Abstract :
A LONG with the growth of power-line carrier communication and consequent crowding of the frequency spectrum between 40 and 200 kc, there has arisen the need for band-pass filters at the carrier receiver input to prevent adjacent channel interference. With FM transmission, performance required of the filters is as follows: 1. Must be adjustable to a frequency from 40 to 200 kc. 2. Maximum midband insertion loss not to exceed 9 db at 40 kc, nor 17 db at 200 kc, and to increase linearly from 40 to 200 kc. 3. Attenuation at frequencies ±8 kc from midband, 100 db minimum below midband loss. 4. Response at frequencies ±3 kc from midband to be within 5 db. 5. Maximum distortion 10 per cent (with 1,000-cycle audio and modulation index = 2.5) when tested with a FM receiver. 6. Response and distortion limits must not be exceeded over a range of temperature from -20 to +70 C, and at humidities up to 95 per cent.
