Filter stabilized single oscillator transceivers

• US 3,931,575 A
• Filed: 10/21/1974
• Issued: 01/06/1976
• Est. Priority Date: 10/21/1974
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Amoroso, Salvatore Jr.
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/516,536
• Time in Patent Office: 442 Days
• Field of Search: 325/17-25, 325/63, 343/179, 343/180, 343/181, 179/15 BM
• US Class Current: 455/75
• CPC Class Codes: H04B 1/408 the transmitter oscillator frequency being identical to the receiver local oscillator frequency
• CPC Class Codes: H04B 1/50 using different frequencies for the two directions of communication

Abstract

A transceiver, adapted for use as either a master or a slave in a duplex pair, has a single, voltage-tunable, solid-state oscillator to provide the carrier frequency wave, a small portion of which is mixed with the received wave and applied therewith to a single ended mixer; an automatic gain-controlled loop cancels transmitter input modulation from the receiver output. The desired oscillator carrier frequency of the master transceiver is locked to a frequency within the pass band of an RF filter at the receiver input and separated from the center frequency of the filter by one-half the receiver IF frequency. The slave transceiver is first locked to a frequency within the pass band of the filter on the opposite side of its center frequency and separated therefrom by one-half the IF frequency (the slave thus offset from the master by their common IF frequency). Thereafter, upon sensing output from its IF amplifier (from the master), the slave is switched to operate in response to AFC developed by the received signal, such that the master and slave transceivers are locked together at frequencies differing by their common IF frequency. The RF filter also limits the signals to which the receiver can respond. An integrating amplifier provides demodulator and AFC filtering and, together with a bistable device, initial sweeping of the oscillator control voltage in respective directions depending on being in the master mode or the slave mode. Internal auxiliary modulation provides for pre-transmission transmitter modulation cancellation and frequency stability.

Claims

1. A transceiver, adapted for use in a duplex transceiver system including a pair of such transceivers settable for operation with one in a master mode and one in a slave mode, said transceiver comprising:

a single, voltage-tunable oscillator having means for providing a frequency-controlling voltage input thereto;

an FM receiver having the same IF frequency in the master mode as in the slave mode and including an RF mixer that drives said FM receiver and that provides a frequency-determining feedback signal;

antenna means for transmitting and receiving microwave energy;

an RF filter, having a center frequency and having a pass band greater than said IF frequency, the output of said RF filter coupled to said RF mixer;

means for coupling energy from said oscillator to said antenna means for transmission thereby and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator to the input of said RF filter; and

frequency control means including means providing an initial frequency sweep controlling voltage to the input of said oscillator to thereby sweep the frequency of said oscillator to a frequency within said band of frequencies, and having an input connected for response to the feedback signal output of said RF mixer, for providing a frequency control voltage to the frequency-controlling voltage input means of said oscillator in response to said feedback signal and to said initial frequency sweep controlling voltage to establish operation of said oscillator at a frequency separated from said center frequency by one half of said IF frequency, and further including means settable to designate said transceiver for operation in the master mode or the slave mode, and operable when set in the slave mode to provide said frequency control voltage to establish operation of said oscillator at one side of said center frequency and operable when set in the master mode to provide said frequency control voltage to establish operation of said oscillator at the other side of said center frequency.

2. A transceiver adapted for use in a duplex transceiver system including a pair of transceivers, said transceiver comprising:

a single, voltage-tunable microwave oscillator having means for providing a frequency-controlling voltage input thereto;

an FM receiver having a mixer with the same design IF frequency in both of such transceivers in the pair;

antenna means for transmitting and receiving microwave energy;

means for coupling energy from said oscillator to said antenna means for transmission thereby, and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator to the input of said FM receiver;

input means for receiving transmitter input modulation and providing an input modulation signal;

auxiliary modulation means for providing internally-generated modulation;

combining means connected to said input means and to the output of said auxiliary modulation means for providing a combined modulation signal as the combination of said input modulation signal and said internally-generated modulation signal;

means responsive to said combining means for providing a modulation control signal to said frequency-controlling voltage input means for controlling the frequency of oscillation of said microwave oscillator in response to said combined modulation signal; and

frequency modulation stabilizer means connected for response to the output of said FM receiver for controlling the oscillator with said auxiliary modulated oscillator signal for providing to said frequency-controlling voltage input means a closed loop frequency stability voltage.

3. A transceiver adapted for use in a duplex transceiver system including a pair of transceivers, said transceiver comprising:

a single, voltage-tunable microwave oscillator having means for providing a frequency-controlling voltage input thereto;

an FM receiver having a mixer with the same design IF frequency in both of such transceivers in the pair;

antenna means for transmitting and receiving microwave energy;

means for coupling energy from said oscillator to said antenna means for transmission thereby, and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator to the input of said FM receiver;

input means for receiving transmitter input modulation and providing an input modulation signal;

auxiliary modulation means for providing internally-generated modulation;

combine means responsive to said auxiliary modulation means and to said input means for providing modulation signals to said frequency-controlling voltage input means as a function of said internally-generated modulation;

a resonant filter means connected for response to the output of said oscillator to provide a modulated signal having its phase dependent on whether the frequency of the output of said oscillator is above or below the resonant frequency of said resonant means and its amplitude dependent on the amount of difference therebetween, within a band of frequency differences; and

frequency control means including a phase sensitive demodulator having its signal input connected for response to the output of said resonant means and its reference input connected to said auxiliary modulation means for providing to said frequency-controlling voltage input means a closed loop frequency stability voltage derived from said modulated signal.

4. In a transceiver, adapted for use in a duplex transceiver system including a pair of such transceivers settable for operation with one in a master mode and one in a slave mode, said transceiver comprising:

a single voltage-tunable microwave oscillator;

an FM receiver;

antenna means for transmitting and receiving microwave energy;

means for coupling energy from said oscillator to said antenna means for transmission thereby, and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator to the input of said FM receiver;

transmitter input means for receiving a transmitter modulation signal and providing a modulation input signal;

auxiliary modulation means providing a low-level internal modulation signal;

control means including a combiner and a variable gain amplifier responsive to said transmitter input means and to said auxiliary modulation means for controlling the frequency of oscillation of said microwave oscillator in response to the sum of said input modulation signal and said internal modulation signal;

cancellation means responsive to the output of said FM receiver and to said auxiliary modulation means for cancelling similar modulation from the output of said FM receiver and for thereby providing a receiver output signal; and

gain control means responsive to said cancellation means for controlling the gain of said variable gain amplifier, in a manner to null the internal modulation in the receiver output signal to zero.

5. In a transceiver, adapted for use in a duplex transceiver system including a pair of such transceivers settable for operation with one in a master mode and one in a slave mode, said transceiver comprising:

a single microwave oscillator having frequency-controlling voltage input means;

an FM receiver;

antenna means for transmitting and receiving microwave energy;

means for coupling energy from said oscillator to said antenna means for transmission thereby, and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator in mixed fashion to the input of said FM receiver;

transmitter input means for receiving a transmitter modulation signal and providing a modulation input signal;

auxiliary modulation means providing an internal modulation signal;

combining means connected to said input means and to the output of said auxiliary modulation means to provide a combined modulation signal as the combination of said input modulation signal and said internal modulation signal;

a variable gain amplifier having a signal input and a gain control input, said signal input being connected to said combining means, the output of said variable gain amplifier being connected to said frequency-controlling voltage input of said oscillator;

delay means responsive to said combining means for providing a delayed combined modulation signal which is delayed by a period of time substantially equal to the signal propagation time from the input of said variable gain amplifier through said FM receiver;

cancellation means responsive to the output of said FM receiver and to the output of said delay means for selectively combining said delayed combined modulation signal with the output of said FM receiver in voltage combining relationship to provide a receiver output signal having transmitter input modulation and internal modulation substantially cancelled therefrom; and

means responsive to the receiver output signal of said cancellation means and to said delayed internal modulation signal for providing a gain control signal to the gain control input of said variable gain amplifier, said gain control signal adjusting the gain of said variable gain amplifier so that the magnitude of internal modulation included in the output of said FM receiver is adjusted with respect to the magnitude of delayed internal modulation provided by said delay unit so that the combined modulation in said receiver output signal is substantially nulled to zero.

6. A transceiver adapted for use in a duplex transceiver system including a pair of transceivers, said transceiver comprising:

a single, voltage-tunable microwave oscillator having means for providing a frequency-controlling voltage input thereto;

an FM receiver having the same design IF frequency in both of such transceivers in a pair;

antenna means for transmitting and receiving microwave energy;

means for coupling energy from said oscillator to said antenna means for transmission thereby, and for simultaneously coupling energy received at said antenna means and a small portion of the energy of said oscillator to the input of said FM receiver;

input means for receiving transmitter input modulation and providing an input modulation signal;

auxiliary modulation means for providing internally-generated modulation;

combining means connected to said input means and to the output of said auxiliary modulation means for providing a combined modulation signal as the combination of said input modulation signal and said internally-generated modulation signal;

means including a variable gain amplifier responsive to said combining means for providing a modulation control signal to said frequency-controlling voltage input means for controlling the frequency of oscillation of said microwave oscillator in response to said combined modulation signal;

cancellation means responsive to the output of said FM receiver and to said combining means for cancelling similar modulation from the output of said FM receiver and for thereby providing a receiver output signal;

gain control means responsive to said cancellation means and to said auxiliary modulation means for controlling the gain of said variable gain amplifier in a manner to null the internal modulation in the receiver output signal to zero; and

frequency control means connected for response to the output of said oscillator and to said auxiliary modulation means for providing to said frequency-controlling voltage input means a closed loop frequency stability voltage.