East Asian VLBI Network (EAVN)

Brief Summary of NRO45 Receiving System

The NRO45 covers an observing frequency range of 20 – 116 GHz with multiple receivers. The VLBI backend system of the NRO45 is currently equipped at K-band and Q-band. Figure 4 illustrates a flow diagram of the VLBI receiving system in the NRO45. The observable RF range and typical receiver noise temperature for the receivers at K- and Q-bands are also summarized in Table 4. The received RF signals are down-converted into an IF range of 5 – 7 GHz, and the IF signals are then mixed down to the base band of 512 – 1024 MHz, which is the input to the A/D sampler.

Table 2: Driving performance of EAVN antennas.
Driving axis Driving range Max. driving speed Max. driving acceleration
Nobeyama
AZa -60◦ ~ 510◦ 0.3◦/sec 0.3◦/sec2
EL 12◦ ~ 80◦ 0.3◦/sec 0.3◦/sec2
Tianma
AZa -60◦ ~ 425◦ 0.5◦/sec 0.27◦/sec2
EL 8◦ ~ 88◦ 0.3◦/sec 0.16◦/sec2
VERA
AZa -90◦ ~ 450◦ 2.1◦/sec 2.1◦/sec2
EL 5◦ ~ 85◦ 2.1◦/sec 2.1◦/sec2
FRa -270◦ ~ 270◦ 3.1◦/sec 3.1◦/sec2
KVN
AZa -90◦ ~ 450◦ 3.0◦/sec 3.0◦/sec2
EL 5◦ ~ 85◦ 3.0◦/sec 3.0◦/sec2
aThe north is 0◦ and the east is 90◦.
bFR is 0◦ when Beam-1 is at the sky side and Beam-2 is at the ground side, and CW is positive when an antenna is seen from a target source.
Table 3: Aperture efficiency and beam size of EAVN antennas.
Antenna Name K-band
ηA
(%)
(22 GHz)
HPBW
(arcsec)
Q-band
ηA
(%)
(43 GHz)
HPBW
(arcsec)
Nobeyama - - 53 39
Tianma 50 44 50 22
Mizusawa 47 141 51 71
Iriki 47 149 44 78
Ogasawara 50 143 45 78
Ishigakijima 49 144 48 79
Yonsei 55 127 63 63
Ulsan 63 124 61 63
Tamna 60 126 63 63

Currently, one of the receivers can be selected by switching the mirrors in the optics in a few minutes manually. In the near future, K- and Q-band observations can be conducted simultaneously by inserting a perforated high-pass dichroic plate. When using the dichroic plate, the gain of the Q-band signals may be reduced by 0.3dB (in 2018 June), causing the rise of the system noise temperature by about 30 K.




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EAVN ( East Asia VLBI Network )