JPH09153835A - Receiver and sampling method for reception signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive receiver through the use of an AD converter and a demodulation computing element by lowering a sampling frequency to be used in the AD converter. SOLUTION: The reception signal is detected in a detection circuit 2 from an FM radio broadcasting signal received in a tuning circuit 1 and a base band signal is outputted. The FM analog signal to be demodulated is filtered from the base band signal through a low pass filter 3. The FM analog signal to be demodulated is sampled with a sampling signal in the AD converter 4 and is AD-converted into a digital signal. The AD-converted digital signal is demodulated in the demodulation computing element 5 and the AD converter is sampled by the sampling signal of a frequency lower than the FM analog signal. Thus, the returned signal of the analog signal, which is generated in an AD conversion, is sampled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for receiving and demodulating analog radio broadcasts, and more particularly to a receiver for AD converting the received and tuned analog signal for demodulation processing.

[0002] Conventionally, as receivers for receiving and demodulating radio broadcasts, there are AM broadcast receivers and FM broadcast receivers due to the way of modulation, and monaural broadcast receivers and stereo broadcast receivers due to the way of sounding. There are various types such as an analog receiver and a digital receiver depending on how the received signal is processed. The AD conversion method according to the present invention is applicable to both AM broadcast receivers and FM broadcast receivers, and is also applicable to both monaural broadcast receivers and stereo broadcast receivers.

Conventionally, there have been radio receivers of this type as shown in FIGS. 9 and 10. FIG. 9 shows an example of an FM stereo broadcast receiver as an example of this type of radio broadcast receiver, which receives an FM stereo broadcast and performs reception processing such as tuning, detection and demodulation.
FIG. 10 is a block diagram of a stereo broadcast receiver, and FIG. 10 is a graph showing the relationship between the frequency of the detection circuit and the frequency of the sampling signal applied in the AD converter of the FM stereo broadcast receiver shown in FIG.

In FIG. 9, reference numeral 21 is a tuning circuit which tunes to a desired frequency (broadcasting station) to select a channel, 22 is an FM detection circuit which detects a necessary frequency band from a main carrier and converts it into a baseband signal, and 23. Is a low-pass filter that passes the low-frequency component of the detection output, 24 is an AD converter that samples the analog signal of the low-pass filter and converts it to a digital signal, and 25 demodulates the digital signal from the AD converter 24. And a left channel output and a right channel output (monaural output when a monaural signal is received).

Next, the operation of the conventional receiver will be described in detail with reference to FIGS. 9 and 10. First, the FM stereo signal selected by the tuning circuit 21 is input to the FM detection circuit 22 and converted into a baseband signal in a required frequency band. The baseband signal is input to the low pass filter 23 and filtered in the band of 57 KHz or less. The output of the low-pass filter 23 is sampled by the AD converter 24 at a frequency of 114 KHz or higher, and then demodulated by the demodulation arithmetic unit 25.

In this conventional example, in order to prevent aliasing noise caused by aliased signals generated during AD conversion, sampling for sampling the baseband signal to be demodulated input to the AD converter is performed. Signal frequency (hereinafter also referred to as sampling frequency)
As shown in FIG. 10, fs uses a sampling frequency that is at least twice the frequency of the signal output from the FM detection circuit 22 to be demodulated. As described above, even in the conventional receiver described above, the modulated signal can be extracted by sufficiently demodulating the received signal.

[0007]

However, in the above-mentioned conventional receiver, the characteristics of the low-pass filter are set in order to prevent aliasing noise generated due to the aliased signal generated during AD conversion. It was necessary to set the sampling frequency fs to 1/2 or less (FIG. 10).

However, the voice band of FM stereo broadcasting is 5
Since it is distributed up to 7 KHz or less, the sampling frequency for AD conversion must be at least 114 KHz or higher. Therefore, such an AD converter for FM stereo broadcasting needs to have a higher speed than an AD converter for audio, and in addition, a demodulation arithmetic unit with high processing capability that operates at high speed. Therefore, there is a problem that the receiver becomes expensive.

The present invention has been made to solve the above-mentioned conventional problems, and uses a low frequency AD converter and a demodulation arithmetic unit by using a low frequency for sampling in the AD converter. The first object is to provide an inexpensive receiver.

The present invention has been made in order to solve the above-mentioned conventional problems. By reducing the amount of calculation required for demodulation and using a demodulating arithmetic unit having a low processing capacity, an inexpensive receiver can be obtained. The second purpose is to provide.

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to reduce the arithmetic means (program) necessary for demodulation and reduce the capacity of the program storage memory associated with the demodulation arithmetic unit. The third object is to provide an inexpensive receiver.

[0012]

A receiver according to the present invention comprises:
The received signal is detected from the radio broadcast signal received by the tuning circuit, a baseband signal is output, the analog signal to be demodulated from the baseband signal is filtered through a low-pass filter, and a sampling signal is generated to demodulate. The analog signal to be sampled is AD-converted into a digital signal by the AD converter, the AD-converted digital signal is demodulated in the demodulation arithmetic unit, and the AD converter uses the sampling signal having a frequency lower than that of the subcarrier of the analog signal. , The folded signal of the analog signal generated at the time of AD conversion is sampled.

According to the present invention, an inexpensive receiver can be obtained by using a low frequency AD converter and a demodulation arithmetic unit by using a low frequency for sampling in the AD converter.

In the receiver according to the present invention, the analog signal to be detected and demodulated from the radio broadcast signal received by the tuning circuit is filtered by the first band pass filter and is filtered by the second band pass filter. Only the carrier wave is filtered from the detected signal and output to the phase synchronization circuit,
When the carrier wave from the second bandpass filter has a predetermined phase, the phase synchronization circuit outputs a sampling execution command to the AD converter, and the AD converter outputs from the first bandpass filter according to the sampling execution command. The AM analog signal is sampled and AD-converted into a digital signal, the digital signal from the AD converter is demodulated by the demodulation arithmetic unit, and the AD converter is subjected to the sampling execution instruction from the phase synchronization circuit at the time of AD conversion. It is configured to sample a signal obtained by folding the generated analog signal.

According to the present invention, by reducing the calculation means (program) required for demodulation and reducing the capacity of the program storage memory associated with the demodulation calculation device,
An inexpensive receiver is obtained.

In the receiver according to the present invention, the phase synchronization circuit outputs a sampling execution command to the AD converter when the phase of the carrier wave from the second bandpass filter becomes 90 degrees or 270 degrees, and AD The converter is configured to sample the folded signal of the AM analog signal generated at the time of AD conversion according to the sampling execution instruction.

According to the present invention, an inexpensive receiver can be obtained by reducing the amount of calculation required for demodulation and using a demodulation arithmetic unit having a low processing capacity.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a tuning circuit for receiving an FM radio broadcast signal and an FM detection circuit for detecting an FM signal input from the tuning circuit and outputting a baseband signal. A low-pass filter for filtering an FM analog signal to be demodulated from the baseband signal, a sampling signal, and the FM analog signal from the low-pass filter is sampled by the sampling signal to be converted into a digital signal. An AD converter,
A demodulation arithmetic unit for demodulating a digital signal from the AD converter, wherein the AD converter generates a signal at the time of AD conversion by a sampling signal having a frequency lower than a subcarrier of an FM analog signal in the low frequency band. The signal obtained by folding back the FM analog signal is sampled, and the FM stereo signal can be demodulated without using a high-speed AD converter and a demodulation arithmetic unit.

According to a second aspect of the present invention, the frequency of the sampling signal is 4 / (4) with respect to the frequency of the carrier of the FM analog signal filtered by the low pass filter.
Since the frequency is n + 1) times (n is an arbitrary natural number), it is not necessary to calculate a complicated trigonometric function at the time of demodulation, and the calculation in demodulation is simplified, so the calculation necessary for demodulation is performed. It is possible to reduce the amount, and it is possible to demodulate the FM stereo signal using the demodulation arithmetic unit having low processing capability.

According to a third aspect of the present invention, a tuning circuit for receiving an FM radio broadcast signal, an FM detection circuit for detecting an FM multiplex signal input from the tuning circuit and outputting a baseband signal, and a base A bandpass filter for filtering an FM multiplex analog signal to be demodulated from a band signal, and an AD converter for generating a sampling signal and sampling the FM multiplex analog signal from the bandpass filter with the sampling signal to convert it into a digital signal And a demodulation arithmetic unit for demodulating the digital signal from the AD converter, wherein the AD converter uses a sampling signal having a frequency lower than that of the subcarrier of the FM multiplex analog signal passed through the band pass filter.
A signal obtained by folding back the FM multiplex analog signal generated at the time of D conversion is sampled, and the FM multiplex signal can be demodulated without using a high-speed AD converter and a demodulation arithmetic unit. It has the effect of being able to.

According to a fourth aspect of the present invention, a tuning circuit for receiving and detecting an AM radio broadcast signal and a first band for filtering a carrier wave containing an AM analog signal to be demodulated from the detected signal. A pass filter, a second band pass filter for filtering only the carrier wave from the detected signal, and a sampling execution instruction to the AD converter when the carrier wave from the second band pass filter has a predetermined phase. From the AD converter for sampling the AM analog signal filtered by the first band-pass filter according to a sampling execution command from the phase synchronization circuit and converting it into a digital signal. Demodulation arithmetic unit for demodulating the digital signal of A line command is used to sample a folded signal of the AM analog signal generated at the time of AD conversion, and it is possible to unify the arithmetic operation or arithmetic expression at the time of demodulation in the demodulation arithmetic unit. This has the effect that the capacity of the program storage memory associated with the demodulation arithmetic unit can be reduced as compared with the above method.

According to a fifth aspect of the present invention, the phase synchronization circuit executes sampling for the AD converter when the phase of the carrier wave from the second band pass filter becomes 90 degrees or 270 degrees. The AD converter outputs a command, and the AD converter samples the folded signal of the AM analog signal generated during the AD conversion by the sampling execution command, and does not require level adjustment processing in demodulation. Therefore, the amount of calculation required for demodulation can be reduced, and an AM stereo signal can be sufficiently demodulated even if a demodulation calculation device having low processing capability is used.

According to a sixth aspect of the present invention, a tuning circuit for receiving an FM radio broadcast signal, an FM detection circuit for detecting the received FM signal and outputting a baseband signal, and the detected base. A low-pass filter for filtering an FM analog signal to be demodulated from a band signal,
A bandpass filter for filtering the FM pilot signal from the detected baseband signal, a phase synchronization circuit for outputting a sampling execution command to the AD converter when the FM pilot signal has a predetermined phase, and the low-pass filter. The FM analog signal filtered by the filter is sampled by the sampling execution instruction and converted into a digital signal A
It comprises a D converter and a demodulation arithmetic unit for demodulating the digital signal from the AD converter, and in the AD converter, the FM generated at the time of AD conversion by a sampling execution command from the phase synchronization circuit. It is designed to sample a folded analog signal, and it is possible to unify the arithmetic operations or arithmetic expressions at the time of demodulation in the demodulation arithmetic unit, and to store the program that accompanies the demodulation arithmetic unit as compared to the conventional system. It has an effect that the capacity of the memory can be reduced.

According to a seventh aspect of the present invention, in the phase lock circuit, when the phase of the FM pilot signal from the band pass filter becomes 90 degrees or 270 degrees, A
A sampling execution instruction is output to the D converter, and the A
The D converter samples the folded signal of the FM analog signal generated at the time of AD conversion according to the sampling execution instruction, and does not require level adjustment processing in demodulation and therefore is required for demodulation. This has an effect that the amount of calculation can be reduced and an FM stereo signal can be sufficiently demodulated even if a demodulation calculation device with low processing capability is used.

According to an eighth aspect of the present invention, an FM radio broadcast signal is received and detected, a baseband signal is output, an FM analog signal to be demodulated is extracted from the baseband signal, and the extraction is performed. The FM analog signal is sampled and AD-converted into a digital signal, and the AD-converted digital signal is demodulated. The sampling step is performed by using a sampling signal having a frequency lower than a subcarrier of the FM analog signal. A signal obtained by folding the FM analog signal generated at the time of AD conversion is sampled.
The FM stereo signal can be demodulated without using the D converter and the demodulation arithmetic unit.

According to a ninth aspect of the present invention, a carrier including an AM analog signal to be detected and demodulated by receiving an AM radio broadcast signal is extracted, and only the carrier is extracted from the detected signal. A sampling execution command is output when the carrier wave has a predetermined phase, the AM analog signal is sampled according to the sampling execution command, AD-converted into a digital signal, and the AD-converted digital signal is demodulated. In the AD conversion, a sampling execution instruction is used to sample a folded signal of an AM analog signal generated in the AD conversion. Can be centralized, and the program storage memory attached to the demodulation arithmetic unit can be It has an effect that it is possible to reduce the amount.

The invention according to claim 10 of the present invention is the FM
A radio broadcast signal is received and detected to output a baseband signal, an FM analog signal to be demodulated is extracted from the baseband signal, an FM pilot signal is extracted from the detected baseband signal, and the FM pilot signal is extracted. A sampling execution instruction is output when the signal has a predetermined phase, the FM analog signal is sampled by the sampling execution instruction, and AD-converted into a digital signal.
Each step of demodulating the AD-converted digital signal comprises sampling a folded analog signal of an FM analog signal generated during AD conversion by a sampling execution instruction in AD conversion.
This has the effect that it is possible to unify the arithmetic operations or arithmetic expressions at the time of demodulation in the demodulation arithmetic device, and to reduce the capacity of the program storage memory that accompanies the demodulation arithmetic device as compared with the conventional system.

According to the eleventh aspect of the present invention, in the step of outputting the sampling execution instruction, the carrier of the AM radio broadcast signal or the phase of the FM pilot signal is 90.
The sampling execution instruction is output when the frequency reaches 270 degrees or 270 degrees, and since the level adjustment processing in demodulation is not required, the amount of calculation required for demodulation can be reduced, and for demodulation with low processing capacity. It has an effect that an AM / FM stereo signal can be sufficiently demodulated even by using an arithmetic device.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings and FIGS. 1 to 8. FIG. 1 is a block diagram showing a configuration of an FM stereo broadcast receiver that receives an FM stereo broadcast and extracts a modulated signal in the first embodiment of the first invention and the embodiment of the second invention. FIG. 2 is a graph showing the relationship between the frequency of the detection circuit and the sampling frequency applied in the AD converter according to the embodiment of the present invention, and FIG. 3 is the AM stereo in the second embodiment of the first invention. FIG. 4 is a block diagram showing a configuration of an AM stereo broadcast receiver for receiving a broadcast and extracting a modulated signal, and FIG. 4 is an F in the third embodiment of the first invention.
It is a block diagram which shows the structure of the FM multiplex broadcast receiver which receives M multiplex broadcast (radio data system) and extracts a modulated signal.

Further, FIG. 5 is a block diagram showing a configuration of an AM stereo broadcast receiver for receiving an AM stereo broadcast and extracting a modulated signal in the first embodiment of the third invention, and FIG. 6 is a third block diagram. FM in the second embodiment of the present invention
FIG. 7 is a block diagram showing a configuration of an FM stereo broadcast receiver that receives a stereo broadcast and extracts a modulated signal, and FIG. 7 receives an AM stereo broadcast according to the first embodiment of the fourth invention and outputs the modulated signal. FIG. 8 is a block diagram showing a configuration of an AM stereo broadcast receiver for extracting, and FIG. 8 shows a configuration of an FM stereo broadcast receiver for receiving an FM stereo broadcast and extracting a modulated signal according to a second embodiment of the fourth invention. It is a block diagram shown.

First, referring to FIG. 1, the first aspect of the first invention is described.
The configuration of the FM stereo broadcast receiver in the embodiment will be described. In FIG. 1, 1 is a tuning circuit that tunes to a desired frequency (broadcasting station) to receive the FM radio broadcast signal, and 2 detects a necessary frequency band from the received FM stereo signal and outputs a baseband signal. FM
The detection circuit 3 is a low-pass filter (may be a band-pass filter) that passes only a signal in the frequency band of 57 KHz or less that is to be demodulated from the detected FM baseband signal, and 4 is a sampling frequency of 38 KHz or more and less than 57 KHz. An AD converter 5 that oscillates and samples an FM analog signal from the low-pass filter 3 (an analog signal made up of an FM signal to be demodulated, the same applies below) to a digital signal is A
This is a demodulation arithmetic unit for demodulating the digital signal from the D converter 4 to obtain left channel and right channel outputs (monaural output when a monaural signal is received).

Next, referring to FIGS. 1 and 2, the first
The operation of the FM stereo broadcast receiver in the first embodiment of the invention will be described in detail. First, tuning circuit 1
The FM stereo signal selected and received by the FM
The baseband signal of the required frequency band is input to the detection circuit 2 and output. The baseband signal is input to the low-pass filter 3 and filtered into only the signal in the frequency band of 57 KHz or less. FM from the low pass filter 3
The analog signal is 38 KHz or more by the AD converter 4 5
It is sampled at an arbitrary sampling frequency (lower than the frequency of the input FM analog signal) of less than 7 KHz, converted into a digital signal, input to the demodulation arithmetic unit 5, and demodulated by the demodulation arithmetic unit 5.

In FIG. 2, fs is a sampling frequency in AD conversion, and fc is a detection circuit (FM detection circuit 2).
, Fc-fs is the center frequency of the folded signal of the output signal of the detection circuit. As shown in FIG. 2, in AD conversion, the FM in the frequency band of 57 KHz or less filtered by the low-pass filter 3 is used.
38K lower than the frequency (fc) of the output signal of the detection circuit 2
The input FM when sampling at an arbitrary sampling frequency (fs) of at least Hz and less than 57 KHz
The analog signal is folded back, and a folded signal having a frequency (fc-fs) lower than the sampling frequency is generated and sampled, so that the analog signal can be generated as a digital signal having a frequency of ½ or less of the sampling frequency.

As described above, according to the FM stereo broadcast receiver in the first embodiment of the first aspect of the present invention, AD conversion is performed at a lower sampling frequency than that of the receiver of the conventional example, and thus high-speed AD is achieved. It is possible to demodulate an FM stereo signal without using a converter and a demodulation arithmetic unit.

Next, referring to FIG. 3, the second aspect of the first invention is described.
The configuration of the AM stereo broadcast receiver in the embodiment will be described. In FIG. 3, reference numeral 41 is a tuning circuit that tunes to a desired frequency (broadcasting station) to receive and detect the AM radio broadcast signal, and 42 is a frequency band of 440 to 460 KHz for demodulating the detected AM stereo signal. Bandpass filter that passes only the signal, 4
Reference numeral 3 oscillates a sampling frequency of 20 KHz or more and less than 450 KHz and samples an AM analog signal from the bandpass filter 42 (an analog signal consisting of a carrier wave including a signal to be demodulated, the same applies hereinafter) at the sampling frequency and converts it into a digital signal. AD converter, 4
Reference numeral 4 denotes a demodulation arithmetic unit for demodulating the digital signal from the AD converter 4 to obtain left channel and right channel outputs (monaural output when a monaural signal is received).

Therefore, referring to FIG. 3 and FIG.
The operation of the AM stereo broadcast receiver in the second embodiment of the invention will be described in detail. First, tuning circuit 4
The AM stereo signal selected by 1 and received and detected is input to the band pass filter 42 and filtered only to a signal in the frequency band of 440 KHz to 460 KHz (carrier wave including the signal to be demodulated). The AM analog signal from the band pass filter 42 is sampled by the AD converter 43 at a sampling frequency of any frequency between 20 KHz and less than 450 KHz (lower than the frequency of the input AM analog signal), converted into a digital signal, and demodulated. It is input to the calculation processing device 44 and demodulated in the demodulation calculation device 44.

In FIG. 2, the sampling frequency fs,
Center frequency fc of carrier wave output from detection circuit, center frequency fc-fs of folded signal of output signal of detection circuit
Is the same as above. In the AD conversion, when the sampling is performed by an arbitrary sampling frequency (fs) of 20 KHz or more and less than 450 KHz lower than the frequency (fc) of the AM analog signal in the frequency band of 440 KHz to 460 KHz filtered by the band pass filter 42, the input signal is obtained. Is folded and a folded signal having a frequency lower than the sampling frequency (fc-fs) is generated and sampled.
It can be generated as a digital signal having a frequency of / 2 or less.

As described above, according to the AM stereo broadcast receiver in the second embodiment of the first aspect of the invention, the AD conversion is performed at a lower sampling frequency than that of the receiver of the conventional example, so that the high-speed AD is performed. It is possible to demodulate an AM stereo signal without using a converter and a demodulation arithmetic unit.

Next, referring to FIG. 4, the third aspect of the first invention is described.
The configuration of the FM multiplex broadcast (radio data system) receiver in the embodiment will be described. In FIG.
Reference numeral 61 is a tuning circuit that tunes to a desired frequency (broadcast station) to receive the FM multiplex broadcast signal, and 62 is an FM detection circuit that detects a required frequency band from the received FM multiplex broadcast signal and outputs a baseband signal. , 63 are 55 KHz to 5 to be demodulated in the input baseband signal
A band-pass filter that passes only a signal in the frequency band of 9 KHz, 64 oscillates a sampling frequency of 2 KHz or more and less than 57 KHz, and F from the band-pass filter 62
An AD that samples an M-multiplexed analog signal (an analog signal composed of an FM-multiplexed signal to be demodulated, the same applies hereinafter) at a sampling frequency thereof and converts it into a digital signal
A converter 65 is a demodulation arithmetic unit for demodulating the digital signal from the AD converter 64 to obtain a radio channel and a data channel.

Next, referring to FIGS. 4 and 2, the first
The operation of the FM multiplex broadcast receiver according to the third embodiment of the present invention will be described in detail. First, the FM multiplex broadcast signal selected and received by the tuning circuit 61 is input to the FM detection circuit 62 and a baseband signal of a required frequency band is output. The baseband signal is input to the bandpass filter 63 and filtered into only the signal in the frequency band of 55 KHz to 59 KHz. The FM multiplex analog signal from the bandpass filter 63 is sampled by the AD converter 64 at a sampling frequency of any frequency between 2 KHz and less than 57 KHz (lower than the frequency of the input FM multiplex analog signal) and converted into a digital signal. Is input to the demodulation arithmetic unit 65 and demodulated in the demodulation arithmetic unit 65.

In FIG. 2, the sampling frequency fs,
Center frequency fc of carrier wave output from detection circuit, center frequency fc-fs of folded signal of output signal of detection circuit
Is the same as above. In the AD conversion, the frequency (f of the output signal of the FM detection circuit 62 in the frequency band of 55 KHz to 59 KHz filtered by the band pass filter 63 (f
c) sampling at an arbitrary sampling frequency (fs) lower than 2 KHz and lower than 57 KHz,
The input FM multiplexed analog signal is folded back to generate a folded signal having a frequency (fc-fs) lower than the sampling frequency, and is sampled, thereby generating a digital signal having a frequency of ½ or less of the sampling frequency. can do.

As described above, according to the FM multiplex broadcast receiver in the third embodiment of the first invention, the AD conversion is performed at a lower sampling frequency than that of the receiver of the conventional example, and thus the high-speed AD is performed. The FM multiplex signal can be demodulated without using a converter and a demodulation arithmetic unit.

Similar to the description of the first embodiment of the first invention, the FM stereo broadcast receiver in the second embodiment of the second invention will be described with reference to FIGS. 1 and 2. . The configuration of the FM stereo broadcast receiver in the present embodiment is the first embodiment of the first invention described above with reference to FIGS. 1 and 2.
Since it is the same as that described in the above embodiment, the repetitive description will be omitted. However, the AD converter 4 according to the embodiment of the present invention is 4 / (4n + 1) times the frequency of the subcarrier of the FM analog signal in the frequency band of 57 KHz or less to be demodulated which is input from the low pass filter 3. The analog signal is sampled at a sampling frequency (n is an arbitrary natural number) (details will be described later).

Next, with reference to FIGS. 1 and 2, the features and operation of the FM stereo broadcast receiver according to the embodiment of the second invention will be described. First, the FM stereo broadcast signal selected and received by the tuning circuit 1 is input to the FM detection circuit 2 and a baseband signal of a required frequency band is output. The baseband signal is input to the low-pass filter 3 and is filtered only into a signal in the frequency band of 57 KHz or less to be demodulated.
The subcarrier of the FM analog signal from the low-pass filter 3 is sampled at a sampling frequency (n is an arbitrary natural number) that is 4 / (4n + 1) times the frequency of the carrier, converted into a digital signal, and a demodulation operation is performed. It is input to the device 5 and demodulated.

As shown in FIG. 2, similar to the first embodiment of the first invention, the FM analog signal input from the low pass filter 3 to the AD converter 4 is folded back to generate a folded signal. Then, when the AD converter 4 performs sampling at a sampling frequency (fs) that is 4 / (4n + 1) times the subcarrier frequency (fc) of the FM analog signal input to the folded signal, the subcarrier frequency is sampled. A digital signal whose frequency is ¼ of the frequency is output.

By setting the sampling frequency to the above value, the calculation in the demodulation calculation unit 5 becomes as follows. That is, inside the demodulation arithmetic unit 5, in order to demodulate the quadrature-modulated signal, the arithmetic operations shown in the following [Equation 1] and [Equation 2] are required. x = cos (2π · fc / fs · t) ··· [Equation 1] y = sin (2π · fc / fs · t) ··· [Equation 2] In the above equation, π is the circumference. Rate, fs is the sampling frequency,
fc is the center frequency of the carrier wave, and t is an arbitrary natural number representing time.

In the above equation, by setting the sampling frequency fs to be 4 / (4n + 1) times the center frequency fc of the subcarrier, the subcarrier is folded back and the center frequency fc-fs of the sampled carrier is the sampling frequency fs. Substituting it, [Equation 1] and [Equation 2] are respectively [Equation 3] and [Equation 4] regardless of the sampling frequency fs and the center frequency fc of the subcarrier. It becomes easy as shown in.

X = cos (π / 2t) [Equation 3] y = sin (π / 2t) [Equation 4] As is clear from this equation, [Equation 3] and Since the value shown in [Equation 4] cyclically circulates values of -1, 0, 1, 0, it is not necessary to calculate a complicated trigonometric function at the time of demodulation, and the calculation in demodulation is simplified.

As described above, according to the FM stereo broadcast receiver in the embodiment of the second aspect of the invention, AD conversion can be performed at a lower sampling frequency than that of the receiver of the conventional example, and the FM stereo broadcast receiver of the conventional example can be used. Since the amount of calculation required for demodulation can be reduced as compared with a receiver, an FM stereo signal can be demodulated using a demodulation calculation device with low processing capability.

Next, referring to FIG. 5, the first aspect of the third invention
The configuration of the AM stereo broadcast receiver in the embodiment will be described. In FIG. 1, reference numeral 71 is a tuning circuit that tunes to a desired frequency (broadcasting station) to receive and detect the AM radio broadcast signal, and 72 is a frequency band of 440 to 460 KHz for demodulating the detected AM stereo signal. Signal (carrier including the signal to be demodulated)
A first band-pass filter for passing only the signal, and a second band-pass filter 75 for filtering only the carrier of 450 KHz in the detected AM stereo signal.

Reference numeral 76 is the second band pass filter 75.
When the carrier wave from (the frequency can be gradually reduced by a known method) reaches a predetermined phase, the AD converter 7
3 is a phase locked loop circuit for outputting a sampling execution command to 73
An AD converter that samples an analog signal according to a sampling execution command from the phase synchronization circuit 76 at the sampling frequency and converts it into a digital signal. Reference numeral 74 demodulates the digital signal from the AD converter 73 to output left channel and right channel ( It is an arithmetic unit for demodulation that obtains a monaural output when a monaural signal is received.

Therefore, referring to FIG. 5 and FIG.
The operation of the AM stereo broadcast receiver in the first embodiment of the invention will be described in detail. First, tuning circuit 7
The AM stereo broadcast signal selected by 1 and received and detected is input to the first band pass filter 72 and
Only the signal in the frequency band of 0 KHz to 460 KHz (carrier wave including the signal to be demodulated) is filtered. Further, in the detected AM stereo signal, only the carrier of 450 KHz is filtered through the second band pass filter 75 and input to the phase lock circuit 76.

The phase synchronization circuit 76 outputs a sampling execution command to the AD converter 73 when the carrier wave from the second band pass filter 75 has a predetermined phase. On the other hand, the AM analog signal from the first band pass filter 72 input to the AD converter 73 is sampled in accordance with the sampling execution instruction from the phase synchronization circuit 76,
It is converted into a digital signal, input to the demodulation arithmetic unit 74, and demodulated in the demodulation arithmetic unit 74. When the frequency of the sampling execution instruction is higher than the frequency of the AM analog signal input to the AD converter 73, the frequency of the carrier wave used can be gradually reduced in the phase synchronization circuit 76.

In FIG. 2, the sampling frequency fs,
Center frequency fc of carrier wave output from detection circuit, center frequency fc-fs of folded signal of output signal of detection circuit
Is the same as above. In AD conversion, 440 KHz to 460 KH filtered by the first band pass filter 72
The frequency (f of the AM analog signal in the frequency band of z
c) The input signal is folded back by sampling by the sampling execution instruction (fs) having a frequency lower than the sampling frequency (f).
The c-fs) folded signal is generated and sampled, so that it can be generated as a digital signal having a frequency considerably lower than the sampling frequency.

As described above, according to the AM stereo broadcast receiver in the first embodiment of the third aspect of the invention, AD conversion can be performed at a lower sampling frequency than that of the conventional receiver, and the carrier wave can be used. By sampling while maintaining a constant phase with respect to, it is possible to unify the arithmetic operations or arithmetic expressions at the time of demodulation in the demodulation arithmetic device, and the program storage memory that accompanies the demodulation arithmetic device in comparison with the conventional method. The capacity of can be reduced.

Next, referring to FIG. 6, the second aspect of the third invention
The configuration of the FM stereo broadcast receiver in the embodiment will be described. In FIG. 6, 81 is a tuning circuit that tunes to a desired frequency (broadcasting station) to receive the FM radio broadcast signal, and 82 detects a necessary frequency band from the received FM stereo signal and outputs a baseband signal. F
M detection circuit, 83 is a low-pass filter that passes only the signal in the frequency band of 57 KHz or less that is to be demodulated from the detected FM baseband signal, and 86 is the 19 KHz FM pilot signal of the detected FM baseband signal It is a bandpass filter that filters only.

Further, 87 is a phase synchronization circuit which outputs a sampling execution command to the AD converter 84 when the FM pilot signal input from the band pass filter 86 has a predetermined phase, and 84 is a low pass filter 83. An AD converter 85 for sampling the FM analog signal that has passed through the phase converter at a sampling frequency in accordance with a sampling execution instruction from the phase synchronization circuit 87 and converting it into a digital signal.
Is a demodulation arithmetic unit for demodulating the digital signal from the AD converter 84 to obtain left channel and right channel outputs (monaural output when a monaural signal is received).

Next, referring to FIG. 6 and FIG.
The operation of the FM stereo broadcast receiver in the second embodiment of the invention will be described in detail. First, tuning circuit 8
The FM stereo signal selected and received by 1 is F
The baseband signal of the required frequency band is input to the M detection circuit 82 and output. The baseband signal is filtered by the low-pass filter 83 into only a signal in the frequency band of 57 KHz or less. Further, the FM baseband signal detected by the FM detection circuit 82 is passed through the bandpass filter 8
Only the FM pilot signal is filtered through 6 and input to the phase synchronization circuit 87.

The phase synchronizing circuit 87, when the input FM pilot signal has a predetermined phase, AD converter 84.
A sampling execution instruction is output to. On the other hand, the AD converter 84 receives the FM from the input low-pass filter 83.
The analog signal is sampled in accordance with a sampling execution instruction from the phase synchronization circuit 87, converted into a digital signal, output to the demodulation arithmetic unit 85, and demodulated by the demodulation arithmetic unit 85.

In FIG. 2, the sampling frequency fs,
Center frequency fc of the output subcarrier from the detection circuit, center frequency fc-f of the folded signal of the output signal of the detection circuit
s is the same as above. In the AD conversion, when the FM analog signal (fc) of 57 KHz or less filtered by the low-pass filter 83 is sampled at a predetermined phase of the FM pilot signal (fs) having a frequency of 19 KHz, the input signal is folded and sampled. A folded signal having a frequency lower than the frequency (fc-fs) is generated and sampled, whereby a digital signal having a frequency considerably lower than the sampling frequency can be generated.

As described above, according to the FM stereo broadcast receiver of the second embodiment of the third aspect of the invention, AD conversion can be performed at a lower sampling frequency than the receiver of the conventional example, and the FM By sampling while maintaining a constant phase for the pilot signal,
It is possible to unify the arithmetic operations or arithmetic expressions at the time of demodulation, and it is possible to reduce the capacity of the program storage memory attached to the demodulating arithmetic unit as compared with the conventional method.

Next, referring to FIG. 7, the first aspect of the fourth invention
The configuration of the AM stereo broadcast receiver in the embodiment will be described. In FIG. 7, reference numeral 91 is a tuning circuit that tunes to a desired frequency (broadcasting station) to receive and detect the AM radio broadcast signal, and 92 is a frequency band of 440 to 460 KHz for demodulating the detected AM stereo signal. Signal (carrier including the signal to be demodulated)
A first band-pass filter that allows only a carrier of 450 KHz out of the detected AM stereo signal is filtered by a second band-pass filter 95.

96 is a second bandpass filter 96
A phase synchronization circuit for outputting a sampling execution command to the AD converter 93 when the phase of the carrier wave (which can also be stepped down by a known method) from 90 degrees to 270 degrees, 93 is a first Band pass filter 92
A / D converter that samples the AM analog signal that has passed through the sampling circuit at the sampling frequency according to the sampling execution instruction from the phase synchronization circuit 96 and converts it into a digital signal. This is a demodulation arithmetic unit that obtains a right channel output (a monaural output when a monaural signal is received).

Therefore, referring to FIG. 5 and FIG.
The operation of the AM stereo broadcast receiver in the first embodiment of the invention will be described in detail. First, tuning circuit 9
The AM stereo broadcast signal selected by 1 and received and detected is input to the first band pass filter 92 and
Only signals in the frequency band of 0 KHz to 460 KHz are filtered. Further, the detected AM stereo signal is the second
Only the carrier wave of 450 KHz is filtered through the band pass filter 95 of FIG.

The phase synchronization circuit 96 outputs a sampling execution command to the AD converter 93 when the phase of the carrier wave from the second band pass filter 95 becomes 90 degrees or 270 degrees. On the other hand, the first input to the AD converter 93
The AM analog signal from the band pass filter 92 is sampled in accordance with the sampling execution instruction from the phase synchronization circuit 96, converted into a digital signal, input to the demodulation arithmetic unit 94, and demodulated in the demodulation arithmetic unit 94. When the frequency of the sampling execution instruction is higher than the frequency of the AM analog signal input to the AD converter 93, the frequency of the carrier wave used can be gradually reduced in the phase synchronization circuit 96.

In FIG. 2, the sampling frequency fs,
Center frequency fc of carrier wave output from detection circuit, center frequency fc-fs of folded signal of output signal of detection circuit
Is the same as above. In AD conversion, 440 KHz to 460 KH filtered by the first band pass filter 92
When the AM analog signal in the frequency band of z is sampled by the sampling execution instruction (fs) generated when the phase of the carrier having a frequency lower than the frequency (fc) becomes 90 degrees or 270 degrees, the input signal is A signal that is folded back and has a frequency lower than the sampling frequency (fc-fs) is generated and sampled, so that it can be generated as a digital signal having a frequency considerably lower than the sampling frequency.
At this time, the amplitude (gain or gain) of the carrier wave of the output signal from the AD converter 93 is always constant, and the level adjustment processing in demodulation is unnecessary, so that the amount of calculation can be reduced.

As described above, according to the AM stereo broadcast receiver in the first embodiment of the fourth aspect of the invention, AD conversion can be performed at a lower sampling frequency than that of the conventional receiver, and the carrier wave can be used. Phase is 90 degrees or 27
By sampling only when it reaches 0 degrees,
Since the level adjustment processing in demodulation is not necessary, the amount of calculation required for demodulation can be reduced, and an AM stereo signal can be sufficiently demodulated even if a demodulation calculation device with low processing capability is used.

Next, referring to FIG. 8, the second aspect of the fourth invention
The configuration of the FM stereo broadcast receiver in the embodiment will be described. In FIG. 8, 101 is a tuning circuit that tunes to a desired frequency (broadcast station) to receive the FM radio broadcast signal, and 102 detects a necessary frequency band from the received FM stereo signal and outputs a baseband signal. FM detection circuit, 103 is a low-pass filter that passes only the signal in the frequency band of 57 KHz or less that is to be demodulated from the detected FM baseband signal, and 106 is the FM of 19 KHz of the detected FM baseband signal.
It is a bandpass filter that filters only pilot signals.

Further, in 107, the phase of the FM pilot signal input from the band pass filter 106 is 90 degrees or 2
A phase synchronization circuit that outputs a sampling execution command to the AD converter 104 when it reaches 70 degrees, and 104 samples an FM analog signal that has passed through the low-pass filter 103 according to a sampling execution command from the phase synchronization circuit 107. An AD converter for sampling at a frequency and converting it into a digital signal, 105 is a demodulation operation for demodulating the digital signal from the AD converter 104 and obtaining left channel and right channel outputs (monaural output when a monaural signal is received) It is a device.

Next, referring to FIG. 6 and FIG.
The operation of the FM stereo broadcast receiver in the second embodiment of the invention will be described in detail. First, tuning circuit 1
The FM stereo signal selected and received by 01 is input to the FM detection circuit 102, and a baseband signal of a required frequency band is output. The baseband signal is filtered by the low-pass filter 103 into only a signal in the frequency band of 57 KHz or less. Furthermore, the FM detection circuit 1
In the FM baseband signal detected in 02, only the FM pilot signal of frequency 19 KHz is filtered through the bandpass filter 106 and input to the phase synchronization circuit 107.

The phase synchronization circuit 107 outputs a sampling execution command to the AD converter 104 when the phase of the input FM pilot signal becomes 90 degrees or 270 degrees. On the other hand, the AD converter 104 receives the input FM analog signal from the low pass filter 103 (including the carrier wave modulated by the signal to be demodulated) in the phase synchronization circuit 1.
Sampling is performed according to the sampling execution instruction from 07, converted into a digital signal, output to the demodulation arithmetic unit 105, and demodulated in the demodulation arithmetic unit 105.

In FIG. 2, the sampling frequency fs,
Center frequency fc of the output subcarrier from the detection circuit, center frequency fc-f of the folded signal of the output signal of the detection circuit
s is the same as above. In AD conversion, the FM analog signal (fc) of 57 KHz or less filtered by the low-pass filter 103 is sampled by a sampling execution command (fs) generated when the FM pilot signal of frequency 19 KHz becomes 90 degrees or 270 degrees. Then,
The input signal is folded and a folded signal having a frequency lower than the sampling frequency (fc-fs) is generated and sampled, whereby a digital signal having a frequency considerably lower than the sampling frequency can be generated. At this time, the amplitude (gain or gain) of the subcarrier of the output signal from the AD converter 104 is always constant, and the level adjustment processing in demodulation is unnecessary, so the amount of calculation can be reduced.

As described above, according to the FM stereo broadcast receiver of the second embodiment of the fourth aspect of the invention, AD conversion can be performed at a lower sampling frequency than the receiver of the conventional example, and the FM The pilot signal phase is 90
Since the level adjustment processing in demodulation is unnecessary by performing sampling only when the frequency reaches 270 degrees or 270 degrees, the amount of calculation required for demodulation can be reduced, and even if a demodulation arithmetic unit with low processing capability is used, FM The stereo signal can be sufficiently demodulated.

[0074]

The receiver and the sampling method thereof according to the first aspect of the present invention are configured as described above, and in particular, the AD
Signal input to converter (FM or AM analog signal)
Is sampled with a sampling signal having a frequency lower than that frequency, the FM stereo signal can be demodulated without using a high-speed AD converter and a demodulation arithmetic unit.

The receiver and the sampling method thereof according to the second aspect of the invention are configured as described above, and in particular, the frequency is 4 / (4n + 1) times the frequency of the carrier (FM analog signal) input to the AD converter. By performing the sampling at 1, the AD conversion can be performed at a lower sampling frequency than that of the conventional receiver, and the amount of calculation required for demodulation can be reduced. The device can be used to demodulate an FM stereo signal.

The receiver and the sampling method therefor according to the third aspect of the invention are configured as described above, and in particular, the carrier wave or FM pilot signal has a predetermined phase with respect to the AM or FM analog signal input to the AD converter. By performing sampling at the time of performing, it is possible to perform AD conversion at a lower sampling frequency as compared with the receiver of the conventional example and to perform sampling while maintaining a constant phase with respect to the carrier wave. The arithmetic expressions for demodulation can be unified, and the capacity of the program storage memory associated with the demodulating arithmetic unit can be reduced as compared with the conventional method.

The receiver and the sampling method thereof according to the fourth aspect of the invention are configured as described above, and in particular, the phase of the carrier wave or FM pilot signal is 90 degrees with respect to the AM or FM analog signal input to the AD converter. 27
By performing sampling when it reaches 0 degrees, AD conversion can be performed at a lower sampling frequency than that of the receiver of the conventional example, and level adjustment processing in demodulation is not required, so that the calculation required for demodulation is performed. The amount can be reduced, and the FM stereo signal can be sufficiently demodulated even if a demodulation arithmetic unit with low processing capability is used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an FM stereo broadcast receiver according to a first embodiment of a first invention and an embodiment of a second invention.

FIG. 2 is a graph showing the relationship between the frequency of the detection circuit and the sampling frequency applied in the AD converter according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an AM stereo broadcast receiver according to a second embodiment of the first invention.

FIG. 4 is a block diagram showing a configuration of an FM multiplex broadcast receiver according to a third embodiment of the first invention.

FIG. 5 is a block diagram showing a configuration of an AM stereo broadcast receiver according to the first embodiment of the third invention.

FIG. 6 is a block diagram showing a configuration of an FM stereo broadcast receiver according to a second embodiment of the third invention.

FIG. 7 is a block diagram showing a configuration of an AM stereo broadcast receiver according to the first embodiment of the fourth invention.

FIG. 8 is a block diagram showing a configuration of an FM stereo broadcast receiver according to a second embodiment of the fourth invention.

FIG. 9 is an FM that performs reception processing of a conventional FM stereo broadcast.
Block diagram showing the configuration of a stereo broadcast receiver

10 is a graph showing the relationship between the frequency of the detection circuit and the sampling frequency applied in the AD converter of the FM stereo broadcast receiver shown in FIG.

[Explanation of symbols]

1, 21, 41, 61, 71, 81, 91, 101 Tuning circuit 2, 22, 62, 82, 102 FM detection circuit 3, 23, 83, 103 Low pass filter 42, 63, 86, 106 Band pass filter 72, 92 1st band pass filter 75, 95 2nd band pass filter 4, 24, 43, 64, 73, 84, 93, 104 A
D converter 5, 25, 44, 65, 74, 85, 94, 105 Demodulation arithmetic unit 76, 87, 96, 107 Phase synchronization circuit fs AD conversion sampling frequency fc Carrier center frequency fc-fs Returned signal Center frequency of

Claims (11)

[Claims] 1. A tuning circuit for receiving an FM radio broadcast signal, an FM detection circuit for detecting an FM signal input from the tuning circuit and outputting a baseband signal, and an FM analog signal to be demodulated from the baseband signal. A low-pass filter for filtering, and an AD for generating a sampling signal and sampling the FM analog signal from the low-pass filter with the sampling signal to convert it into a digital signal.
The AD converter includes an analog-to-digital converter and a demodulation arithmetic unit that demodulates the digital signal from the AD converter. The AD converter performs AD conversion using a sampling signal having a frequency lower than the subcarrier of the FM analog signal in the low frequency band. A receiver which is adapted to sample a folded signal of the FM analog signal generated at the time. 2. The frequency of the sampling signal is 4 / (4n + 1) times the frequency of the carrier of the FM analog signal filtered by the low pass filter (n is an arbitrary natural number). The receiver according to claim 1. 3. A tuning circuit for receiving an FM radio broadcast signal, an FM detection circuit for detecting an FM multiplex signal input from the tuning circuit and outputting a baseband signal, and an FM multiplex analog for demodulating the baseband signal. A band-pass filter for filtering the signal, an AD converter for generating a sampling signal, sampling the FM multiplex analog signal from the band-pass filter with the sampling signal and converting it into a digital signal, and a digital signal from the AD converter A demodulation arithmetic unit for demodulating
In the converter, the FM passed through the bandpass filter
A receiver characterized in that a folded signal of the FM multiplex analog signal generated during AD conversion is sampled by a sampling signal having a frequency lower than a subcarrier of the multiplex analog signal. 4. A tuning circuit for receiving and detecting an AM radio broadcast signal, a first band pass filter for filtering a carrier including an AM analog signal to be demodulated from the detected signal, and the detected signal. A second bandpass filter for filtering only the carrier wave; and a phase synchronization circuit for outputting a sampling execution command to the AD converter when the carrier wave from the second bandpass filter has a predetermined phase.
An AD converter for sampling the AM analog signal filtered by the first band-pass filter according to a sampling execution command from the phase synchronization circuit and converting it into a digital signal, and for demodulation for demodulating the digital signal from the AD converter. Comprising an arithmetic unit, in the AD converter,
By the sampling execution instruction from the phase synchronization circuit,
A receiver characterized by sampling a folded signal of the AM analog signal generated during AD conversion. 5. The phase synchronization circuit outputs a sampling execution command to the AD converter when the phase of the carrier wave from the second band pass filter becomes 90 degrees or 270 degrees, and the AD converter. 5. The receiver according to claim 4, wherein the sampling execution instruction samples a folded signal of the AM analog signal generated during AD conversion. 6. A tuning circuit for receiving an FM radio broadcast signal, an FM detection circuit for detecting the received FM signal and outputting a baseband signal, and an FM analog signal to be demodulated from the detected baseband signal. And a low-pass filter for filtering
A band pass filter for filtering the M pilot signal,
A phase synchronization circuit that outputs a sampling execution command to the AD converter when the pilot signal has a predetermined phase, and an FM analog signal that has been filtered by the low-pass filter are sampled by the sampling execution command into a digital signal. It is composed of an AD converter for conversion and a demodulation arithmetic unit for demodulating the digital signal from the AD converter. In the AD converter, a sampling execution command from the phase locked loop circuit is generated during AD conversion. A receiver characterized in that a signal obtained by folding back the FM analog signal is sampled. 7. The phase-locked loop circuit wherein the phase of the FM pilot signal from the band-pass filter is 90 degrees or 270.
A sampling execution command is output to the AD converter when the frequency reaches, and the AD converter samples the folded signal of the FM analog signal generated during AD conversion according to the sampling execution command. 7. The receiver according to claim 6, wherein: 8. An FM analog signal to be demodulated is extracted from the baseband signal by receiving and detecting an FM radio broadcast signal, outputting the baseband signal, and the extracted FM.
Analog signal is sampled and digital signal is AD
The step of converting and demodulating the AD-converted digital signal comprises the step of sampling, wherein the sampling signal of a frequency lower than the subcarrier of the FM analog signal is used to generate the FM analog signal generated during the AD conversion. A sampling method characterized by sampling a folded signal 9. A carrier including an AM analog signal to be detected and demodulated by receiving an AM radio broadcast signal is extracted,
Only a carrier wave is extracted from the detected signal, a sampling execution command is output when the carrier wave has a predetermined phase, and the AM analog signal is sampled according to the sampling execution command and AD-converted into a digital signal, The present invention is characterized by comprising respective steps of demodulating the AD-converted digital signal, and in AD conversion, a sampling execution instruction is used to sample a folded signal of an AM analog signal generated at the time of AD conversion. Sampling method 10. An FM analog signal to be demodulated is extracted from the baseband signal by receiving and detecting an FM radio broadcast signal, outputting the baseband signal, and an FM pilot signal is extracted from the detected baseband signal. Extract and
When the FM pilot signal has a predetermined phase, a sampling execution instruction is output, the FM analog signal is sampled by the sampling execution instruction, AD-converted into a digital signal, and the AD-converted digital signal is demodulated. In the AD conversion, a sampling execution instruction is used to sample a folded signal of the FM analog signal generated in the AD conversion. 11. The step of outputting the sampling execution instruction is such that the sampling execution instruction is output when the phase of the carrier wave of the AM radio broadcast signal or the FM pilot signal becomes 90 degrees or 270 degrees. The sampling method according to claim 9 or 10.