Electric power conversion systems – Frequency conversion without intermediate conversion to d.c.
Patent
1991-07-29
1993-06-22
Voeltz, Emanuel T.
Electric power conversion systems
Frequency conversion without intermediate conversion to d.c.
455326, 330262, 332117, 332141, H02M 500, H04B 126
Patent
active
052220168
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a frequency converter used for converting, e.g., an FM reception signal of an FM receiver into an intermediate-frequency signal.
BACKGROUND ART
Conventionally, a frequency converter used for converting, e.g., an FM reception signal of an FM receiver into an intermediate-frequency signal, is arranged as shown in FIGS. 1 to 3.
In a circuit in FIG. 1, reference numeral 31 denotes a frequency mixer for mixing an FM reception signal (high-frequency signal) and a local oscillation signal. The mixer 31 is formed in a bipolar integrated circuit, 30. Reference numeral 32 denotes an intermediate-frequency transformer for extracting an intermediate-frequency component of 10.7 MHz from an output of the frequency mixer 31. The transformer 32 is connected between a Vcc power source terminal 34 and a frequency mixing output terminal 35 outside the integrated circuit 35. Reference numeral 33 denotes a ceramic filter (center frequency is 10.7 MHz), for obtaining desired selectivity, connected to the secondary coil of the intermediate-frequency transformer 32.
The frequency mixer 31 comprises a first npn transistor Q11 the base of which receives an FM reception signal (high-frequency signal) input, a second npn transistor Q12 the base of which receives a DC bias potential, a resistor R connected between the emitters of the npn transistors Q11 and Q12, a first current source Ia connected between the emitter of the first npn transistor Q11 and a ground potential GND, a second current source Ib connected between the emitter of the npn transistor Q12 and the GND, a third npn transistor Q13 the collector-emitter path of which is connected between the Vcc power source terminal 34 and the first npn transistor Q11, a fourth npn transistor Q14 the collector-emitter path of which is connected between the Vcc power source terminal 34 and the second npn transistor Q12, a fifth npn transistor Q15 the emitter of which is connected to the emitter of the third npn transistor Q13, the base of which is connected to the base of the fourth npn transistor Q14, and the collector of which is connected to the frequency mixing output terminal 35, and a sixth npn transistor Q16 the emitter of which is connected to the emitter of the fourth npn transistor 14, the base of which is connected to the base of the third npn transistor Q13, and the collector of which is connected to the frequency mixing output terminal 35. Local oscillation signal inputs are applied between the bases of the third and fifth npn transistors Q13 and Q15 and between the bases of the sixth and fourth npn transistors 16 and 14.
In the circuit in FIG. 1, in order to match the secondary coil of the intermediate-frequency transformer 32 with the impedance of the ceramic filter 33, a turn ratio of the secondary coil to the primary coil of the intermediate-frequency transformer 32 must be decreased. Therefore, a large intermediate-frequency conversion gain is difficult to obtain.
On the other hand, in a circuit shown in FIG. 2, a frequency mixer 41, an impedance converting emitter follower 42 connected to the output of the frequency mixer 41, and a resistor 43 one terminal of which is connected to the output of the emitter follower 42 are arranged in a bipolar integrated circuit 40. Reference numeral 44 denotes a Vcc power source terminal; 45, a first frequency mixing output terminal connected to the output terminal of the frequency mixing circuit 41; and 46, a second frequency mixing output terminal connected to the other terminal of the resistor 43. Reference numeral 47 denotes an intermediate-frequency tuner consisting of an LC tuner for tuning an intermediate-frequency component of 10.7 MHz of the output from the frequency mixer 41. The tuner 47 is connected between the Vcc power source terminal 44 and the first frequency mixing output terminal 45 outside the integrated circuit 40. Reference numeral 48 denotes a ceramic filter, for obtaining desired selectivity, connected to the second frequency mixing output terminal 46 outside
REFERENCES:
patent: 4695940 (1987-09-01), Rein
patent: 4910801 (1990-03-01), Anzini et al.
Hashimoto Masaru
Matsumoto Susumu
Kabushiki Kaisha Toshiba
Voeltz Emanuel T.
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