Five-hundred-meter Aperture Spherical radio Telescope

 

Receiver System

The feeds and receivers are planned to be built through international cooperation, which cover a frequency range from 70 MHz to 3GHz. The present 9 feeds and receivers in plan are displayed in the table.

ID

Freq (MHz)

Pol

Beam

IF (MHz)

Gain (dB)*

Tsys
degree

B01

70-140

C

1

300-370

71

<100

B02

140-280

C

1

300-440

72

<80

B03

280-560

C

1

300-580

73

<40

B04

560-1020

C

1

70-530

75

<10

B05

320-334

C

1

70-84

85

<40

B06

550-640

C

1

300-390

82

<10

B07

1150-1720

C

1

70-640

78

<10

B08

1230-1530

L

19

300-600

80

<10

B09

2000-3000

C

1

70-1070

75

<10

The proposed construction mainly includes:

(1) Feeds and low-noise receivers: to develop feeds and polarizer at 9 bands, LNAs, band selection filters, radio frequency circuit, frequency mixers and IF circuits.

(2) Refrigeration machine: Helium GM refrigeration machines and vacuum Dewar are used to refrigerate the head amplifier and other key instruments, especially for receiver at bands higher than 560 MHz, which requires a temperature of 10-20 K to keep low noise.

(3) Optical fiber to transform IF data: to develop a wide-band optical fiber transformation. IF data is converted to light signal, and then transform in the optical fiber over a distance of about 3 km, and convert back to IF data to the digital terminals.

(4) Digital data-processing terminals: to construct multi-band terminals for cosmic neutral hydrogen, pulsar de-dispersion, molecular lines observations, VLBI data-record terminal, SETI terminal and digital record and process terminal based on computer clusters.

(5) Receiver monitor and diagnosis system: to monitor the receiver in real-time, and test the remote trouble diagnosis to shorten the feed cabin maintenance time in harbor.

(6) The time frequency standard: this will be provided by GPS and high stationary hydrogen clock to fulfill the requirements of pulsar, spectral lines and VLBI observations, etc.