Tunable Band Pass
Defines a tunable band pass filter with the parameters shown in the configuration window above. A tunable band pass filter passes frequencies in the pass bands with minimal attenuation and rejects (attenuates) signals outside of the pass bands. A tunable band pass filter will attenuate both low and high frequencies and pass a specific band of frequencies as seen below in the plot of a band pass filter in EMIT.
Tunable band pass filters are defined in terms of a tuning range and a percent bandwidth. For each channel within a transceiver, the spectral profile of the tunable filter will be recreated. For example, assume a transmitter is defined that operates from 100-110 MHz in 2 MHz channels and the filter has a 10% bandwidth. When EMIT is simulating the 100 MHz channel, the filter is centered at 100 MHz with a bandwidth of 10 MHz (red). For the 102 MHz channel, the filter is centered at 102 MHz with a 10.2 MHz bandwidth (blue). For the 110 MHz channel, the filter is centered at 110 MHz with an 11 MHz bandwidth (green). This is illustrated in the plot below.
When a transceiver is operating at a different frequency for transmit than for receive (e.g. for self interaction with a Tx Offset), the tunable filter always tunes based on the transmit channel frequency.
Noise Temperature (K): Noise power added by the filter.
Insertion Loss: Insertion loss defines the magnitude by which pass band signals are attenuated and is specified in dB.
Stop Band Attenuation: Stop band attenuation defines the magnitude of the attenuation for signals with frequencies outside the pass band.
Lowest Tuned Frequency: The lowest tuned frequency defines the lower end of the tuning range for the filter. If any Tx and/or Rx channels are defined below this frequency, then the filter will be centered at the lowest tuned frequency, rather than at the channel frequency.
Highest Tuned Frequency: The highest tuned frequency defines the higher end of the tuning range for the filter. If any Tx and/or Rx channels are defined above this frequency, then the filter will be centered at the highest tuned frequency, rather than at the channel frequency.
Percent Bandwidth (%): The percent bandwidth defines the the bandwidth of the filter stop band (notch) with respect to the center frequency of the filter.
Shape Factor: The shape factor describes the roll-off of the filter between the 3 dB and 30 dB bandwidth points.
