Apparatus for controlling the receive and transmit frequency of a transceiver

• US 4,489,413 A
• Filed: 07/19/1982
• Issued: 12/18/1984
• Est. Priority Date: 07/19/1982
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: M/A Com
• Inventors: Richmond, Robert L., Wyar, Paul F., Corrigan, John E.
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US06/399,573
• Time in Patent Office: 883 Days
• Field of Search: 370/30, 370/32, 455/75, 455/86, 455/87
• US Class Current: 370/278
• CPC Class Codes: H03J 7/02 Automatic frequency control H03J7/18 takes precedence
• CPC Class Codes: H04B 1/50 using different frequencies for the two directions of communication

Abstract

Apparatus for maintaining a transmit radio signal frequency in a predetermined frequency relationship with a received radio signal. A common voltage controlled frequency source serves as an Lo signal generator for both the receiver and transmitter. A reference frequency oscillator is phase compared with a receive IF signal to derive a control voltage for the voltage controlled frequency source. The resulting phase lock loop provides transmit signal frequency control with respect to a received signal.

Claims

1. An apparatus for controlling the receive and transmit frequency of a transceiver comprising:

means for receiving a radio frequency carrier signal having information for demodulating at a first radio frequency;

first frequency conversion means comprising a first mixer having a first input connected to receive said radio frequency carrier signal;

a voltage controlled frequency source having an output signal connected to a second input of said mixer whereby said mixer provides a first intermediate frequency signal;

a second frequency conversion means having a second mixer connected to receive said first intermediate frequency signal containing information for demodulating and producing a second mixer output signal;

a local oscillator providing a reference signal to said second mixer;

frequency detector means providing a control signal to said voltage controlled frequency source estabilishing frequency control for said voltage controlled frequency source to produce a voltage controlled signal;

means for mixing said voltage controlled signal with a signal to be transmitted;

whereby said signal to be transmitted and said signal containing information are frequency controlled by said voltage controlled frequency source.

2. In an apparatus for simultaneously transmitting and receiving modulated radio frequency signals, a frequency control apparatus for generating a transmit carrier and receive intermediate frequency signal comprising:

a voltage controlled frequency source having an output signal with frequency proportional to a control voltage;

means for mixing said voltage controlled frequency source output signal with an incoming radio frequency signal whereby an intermediate frequency signal is provided;

a fixed frequency reference oscillator;

means for phase comparing the intermediate frequency signal with said fixed frequency oscillator signal, said means applying an error signal to said voltage controlled frequency source whereby said voltage controlled frequency source output signal maintains a substantially constant frequency relationship with said incoming radio frequency signal; and

means for combining an informaion signal with said voltage controlled frequency source output signal whereby a transmit signal is formed having a frequency determined by said incoming radio frequency signal.

3. The apparatus of claim 2 wherein said means for mixing comprises:

PG,17

a first mixer for receiving said voltage controlled frequency source output signal and an incoming receive signal; and

a second mixer for receiving an output signal from said first mixer and said reference signal oscillator, said second mixer providing said intermediate frequency signal having said information contained therein.

4. The apparatus of claim 3 wherein said means for phase comparing includes a frequency divider connected to said reference signal oscillator;

and

a phase detector connected to receive a signal from said divider and said intermediate frequency signal, said phase detector operatively connected to provide a control voltage for said voltage controlled frequency source.

5. The apparatus of claim 4 wherein said means for combining an information signal comprises a third mixer connected to receive an intermediate frequency signal modulated with an information signal and said voltage controlled frequency source output signal.

6. The apparatus of claim 5, further comprising a directional circulator, having a first port for receiving a signal from said means for combining, a second port connected to a channel for transmitting and receiving radio frequency signals, and a third port connected to said first mixer whereby incoming radio frequency signals are transmitted to said first mixer and outgoing radio frequency signals are transmitted to said channel.

7. An apparatus for controlling the transmit and receive frequency for a transceiver, said transceiver of the type for simultaneously receiving and transmitting radio frequency signals at different frequencies comprising:

a directional circulator having a first port connected to a communications channel, second and third ports providing a receive path and transmit path for said transceiver;

a voltage controlled frequency source;

a mixing means having an RF port connected to said receive path, and an Lo port connected to said voltage controlled frequency source, and an intermediate frequency port;

a frequency translator having an output port connected to said transmit port and first and second input ports connected to receive a voltage controlled frequency source output signal and a transmit information signal;

a reference signal generator for providing a signal for phase comparison with an intermediate frequency signal from said mixing means; and

phase comparison means connected to receive a signal from said reference signal generator and said intermediate frequency signal from said mixing means intermediate frequency port, said phase comparison means providing a control voltage for said volage controlled frequency source whereby the intermediate frequency signal and transmit signal are frequency controlled by received radio frequency signals.

8. The apparatus of claim 7 wherein said mixing means includes first and second mixing stages, said first mixing stage having an Lo input connected to said voltage controlled frequency source, and an RF port connected to said receive path, and

said second mixing stage connected to receive a first intermediate frequency signal from said first mixing stage and connected to receive a second Lo signal from said reference signal generator whereby a second intermediate frequency signal is produced containing a received information signal.

9. The apparatus of claim 8 wherein said reference signal generator provides first and second frequency related signals, said first frequency related signal connected to said phase comparison means and said second frequency related signal comprising said second Lo signal for said second mixing stage.

10. In a system for simultaneously transmitting and receiving information on a radio frequency signal carrier, apparatus for establishing a transmit frequency under control of a received carrier frequency signal comprising:

a transmit-receive isolator having a first port connected to a communications channel and second and third ports for providing isolated transmit and receive paths to and from said communications channel;

a voltage controlled local frequency source;

a source of data to be transmitted;

a first frequency conversion means for providing a transmit signal to said transmit path, said first frequency conversion means having a first input connected to receive said data, a second input connected to receive a signal from said voltage controlled frequency source;

a mixing means connected to receive a signal from said receive path and a signal from said voltage controlled frequency source, said mixing means providing an intermediate frequency signal;

a reference oscillator having a frequency substantially identical with the frequency of said intermediate frequency signal; and

error detecting means connected to receive said intermediate frequency signal, and a signal from said reference oscillator, said error detecting means providing a control voltage to said volage controlled frequency source whereby transmit signal frequency stability is controlled in response to a received radio frequency signal.

11. The apparatus of claim 10 wherein said received radio frequency signal has a frequency stability greater than said reference oscillator output signal.

12. The apparatus of claim 10 wherein said reference oscillator output signal stability is 1/10 said receiver signal stability.

13. In a system for transmitting an information signal at a first carrier frequency, and receiving an information signal at a second carrier frequency, an apparatus for maintaining the transmitted information signal carrier frequency in a predetermined frequency relationship with the received information signal carrier frequency comprising:

a fixed frequency reference oscillator;

a voltage controlled frequency source;

means forming an intermediate frequency signal from said voltage controlled frequency source output signal and said received information carrier signal;

means for comparing the phase of said intermediate frequency signal and said fixed frequency reference oscillator output signal generating an error signal in response thereto, said error signal connected to a frequency control input of said voltage controlled frequency source;

whereby said voltage controlled frequency source frequency is established in a fixed relationship with said information signal carrier frequency; and

means for combining a portion of said voltage controlled frequency source output signal with an information signal whereby a carrier frequency signal bearing said transmitted information is produced having a frequency controlled by said received information signal carrier.

14. In a transceiver apparatus for simultaneously transmitting information at a first carrier frequency and receiving information at a second carrier frequency, an apparatus for maintaining a transmit signal in a predetermined frequency relationship with a receive signal comprising:

an insolator for providing a receive and transmit path from and to a communications channel;

a frequency translator having an output port connected to said transmit path, and first and second input ports,

a mixer having an RF input port connected to said receive port, an Lo port and IF port;

a fixed frequency source providing a signal to said Lo port and said second input port whereby said frequency translator provides a signal combined from said frequency source signal and an input IF signal on said first port, and said mixer provides a first baseband IF receive signal;

a baseband demodulator connected to receive said receive IF signal, said demodulator including;

a mixing stage connected to receive said receive IF signal;

a voltage controlled oscillator connected to said receive mixing stage;

a second fixed reference signal generator for generating a signal having a frequency within the frequency range of said voltage controlled oscillator;

and means for comparing the frequency of said second fixed frequency reference oscillator with said mixing stage output signals, said means for comparing providing an error signal to said voltage controlled oscillator whereby said voltage controlled oscillator assumes a frequency under control of said IF signal frequency;

a baseband transmitter comprising;

a modulator for providing a modulated output signal; and

baseband translation means for combining a portion of said voltage controlled oscillator output signal with said modulator output signal thereby forming a transmit IF signal, said translation means connected to provide said baseband transmit signal to said frequency translator first port whereby an RF transmit signal is produced, said transmit signal frequency being controlled by a receive signal.

15. A transceiver for generating a transmit signal which is related in frequency to a received signal and time coincident therewith comprising:

a first frequency conversion means responsive to a receive signal for producing an IF signal,

a second frequency conversion means responsive to a transmit signal for translating said transmit signal in frequency;

a reference oscillator producing an signal at a reference frequency; and

a frequency comparing means responsive to said reference oscillator signal and to said IF signal for producing a control signal related to a frequency difference between said first IF signal and reference frequency;

said first and second frequency conversion means including a common voltage controlled frequency source and means coupling said control signal to control the frequency of oscillations of said voltage controlled frequency source.

16. A transceiver for generating a transmit signal which is different in frequency to a received signal and time coincident therewith comprising:

a first frequency conversion means responsive to a receive signal for producing an IF signal;

a second frequency conversion means response to a transmit signal for translating said transmit signal in frequency to a frequency different from said receive signal frequency;

frequency detector means connected to receive said IF signal, said detector providing a voltage indicating a frequency error of said IF signal;

voltage responsive frequency control means operatively connected to provide a local oscillator signal and frequency translation signal to said first and second frequency conversion means, and to said frequency detector means to receive a frequency control signal, whereby a translated transmit signal frequency and derived IF signal frequency stability are commonly controlled in response to said receive signal.