rpw3%rigden.wpd@sgi.com (Rob Warnock) (04/12/90)
In article <6236@accuvax.nwu.edu> rees@citi.umich.edu (Jim Rees) writes: | I assume that any cellphone has to have an RF duplexor... These are usually | mechanical cavity resonators. At 900Mhz these would be about 8cm tall. | But in a cellphone, they must use something more sophisticated, | because the transmitter and receiver both have to be frequency-agile. No problem. All of the receiver freqs are above all of the transmitter freqs, so each is agile only on it's own side of the fence. A simple duplexor will do. John Covert gave the formula for the frequencies in <6156@accuvax.nwu.edu> (Telecom-Digest: V.10, I.239, Msg 5 of 6): | receive_freq = (if channel<991 then 870.030 MHz else 869.04) !chan 1/991 | + 30kHz x (channel - 1 or 991) | transmit_freq= (if channel<991 then 825.030 MHz else 824.04) !chan 1/991 | + 30kHz x (channel - 1 or 991) Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311