Knowledge back pager with frequency control apparatus

• US 4,823,123 A
• Filed: 01/07/1988
• Issued: 04/18/1989
• Est. Priority Date: 01/07/1988
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Siwiak, Kazimierz
• Primary Examiner(s): Brigance, Gerald L.
• Application Number:
  US07/141,653
• Time in Patent Office: 467 Days
• Field of Search: 340/825.44, 340/825.47, 340/825.48, 340/311.1, 370/92, 370/93, 370/94, 370/50, 370/69.1, 370/73, 370/76, 455/31, 455/89, 455/92, 379/56, 379/57
• US Class Current: 340/7.23
• CPC Class Codes: G08B 3/1016 using wireless transmission calling systems using transmission by inductive loop H04B5/00
• CPC Class Codes: G08B 3/1091 Group calling
• CPC Class Codes: H01S 3/094034 the pumped medium being a dye
• CPC Class Codes: H01S 3/10092 Coherent seed, e.g. injection locking
• CPC Class Codes: H04W 84/025 with acknowledge back capability

Abstract

An acknowledge back (ack-back) pager is provide for use in a paging system which includes 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. The invention provides apparatus for controlling the frequency of the selected sub-band with very high accuracy.

Claims

1. An acknowledge back pager for processing paging signals transmitted at a paging channel frequency of F_RX from a central paging station, said pager comprising;

a local oscillator oscillating at a frequency F_LO to generate an F_LO signal;

first mixing means, coupled to said oscillator, for mixing said paging signals with said F_LO signal to generate a down-converted signal at a frequency F_C ;

frequency determining means, coupled to said first mixing means, for determining the frequency F_C of the down-converted signal;

sub-band selection means for selecting one of a plurality of frequency sub-bands on which said pager is to transmit an acknowledge back signal, said selection means determining a selected sub-band and a frequency offset F_D corresponding to said selected sub-band, said offset F_D being with respect to the frequency F_RX ;

memory means for storing the value of the frequency F_RX ;

determining means for determining the value of N for the selected sub-band wherein

space="preserve" listing-type="equation">N=(F.sub.RX -F.sub.C)/(F.sub.D +F.sub.C)

dividing means, coupled to said determining means, for dividing the F_LO signal by N to generate an F_LO /N signal, and

second mixing means, coupled to said dividing means and said oscillator means, for mixing said F_LO signal with said F_LO /N signal to generate a carrier signal for said acknowledge back signal.

2. The acknowledge back pager of claim 1 including a response indicating means wherein a user of said pager indicates a response to said pager for transmission in said acknowledge back signal, indicia of said response being modulated on said carrier signal to form said ack-back signal.

3. The acknowledge back pager of claim 1 including means for receiving and displaying message signals transmitted by said central station.

4. An acknowledge back pager for processing paging signals transmitted at a paging channel frequency of F_RX from a central paging station, said pager comprising;

a local oscillator oscillating at a frequency F_LO to generate an F_LO signal;

mixing means, coupled to said oscillator, for mixing said paging signals with said F_LO signal to generate a down-converted signal at a frequency F_C ;

frequency determining means, coupled to said mixing means, for determining the frequency F_C of the down-converted signal;

memory means for storing a look-up table including indicia of a plurality of frequency offsets, F_D, with respect to said frequency F_RX, said offsets F_D corresponding respectively to a plurality of frequency sub-bands, and for storing the value of F_RX, and further for storing the frequency F_C determined by said frequency determining means;

sub-band selection means for selecting which one of said sub-bands on which said pager is to transmit an acknowledge back signal, said selection means thus determining a selected sub-band;

microcomputer means for determining the value of N for the selected sub-band wherein

space="preserve" listing-type="equation">N=(F.sub.RX -F.sub.C)/(F.sub.D +F.sub.C)

dividing means, coupled to said microcomputer means, for dividing the F_LO signal by N to generate an F_LO /N signal

mixing means, coupled to said dividing means and said oscillator means, for mixing said F_LO signal with said F_LO /N signal to generate a carrier signal for said acknowledge back signal.

5. The acknowledge back pager of claim 4 including a response indicating means wherein a user of said pager indicates a response to said pager for transmission in said acknowledge back signal, indicia of said response being modulated on said carrier signal to form said ack-back signal.

6. The acknowledge back pager of claim 4 including means for receiving and displaying message signals transmitted by said central station.

7. In a radio paging system including a central paging station for transmitting paging signals on a paging channel frequency F_RX to a plurality of remotely located acknowledge back radio pagers, said pager including a memory for storing the value of the frequency F_RX, a method of controlling the frequency on which said acknowledge back pager transmits an acknowledge back signal comprising the steps of:

generating a local oscillator signal at a frequency F_LO, said local oscillator signal being designate the F_LO signal;

mixing said paging signals with said F_LO signal to generate a down-converted signal at a frequency F_C ;

determining the frequency F_C of the down-converted signal;

selecting which one of a plurality of frequency sub-bands said pager is to transmit acknowledge back signals on, thus determining a selected sub-band, said selecting step including selecting a frequency offset F_D corresponding to said selected sub-band, said offset frequency F_D being with respect to the frequency F_RX ;

determining the value of N for the selected sub-band wherein

space="preserve" listing-type="equation">N=(F.sub.RX -F.sub.C)/(F.sub.D +F.sub.C)

dividing the F_LO signal by N to generate an F_LO /N signal

mixing said F_LO signal with said F_LO /N signal to generate a carrier signal for said ack-back signal.