Journal: Proceedings of the International Astronomical Union

Article Title: 100 GHz Room-Temperature Laboratory Emission Spectrometer

doi: 10.1017/s1743921317007803

Figure Lengend Snippet: Figure 2. Electronics scheme of the room-temperature heterodyne receiver. The receiver con- sists of the corrugated horn antenna (1), followed by a W LNA (2), and a mixer (3), operational between 75-110 GHz. The mixer downconverts the molecular signal using the LO 1 signal (7). The LO 1 signal is based on a synthesizer signal which is amplified (6) and multiplied (x6) (5). To match the conversion loss a waveguide tuneable attenuator is used (4). The mixer output is amplified using an LNA (Miteq, +34 dB) (8) before entering the IF processor.

Article Snippet: A digital step attenuator (Mini Circuits, up to 31 dB, 8) mounted in front of a directional coupler (Mini Circuits, 9) matches the power level to the input requirements of the XFFT-spectrometer.

Techniques:

Journal: Proceedings of the International Astronomical Union

Article Title: 100 GHz Room-Temperature Laboratory Emission Spectrometer

doi: 10.1017/s1743921317007803

Figure Lengend Snippet: Figure 3. The intermediate Frequency Processor. The intermediate frequency signal (IF′) is amplified (25 dB, 1) and a bandpass filter (2) allows for frequencies of 6.35 ±1.25 GHz to pass. The signal is attenuated by 7 dB (3) before reaching the second mixing stage (4). Here, the IF′ is multiplied with the output of a 7.6 GHz direct digital syntheizser (DDS, 13), synchronized to a Rubidum clock. The LO (13) is then amplified by 24 dB (14) and attenuated by 3 dB (15). The mixing process results in frequencies of 7.6 GHz ± 6.35 GHz (4). The IF then gets attenuated (2 x 3 dB, 5 and 6), and amplified by +24 dB (7). A digital step attenuator (maximum 31 dB, 8) is controlled by a microcontroller (19). A small portion (about 1%) of the signal is coupled out by a directional coupler (9). Here, we obtain a continuum signal over the whole frequency range by using a continuum detector (tunnel diode, 16). A lowpass filter is applied for better signal stability (17). The counts are amplified (18) and a micro-controller (μC, 19) outputs the signal onto an LC-display (20). The remaining signal (about 99 %) passes the directional coupler (9), gets amplified (24 dB, 10), is send through a lowpass filter (loss 1 dB, 11), gets attenuated (7 dB, 12), and is fed into the XFFTS.

Article Snippet: A digital step attenuator (Mini Circuits, up to 31 dB, 8) mounted in front of a directional coupler (Mini Circuits, 9) matches the power level to the input requirements of the XFFT-spectrometer.

Techniques: