# US 4,394,776 A · Priority channel system for a synthesized transceiver

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- Number: US 4,394,776 A
- Document ID: US4394776A
- Status: Granted
- Kind: A
- Application number: 06/251,565
- Filed: 1981-04-06
- Granted: 1983-07-19
- Earliest claimed: 1981-04-06
- Assignees: Motorola, Inc.
- Inventors: Jaime A. Borras; Ruben J. Gonzalez; Daniel M. Smith; Alfred B. Wieczorek
- Web page: https://patentgrep.com/patent/US4394776A

## CPC

- H03K 23/66: with a variable counting base, e.g. by presetting or by adding or suppressing pulses
- H03C 3/0933: {using fractional frequency division in the feedback loop of the phase locked loop}
- H03C 3/0941: {applying frequency modulation at more than one point in the loop}
- H03C 3/0958: {applying frequency modulation by varying the characteristics of the voltage controlled oscillator}
- H03C 3/0966: {modulating the reference clock}
- H03C 3/227: {using a combination of bipolar transistors and field effect transistors}
- H03D 13/00: Circuits for comparing the phase or frequency of two mutually-independent oscillations {(measuring phase G01R25/00; phase-discriminators with yes/no output G01R25/005)}
- H03J 5/0281: {the digital values being held in an auxiliary non erasable memory}
- H03K 23/667: {by switching the base during a counting cycle}
- H03L 7/0802: {the loop being adapted for reducing power consumption (H03L7/14 takes precedence)}
- H03L 7/193: the frequency divider/counter comprising a commutable pre-divider, e.g. a two modulus divider
- H03L 7/199: with reset of the frequency divider or the counter, e.g. for assuring initial synchronisation
- H04B 1/405: with multiple discrete channels
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)
- H03C: MODULATION (masers or lasers H01S; coding, decoding or code conversion H03M)
- H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66)
- H03J: TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
- H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B)
- H04B: TRANSMISSION

## Abstract

A frequency synthesized transceiver capable of tuning to a plurality of communication channels is disclosed. The transceiver includes a receiver section and a transmitter section which are coupled to the synthesizer which generates the appropriate injection signals to achieve tuning. The frequency synthesizer includes a multiposition switch which accesses various addressable memory locations in a programmable read-only memory where the appropriate divisors are stored to cause tuning of the synthesizer to the appropriate communication channel. A zone selector switch enables grouping and easy retrievability of channels. The synthesizer includes a priority channel monitoring system utilizing a channel element for rapid sampling. The divisors are supplied to a single synchronous binary swallow counter which works in conjunction with a dual modulus prescaler to monitor the frequency output of the voltage controlled oscillator. A programmable divider coupled to a reference oscillator source is compared with the output of the synchronous counter in a digital and analog phase detector. The phase detector supplies signals through a loop filter to apply the appropriate voltage to the voltage controlled oscillator. The phase detector includes means to rapid advance the voltage controlled oscillator to cause frequency tuning.

## Claims

### Claim 1

A portable transceiver including a digital frequency synthesizer capable of tuning a plurality of communications channels, said transceiver including a priority channel monitoring system comprising:
a crystal channel element capable of providing injection signals to the transceiver for tuning to a predesignated priority channel;
sampling means coupled to the digital frequency synthesizer and the crystal channel element, alternately supplying injection signals from said synthesizer and said channel element to the receiver portion of the transceiver;
carrier detection means detecting the presence of carrier signal in the receiver section of the transceiver;
priority means coupled to said carrier detection means and said sampling means, disrupting the operation of the sampling means and establishing tuning of the transceiver for transmission or reception at the communication channel corresponding to said crystal controlled channel element when a carrier signal is detected on that frequency corresponding to said crystal controlled channel element; and delay means coupled to said sampling means to maintain the tuning of the transceiver at said priority channel for a predetermined interval to enable a responding transmission on said priority channel from a transceiver operator.

### Claim 2 (depends on 1)

The priority channel system of claim 1 wherein said sampling means operates continuously with a predetermined period and duty cycle including during reception of a communication over a channel selected by said synthesizer.

### Claim 3 (depends on 2)

The priority channel system of claim 2 wherein the predetermined period and duty cycle are chosen so that no loss of intelligibility occurs during the reception of a communication on a synthesizer selected channel while said priority channel is sampled.

### Claim 4 (depends on 3)

The priority channel system of claim 3 further including blanking means for blanking the noise due to the absence of a carrier signal on said sampled priority channel.

### Claim 5 (depends on 4)

The priority channel system of claim 4 wherein said delay means includes means accessible to the transceiver operator to adjust the magnitude of said predetermined interval.

### Claim 6 (depends on 5)

The priority channel system of claim 5 further including alert means responsive to said delay means to indicate to the transceiver operator that his transmission is on said priority channel.

### Claim 7 (depends on 6)

The priority channel system of claim 6 wherein said sampling means includes means responsive to the termination of said predetermined interval for resuming the operation of supplying injection signals to the receiver portion of said transceiver.