Standard BPF Filter for Aircraft Communication

In the VHF and UHF radio spectrum allocated a group of frequencies to radio communication in civil and military aviation that also referred as Aircraft band or Airband. Frequency band assignment by FCC and FAA is from 108 to 137 MHz for civil aircraft communications; from 225 to 400 MHz for military aviations. Within the aircraft band is mostly used for navigational by radio aids and air traffic control.

Navigational by radio aids (for aviation) is navigation information derives from ground radio beacons such as VOR (Very high frequency Omni-directionalRange), DME (Distance Measuring Equipment) and NDB (Non Directional Beacon), ILS (Instrument Landing System) aviation equipments or broadcast stations. It can provide services as distance measurement between the communication station and the aircraft’s position, time signals, assist pilots landing in low visibility conditions, medical advice, stations broadcasting navigational warnings etc.

Air traffic control (ATC) is a service provided by ground-based personnel who in the air traffic control center on the monitoring of air traffic in a controlled airspace, specifically tower control, approach and departure control, and route control. They also can provide advisory services to aircraft in non-controlled airspace.

In aircraft communication radio, the reception of radio signals are usually disrupted by non-RTF (Radio Telephony) frequency users where come from commercial stations on the ground, and affected by weather and atmospheric conditions. A typical situation as following:

Several airports, hundred nautical miles apart, are shared the same frequency. In the static generated by thunderstorm clouds or in high pressure, radio transmission station using the same frequency as authorized aeronautical transmitter be jamming even it is beyond the protected range, e.g. result in aircraft landing to one airport having interference from the ATC. The air traffic control center personnel on the ground perhaps not aware the landing aircraft is suffering radio interference because he may unable to hear the transmissions relating to the other airport.

Some interference is from unauthorized or malicious transmissions. On rare occasions when unauthorized stations have made malicious transmissions on the same frequency, probably the intention of misleading pilots at critical stages e.g. phases of flight (takeoff and landing) were false messages.

To consider BPF filter design into the wiring for the audio's transponders, and GPS would be an efficient method to eliminate inside and outside interference of aircraft communications coverage.

The engineering team of TEMWELL specialty RF Band Pass Filter design in VHF and UHF can support standard and custom frequencies in different bandwidths for aircraft bands. The following is the demo part number table. Featured specs are very low insertion loss, flat in passband as ripple less than 1.0dB, stopband attenuation steeper can upon user requirement. The package supports Pin (thru-hole) and Connector (SMA female or N female).

Demo center frequencies are different but have various bandwidth options. Each demo center frequency accepts to specify a new one within a particular range. We can re-design the BPF filter accordingly to your wanted new center frequency in the same bandwidth and the same other specs.

Table A has various bandwidth options are 5 MHz, 10 MHz, 20 MHz, and 30 MHz. Each demo center frequency can accept a re-design range from 126 to 145 MHz, e.g. TT6755D1 demo at 140 MHz, but can be specified at 128 MHz.