Nec Corporation

Shinichi Ohmagari

Osamu Yamamoto

Masakazu Nishida

Yasunori Yoshizawa

The invention provides a radio station apparatus which converts a plurality of inputs digital transmission signals whose data transmission rates are different into an analog signal, modulates the analog signal with a radio carrier frequency and transmits the modulated signal, and a signal transmission method through radio station apparatus. The radio station apparatus of the present invention includes indoor unit 10, outdoor unit 20, and coaxial cable 60 which connects indoor unit 10 and outdoor unit 20 to each other. An inputted first binary digital signal is converted into a serial second binary digital signal by parallel/serial converter 2 and modulated by amplitude shift keying (ASK) into a third binary digital signal by modulator 13 with carrier f.sub.3 (Hz) whose frequency is a common multiple of respective value of n (sampling number).times.m (quantization bit number) times the data rate of all inputted data. The third binary digital signal is multiplexed by frequency division multiplexing with another signal or signals by multiplexer 3 and transferred to outdoor unit 20 through coaxial cable 60. In outdoor unit 20, transferred third binary digital signal is demultiplexed and converted into an analog signal by a D/A converter.

Radio station apparatus and signal transmission method thereof

It is an object of the present invention to provide a transmitter which is inexpensive and small in size and is reduced in power dissipation and besides wherein the output power of a power amplifier can be varied to an arbitrary value. A phase modulator, a variable attenuator, a high power amplifier, a directional coupler, a detector, an error amplifier, a switch and an analog multiplier form an envelope feedback loop. The envelope feedback loop controls an envelope of a modulated wave detected by the detector so that a base band signal and the envelope of the modulated wave may coincide with each other. The circuits mentioned above, a smoothing circuit, another error amplifier, another switch and an adder form an operation point feedback loop. The operation point feedback loop smoothes an error of an output envelope detection signal of the detector and controls so that the smoothed error may be in the minimum.

Transmitter having envelope feedback loop and automatic level control

A phase modulator for a microwave band having a desirable modulation characteristic by maintaining the impedance thereof constant, includes two PIN diodes 2 and 3 connected to a merchant balun 1 and a bias circuit 18 which supplies bias voltages to the PIN diodes 2 and 3 such that the sum of the bias voltages applied to the diodes 2 and 3 is constant. The bias voltages are selected so as to have the input and output impedances to be in the most stable state when a modulation signal is equal to zero.

Balanced phase modulator used in microwave band

A high-frequency choke circuit comprises a dielectric layer covered with grounding conductors, a lead line of high-impedance and at least one capacitance land formed within the dielectric layer, and at least one through-hole connecting the lead line and the capacitance land. The capacitance lands are disposed closer to the grounding conductors, resulting in large capacitances with small areas. The capacitance lands are formed on a layer distant from the layer on which the lead line is formed. Therefore, unnecessary electromagnetic coupling with other circuits formed on the same layer as the lead line can be reduced. The grounding conductors cover both surfaces of the dielectric layers that incorporate the capacitance lands and the lead line to thereby shield the circuit formed in the dielectric layers electromagnetically from outside.

High-frequency choke circuit

A transmitter using a dual conversion system which effects frequency conversion twice has a local oscillator (113) for generating a first local oscillation signal, a multiplier (118) for multiplying the frequency of the first local oscillation signal to produce a second local oscillation signal, a first mixer (115) for mixing the first local oscillation signal and first IF signal to produce a second IF signal, and a second mixer (120) for mixing the second local oscillation signal and second IF signal to produce a signal to be transmitted. A voltage controlled filter (116) whose center frequency varies with the frequency of the first local oscillation signal is connected to the output of the first mixer (115).

Dual conversion transmitter

A multi-phase PSK modulation apparatus includes a multi-phase PSK modulator and baseband signal modification circuitry which modifies the baseband signal in accordance with modulation frequencies to correct all or a portion of any offset error, amplitude error and orthogonality errors. The baseband signal modification circuitry permits error correction over a wide range of frequencies using a rather simple arrangement. In addition, spurious outputs, volume and cost of the apparatus are reduced.

Multi-phase PSK modulation apparatus

A time division communication system tends to develop noise responsive to variations of the output of the voltage supply which occur as the time slot signals switch on or off to thereby vary the load demand placed upon the power supply. The invention eliminates these voltage variations by providing a second and complementarily acting switch which applies a load across the power supply when the load of the time slot signals is removed. This way, the total load across the power supply remains generally unvarying.

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Tokyo, Japan

Shinichi Ohmagari