Waveguide components are currently preferred for low-frequency (<100GHz) single-moded applications or when an experiment requires extremely high performance and accuracy. Examples of such components are Corrugated Horns, Ortho-Mode Transducers, Phase Shifters and Polarisation Modulators developed for CMB polarisation experiments such as Planck and Clover.
- Corrugated horns:
For Planck-HFI, Clover and Quijote, we have developed single-mode corrugated horns producing a Gaussian main beam, controlled cut-on frequency, low side lobes and low return loss. These high performance horns coupled to a telescope system allow it easily to reach a very high gain with a spillover of 1% – 2%. Besides performance improvements we are now developing large-scale manufacturing techniques for future large focal plane arrays. Based on our successful on-going collaboration with Maynooth (National University of Ireland), we are working on performance improvement of multimoded horns to match that of single-mode operation, to reach the high performance required for CMB applications.
- B. Maffei, et al, Proceedings of the SPIE, 5498, pp. 812-817 (2004)
- Gleeson, E., et al., Infrared Physics & Technology, 46, Issue 6, p. 493-505, 2005
- J.Anthony Murphy, et al., InfPhT., 42, pp 515-528 (2001), ISSN1350-4495
- E. Gleeson, J. A. Murphy, B. Maffei, IJIMW, 23, No.5, May 2002
- Ortho-Mode Transducers:
We have developed a turnstile junction OMT with performance exceeding those detailed in the literature. Building on this success we will improve OMT performance by: 1/ reducing its size, 2/ adjusting the geometry to suit manufacturing capabilities, and 3/ improvements in machining tolerance. These will make it easier to scale the device to higher frequencies.
- G. Pisano et al., IEEE Microwave and Wireless Components Letters, 17, Issue 4, pp. 286-288 (2007)
- Phase shifters:
We have developed a mechanical phase shifter based on a rotating Half-Wave Section (HWS) between two fixed Quarter-Wave Sections (QWSs). The performance is superior to that of any phase-shifter available commercially. We measure RL and IL of better than –18 dB/–0.3 dB respectively over the 80-95 GHz band. The phase-shift accuracy is better than 1%, and is flat to 1.2° rms over 29% bandwidth. Our goal is to design broader bandwidth QWSs (polarisers) for phase shifters achieving this performance over a 40% bandwidth.
- G. Pisano et al., IEEE Microwave and Wireless Components Letters, 17, Issue 3, pp. 208-210 (2007)
- Polarisation modulators:
We have designed, realized and tested a broadband 97-GHz waveguide polarisation modulator based on the rotating waveguide HWS, which has extremely low cross-polarisation (~ –40dB) and excellent S11, S21 over the band. This device is the best-performing and cleanest polarisation modulator we are aware of. The next step is to design broader band sections to be used in more compact polarisation modulators with 40% bandwidth.