Transceiver with rapid mode switching capability

• US 5,239,686 A
• Filed: 04/29/1991
• Issued: 08/24/1993
• Est. Priority Date: 04/29/1991
• Status: Expired due to Term

• Current Assignee: Echelon Corporation (Renesas Electronics Corporation)
• Original Assignee: Echelon Corporation (Renesas Electronics Corporation)
• Inventors: Downey, Walter J.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Charouel, Lisa
• Application Number:
  US07/693,965
• Time in Patent Office: 848 Days
• Field of Search: 455/75, 455/76, 455/77, 455/78, 455/82, 455/83, 455/84, 455/86, 455/87, 455/89, 455/85, 455/106, 455/112, 455/114, 455/127, 455/295, 455/296, 455/317, 455/340, 455/343, 455/125, 370/94.1
• US Class Current: 455/78
• CPC Class Codes: H04B 1/44 Transmit/receive switching

Abstract

An RF transceiver achieves a fast switching time between transmit and receive modes by leaving the transmit oscillator on all the time. The transmit chain comprises a wide pulling voltage controlled crystal oscillator that operates at one third the transmit frequency followed by a frequency tripler/filter/amplifier chain that can be quickly switched on and off. By operating the transmit oscillator at one third the transmit frequency, only the third harmonic of the oscillator falls into the sensitive receive frequency band. Further isolation during the receive mode is achieved by gating off the frequency tripler, pulling the frequency of the oscillator out of the receive band, electronically detuning the harmonic filter and switching off the transmitter'"'"'s power amplifier.

Claims

1. A transceiver having a receiver section and a transmitter section both coupled to an antenna for transmission and reception of electromagnetic signals at a communication frequency, and further having mode control means to place the transceiver in a receive mode for the reception of the electromagnetic signals and in a transmit mode for the transmission of the electromagnetic signals, said transmitter section comprising:

oscillator means for generating a first electrical signal at a first fundamental frequency that is a submultiple of the communication frequency;

frequency multiplier means coupled to the oscillator means for receiving the first electrical signal and generating a second electrical signal in response thereto at a second fundamental frequency nominally equal to the communication frequency;

filter means coupled to the frequency multiplier means for receiving the second electrical signal and attenuating frequency components other than the communication frequency, thereby producing a filtered communication signal, wherein the filter means includes detuning means coupled to the mode control means for causing the filter means to attenuate the communication frequency in the receive mode;

power amplifier means coupled to the filter means for receiving the filtered communication signal and for amplifying the power thereof, thereby producing an amplified communication signal;

antenna coupling means for electrically connecting the amplified communication signal to the antenna.

2. The device of claim 1 wherein the first fundamental frequency is one third of the communication frequency.

3. The device of claim 2 wherein the communication frequency is in the range of 49 to 50 MegaHertz.

4. The device of claim 1 wherein the frequency multiplier means includes means coupled to the mode control means for selectively disabling the frequency multiplier means in the receive mode.

5. The device of claim 1 wherein the oscillator means includes frequency pull off means coupled to the mode control means for selectively causing the oscillator means to generate the first electrical signal at the frequency offset from said submultiple of the communication frequency in the receive mode.

6. The device of claim 5 wherein the frequency of the first electrical signal is offset from said submultiple of the communication frequency by at least 40 kiloHertz.

7. The device of claim 1 wherein the power amplifier means includes means coupled to the mode control means for selectively disabling the power amplifier means in the receive mode.

8. A transceiver having a receiver section and a transmitter section both coupled to an antenna for transmission and reception of electromagnetic signals at a communication frequency, mode control means to place the transceiver in a receive mode for the reception of the electromagnetic signals and in a transmit mode for transmission of the electromagnetic signals, said transmitter section comprising:

oscillator means for generating a first electrical signal at a first fundamental frequency that is a submultiple of the communication frequency, the oscillator means including frequency pull off means coupled to the mode control means for selectively causing the oscillator means to generate the first electrical signal at a frequency offset from said submultiple of the communication frequency in the receive mode;

frequency multiplier means coupled to the oscillator means for receiving the first electrical signal and generating a second electrical signal in response thereto at a second fundamental frequency nominally equal to the communication frequency, the frequency multiplier means including means coupled to the mode control means for selectively disabling the frequency multiplier means in the receive mode;

filter means coupled to the frequency multiplier means for receiving the second electrical signal and attenuating frequency components other than the communication frequency, thereby producing a filtered communication signal, the filter means including detuning means coupled to the mode control means for causing the filter means to attenuate the communication frequency in the receive mode;

power amplifier means coupled to the filter means for receiving the filtered communication signal and for amplifying the power thereof, thereby producing an amplified communication signal, the power amplifier means including means coupled to the mode control means for selectively disabling the power amplifier means in the receive mode; and

antenna coupling means for electrically connecting the amplified communication signal to the antenna.

9. The device of claim 8 wherein the first fundamental frequency is one third of the communication frequency.

10. The device of claim 9 wherein the communication frequency is in the range of 49 to 50 MegaHertz.

11. In a transceiver having a receiver section and a transmitter section both coupled to an antenna for transmission and reception of electromagnetic signals at a communication frequency, the transmitter section including mans for generating a transmitter oscillator signal, power amplifier means for amplifying the transmitter oscillator signal to a transmission level, and a harmonic filter coupled between the means for generating the transmitter oscillator signal and the power amplifier means for attenuating harmonics of the communication frequency during the transmission of the electromagnetic signals, a method for isolating the receiver section from the transmitter section during reception of the electromagnetic signals comprising the steps of:

(a) generating the transmitter oscillator signal at a first fundamental frequency that is nominally a submultiple of the communication frequency;

(b) multiplying the frequency of the transmitter oscillator signal up to the communication frequency only when transmitting the electromagnetic signals; and

(c) detuning the harmonic filter so as to attenuate the communication frequency within the harmonic filter during the reception of the electromagnetic signals.

12. The method of claim 11 further comprising the step of disabling the power amplifier means during the reception of the electromagnetic signals.

13. The method of claim 11 further comprising the step of pulling the frequency of the transmitter oscillator signal away from said submultiple of the communication signal during the reception of electromagnetic signals.

14. A transceiver comprising:

a transmitter section;

a receiver section;

an antenna coupled to both the transmitter and receiver sections for transmission and reception of electromagnetic signals at a communication frequency;

mode control means for placing the transceiver in a receive mode for the reception of the electromagnetic signals and in a transmit mode for the transmission of the electromagnetic signals;

the transmitter section including a selectively tunable harmonic filter tuned in the transmit mode to pass the communications frequency and attenuate harmonics of the communication frequency and tuned in the receive mode to attenuate the communication frequency.