Source (software & hardware) for PSR detection
- PSR channelizer (GNU Radio flowgraph that performs real-time digital signal processing and writes the data directly to a filterbank-formatted file for further processing & analysis with e.g. PRESTO). To be uploaded.
- PRESTO for de-dispersion and folding (DM-search and P-search also used).
- Potentially a variation of simpleReader in the future for further feature support.
- Parabolic antenna aperture: 1.5m (PICTOR)
- Feed: Cloverleaf Antenna (identical to the one used on CHIME)
- First-stage LNA: Mini-Circuits ZX60-P103LN+ (NF ≈ 0.4 dB, G ≈ 20 dB)
- In-line amplifier: Mini-Circuits ZX60-P103LN+ (NF ≈ 0.4 dB, G ≈ 20 dB)
- Transmission line: 3-meter LMR-400 Coaxial Cable (insertion loss: ~0.3 dB)
- Receiver: LimeSDR Mini*
- Computer for real-time DSP: Jetson Nano Developer Kit*
*Installed inside a custom-built double-shielded Faraday cage for EMI mitigation and EMC maximization.
For EMI suppresion (spurious emission reduction), two Faraday cages were considered: one that had a single layer of shielding, and one that had a double layer of shielding (custom-built with two fans for heat dissipation). For a sample frequency of 460 MHz, preliminary EMI tests (conducted with CygnusRFI) have given the following results:
The apparent inconsistency appears to be due to SDR noise floor variability with time (e.g. SDR temperature (T) is proportional to the system noise temperature (T_sys) and dT/dt ≠ 0). Therefore, because the measurements were taken at slightly different times (waiting for each measurement to finish), the noise floor varies (T ∝ T_sys ∧ dT/dt ≠ 0 ∴ dT_sys/dt ≠ 0)). Besides internal factors, T_ant variability (caused by DUT-unrelated RFI) may also have a significant impact.
Further preliminary EMI checks, this time on a different receiving computer candidate:
EMI Source (DUT under suspicion) out of the antenna's beam (equivalent to turning it off):
More to be added soon...