Multi-band tuner with fixed broadband input filters

• US 4,132,952 A
• Filed: 01/31/1978
• Issued: 01/02/1979
• Est. Priority Date: 11/11/1975
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Niimura, Tsutomu, Kawakami, Hiromi, Hongu, Masayuki
• Primary Examiner(s): Richardson, Robert L.
• Assistant Examiner(s): Ng, Jin F.
• Application Number:
  US05/873,963
• Time in Patent Office: 336 Days
• Field of Search: 325/308, 325/344, 325/388, 325/427, 325/435-439, 325/453, 325/458, 325/459, 325/461, 325/489, 325/473, 325/477, 358/160, 358/167
• US Class Current: 455/188.1
• CPC Class Codes: H03D 7/00 Transference of modulation from one carrier to another, e.g. frequency-changing H03D9/00, H03D11/00 take precedence; dielectric amplifiers, magnetic amplifiers, parametric amplifiers used as a frequency-changers H03F
• CPC Class Codes: H03D 7/18 Modifications of frequency-changers for eliminating image frequencies H03D7/16 takes precedence
• CPC Class Codes: H03J 5/244 using electronic means
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/006 using switches for selecting the desired band H04B1/0057 takes precedence
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04N 5/44 Receiver circuitry for the reception of television signals according to analogue transmission standards H04N5/14 takes precedence

Abstract

A tuner for receiving signals broadcast on two spaced bands, each divided into several channels, has two fixed bandpass filters, one to pass all of the channels in the lower frequency band and the other to pass all of the channels in the higher frequency band. The tuner includes a mixer to which signals of either band are supplied by selective operation of a double-throw switch. A tunable local oscillator supplies a heterodyning signal to the mixer to convert any selected channel of the received signal to an intermediate frequency (i.f.) band chosen to avoid image interference from undesired channels, whether the local oscillator frequency is above or below the selected channel. To ease the constraints on the choice of the i.f. band, different i.f. filters tuned to first and second i.f. bands may be used for the higher and lower received bands. A second double-throw switch ganged with the first switch can then be used to direct the heterodyned signals to the proper i.f. filter.

Claims

1. A tuner for receiving a selected channel of a group of channels divided into a lower band comprising a plurality of lower band channels and a higher band comprising a plurality of higher band channels, said tuner comprising:

first filter means having a fixed pass band tuned to pass said lower band;

second filter means having a fixed pass band tuned to pass said higher band;

switching means connected to said first and second filter means to provide a signal path through a selective one of said first and second filter means;

a mixer connected to said signal path to receive the output signal thereof;

a local oscillator connected to said mixer to supply thereto a frequency-converting signal to convert the frequency of said selected channel to an intermediate frequency band having a lowest frequency f_L determined by the following conditions when the frequency of the frequency-converting signal is higher than the highest frequency of a selected channel;

##EQU18## and one of the following;

##EQU19## and one of the following;

##EQU20## and the lowest frequency f_L in the intermediate frequency band is determined by the following conditions when the frequency of the frequency-converting signal is lower than the lowest frequency of a selected channel;

space="preserve" listing-type="equation">f.sub.L >

f.sub.S - f.sub.B - f.sub.P

and

space="preserve" listing-type="equation">f.sub.L <

f.sub.T - f.sub.S

and

space="preserve" listing-type="equation">f.sub.L >

f.sub.W - f.sub.B - f.sub.T

and one of the following;

##EQU21## and one of the following;

##EQU22## where;

f_B is the bandwidth of each channel,

f_P is the lower frequency in the lower band,

f_S is the higher frequency in the lowest band,

f_T is the lowest frequency in the highest band, and

f_W is the highest frequency in the higher band.

2. A tuner as claimed in claim 1 comprising high frequency amplifier means connected in cascade between said first and second filter means and said mixer.

3. A tuner as claimed in claim 2 in which said switching means is connected to output terminals of each of said first and second filter means and comprises an output terminal connected to said high frequency amplifier means to supply to said amplifier means, selectively, either lower band signals that pass through said first filter means or higher band signals that pass through said second filter means.

4. A tuner as claimed in claim 1 further comprising two intermediate frequency filters connected in parallel to the output of said mixer.

5. A tuner as claimed in claim 4 comprising a second switch means changeably connected to output sides of said two intermediate frequency filters.

6. A tuner as claimed in claim 1 in which said first filter has a pass band with a lowest frequency of about 54MHz and a highest frequency of about 88MHz, and said second filter has a pass band with a lowest frequency of about 174MHz and a highest frequency of about 216MHz, and f_L is greater than 88MHz.

7. A tuner as claimed in claim 6 comprising an intermediate frequency band filter connected to said mixer and having a pass band not substantially greater in width than f_B and having an upper pass band frequency less than 108MHz.