Sideband separation mixer for ALMA Band 7

Following the design described in ALMA Memo 316 [1], and using two double side band (DSB) mixer units designed by Navarinni et al. [2], a sideband separation mixer for ALMA Band 7 has been built and tested at IRAM (Fig. 4,5).

An image rejection better than 10 dB has been obtained across the Band 7 (Fig. 6). The single side band (SSB) T_rec was measured for two intermediate frequency (IF) bandwidths (Fig. 7, 8. These tests were performed with a mixer IF impedance transformer that is not fully optimized for the 4-8 GHz ALMA required band. Further tests will include mixers with better noise temperature and a full 4-8 GHz IF.

It is interesting to note that the system proved to be quite simple to operate, i.e. not any more difficult than a DSB mixer.

References:

[1: ] S. M. X. Claude, C. T. Cunningham, A. R. Kerr, and S.-K. Pan, Design of a Sideband-Separating Balanced SIS Mixer Based on Waveguide Hybrids, ALMA Memo No. 316
[2: ] A. Navarrini, D. Billon-Pierron, I. Peron, B. Lazareff, "Design and characterization of a 225-370 GHz DSB and a 247-360 GHz SSB waveguide SSB mixers",Proceedings of the 26th. International Conferenceon Infrared and Millimeter Waves, Toulouse, FRANCE, 10/09/2001- 14/09/2001

Stephan CLAUDE

**Figure 4:** Assembled 2SB Mixer
$\begin{figure}\begin{center} \mbox{\psfig{file=aug02-2SB.ps,width=14cm} } \end{center} \end{figure}$

**Figure 5:** Open 2SB Mixer
$\begin{figure}\begin{center} \mbox{\psfig{file=aug02-vueeclatee.ps,width=14cm} } \end{center} \end{figure}$

**Figure 6:** Sideband rejection for LSB and USB tuning
$\begin{figure}\begin{center} \mbox{\psfig{file=aug02-t3.ps,width=15cm} } \end{center} \end{figure}$

**Figure 7:** SSB T_rec, for an IF of 4-6 GHz
$\begin{figure}\begin{center} \mbox{\psfig{file=aug02-t1.ps,width=15cm} } \end{center} \end{figure}$

**Figure 8:** SSB T_rec, for an IF of 5 GHz
$\begin{figure}\begin{center} \mbox{\psfig{file=aug02-t2.ps,width=15cm} } \end{center} \end{figure}$

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