2.2.2 Wideband interference Wideband signals or noise which reduces the signal-to-noise ratio, affects both the carrier tracking and the data channels. In the case of the telemetering channel, the spectral density of the interfering signal must be at least 5.9 dB below the spectral density of the receiver noise, in order not to degrade the threshold performance by more than 1 dB. Maximum levels of wideband interference are shown in Table III. TABLE III - Wideband interference with telemetering 2.2.3 Interference to maser operation Mixing of signals with the idler frequency of the maser pump can cause interference and saturation in the receiver passband. There are-many frequencies at which such mixing can occur, all of which are far removed from the normal frequency of reception. Table IV gives possible interference frequencies for the two frequency bands currently used for reception at deep-space research earth stations. Interfering signals must be above —120 dBW in the idler bandwidth (which is very broad) at the maser input, to be significant. TABLE IV - Frequencies at which interference may be caused by mixing in the maser 2.2.4 Adjacent channel receiver saturation The cryogenically cooled maser of the deep-space receiver has a bandpass of approximately 50 MHz. Adjacent channel signals, if received at total power levels greater than - 120 dBW, can generate intermodulation products in the mixer and other receiver elements, causing saturation of the receiver.
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