"The 22 GHz receiver of the CAY"
Author: Inmaculada Malo Gómez, José Antonio López Fernández
Abstract: The 40m radiotelescope of the Centro Astronómico de Yebes, in Spain, will cover the frequency band from 2 to 120 GHz. The present abstract summarizes the main characteristics of our 22GHz superheterodyne receiver. Its main purposes will be VLBI observations and pointing with the 40 meter radiotelescope.The frequency band will extent from 21.75 to 24.45 GHz.
It is a cooled, low noise, dual circular polarization (RCP / LCP) receiver. It will have two observational modes, called VLBI and Single Dish, SD. At VLBI mode the receiver will have two frequency conversions and an IF output bandwith of 500MHz (from 500 to1000MHz). At SD mode, there are three frequency conversions and an IF output of 100MHz (from 170 to 270MHz).
Two sky frequency bands can be selected:
- - In VLBI mode: an Upper Band, from 23.35 - 24.45 GHz, and a Lower Band, from 21.75 - 22.85 GHz.
- - In SD mode: an Upper Band, from 23.57 - 24.27 GHz, and a Lower Band, from 21.97-22.67 GHz.
Horn and lens, polarizer, directional coupler and low noise amplifiers are cooled down to cryogenic temperatures inside a cryostat made in our labs. This cryostat has two stages, the coolest one at 12 Kelvin and an intermediate radiation shield at 66 Kelvin. The measured noise temperature of the receiver is about 21,5 k. The low noise amplifiers are made at CAY facilities with InP technology, with a noise temperature about 9 k.
Additionaly the 22GHz Receiver is provided with a Noise Source for gain calibration in VLBI mode.