We have developed a novel mm-wave spectrometer based on a Photonic Band Gap (PBG) channel-drop filter (CDF).
There is a need for a compact wide-band versatile and configurable mm-wave spectrometer for applications in mm-wave
communications and remote sensing. CDFs present us with a unique means for filtering frequencies at mm-waves. CDF
is a novel concept allowing filtering the frequency spectra and channeling selected frequencies into separate waveguides
through a PBG structure. We have designed a spectrometer with a CDF working in the frequency range of 90-130 GHz.
The CDF can be connected to any type of antenna and detector. A large ground based outdoor antenna can be used for
remote sensing with radars. A compact antenna can be used for indoor or space applications. The signal in the
waveguide channels can be measured with any type of sensor such as a cooled bolometer or a room temperature mm-wave
diode. The size of the spectrometer is under 5 inches by 5 inches and just a quarter of an inch in thick. Multiple
filters can be stacked together to construct a mission specific package. We propose to construct the filter with silicon
rods on a 100mm silicon wafer using MEMS technology. We will then evaluate the filter at our mm-wave laboratory to
demonstrate the channeling of frequencies in a proof-of-principle experiment at 100GHz. This technology will work
well for frequencies from 60GHz to 1000GHz.
We propose to use photonic band gap (PBG) structures for constructing traveling wave tubes (TWTs) at 100 GHz, a completely novel approach. Using a PBG fiber allows us to create an all-dielectric slow-wave structure with very large band width and low losses in the mm-wave regime, compared to TWTs made out of metals. Additional capabilities such as mode selectivity are also achievable. We designed two 100 GHz pencil beam PBG TWTs using Ansoft's HFSS, 3D electromagnetic simulation software for high frequency applications. The first design is a periodic array of vacuum rods in a dielectric matrix, with a smaller vacuum rod forming the line defect. A fiber drawing procedure is being utilized to construct this design out of fused silica. The second structure is a periodic array of dielectric rods in a vacuum matrix, surrounding a thick hollow dielectric tube that accommodates the electron beam. This model is being fabricated out of silicon by means of high-pressure laser chemical vapor deposition (HP-LCVD), a versatile approach to synthesize fibers from the vapor phase. Additionally, a scaled 10 GHz cold test made from alumina rods is being produced for design confirmation purposes, and a 100 GHz sheet beam PBG TWT is being investigated for even greater power generation.