FSK or FM burst signal generating apparatus

Claim 2

A burst signal generating apparatus comprising: a modulator circuit for modulating a carrier wave of an intermediate frequency with a modulating signal; a frequency converter circuit for converting the output frequency of said modulator circuit into a radio frequency; an amplitude control unit responsive to a burst control signal for controlling the amplitude of the carrier wave of said radio frequency; and means responsive to said burst control signal for switching the carrier wave of said intermediate frequency.

Claim 3

A burst signal generating apparatus, as claimed in Claim 1, wherein said switching means is connected to the output side of said modulator circuit.

Claim 4

A burst signal generating apparatus, as claimed in Claim 1 or 2, wherein said amplitude control circuit comprises a power amplifier circuit for power-amplifying the carrier wave of said radio frequency; an envelope detector circuit for branching the output of said power amplifier circuit and detecting the amplitude thereof; a comparator circuit for amplitude-comparing said burst control signal and the output of said envelope detector circuit to provide the resultant error signal; and a circuit responsive to said error signal for controlling the amplitude of the carrier wavetof said radio frequency.

Claim 5

A burst signal generating apparatus, as claimed in Claim 3, further comprising an envelope generator circuit for smoothening the leading and trailing edges of said burst control signal to be supplied to said comparator circuit.

Claim 6

A burst signal generating apparatus, as claimed in Claim 4, wherein said envelope generator circuit comprises a pulse generator circuit for generating pulses having a prescribed-width after the trailing edge of siad burst control signal; a differentiating circuit for differentiating the output of said pulse generator circuit; an integrating circuit for integrating said burst control signal in one direction; a variable reactance circuit responsive to the output voltage of said differentiating circuit for varying the resistance and thereby controlling the discharge time of the output of said integrating circuit; and a filter circuit connected between the output of said integrating circuit and the input of said variable reactance circuit for low-pass filtering the integrated output to generate the filtered output as the output of said envelope generator circuit.

Claim 7

,A burst signal generating apparatus, as claimed in Claim 5, wherein said integrating circuit comprises a resistor receiving said burst control signal at one end; a diode whose anode is connected to the other end of said resistor; and a capacitor of which one end is connected to the cathode of said diode and the other is grounded, the connecting point between said cathode and said capacitor being made the output end of said integrating circuit.

Claim 8

A burst signal generating apparatus, as claimed in Claim 5 or 6, wherein said variable reactance circuit comprises a field-effect transistor having a gate receiving the output of said differentiating circuit, a drain receiving said integrated output and a source connected to one end of a first resistor; and a second resistor connected between said drain and source.

Claim 9

A burst signal generating apparatus, as claimed in Claim 4, wherein said envelope generator circuit comprises a buffer amplifier receiving said burst control signal; a switching circuit having a first diode conductive in the direction of the output of said buffer amplifier and a second diode conductive in the direction reverse to the output of said buffer amplifier, one end each of those diodes being connected to the output end of said buffer amplifier; a constant current circuit connected to the other end of said first diode; a variable reactance circuit of which one end is connected to the other end of said second diode; a capacitor of which one end is connected to the output connecting point between the output end of said constant current circuit and the other end of said variable reactance circuit and the other end is grounded; and a filter circuit coupled to said cutput connecting point for low-pass filtering the input signal to generate the filtered output as the output of said envelope generator circuit.

Claim 10

A burst signal generating apparatus, as claimed in Claim 8, wherein said variable reactance circuit comprises first and second resistors each of which one end is connected to the other end of said second diode; a third resistor of which one end is connected to the other end of said second resistor and the other is grounded; and a field-effect transistor of which the source is connected to the other end of said first resistor, the cate is connected to the connecting point between said second and third resistors and the drain is connected to said output connecting point.

Claim 11

A burst signal generating apparatus, as claimed in any of Claims 1 to 9, wherein said modulator circuit includes a frequency modulator circuit.

Claim 12

A burst signal generating method comprising the following steps: smoothening the leading and trailing edges of a burst control signal; modulating a carrier wave of an intermediate frequency with a modulating signal; switching the modulated carrier wave of said intermediate frequency in response to said burst control signal; converting the modulated carrier of said intermediate frequency which has been switched into a carrier wave of a radio frequency; amplitude-controlling the carrier wave of said radio frequency in response to a smoothened burst control signal; and power amplifying the amplitude-controlled output.

Claim 13

A burst signal generating method comprising the following steps: smoothening the leading and trailing edges of a burst control signal; modulating a carrier wave of an intermediate frequency with a modulating signal; switching the modulated carrier wave of said intermediate frequency in response to said burst control signal; converting the modulated carrier of said intermediate frequency which has been switched into a carrier wave of a radio frequency; amplitude-controlling the carrier wave of said radio frequency in response to a smoothened burst control signal; and power amplifying the amplitude-controlled output.

Claim 14

A burst signal generating method, as claimed in Claim 11, wherein said amplitude-controlling step comprises the following steps: detecting the power-amplified output; comparing said burst control signal and the detected output to generate an error signal; and amplitude-controlling said carrier wave of the radio frequency in accordance with said error signal.

Claim 15

A burst signal generating method, as claimed in Claim 1 1 or 12, wherein said smoothening step comprises the following steps: integrating said burst control signal in one direction; generating pulses having a prescribed width after the trailing edge of said burst control signal; differentiating said pulses; and discharging with a prescribed time constant the charge integrated in one direction in response to the differentiated pulse voltage.

Claim 16

A burst signal generating method, as claimed in Claim 11 or 12, wherein said smoothening step comprises the following steps: responsive to said burst control signal, charging a capacitor at a constant amperage; discharging it with a prescribed time constant; and low-pass filtering the charged or discharged voltage of said capacitor.

Claim 17

A burst signal generating method, as claimed in any of Claims 11 to 14, wherein the modulating steps is frequency modulation.