Pulsar huge array with Nyquist rate digital lens and prism

An 8×8 = 64 element digital interferometer was developed at Waseda University (1989-1995). It was an equally spaced two dimentional array of 2.4 m dishes at 10.6 GHz, and a 2D FFT processor was used for Nyquist rate imaging. Recently a spatial-temporal (2+1)D FFT processor has been developed for pulsar survey (1996-2000), in which a first 2D spatial FFT transforms the electric fields of cordinate represented to those of momentum represented. We obtain the electric fields in each 64 direction at Nyquist rate by the 2D spatial Fourier transform. The following temporal 1D FFT gives the spectrum of 64ch or 256ch to 64 directions respectively also at Nyquist rate. The total bandwidths of each direction are 20 MHz and the resulting frequency resolutions are 20/64 MHz or 20/256 MHz. For sensitive pulsar survey, we also have developed an interferometric array of 20 m spherical dishes in Nasu flat, 160 km north of Tokyo. Five dishes are completed at present. Normal temperature receivers of high electron mobility transistors (HEMT) are used at 1.4GHz observation and the receiver noise temperatures are below 40K. Expected rms detection limit ΔT is about 10 ^-2 K under the condition of 20 MHz band widths and 1s integration time. Preliminary results of zenith survey at δ = 40 deg using a single dish show ΔT = 0.03 K without switching. Sub-reflecters and feed horns were designed so as to observe 5 deg off directions from zenith and they rotate around Az axis. It enable us to survey the declination zone of 32≤δ≤42 deg.