Acknowledge back pager with apparatus for controlling transmit frequency

• US 4,891,637 A
• Filed: 01/07/1988
• Issued: 01/02/1990
• Est. Priority Date: 01/07/1988
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Siwiak, Kazimierz, Keba, James M., Steel, Francis R.
• Primary Examiner(s): Brigance, Gerald
• Application Number:
  US07/141,655
• Time in Patent Office: 726 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, 379/56, 379/57, 455/31, 455/89, 455/92
• US Class Current: 340/7.23
• CPC Class Codes: B63B 21/48 Sea-anchors; Drogues
• CPC Class Codes: G08B 3/1016 using wireless transmission calling systems using transmission by inductive loop H04B5/00
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04W 84/025 with acknowledge back capability

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_RX signal thus producing a down-converted F_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_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_C +F_D)-F_CTX and up-converts such signal to a transmit frequency F_TX corresponding to said selected sub-band, F_CTX being the frequency of a down-converted sample of the F_TX signal.

Claims

1. In a radio paging system including a central paging station for transmitting paging signals including a group of pager addresses on a paging channel frequency F_RX to a group of corresponding remotely located acknowledge back radio pagers, said central station transmitting said pager addresses in a predetermined order over a first time interval, each acknowledge back pager capable of controlling a sub channel frequency F_TX on which it transmits acknowledge back signals, an acknowledge back pager of said system comprising:

receiving means for receiving said paging signal on the channel frequency F_RX ;

measuring means, coupled to said receiving means, for measuring the channel frequency of the received paging signal;

selecting means for selecting a sub-band frequency from a plurality of frequency sub-bands within a predetermined range of frequencies in accordance with a predetermined relationship based on the predetermined order in which said pager'"'"'s address is being transmitted in said group, said selected frequency sub-band being the sub-channel frequency for transmission on an acknowledge back signal by said pager;

determining means for determining a frequency offset F_D of the measured channel frequency corresponding to said selected sub-band frequency;

transmitter means, coupled to said determining means, for generating an acknowledge back signal at said selected sub-band frequency including both the measured channel frequency and the determined offset frequency.

2. 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, a method of controlling a sub-channel frequency F_TX on which an acknowledge back pager of said system transmits an acknowledge back signal, said method comprising the steps of;

receiving the paging signal and down-converting the channel frequency F_RX thereof to produce a signal at a down-converted frequency F_C ;

measuring the frequency F_c of said down-converted signal;

selecting a sub-band frequency unique to said acknowledge back pager from a plurality of frequency sub-bands within a predetermined range of frequencies as the sub-channel frequency for transmission of an acknowledge back signal from said pager;

determining a frequency offset F_D corresponding to the selected sub-band frequency;

generating a modulated signal at an initial frequency based on a desired frequency setting (F_C +F_D) and up-converting the initial frequency of the modulated signal to a transmit sub-channel frequency F_TX corresponding substantially to said selected sub-band frequency;

down-converting the frequency F_TX of said generated up-converted signal and measuring the down-converted frequency F_CTX thereof; and

adjusting said initial frequency of said modulated signal in a direction to converge the measured frequency F_CTX to the desired frequency setting F_C +F_D, whereby the transmit sub-channel frequency F_TX of the pager'"'"'s acknowledge back signal is caused to be set precisely at the selected sub-band frequency,

3. 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, a method of controlling a sub-channel frequency F_TX on which an acknowledge back pager of said system transmits an acknowledge back signal, said method comprising the steps of;

A. receiving the paging signal and down-converting the channel frequency F_RX thereof to produce a signal at a down-converted frequency F_C ;

B. measuring the frequency F_C of said down-converted signal;

C. selecting a sub-band frequency unique to said acknowledge back pager from a plurality of frequency sub-bands within a predetermined range of frequencies at the sub-channel frequency for transmission of an acknowledge back signal from said pager, said sub-channel frequency being unique to said pager;

D. determining a frequency offset F_D corresponding to the selected sub-band frequency;

E. generating a modulated signal at an initial frequency based on a desired frequency setting (F_C +F_D) and up-converting said initial frequency of the modulated signal to an initial transmit sub-channel frequency F_TX approximately corresponding in frequency to said selected sub-band;

F. down-converting said frequency F_TX of the generated signal to generate a signal with a down converted frequency F_CTX ;

G. generating the modulated signal at an adjusted frequency in a direction to converge the measured frequency F_CTX to the desired frequency setting (F_C +F_D) and up-converting said adjusted signal to a transmit sub-channel frequency F_TX corresponding more closely in frequency to said selected sub-band; and

H. repeating steps F and G until the frequency of the transmit signal F_TX is substantially equal to the frequency of the selected sub-band.

4. 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 pagers, an acknowledge back pager capable of controlling a sub-channel frequency F_TX on which it transmits acknowledge back signals, said pager comprising:

means for receiving the paging signal on the channel frequency F_RX ;

means for measuring the channel frequency of the received paging signal;

controller means for determining a desired sub-channel frequency setting based on the measured channel frequency and a selected frequency offset frequency unique to said acknowledge back pager and for generating a control signal with an initial value substantially representative thereof;

frequency synthesizer governed by said control signal to generate a signal at a frequency which is used by said pager for transmitting the acknowledge back signal thereof; and

means for measuring the frequency of said signal generated by said frequency synthesizer, said controller means further operative to adjust the initial value of said control signal in a direction to converge the measured frequency of said signal to the desired sub-channel frequency.

5. The acknowledge back pager in accordance with claim 4 including:

means for amplifying the acknowledge back signal of said paper prior to transmission thereof in accordance with a controlled amplification setting;

means for measuring the magnitude of the amplified acknowledge back signal; and

means governed by said magnitude measurement of the measuring means to control the amplification setting of said amplifying means.

6. The acknowledge back pager in accordance with claim 4 wherein the controller means comprises a programmed digital controller which generates a digital control signal, the digital code of which represents a value of the frequency setting;

and wherein the frequency synthesizer comprises a voltage controlled oscillator which is digitally controlled by said digital control signal to generate the sub-channel frequency signal.

7. The acknowledge back pager in accordance with claim 4 including a modulating means for modulating the sub-channel frequency signal, said controller means being further operative to govern the modulating means to modulate the sub-channel frequency signal with the acknowledge back signal of said pager.