KVN and VERA Array (KaVA)

Brief Summary of KVN Receiving System

The KVN quasi-optics are uniquely designed to observe 22, 43, 86 and 129 GHz band simultaneously (Han et al. 2008, 2013). Figure 7 shows the layout of quasi-optics and receivers viewing from sub-reflector side. The quasi-optics system splits one signal from sub-reflector into four using three dichroic low-pass filters marked as LPF1, LPF2 and LPF3 in the Figure 7. The split signals into four different frequency bands are guided to corresponding receivers.

Figures 8 shows a signal flows in KVN system. The 22, 43 and 86 GHz band receivers are cooled HEMT receivers and the 129 GHz band receiver is a SIS mixer receiver. All receivers receive dual-circular-polarization signals. Among eight signals (four dual-polarization signals), four signals selected by the IF selector are down-converted to the input frequency band of the sampler. The instantaneous bandwidth of the 1st IF of each receiver is limited to 2 GHz by the band-pass lter. The 1st IF signal is down-converted by BBCs to the sampler input frequency (512-1024 MHz) band.

Typical noise temperatures of K and Q bands are presented in Table 5. Since the calibration chopper is located before the quasi-optics as shown in Figure 7, the loss of quasi-optics contributes to receiver noise temperature instead of degrading antenna aperture efficiency. Therefore, the noise temperature in the table includes the contribution due to the quasi-optics losses.

The receiver noise temperatures of three stations are similar to each other except that the noise temperature of the Ulsan 43 GHz because of the different type of thermal isolator, which is used to reduce heat flow from the feed horn in room temperature stage to cryogenic cooled stage more effectively.

Figure 6: Flow diagram of signals from receiver to recorder for VERA.

Figure 7: KVN multi-frequency receiving system (Han et al. 2008, 2013).

Figure 8: Flow diagram of signals from receiver to recorder for KVN (Oh et al. 2011).

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KaVA ( KVN and VERA Array )