italian award, 1 best paper award, 1 keynote speech selection, 3 invited and 8 regular papers at International Journals, 4 invited and 21 regular contributions at International Conferences. It interacts with the INSIDE project within the European NEXPRESSO framework and the European Eurofos project. Moreover the ERC PoC “PREPARE: PRE-industrial Photonic-based Radar dEsign” allowed to present the PHODIR results to the industry, generating 3 industrial patents, and few joint project proposals currently under revision. A final workshop has been also organized with the participation of almost 100 international people from Industry, Academy, and Authority Institutions.
Next radar will need software-defined radio (SDR) paradigm to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today’s digital microwave components (synthesizers and analog-to-digital converters (ADCs)) suffer limited bandwidth with high noise at increasing frequencies, on the contrary, photonics has proved high precision and ultra-wide bandwidth, allowing the flexible generation of extremely stable radio-frequency (RF) signals with arbitrary waveforms up to the millimeter waves, and their detection and precise direct digitization without down-conversions. PHODIR has pioneered the fully photonics-based radar verifying for, the first time, photonic technologies in a radar system. The proposed architecture exploits a single pulsed mode locked laser (MLL) for both generating tunable radar signals and receiving their echoes, avoiding RF up-/down-conversions and guaranteeing software-defined approach and at the same time reducing the impact of photonics on the system costs. The flexible and high frequency photonic generation of RF signals is based on the extremely stable heterodyning of two spectral MLL lines in a photodiode. Two tunable optical filters select two modes from the spectrum of the MLL, one is modulated by the baseband radar pulse in a Mach-Zehnder modulator, whereas the other is shifted in frequency. The receiver exploits photonics for realizing an ADCs accepting input signals over several tens of GHz, with fast sampling rates. The train of short optical pulses provided by the MLL is directly modulated by the RF signal to be digitized. The modulated pulses are then serial-to-parallel converted to multiple lower-rate sample streams so that, after opto-electronic conversion, multiple electronic ADCs with low sampling frequency and high precision can be used to digitize the pulse peak power carrying the sample information. The parallel digital samples are then interleaved at the digital signal processor to reconstruct the original signal. A frequency shift is added in the transmitter stage the carrier frequency different from a multiple of the sampling rate.
The precision of photonics can be particularly appreciated in coherent radars, for this reason the PHODIR transceiver also generates the reference signal.
The test of the PHODIR transceiver demonstrates its performance exceeding the state-of-the-art electronics at carrier frequencies above 2GHz. It enables radars with unprecedented frequency flexibility and signal quality, and with a record receiver resolution at high carrier frequency. It has been tested producing and receiving signals with carriers up to 40GHz. At the transmitter it has a signal-to-noise ratio>73dB/MHz and a spurious-free dynamic range >70dBc and at the receiver an effective number of bit >7 up to 40 GHz. Performance improvements can be obtained exploiting photonic integration techniques.
The PHODIR transceiver has been tested in radar field-trials working at 10GHz. To this extent, a RF front-end has been designed and developed. The cooperation with local traffic Authorities (Livorno port and Pisa airport) allowed to consider naval and aerial traffic in both long and short distance scenarios, detecting non-cooperating targets. The PHODIR results have been compared and validated with official data provided by the involved Authorities. The PHODIR outcomes have been selected to be divulged through an official video by ERC and they have been accepted for publication on NATURE. Moreover the PHODIR project produced 1 Italian award, 1 best paper award, 1 keynote speech selection, 3 invited and 8 regular papers at International Journals, 4 invited and 21 regular contributions at International Conferences. It interacts with the INSIDE project within the European NEXPRESSO framework and the European Eurofos project. Moreover the ERC PoC “PREPARE: PRE-industrial Photonic-based Radar dEsign” allowed to present the PHODIR results to the industry, generating 3 industrial patents, and few joint project proposals currently under revision. A final workshop has been also organized with the participation of almost 100 international people from Industry, Academy, and Authority Institutions.