Frequency converter

Claim 2

A frequency converter comprising: an input terminal for receiving a broadcast signal with a first frequency; a first variable gain amplifier for amplifying said broadcast signal applied from said input terminal comprising a first transistor connected in a grounded emitter configuration and a second transistor connected in a grounded base configuration; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers an AGC signal which is obtained from a signal output from said second variable gain amplifier wherein said AGC signal serves to simultaneously adjust the gain of said first variable gain amplifier by a first amount for a given value of said AGC signal and adjust the gain of said second variable gain amplifier by a second amount, greater than said first amount, for said given value of said AGC signal.

Claim 3

A frequency converter according to claim 1, further comprising: a second local oscillator for generating a second local oscillation signal; and a second frequency mixer circuit for converting said second frequency of said signal applied from said second variable gain amplifier to a third frequency using said second local oscillation signal output from said second local oscillator.

Claim 4

A frequency converter according to claim 2, wherein the frequency of said oscillation signal of said first local oscillator is variable and the frequency of said second oscillation signal of said second local oscillator is fixed.

Claim 5

A frequency converter according to claim 3, wherein said first frequency mixer circuit converts said first frequency which is to said second frequency higher than said first frequency and said second frequency mixer circuit converts said second frequency which is to said third frequency lower than said second frequency.

Claim 6

A frequency converter according to claim 1, wherein said second variable gain amplifier carries out a gain reduction greater than said first variable gain amplifier in response to said AGC signal.

Claim 7

A frequency converter according to claim 1, wherein said grounded-emitter configuration amplifier is provided with a diode in an emitter impedance circuit of said first transistor and wherein said AGC signal is applied to said diode.

Claim 8

A frequency converter according to claim 6, wherein said diode is a PIN diode.

Claim 9

A frequency converter according to claim 7, wherein said second variable gain amplifier is comprised of an FET and said AGC signal is applied to a second gate of said FET.

Claim 10

A frequency converter comprising: an input terminal for receiving a broadcast signal with a first frequency; a first variable gain amplifier for amplifying said broadcast signal applied from said input terminal; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers an AGC signal which is obtained from a signal output from said second variable gain amplifier, wherein said AGC signal serves to simultaneously adjust the gain of said first variable gain amplifier by a first amount for a given value of said AGC signal and adjust the gain of said second variable gain amplifier by a second amount, greater than said first amount, for said given value of said AGC signal.

Claim 11

A frequency converter comprising: an input terminal for receiving a broadcast signal with a first frequency; a first variable gain amplifier for amplifying said broadcast signal applied from said input terminal; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers an AGC signal which is obtained from a signal output from said second variable gain amplifier, wherein said AGC signal serves to simultaneously adjust the gain of said first variable gain amplifier by a first amount for a given value of said AGC signal and adjust the gain of said second variable gain amplifier by a second amount, greater than said first amount, for said given value of said AGC signal.

Claim 12

A frequency converter of claim 9 wherein said first variable gain amplifier comprises: first and second transistors each with a base, an emitter and a collector; a variable impedance connected to receive said AGC signal, wherein the value of said variable impedance is controlled by said AGC signal; said emitter of said first transistor being connected to said variable impedance; said base of said first transistor being connected to receive said broadcast signal; said collector of said first transistor being connected to the emitter of said second transistor; said base of said second transistor being connected to a ground potential; and said collector of said second transistor being connected to said frequency mixer circuit, wherein the gain imparted by said first variable gain amplifier to said broadcast signal is controlled by the value of said variable impedance.

Claim 13

The frequency converter of claim 10 wherein said variable impedance is a PIN diode.

Claim 14

A gain control circuit which receives an input signal and an AGC signal and produces an output signal comprising: first and second transistors each with a base, an emitter and a collector; a variable impedance connected to receive said AGC signal, wherein the value of said variable impedance is controlled by said AGC signal; said emitter of said first transistor being connected to said variable impedance; said base of said first transistor being connected to receive said input signal; said collector of said first transistor being connected to the emitter of said second transistor; said base of said second transistor being connected to a ground potential; and said collector of said second transistor providing said output signal, wherein the gain imparted by said gain control circuit to said input signal is controlled by the value of said variable impedance.

Claim 15

A gain control circuit which receives an input signal and an AGC signal and produces an output signal comprising: first and second transistors each with a base, an emitter and a collector; a variable impedance connected to receive said AGC signal, wherein the value of said variable impedance is controlled by said AGC signal; said emitter of said first transistor being connected to said variable impedance; said base of said first transistor being connected to receive said input signal; said collector of said first transistor being connected to the emitter of said second transistor; said base of said second transistor being connected to a ground potential; and said collector of said second transistor providing said output signal, wherein the gain imparted by said gain control circuit to said input signal is controlled by the value of said variable impedance.

Claim 16

The gain control circuit of claim 12 wherein said variable impedance is a PIN diode.

Claim 17

A frequency converter comprising: an input terminal for receiving a broadcast signal with the first frequency; a first variable amplifier gain for amplifying said broadcast signal applied from said input terminal; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers an AGC signal which is obtained from a signal output from said second variable gain amplifier, wherein said first variable gain amplifier comprises: first and second transistors each with a base, an emitter and a collector, a variable impedance connected to receive said AGC signal, wherein the value of said variable impedance is controlled by said AGC signal, said emitter of said first transistor being connected to said variable impedance, said base of said transistor being connected to receive said broadcast signal, said collector of said first transistor being connected to the emitter of second transistor, the base of said second transistor being connected to a ground potential, and the collector of said second transistor being connected to said local oscillator.

Claim 18

A frequency converter comprising: an input terminal for receiving a broadcast signal with the first frequency; a first variable amplifier gain for amplifying said broadcast signal applied from said input terminal; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers an AGC signal which is obtained from a signal output from said second variable gain amplifier, wherein said first variable gain amplifier comprises: first and second transistors each with a base, an emitter and a collector, a variable impedance connected to receive said AGC signal, wherein the value of said variable impedance is controlled by said AGC signal, said emitter of said first transistor being connected to said variable impedance, said base of said transistor being connected to receive said broadcast signal, said collector of said first transistor being connected to the emitter of second transistor, the base of said second transistor being connected to a ground potential, and the collector of said second transistor being connected to said local oscillator.

Claim 19

The frequency converter of claim 14 wherein said the variable impedance is a PIN diode.

Claim 20

A frequency converter comprising: an input terminal for receiving a broadcast signal with a first frequency; a first variable gain amplifier for amplifying said broadcast signal applied from said input terminal comprising a first transistor connected in a grounded emitter configuration and a second transistor connected in a grounded base configuration; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers a same AGC signal which is obtained from a signal output from said second variable gain amplifier wherein said same AGC signal serves to simultaneously adjust the gain of said first variable gain amplifier by a first amount for a given value of said AGC signal and adjust the gain of said second variable gain amplifier by a second amount, greater than said first amount, for said given value of said AGC signal.

Claim 21

A frequency converter comprising: an input terminal for receiving a broadcast signal with a first frequency; a first variable gain amplifier for amplifying said broadcast signal applied from said input terminal comprising a first transistor connected in a grounded emitter configuration and a second transistor connected in a grounded base configuration; a local oscillator for generating a local oscillation signal; a frequency mixer circuit for converting said first frequency of said broadcast signal applied from said first variable gain amplifier to a second frequency using said local oscillation signal output from said local oscillator; a second variable gain amplifier for amplifying a signal with said second frequency applied from said frequency mixer circuit; and an AGC circuit means for feeding back to said first and second variable gain amplifiers a same AGC signal which is obtained from a signal output from said second variable gain amplifier wherein said same AGC signal serves to simultaneously adjust the gain of said first variable gain amplifier by a first amount for a given value of said AGC signal and adjust the gain of said second variable gain amplifier by a second amount, greater than said first amount, for said given value of said AGC signal.