WO2006135138A1 - Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof - Google Patents
Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof Download PDFInfo
- Publication number
- WO2006135138A1 WO2006135138A1 PCT/KR2005/004197 KR2005004197W WO2006135138A1 WO 2006135138 A1 WO2006135138 A1 WO 2006135138A1 KR 2005004197 W KR2005004197 W KR 2005004197W WO 2006135138 A1 WO2006135138 A1 WO 2006135138A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- frequency
- stereo
- block
- integrated circuit
- audio
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03C—MODULATION
- H03C3/00—Angle modulation
- H03C3/02—Details
- H03C3/09—Modifications of modulator for regulating the mean frequency
- H03C3/0908—Modifications of modulator for regulating the mean frequency using a phase locked loop
- H03C3/095—Modifications of modulator for regulating the mean frequency using a phase locked loop applying frequency modulation to the loop in front of the voltage controlled oscillator
Definitions
- the present invention relates to a method of designing and controlling a frequency modulated audio transmitter chip, and more particularly, to a frequency modulated audio transmitter integrated circuit using a complementary metal- oxide-semiconductor (CMOS) device, which is composed entirely of CMOS devices and improves a stereo multiplexing block to remarkably enhance the performance of the integrated circuit, and a method for controlling the same.
- CMOS complementary metal- oxide-semiconductor
- FM frequency modulation
- FIG. 1 is a block diagram of a conventional FM transmitter chip.
- the FM transmitter chip includes audio blocks 100 and 200 respectively consisting of pre-emphasis circuits 110 and 120 for continuously increasing high frequency signals included in audio signals L and R input through left and right channels, limiters 120 and 220 for making the left and right audio signals that have passed through the pre-emphasis circuits have uniform levels, and low pass filters LPF 130 and 230 for removing frequencies higher than the left and right audio signal frequencies, a stereo multiplexing block (MPX) 300 for modulating the left and right audio signals that have passed through the audio blocks 100 and 200 with a 38KHz pilot signal, an oscillator block 400 including an oscillator 410 for generating a reference frequency, a crystal element connected to the oscillator and a plurality of frequency dividers 420, 430 and 440 for reducing the reference frequency by integer times to generate a clock frequency required for stereo multiplexing and a frequency required for a phase frequency detector, a PLL frequency synthesizer block 500 having
- a stereo signal is transmitted using the same method as that the conventional FM sky-wave broadcasting adopts.
- a signal corresponding to the sum L+R of left and right input audio signals and a signal corresponding to the difference L-R between the two audio signals are generated first, a 19kHZ stereo pilot tone is generated, and then a 38kHz carrier signal having the same phase as that of the 19kHz stereo pilot tone is generated to amplitude-modulate the signal L-R.
- 19kHZ pilot tone are mixed, frequency-modulated and then transmitted.
- a receiver detects the stereo signal input thereto based on the 19kHz pilot tone and stereo-demodulates the input signal into the original left and right signals using the signal L+R and L-R.
- the stereo multiplexing block 300 of FIG. 1 One of the important factors determining the quality of the stereo audio signal in the audio transmitter chip is the stereo multiplexing block 300 of FIG. 1.
- the level of a noise component included in a composite signal generated by the stereo multiplexing block is determined according to the waveform of a 38kHZ chopper clock signal used for multiplexing. That is, a harmonic noise component does not exist in a frequency domain when the waveform of the chopper clock signal is an ideal sine wave (referring to FIG. 2) .
- the harmonic component increases as the waveform of the chopper clock signal is deviated from the sine wave and generates a noise signal due to intermodulation while passing through a nonlinear system.
- a stereo multiplexing method adopted by the conventional audio transmitter chip uses two-state sampling.
- the stereo multiplexing method respectively samples a right input signal R and a left input signal L once for one cycle of a chopper clock signal using the chopper clock signal as shown in FIG. 3.
- the chopper clock signal has a square waveform and includes countless harmonic signals in a frequency domain as shown in FIG. 4.
- a noise component is increased due to intermodulation caused by harmonic components in a stereo modulated composite signal to result in deterioration in the quality of an audio signal.
- the deterioration of multiplexing audio signal directly affects the quality of an audio signal output through speakers of cars and home audio systems using the audio transmitter chip, and thus the audio transmitter chip cannot fully perform the function thereof.
- a band pass filter is used in addition to the audio transmitter chip to remove harmonic components caused by a square wave to prevent deterioration of audio quality.
- the aforementioned conventional audio transmitter chip constructs its component circuits other than the frequency synthesizer using a bipolar device technique.
- a bipolar semiconductor device can easily construct an oscillator circuit required for a crystal oscillator and an FM oscillator because it has a high gain.
- the bipolar semiconductor device requires a large area to increase the chip size of an audio transmitter integrated circuit using the bipolar semiconductor device. This raises manufacturing cost and makes utilization of a compact package difficult. That is, the audio transmitter integrated circuit occupies a large area on an internal circuit board of a small portable terminal using the audio transmitter chip to restrict miniaturization of the entire module.
- the conventional stereo multiplexing method respectively samples left and right input signals L and R once for one cycle of a 38kHZ square wave signal.
- a composite signal generated by the stereo multiplexing block includes lots of harmonic noise components and intermodulated noise components caused by the harmonic components because the square wave is different from the ideal sine wave.
- the number of sampling the left and right signals can be increased.
- this solution cannot be actually used because the chopper frequency is increased more than 38kHZ.
- the present invention has been made to solve the aforementioned problem in that audio signals are deteriorated in the conventional frequency modulated radio audio transmitter chip, and it is an object of the present invention to implement a stereo modulation block of a wireless audio transmitter chip in an 8 -state weighted stereo multiplexing structure for high quality audio transmission to improve low noise characteristic and enhance stereo audio signal quality, and reduce the number of external devices such as a band pass filter.
- Another object of the present invention is to provide a frequency modulated audio transmitter integrated circuit using
- CMOS devices which is composed entirely of CMOS devices to reduce power consumed to operate the audio transmitter chip and the chip size, and a method for controlling the same.
- a frequency- modulated audio transmitter integrated circuit using a CMOS device which includes audio blocks for receiving audio signals, a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency-modulating a mixed signal, and a stereo multiplexing block carrying out multi-state stereo multiplexing on the audio signal in at least 3 states .
- the stereo multiplexing block modulates a frequency using 8-state weighted stereo modulation in the multi-state stereo multiplexing.
- the stereo multiplexing block is constructed such that it has 8 states, and the oscillating frequency of a crystal oscillator of the stereo multiplexing block is 21.25MHz or 21.28MHz.
- the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices .
- a method for controlling a frequency modulated audio transmitter integrated circuit including audio blocks for receiving audio signals, a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency-modulating a mixed signal, and a stereo multiplexing block carrying out multi- state stereo multiplexing on the audio signal, in which the stereo multiplexing block performs multi-state stereo multiplexing on the audio signal in at least 3 states.
- FIG. 1 is a block diagram of a conventional frequency modulated audio transmitter chip
- FIG. 2 illustrates the spectrum of a general sine wave
- FIG. 3 illustrates a general square-wave chopper clock
- FIG. 4 illustrates the spectrum of a general square wave signal
- FIG. 5 is a block diagram of a frequency modulated audio transmitter integrated circuit using a CMOS device according to 8-state weighted stereo multiplexing of the present invention
- FIG. 6 is a waveform diagram showing a clock signal for driving an 8-state weighted stereo multiplexing switch
- FIG. 7 illustrates an 8-state weighted stereo multiplexing block according to the present invention
- FIG. 8 is a conceptual view of a switch block for 8-state weighted stereo multiplexing according to the present invention
- FIG. 9 is a graph showing comparison of a sine wave with a digital sine wave
- FIG. 10 is a graph showing the results of simulations of 2 -state weighted stereo multiplexing and 8-state weighted stereo multiplexing
- FIG. 11 is a graph showing comparison of 2-state weighted stereo multiplexing spectrum and 8-state weighted stereo multiplexing spectrum.
- FIG. 5 is a block diagram of a frequency modulated audio transmitter integrated circuit using a CMOS device according to 8 -state weighted stereo multiplexing of the present invention
- FIG. 6 is a waveform diagram showing a clock signal for driving an 8-state weighted stereo multiplexing switch
- FIG. 7 illustrates an 8 -state weighted stereo multiplexing block according to the present invention
- FIG. 8 is a conceptual view of a switch block for 8 -state weighted stereo multiplexing according to the present invention
- FIG. 9 is a graph showing comparison of a sine wave with a digital sine wave.
- FIG. 10 is a graph showing the results of simulations of 2 -state weighted stereo multiplexing and 8 -state weighted stereo multiplexing
- FIG. 11 is a graph showing comparison of 2 -state weighted stereo multiplexing spectrum and 8 -state weighted stereo multiplexing spectrum.
- the frequency modulated audio transmitter integrated circuit includes audio blocks 100 and 200 for receiving audio signals, a frequency oscillator block 400 and a frequency synthesizer block 500 for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block 600 for frequency-modulating a mixed signal, and a stereo multiplexing block 700 for multi-state-stereo-multiplexing the audio signals in at least three state.
- the stereo multiplexing block 700 modulates a frequency using 8 -state weighted stereo modulation in the multi-state stereo modulation and uses 21.25MHz or 21.28MHz as the oscillating frequency of a crystal oscillator thereof.
- the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices .
- a signal corresponding to the sum L+R of left and right input audio signals and a signal corresponding to the difference L-R between the two audio signals are generated first, a 19kHZ stereo pilot tone is generated, and then a
- 38kHz carrier signal having the same phase as that of the 19kHz stereo pilot tone is generated to amplitude-modulate the signal L-R.
- the signal L-R When the signal L-R is amplitude-modulated, two L-R signals which respectively belong to frequency bands corresponding to upper 15kHz and lower ISkHZ from 38kHz, that is, 53hkHZ and 23kHZ, and are opposite to each other are generated.
- the amplitude-modulated signal L-R, signal L+R, 19kHZ pilot tone are mixed, frequency-modulated and then transmitted.
- a receiver detects the stereo signal input thereto based on the 19kHz pilot tone and stereo-demodulates the input signal into the original left and right signals using the signal L+R and L-R.
- one of the important components determining the quality of the stereo audio signal in the audio transmitter chip is the stereo multiplexing block 700 of FIG. 5 in the present invention.
- the level of a noise component included in a composite signal generated by the stereo multiplexing block is determined according to the waveform of a chopper clock signal used for multiplexing.
- the present invention obtains a digital sine wave having a high frequency of 608KHz as a fundamental frequency (referring to FIG. 6) , which is similar to a sine wave, using an 8 -state weighted sampling method in stereo multiplexing of the audio transmitter chip to minimize noise components due to harmonic waves caused by multiplexing and remarkably improve the quality of transmitted audio signals. Accordingly, the quality of sounds reproduced through car and home audio systems can be optimized.
- the 8 -state weighted stereo multiplexing is a method of generating digital sine wave by dividing a half cycle of the frequency of a sine wave by 8 states.
- FIG. 7 shows an 8-state weighted stereo multiplexing block according to the present invention and
- FIG. 8 shows a switch block composed of a series of switches and resistors. Seven switches respectively corresponding to upper and lower input signals are operated to carry out the 8 -state weighted stereo multiplexing.
- resistances RO to R6 required for the 8 -state stereo multiplexing are determined, values of a minimum output to the maximum output through the respective resistances are calculated according to appropriate operations of the switches and an 8-state weighted sum is obtained based on the calculated values.
- FIG. 10 shows the result of a computer simulation of 8- state weighted stereo multiplexing.
- 2-state stereo multiplexing used in a conventional audio transmitter chip is compared to 8 -state stereo multiplexing used in the audio transmitter chip according to the present invention.
- the digital sine wave generated by the 8-state stereo multiplexing according to the present invention approximates to a sine wave. That is, the 8 -state stereo multiplexing according to the present invention can be an optimized stereo multiplexing method capable of improving the quality of reproduced signals after transmission while preserving the input original signals. Results of computer simulations with respect to harmonic components and noise components can be confirmed in FIG. 11.
- the 8 -state stereo multiplexing requires a 608kHz multiplexing clock signal.
- Crystal oscillators having oscillating frequencies of 21.28MHz and 21.25MHz are used in consideration of setting of a comparison frequency of a frequency synthesizer.
- the multi-state weighted stereo multiplexing circuit in addition to other component blocks of the audio transmitter chip of the present invention are constructed using a CMOS device process technique.
- the present invention can employ a multi-state stereo multiplexing circuit for stereo multiplexing of a frequency modulated audio transmitter chip to minimize a noise component that may be included in a transmitted signal, thereby improving the quality of reproduced audio signals compared to conventional techniques.
- an FM audio transmitter chip including a stereo multiplexing block is designed and manufactured using a CMOS device technique, and thus power consumed for operating the chip can be reduced less than 50% of the conventional audio transmitter chip using a semiconductor device technique and the chip size can be decreased to half the size of the conventional chip having the same performance. This can enhance price competitiveness.
- the manufacturing cost of an audio transmitter module can be reduced by using a crystal oscillator having an oscillating frequency of 21.25MHz generally used in a 900MHz home wireless telephone. Accordingly, the frequency modulated audio transmitter chip according to the present invention can remarkably reduce battery power because of its low consumption power and small chip size and be effectively built in a portable multimedia terminal having a dense internal package
Abstract
Provided are a frequency modulated audio transmitter integrated circuit using a CMOS device and a method for controlling the same. The frequency modulated audio transmitter integrated circuit includes audio blocks for receiving audio signals, a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency- modulating a mixed signal, and a stereo multiplexing block carrying out multi- state stereo multiplexing on the audio signal in at least 3 states. A stereo multiplexing method and a process technique applied to the audio transmitter integrated circuit are proposed. A multi-state weighted stereo multiplexing method is applied to the stereo multiplexing block of the audio transmitter integrated circuit to minimize harmonic noise components caused by multiplexing and remarkably improve the quality of transmitted audio signals. The audio transmitter integrated circuit is manufactured using a CMOS device technique to realize a small chip having low power consumption. The audio transmitter chip can be effected used in various portable terminals having batteries .
Description
Frequency modulated audio transmitter circuit using full-CMOS and fabrication method thereof
Technical Field The present invention relates to a method of designing and controlling a frequency modulated audio transmitter chip, and more particularly, to a frequency modulated audio transmitter integrated circuit using a complementary metal- oxide-semiconductor (CMOS) device, which is composed entirely of CMOS devices and improves a stereo multiplexing block to remarkably enhance the performance of the integrated circuit, and a method for controlling the same.
Background Art Music played by various multimedia terminals such as MP3 players, MP3 phones, portable CD players, personal computers and notebook computers can be radio-transmitted to FM radios of cars or FM tuners of home audio systems using frequencies
(70MHz to 120MHz) generally used in frequency modulation (FM) broadcasting such that users can hear the music through speakers of the cars or home audio systems .
FIG. 1 is a block diagram of a conventional FM transmitter chip. The FM transmitter chip includes audio
blocks 100 and 200 respectively consisting of pre-emphasis circuits 110 and 120 for continuously increasing high frequency signals included in audio signals L and R input through left and right channels, limiters 120 and 220 for making the left and right audio signals that have passed through the pre-emphasis circuits have uniform levels, and low pass filters LPF 130 and 230 for removing frequencies higher than the left and right audio signal frequencies, a stereo multiplexing block (MPX) 300 for modulating the left and right audio signals that have passed through the audio blocks 100 and 200 with a 38KHz pilot signal, an oscillator block 400 including an oscillator 410 for generating a reference frequency, a crystal element connected to the oscillator and a plurality of frequency dividers 420, 430 and 440 for reducing the reference frequency by integer times to generate a clock frequency required for stereo multiplexing and a frequency required for a phase frequency detector, a PLL frequency synthesizer block 500 having a phase frequency detector 520 for controlling the frequency and phase of a signal, which is generated by an RF oscillator 610 and passes through a frequency divider 510, to be identical to those of a reference signal and a loop filter 530, and an FM frequency modulation block 600 having the RF oscillator 610 and an RF amplifier 620 for amplifying a frequency modulated signal to a predetermined
level .
A stereo signal is transmitted using the same method as that the conventional FM sky-wave broadcasting adopts. To generate and transmit the stereo signal, a signal corresponding to the sum L+R of left and right input audio signals and a signal corresponding to the difference L-R between the two audio signals are generated first, a 19kHZ stereo pilot tone is generated, and then a 38kHz carrier signal having the same phase as that of the 19kHz stereo pilot tone is generated to amplitude-modulate the signal L-R.
When the signal L-R is amplitude-modulated, two L-R signals which respectively belong to frequency bands corresponding to upper 15kHz and lower 15kHZ from 38kHz, that is, 53hkHZ and 23kHZ, and are opposite to each other are generated. The amplitude-modulated signal L-R, signal L+R,
19kHZ pilot tone are mixed, frequency-modulated and then transmitted. A receiver detects the stereo signal input thereto based on the 19kHz pilot tone and stereo-demodulates the input signal into the original left and right signals using the signal L+R and L-R.
One of the important factors determining the quality of the stereo audio signal in the audio transmitter chip is the stereo multiplexing block 300 of FIG. 1. The level of a noise component included in a composite signal generated by the
stereo multiplexing block is determined according to the waveform of a 38kHZ chopper clock signal used for multiplexing. That is, a harmonic noise component does not exist in a frequency domain when the waveform of the chopper clock signal is an ideal sine wave (referring to FIG. 2) . The harmonic component increases as the waveform of the chopper clock signal is deviated from the sine wave and generates a noise signal due to intermodulation while passing through a nonlinear system. A stereo multiplexing method adopted by the conventional audio transmitter chip uses two-state sampling. That is, the stereo multiplexing method respectively samples a right input signal R and a left input signal L once for one cycle of a chopper clock signal using the chopper clock signal as shown in FIG. 3. In this case, the chopper clock signal has a square waveform and includes countless harmonic signals in a frequency domain as shown in FIG. 4.
That is, a noise component is increased due to intermodulation caused by harmonic components in a stereo modulated composite signal to result in deterioration in the quality of an audio signal. The deterioration of multiplexing audio signal directly affects the quality of an audio signal output through speakers of cars and home audio systems using the audio transmitter chip, and thus the audio transmitter
chip cannot fully perform the function thereof. To solve this problem, a band pass filter is used in addition to the audio transmitter chip to remove harmonic components caused by a square wave to prevent deterioration of audio quality. However, the aforementioned conventional audio transmitter chip constructs its component circuits other than the frequency synthesizer using a bipolar device technique. A bipolar semiconductor device can easily construct an oscillator circuit required for a crystal oscillator and an FM oscillator because it has a high gain. However, the bipolar semiconductor device requires a large area to increase the chip size of an audio transmitter integrated circuit using the bipolar semiconductor device. This raises manufacturing cost and makes utilization of a compact package difficult. That is, the audio transmitter integrated circuit occupies a large area on an internal circuit board of a small portable terminal using the audio transmitter chip to restrict miniaturization of the entire module.
Furthermore, the conventional stereo multiplexing method respectively samples left and right input signals L and R once for one cycle of a 38kHZ square wave signal. In this case, a composite signal generated by the stereo multiplexing block includes lots of harmonic noise components and intermodulated noise components caused by the harmonic components because the
square wave is different from the ideal sine wave. To solve this problem, the number of sampling the left and right signals can be increased. However, this solution cannot be actually used because the chopper frequency is increased more than 38kHZ.
Disclosure of Invention Technical problem
Accordingly, The present invention has been made to solve the aforementioned problem in that audio signals are deteriorated in the conventional frequency modulated radio audio transmitter chip, and it is an object of the present invention to implement a stereo modulation block of a wireless audio transmitter chip in an 8 -state weighted stereo multiplexing structure for high quality audio transmission to improve low noise characteristic and enhance stereo audio signal quality, and reduce the number of external devices such as a band pass filter.
Another object of the present invention is to provide a frequency modulated audio transmitter integrated circuit using
CMOS devices, which is composed entirely of CMOS devices to reduce power consumed to operate the audio transmitter chip and the chip size, and a method for controlling the same.
Technical Solution
To accomplish the above objects, according to an aspect of the present invention, there is provided a frequency- modulated audio transmitter integrated circuit using a CMOS device, which includes audio blocks for receiving audio signals, a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency-modulating a mixed signal, and a stereo multiplexing block carrying out multi-state stereo multiplexing on the audio signal in at least 3 states .
The stereo multiplexing block modulates a frequency using 8-state weighted stereo modulation in the multi-state stereo multiplexing. The stereo multiplexing block is constructed such that it has 8 states, and the oscillating frequency of a crystal oscillator of the stereo multiplexing block is 21.25MHz or 21.28MHz.
Preferably, the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices .
According to another aspect of the present invention, there is provided a method for controlling a frequency modulated audio transmitter integrated circuit including audio blocks for receiving audio signals, a frequency oscillator
block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency-modulating a mixed signal, and a stereo multiplexing block carrying out multi- state stereo multiplexing on the audio signal, in which the stereo multiplexing block performs multi-state stereo multiplexing on the audio signal in at least 3 states.
Brief Description of the Drawings
Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a block diagram of a conventional frequency modulated audio transmitter chip;
FIG. 2 illustrates the spectrum of a general sine wave;
FIG. 3 illustrates a general square-wave chopper clock
signal;
FIG. 4 illustrates the spectrum of a general square wave signal;
FIG. 5 is a block diagram of a frequency modulated audio transmitter integrated circuit using a CMOS device according to 8-state weighted stereo multiplexing of the present invention;
FIG. 6 is a waveform diagram showing a clock signal for driving an 8-state weighted stereo multiplexing switch;
FIG. 7 illustrates an 8-state weighted stereo multiplexing block according to the present invention; FIG. 8 is a conceptual view of a switch block for 8-state weighted stereo multiplexing according to the present invention;
FIG. 9 is a graph showing comparison of a sine wave with a digital sine wave; FIG. 10 is a graph showing the results of simulations of 2 -state weighted stereo multiplexing and 8-state weighted stereo multiplexing; and
FIG. 11 is a graph showing comparison of 2-state weighted stereo multiplexing spectrum and 8-state weighted stereo multiplexing spectrum.
Best Mode for Carrying Out the Invention
The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings. For reference, like reference characters designate corresponding parts throughout several views .
FIG. 5 is a block diagram of a frequency modulated audio transmitter integrated circuit using a CMOS device according
to 8 -state weighted stereo multiplexing of the present invention, FIG. 6 is a waveform diagram showing a clock signal for driving an 8-state weighted stereo multiplexing switch, and FIG. 7 illustrates an 8 -state weighted stereo multiplexing block according to the present invention. FIG. 8 is a conceptual view of a switch block for 8 -state weighted stereo multiplexing according to the present invention, and FIG. 9 is a graph showing comparison of a sine wave with a digital sine wave. FIG. 10 is a graph showing the results of simulations of 2 -state weighted stereo multiplexing and 8 -state weighted stereo multiplexing, and FIG. 11 is a graph showing comparison of 2 -state weighted stereo multiplexing spectrum and 8 -state weighted stereo multiplexing spectrum.
Referring to FIG. 5, the frequency modulated audio transmitter integrated circuit according to the present invention includes audio blocks 100 and 200 for receiving audio signals, a frequency oscillator block 400 and a frequency synthesizer block 500 for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block 600 for frequency-modulating a mixed signal, and a stereo multiplexing block 700 for multi-state-stereo-multiplexing the audio signals in at least three state.
Preferably, the stereo multiplexing block 700 modulates a
frequency using 8 -state weighted stereo modulation in the multi-state stereo modulation and uses 21.25MHz or 21.28MHz as the oscillating frequency of a crystal oscillator thereof.
Preferably, the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices .
The operation of the frequency modulated audio transmitter integrated circuit according to the present invention will now be explained in detail.
As described above, to generate and transmit the stereo signal, a signal corresponding to the sum L+R of left and right input audio signals and a signal corresponding to the difference L-R between the two audio signals are generated first, a 19kHZ stereo pilot tone is generated, and then a
38kHz carrier signal having the same phase as that of the 19kHz stereo pilot tone is generated to amplitude-modulate the signal L-R.
When the signal L-R is amplitude-modulated, two L-R signals which respectively belong to frequency bands corresponding to upper 15kHz and lower ISkHZ from 38kHz, that is, 53hkHZ and 23kHZ, and are opposite to each other are generated. The amplitude-modulated signal L-R, signal L+R, 19kHZ pilot tone are mixed, frequency-modulated and then transmitted. A receiver detects the stereo signal input thereto based on the 19kHz pilot tone and stereo-demodulates
the input signal into the original left and right signals using the signal L+R and L-R.
Here, one of the important components determining the quality of the stereo audio signal in the audio transmitter chip is the stereo multiplexing block 700 of FIG. 5 in the present invention. The level of a noise component included in a composite signal generated by the stereo multiplexing block is determined according to the waveform of a chopper clock signal used for multiplexing. The present invention obtains a digital sine wave having a high frequency of 608KHz as a fundamental frequency (referring to FIG. 6) , which is similar to a sine wave, using an 8 -state weighted sampling method in stereo multiplexing of the audio transmitter chip to minimize noise components due to harmonic waves caused by multiplexing and remarkably improve the quality of transmitted audio signals. Accordingly, the quality of sounds reproduced through car and home audio systems can be optimized.
The 8 -state weighted stereo multiplexing is a method of generating digital sine wave by dividing a half cycle of the frequency of a sine wave by 8 states. FIG. 7 shows an 8-state weighted stereo multiplexing block according to the present invention and FIG. 8 shows a switch block composed of a series of switches and resistors.
Seven switches respectively corresponding to upper and lower input signals are operated to carry out the 8 -state weighted stereo multiplexing. When resistances RO to R6 required for the 8 -state stereo multiplexing are determined, values of a minimum output to the maximum output through the respective resistances are calculated according to appropriate operations of the switches and an 8-state weighted sum is obtained based on the calculated values.
When the weighted sum of output values in response to switch circuit resistances is compared to a weighted sum of sine values obtained when a half cycle of a sine wave is divided by 8, the output values obtained by the operation of the switches and the weighted sum of the output values are very similar to values calculated at corresponding angles of the sine wave. It can be confirmed from FIG. 9 that the digital sine wave generated based on the 8-state weighted sum approximates to the sine wave.
FIG. 10 shows the result of a computer simulation of 8- state weighted stereo multiplexing. In FIG. 10, 2-state stereo multiplexing used in a conventional audio transmitter chip is compared to 8 -state stereo multiplexing used in the audio transmitter chip according to the present invention. Referring to FIG. 10, the digital sine wave generated by the 8-state stereo multiplexing according to the present invention
approximates to a sine wave. That is, the 8 -state stereo multiplexing according to the present invention can be an optimized stereo multiplexing method capable of improving the quality of reproduced signals after transmission while preserving the input original signals. Results of computer simulations with respect to harmonic components and noise components can be confirmed in FIG. 11.
The 8 -state stereo multiplexing requires a 608kHz multiplexing clock signal. Crystal oscillators having oscillating frequencies of 21.28MHz and 21.25MHz are used in consideration of setting of a comparison frequency of a frequency synthesizer.
The multi-state weighted stereo multiplexing circuit in addition to other component blocks of the audio transmitter chip of the present invention are constructed using a CMOS device process technique.
Industrial Applicability
As described above, the present invention can employ a multi-state stereo multiplexing circuit for stereo multiplexing of a frequency modulated audio transmitter chip to minimize a noise component that may be included in a transmitted signal, thereby improving the quality of reproduced audio signals compared to conventional techniques.
Furthermore, an FM audio transmitter chip including a stereo multiplexing block is designed and manufactured using a CMOS device technique, and thus power consumed for operating the chip can be reduced less than 50% of the conventional audio transmitter chip using a semiconductor device technique and the chip size can be decreased to half the size of the conventional chip having the same performance. This can enhance price competitiveness.
Moreover, the manufacturing cost of an audio transmitter module can be reduced by using a crystal oscillator having an oscillating frequency of 21.25MHz generally used in a 900MHz home wireless telephone. Accordingly, the frequency modulated audio transmitter chip according to the present invention can remarkably reduce battery power because of its low consumption power and small chip size and be effectively built in a portable multimedia terminal having a dense internal package
structure .
While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.
Claims
1. A frequency modulated audio transmitter integrated circuit using a CMOS device, comprising: audio blocks for receiving audio signals,- a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal; an FM modulation block for frequency-modulating a mixed signal; and a stereo multiplexing block carrying out multi-state stereo multiplexing on the audio signal in at least 3 states.
2. The frequency modulated audio transmitter integrated circuit as claimed in claim 1, wherein the stereo multiplexing block modulates a frequency using 8 -state weighted stereo modulation in the multi-state stereo multiplexing.
3. The frequency modulated audio transmitter integrated circuit as claimed in claim 1 or 2, wherein the stereo multiplexing block is constructed such that it has 8 states, and the oscillating frequency of a crystal oscillator of the stereo multiplexing block is 21.25MHz or 21.28MHz.
4. The frequency modulated audio transmitter integrated circuit as claimed in claim 3, wherein the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices.
5. A method for controlling a frequency modulated audio transmitter integrated circuit including audio blocks for receiving audio signals, a frequency oscillator block and a frequency synthesizer block for generating and determining a frequency required for stereo modulation and generation of an FM carrier signal, an FM modulation block for frequency- modulating a mixed signal, and a stereo multiplexing block carrying out multi-state stereo multiplexing on the audio signal, wherein the stereo multiplexing block performs multi- state stereo multiplexing on the audio signal in at least 3 states.
6. The method for controlling a frequency modulated audio transmitter integrated circuit as claimed in claim 5, wherein the stereo multiplexing block modulates a frequency using 8-state weighted stereo modulation in the multi-state stereo multiplexing.
7. The method for controlling a frequency modulated audio transmitter integrated circuit as claimed in claim 5 or 6, wherein the stereo multiplexing block is constructed such that it has 8 states, and the oscillating frequency of a crystal oscillator of the stereo multiplexing block is 21.25MHz or 21.28MHz.
8. The method for controlling a frequency modulated audio transmitter integrated circuit as claimed in claim 7, wherein the frequency modulated audio transmitter integrated circuit is composed entirely of CMOS devices .
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR20050050291 | 2005-06-13 | ||
| KR10-2005-0050291 | 2005-06-13 | ||
| KR10-2005-0110495 | 2005-11-18 | ||
| KR1020050110495A KR100599903B1 (en) | 2005-06-13 | 2005-11-18 | Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2006135138A1 true WO2006135138A1 (en) | 2006-12-21 |
Family
ID=37532469
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/KR2005/004197 WO2006135138A1 (en) | 2005-06-13 | 2005-12-08 | Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO2006135138A1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0418862A2 (en) * | 1989-09-19 | 1991-03-27 | Sanyo Electric Co., Ltd. | Frequency modulation circuit using VCO |
| KR19990024517A (en) * | 1997-09-03 | 1999-04-06 | 정선종 | Digital FM Stereo Synthesis Signal Generator |
| KR20030042088A (en) * | 2001-11-21 | 2003-05-28 | 삼성전기주식회사 | Direct conversion type tuner for fabricating by cmos |
| JP2003318732A (en) * | 2002-04-26 | 2003-11-07 | Hitachi Ltd | Semiconductor integrated circuit for communication, and radio communication system |
-
2005
- 2005-12-08 WO PCT/KR2005/004197 patent/WO2006135138A1/en active Application Filing
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0418862A2 (en) * | 1989-09-19 | 1991-03-27 | Sanyo Electric Co., Ltd. | Frequency modulation circuit using VCO |
| KR19990024517A (en) * | 1997-09-03 | 1999-04-06 | 정선종 | Digital FM Stereo Synthesis Signal Generator |
| KR20030042088A (en) * | 2001-11-21 | 2003-05-28 | 삼성전기주식회사 | Direct conversion type tuner for fabricating by cmos |
| JP2003318732A (en) * | 2002-04-26 | 2003-11-07 | Hitachi Ltd | Semiconductor integrated circuit for communication, and radio communication system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN1047898C (en) | Frequency synthesizer | |
| CN1774868B (en) | Tuner for radio frequency receivers and associated method | |
| CN1993893B (en) | Integrated low-if terrestrial audio broadcast receiver and associated method | |
| CN102405600B (en) | Jammer detection based adaptive PLL bandwidth adjustment in FM receiver | |
| JP2000196376A (en) | Dual mode grade d amplifier | |
| CN104620510A (en) | Transmitter | |
| Kuhn | Design of integrated, low power, radio receivers in BiCMOS technologies | |
| US9077511B2 (en) | Phase interpolator | |
| KR20040099283A (en) | Method and Apparatus for Down Conversion of Radio Frequency(RF) Signals | |
| WO2007099631A1 (en) | Fm transmitter | |
| CN201813364U (en) | Ship platform deck frequency modulation interphone circuit | |
| US20080285761A1 (en) | Filter circuit | |
| CN101237287A (en) | Number modulator and number modulating method | |
| WO2012093424A1 (en) | Delta-sigma modulating fractional-n pll frequency synthesizer and wireless communication device equipped with same | |
| WO2006135138A1 (en) | Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof | |
| US8260218B2 (en) | Mixer circuit and RF transmitter using such mixer circuit | |
| KR100599903B1 (en) | Frequency modulated audio transmitter circuit using full-cmos and fabrication method thereof | |
| AU712092B2 (en) | Spurious signal reduction in RF transmitter integrated circuits | |
| JP2008219860A (en) | Fm transmitter and electronic device using same | |
| US20080192875A1 (en) | Analog/digital circuit | |
| US20070195961A1 (en) | FM transmitter | |
| US7496419B2 (en) | Modulation output device | |
| JP4389358B2 (en) | High frequency communication equipment | |
| JP4892466B2 (en) | Analog digital circuit | |
| KR20050088491A (en) | Multi-mode modulator and transmitter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
| NENP | Non-entry into the national phase |
Ref country code: DE |
|
| 122 | Ep: pct application non-entry in european phase |
Ref document number: 05821330 Country of ref document: EP Kind code of ref document: A1 |