TH23326A - Combined AM and FM stereo receivers - Google Patents

Abstract

An improved combined AM and FM stereo receiver (100) is provided with a single processor (155) for eliminating arctangent distortion in FM and for processing the phase values from the arctangent (formula) in AM to determine (formula). In addition, the radio contains a single discriminator circuit (161, 137, 139), in which in FM the discriminator tank circuit (137, 139) is used to convert the frequency deviations into the fundamental band noise, and in AM the discriminator tank circuit is used as the frequency determination component for the voltage-controlled frequency generator (VCO) (101). The VCO circuit is used to convert the center frequency signal into the fundamental band.

Claims (10)

1. Radio (100) for receiving FM stereo signals in FM mode using a modulation basis of frequency deviation and for receiving AM stereo signals in AM mode using a modulation basis of phase deviation and has a single discriminator circuit with a frequency generator circuit (101) and a FM stereo circuit path for detecting phase deviation signals, an FM stereo circuit path for detecting frequency deviation and a tank circuit (137, 139) with the first tuned frequency for FM and the second tuned frequency for AM, in FM mode the discriminator circuit is arranged to convert the modulation frequency deviation to the fundamental band frequency and in AM mode the discriminator circuit is arranged to convert the zero frequency of the modulation phase deviation from the center frequency (IF) to zero (0) as the frequency determination element for the frequency generator circuit. A frequency generator circuit is used to convert the IF signal into the fundamental band. 2. The radio of claim 1, whose discriminator tank circuit (137, 139) contains instruments (133, 135) for switching between the AM stereo circuit path and the FM circuit path. 3. The radio of claim 2, in the AM version, the frequency that is tuned to the second frequency of the tank circuit is processed by a divider circuit (163) to obtain a different conversion frequency, which is half a multiple of the frequency of the tank circuit. 4. The radio of claim 2, whose tank circuits (137, 139) are said to consist of a ceramic resonant element with a naturally occurring inductive component (L) (137) and a naturally occurring capacitive component (C) (139). 5. Radio under claim 4, in AM format, the second tuning frequency is typically 10.8 MHz, and in FM format, the primary tuning frequency is typically 10.7 MHz. 10.8 MHz is a multiple of the standard 450 kHz AM center frequency (AM IF), and 10.7 MHz is the FM center frequency (FM IF). 6. The radio of claim 5, in which the switch (133) is positioned to connect the special capacitor (151) in series with the tank circuits (137, 139) in FM mode. 7. Radio of claim 6 in which the special capacitor (151) is used as a 90 degree phase shifter for the FM discriminator circuit. 8. The radio of claim 2, whose tank circuit (137, 139) is said to consist of an inductor coil (L) (137) and a capacitor (C) (139). 9. Radio under Policy 8, in AM format, the second tuning frequency is typically 10.8 MHz, and in FM format, the primary tuning frequency is typically 10.7 MHz. 10.8 MHz is a multiple of the standard 450 kHz AM center frequency, and 10.7 MHz is the FM center frequency. 10. The radio of claim 9 in which the switch (133) is positioned to connect the special capacitor (151) in series with the tank circuit (137, 139) in FM mode (Clause 10, page 2, figure 6).