Transmitter-receiver

• US 5,689,819 A
• Filed: 11/22/1995
• Issued: 11/18/1997
• Est. Priority Date: 06/05/1995
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Nishimura, Shuji, Itoh, Kenji
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/562,066
• Time in Patent Office: 727 Days
• Field of Search: 455/78, 455/79, 455/82, 455/83, 455/84, 455/85, 455/86, 455/87, 455/310
• US Class Current: 455/86
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator
• CPC Class Codes: H04B 1/40 Circuits

Abstract

In a transmitter-receiver having a transmitting circuit and a receiving circuit, the present invention mitigates an interference between the transmitting circuit and the receiving circuit. A quartz-crystal oscillator is provided as a common reference signal source for the local oscillators and the relation among frequencies is determined so that the frequencies such as local oscillating frequencies and intermediate frequencies within the transmitter-receiver do not overlap each other. Interferences between the transmitting circuit and the receiving circuit are mitigated to prevent a characteristic deterioration, spurious radiation, etc. Thereby the transmitter-receiver may be reduced in size and weight. Further, by sharing a quartz-crystal oscillator having a high frequency stability, narrowing of bands in radio channel spacing may be readily achieved.

Claims

1. A transmitter-receiver comprising:

a transmitting local oscillator for generating a transmitting oscillation signal having a transmitting local oscillating frequency based on a reference signal;

a transmitting circuit for providing an output by converting frequency of a transmitted signal input thereto in accordance with said transmitting oscillation signal;

a receiving local oscillator for generating a receiving oscillation signal having a receiving local oscillating frequency based on said reference signal;

a receiving circuit for providing an output by converting a frequency of a received signal input thereto in accordance with said receiving oscillation signal;

a reference signal oscillator provided as a common reference signal source for supplying said reference signal to said transmitting local oscillator and to said receiving local oscillator;

wherein a frequency arrangement of said transmitting local oscillating frequency, frequency of signals existing within said transmitting circuit, said receiving local oscillating frequency and frequency of signals existing within said receiving circuit being set such that the frequencies of the signals existing within the transmitter-receiver avoid overlapping one another;

wherein said transmitting circuit comprises;

a transmitting intermediate amplifier for amplifying a transmitted signal input as having a transmitting intermediate frequency;

a transmitting mixer for providing an output by mixing an output from the transmitting intermediate amplifier and an output of said transmitting local oscillator to effect a frequency conversion thereof from the transmitting intermediate frequency to a predetermined transmitting frequency;

a transmitting band-pass filter for removing unnecessary wave components from the output of the transmitting mixer; and

a transmitting power amplifier for amplifying an output of the transmitting band-pass filter and delivering it to an antenna;

wherein said receiving local oscillator comprises;

a receiving first local oscillator for generating a receiving oscillation signal having a receiving first local oscillating frequency based on said reference signal; and

a receiving second local oscillator for generating a receiving oscillation signal having a receiving second local oscillating frequency based on said reference signal; and

wherein said receiving circuit comprises;

a low-noise amplifier for amplifying a received wave input from an antenna;

a receiving first band-pass filter for removing unnecessary wave components from an output of the low-noise amplifier;

a receiving first mixer for mixing an output of the receiving first band-pass filter and the output of said receiving first local oscillator to provide an output by converting the receiving frequency into a receiving first intermediate frequency;

a receiving first intermediate amplifier for amplifying the output of the receiving first mixer;

a receiving second band-pass filter for removing unnecessary wave components from an output of the receiving first intermediate amplifier; and

a receiving second mixer means for mixing an output of the receiving second band-pass filter and an output of said receiving second local oscillator to provide an output by converting the receiving first intermediate frequency into a receiving second intermediate frequency;

further comprising damping means for damping a leakage signal provided between said transmitting local oscillator and said receiving first and second local oscillators, wherein buffer means are provided as said damping means respectively between said reference signal oscillator and said transmitting local oscillator, between said reference signal oscillator and said receiving first local oscillator, and between said reference signal oscillator and said receiving second local oscillator.

2. The transmitter-receiver according to claim 1 wherein a buffer amplifier is used as said buffer means.

3. The transmitter-receiver according to claim 1 wherein an isolator is used as said buffer means.

4. The transmitter-receiver according to claim 2 wherein a quasi-synchronization detector circuit is used as said receiving second mixer means.

5. The transmitter receiver according to claim 2 wherein, while a transmitting local oscillator for outputting a transmitting oscillation signal to said transmitting mixer is provided as a transmitting second local oscillator, a transmitting first local oscillator having a transmitting local oscillating frequency different from the transmitting second local oscillator is provided as said transmitting local oscillator;

and further comprising an orthogonal converter receiving an output of the transmitting first local oscillator and a baseband signal for outputting a transmitted signal having a modulated intermediate frequency to said transmitting intermediate amplifier.

6. The transmitter-receiver according to claim 5 wherein a buffer amplifier is provided between said reference signal oscillator and said transmitting first local oscillator.

7. The transmitter receiver according to claim 5 wherein a quasi-synchronization detector circuit is used as said receiving second mixer means.