Transmitter/receiver apparatus

#The present invention relates to a transmitter/receiver apparatus having an application to microwave band communications such as satellite communication, and more particularly, to a miniature transmitter/receiver apparatus which is small enough to be installed in, for example, the feeder section of an antenna.

#While the tendency to apply satellite communication channels to commercial communications is increasing, a prerequisite for facilitating such an application is reducing the cost and size of a transmitter/receiver apparatus. For example, a miniature transmitter/receiver apparatus which can be incorporated in the feeder section of an antenna, which is about 2 meters in diameter, is desired.

#A transmitter/receiver apparatus which is applicable to commercial communications uses a microwave band, e.g., satellite communication. The transmit level is in the order of 1 watt. The receive level is more than 100 dB lower than the transmit level. Hence, it is very important with this type of transmitter/receiver apparatus to set up a sufficient isolation between discrete circuits in order to minimize interference from a transmit system to a receive system. However, for miniaturization and presupposing the overall dimensions of the apparatus housing, the freedom of circuit layout is so limited that a sufficient isolation between independent circuits is impractical.

#FIG. 1 is a block diagram of a transmitter/receiver apparatus embodying the present invention;

#FIG. 2 is a diagram showing a frequency distribution; and

#FIG. 3 is a side elevation showing the apparatus of FIG. 1 which is installed in the feeder section of an antenna, by way of example.

#Referring to FIG. 1 of the drawings, a transmitter/receiver apparatus in accordance with the present invention is shown and generally designated by the reference number 100. The apparatus 100 has a miniature box-like configuration and may be mounted in, for example, the feeder section of an outdoor antenna 1. Basically, the apparatus 100 comprises a local oscillator 2, a duplexer 3, a low noise amplifier 4, a receive frequency converter 5, a transmit frequency converter 6, a power amplifier 7, and a frequency multiplexer 8. The frequency multiplexer 8 is connected by a single signal cable, e.g., a coaxial cable 9, to a frequency multiplexer 10 of indoor main equipment 101. Connected to the frequency multiplexer 10 are a demodulator 11 and a modulator 12.

#The local oscillator 2 oscillates at a local oscillation frequency LO (FIG. 2) at a predetermined frequency position located between a transmit frequency band T and a receive frequency band R. The local oscillation frequency LO is fed to the transmit and receive frequency converters 6 and 5. More particularly, assuming that the transmit frequency T lies in a range of 14.0 to 14.5 GHz and the receive frequency R in a range of 11.7 to 12.2 GHz by way of example, the local oscillation frequency LO is preselected to be 12.7 GHz.

#A signal modulated by the modulator 12 has a frequency which lies in a transmit intermediate frequency band TIF and which is fed to the transmit frequency converter 6 via the frequency multiplexer 10 of the indoor equipment 101, the signal cable 9, and the frequency multiplexer 8. Responsive to the local oscillator frequency LO, the transmit frequency converter 6 converts the input signal having the frequency TIF into a signal which belongs to the transmit frequency band T. The transmit image frequency TIMG does not overlap the receive frequency band R. The signal with the frequency T is amplified by the power amplifier 7 and, then, radiated from the antenna 1 toward a satellite. In this particular embodiment, the transmit intermediate frequency band TIF ranges from 1.3 to 1.8 GHz while the transmit image frequency band TIMG ranges from 10.9 to 11.4 GHz.