Abstract: A structure for reducing intermodulation interference in satellite signal transmission includes receiving antennas for receiving satellite polarized signals, an RF amplifying system for amplifying and down-converting the received signals, first and second mixers and a first-stage common local oscillator for executing a frequency subtraction, mid-frequency amplifiers and low-pass filters for amplifying and filtering signals output from the first and second mixers to generate a mid-band, a third mixer and a second-stage local oscillator for executing a frequency addition, a band-pass filter for filtering and isolating the resultant signal, and a fourth mixer and a third-stage local oscillator for executing another frequency subtraction, a high-pass filter for filtering the resultant signal to generate another non-repeated optimal mid-band, and a multiplex adder for combining the two mid-bands.

Abstract: A structure for preventing intermodulation interference in satellite transmission is characterized in that a frequency subtraction is executed at a first mixer and a local oscillator on one of the received satellite vertical and horizontal polarized signals to obtain a first mid-band, while a frequency subtraction is executed at a second mixer and a first-stage local oscillator on the other received signal to obtain a reverse-phase signal thereof, and a frequency addition is executed at a third mixer and a second-stage local oscillator on the reverse-phase signal to obtain a second mid-band, and that second and third harmonic differences between a frequency obtained by subtracting the oscillating frequency of the second-stage local oscillator from the oscillating frequency of the first-stage local oscillator and the oscillating frequency of the local oscillators do not fall in the first and the second mid-bands, respectively, and an intermodulation interference is prevented.

Abstract: A side-mounting waveguide including a satellite down converter and a receiving horn antenna connected to the satellite down converter is characterized in that a circuit board of the satellite down converter is located at one side of the receiving horn antenna such that a transverse plane of the circuit board is in parallel with a direction in which the receiving horn antenna extends, and that a plastic rod is plugged into an opening of the receiving horn antenna to provide enhanced wave converging ability. With the side-mounting waveguide, the spacing between two adjacent satellite down converters and accordingly two adjacent receiving horn antennas is effectively reduced to correspond to the reduced angle contained between two satellites.

Abstract: A method of using a bipolar junction transistor as a local oscillator in a satellite down converter to eliminate second and third harmonic interference between two local oscillators mainly includes serial connection of a mixer between a low-noise amplifier and an intermediate frequency amplifier in the satellite down converter, and serial connection of a bipolar junction transistor (BJT) to the mixer, so that the satellite down converter may have reduced phase noise and reduced power consumption, and that second and third harmonic interference at the same frequency range is eliminated.

Abstract: A multiplexer using a ceramic filter as stacked satellite down converter is operative to reduce useless wave ranges in a wave frequency and to largely reduce external interferences with frequency ranges. The multiplexer is implemented by serially connecting a low-noise amplifier, a mixer, and an IF amplifier between a receiver and an output port of a satellite down converter, and the multiplexer is characterized in that a ceramic filter is serially connected between the IF amplifier and themixer. The ceramic filter has characteristics that enable reduction of useless wave ranges in a wave frequency and largely reduced external interference with frequency ranges.

Abstract: A method of effectuating frequency switching by using two self-oscillating frequency reducers having a common input includes the use of a three-way coupler to connect two field effect transistors (or two bipolar junction field effect transistors) and two dielectric resonator oscillators between a low-noise amplifier and an intermediate frequency (IF) amplifier, so as to effectuate switching between different frequency ranges. Thus, a simplified switch circuit for switching frequencies is possible to enable reduced manufacturing cost and reduced volume of device.

Abstract: A waveguide is provided on a circuit board thereof with two printed probes that are perpendicular to and spaced from each other by a predetermined distance to receive electric waves guided into the waveguide in two different directions. The two probes are separately located in two rectangular patterns that are provided outside a round pattern. The two rectangular patterns are separately located at a lower or an upper side and to a lateral side of the round pattern and both have a feed opening provided at an edge adjacent to the round pattern. Thus, it is possible to obtain a good cross-polarization isolation between the two probes for them to more effectively receive electric waves without interfering with each other.