Acknowledge back pager with apparatus for controlling transmit frequency

Abstract

An acknowledge back (ack-back) pager is provided for use in a paging system including a central station which transmits a group of message signals to a group of ack-back pagers which are addressed as a group. The users of the group of addressed ack-back pagers indicate a response to their respective pagers thus providing ack-back data. The pagers in the group of addressed ack-back pagers then simultaneously transmit back to the central station their ack-back data on different frequency sub-bands, a different frequency sub-band being allocated to each of the pagers in the group. To accurately control the ack-back transmit frequency, the pager receives and down-converts the F.sub.RX signal thus producing a down-converted F.sub.C signal, the frequency of which is measured and stored. The pager selects which sub-band of a plurality of frequency sub-bands within a predetermined range of frequencies is to be used for transmission of the ack-back signal. The pager determines a frequency offset F.sub.D corresponding to the selected sub-band, such offset being with respect to a predetermined frequency within such range of frequencies. The pager generates an acknowledge back signal at a frequency (F.sub.C +F.sub.D)-F.sub.CTX and up-converts such signal to a transmit frequency F.sub.TX corresponding to said selected sub-band, F.sub.CTX being the frequency of a down-converted sample of the F.sub.TX signal.