Radio receiver with amplitude limiter prior to mixer and band limiting filter

• US 5,930,695 A
• Filed: 12/01/1995
• Issued: 07/27/1999
• Est. Priority Date: 12/05/1994
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nakagawa, Jun'ichi, Itukaiti, Fuminori, Yamaguchi, Tsutomu, Higuchi, Kazutoshi
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/566,113
• Time in Patent Office: 1,334 Days
• Field of Search: 455/232.1, 455/254, 455/308, 455/310, 455/311, 455/317, 455/210, 455/217, 455/309, 455/314, 455/296, 375/346
• US Class Current: 455/308
• CPC Class Codes: H03G 7/001 without controlling loop H03G7/007, H03G7/02, H03G7/06 take precedence
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16

Abstract

A radio receiver is disclosed. An arbitrary receive signal received through an antenna is amplified by an input amplifier. The signal amplified by the input amplifier is converted into a predetermined frequency by a mixer. The signal frequency-converted by the mixer is shaped in waveform by a band-limiting filter. The signal thus shaped in waveform is amplified and amplitude-limited by a limiting amplifier. The signal limited in amplitude is demodulated by a demodulator. In order to prevent the mixer circuit from generating a distortion due to an excessive input, another amplitude-limiting circuit operated at a level not saturating the mixer circuit is arranged in a stage before the mixer circuit.

Claims

1. A radio receiver comprising:

an antenna;

an input amplifier for amplifying an information input signal received through said antenna;

a mixer for converting said information input signal amplified by said input amplifier into a predetermined frequency;

a band-limiting filter for waveform-shaping said information input signal frequency-converted by said mixer;

a limiting amplifier for amplitude-limiting said information input signal shaped in a waveform by said band-limiting filter;

a demodulator for demodulating said information input signal amplitude-limited by said limiting amplifier; and

an information signal waveform clipper performing clipping of information components of said information input at a level where said mixer begins to be saturated, said clipper being provided in a preceding circuit to said mixer which requires preventative clipping to prevent saturation thereof.

2. A radio receiver according to claim 1, wherein said demodulator is of delayed detection type.

3. A radio receiver according to claim 2, wherein said information input signal is a digital modulation signal, and said band-limiting filter is a roll-off filter.

10. A radio receiver according to any of claims 1, 4 and 5, wherein said information signal waveform clipper is incorporated as part of said preceding circuit requiring preventative clipping to prevent saturation thereof.

11. A radio receiver according to claim 10, wherein said demodulator is of delayed detection type.

12. A radio receiver according to claim 11, wherein said information input signal is a digital modulation signal, and said band-limiting filter is a roll-off filter.

4. A radio receiver comprising:

an antenna;

an input amplifier for amplifying an information input signal received through said antenna;

a first mixer for converting said information input signal received by said input amplifier into a first frequency;

an intermediate frequency amplifier for amplifying said information input signal frequency-converted by said first mixer;

a second mixer for converting said information input signal amplified by said intermediate frequency amplifier into a second frequency;

a band-limiting filter for shaping a waveform of said information input signal frequency-converted by said second mixer;

an information signal waveform clipper in a form of clipping amplifier for amplitude-clipping information components of said information input signal shaped in waveform by said band-limiting filter; and

a demodulator for demodulating said information input signal amplitude clipped by said clipper;

wherein said intermediate frequency amplifier has a limiting function which carries out a linear amplification until said second mixer begins to be saturated so as not to output amplification output exceeding a level by which said second mixer is saturated.

5. A radio receiver according to claim 4, wherein another information signal waveform clipper is incorporated also in a preceding circuit to a second circuit which generates a distortion by saturation next to a first circuit.

6. A radio receiver according to claim 5, wherein said demodulator is of delayed detection type.

7. A radio receiver according to claim 6, wherein said information input signal is a digital modulation signal, and said band-limiting filter is a roll-off filter.

8. A radio receiver according to claim 4, wherein said demodulator is of delayed detection type.

9. A radio receiver according to claim 8, wherein said information input signal is a digital modulation signal, and said band-limiting filter is a roll-off filter.