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. Note that only the Q-band receiver (which is cooled HEMT) is available for the EAVN 2018B open-use operation, while the K-band receiver will be available in the next semester.
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 0.3 dB (in 2018 June), causing the rise of the system noise temperature by about 30 K.
|K||20 - 25||~ 85||LCP/RCP|
|Q||42.5 - 44.5||~ 111||LCP|
|K||18.0 - 26.5||16 - 35||LCP/RCP|
|Q||39 - 47||35 - 50||LCP/RCP|
|K||21.5 - 23.8||30 - 50||LCP|
|Q||42.5 - 44.5||70 - 90||LCP|
|K||21.25 - 23.25||30 - 40||LCP/RCP|
|Q||42.11 - 44.11||70 - 80
(40 - 50 for Ulsan)