TW201803205A - Electronic device with FM function and FM antenna switching method thereof - Google Patents

Abstract

The invention provides an FM-enabled electronic device, comprising an earphone interface, an FM chip, a processing unit and a switching unit, the earphone interface comprising a left channel pin, a right channel pin and a ground pin; Processing the FM signal, and feeding back an RSSI value to the processing unit, the processing unit is configured to compare the RSSI value with a preset threshold, and further control switching of the switching unit according to the comparison result to select The left channel pin and the right channel pin constitute a signal receiving point of the FM antenna or the ground pin is selected as a signal receiving point of the FM antenna.

Description

Electronic device with FM function and FM antenna switching method thereof

The invention relates to an electronic device with FM function and an FM antenna switching method thereof.

At present, many electronic devices, such as mobile phones, personal digital assistants (PDAs), etc., generally have a frequency modulation (FM) radio function. In order to simplify the structure of the electronic device, the conventional electronic device mostly uses the earphone as the FM antenna. For example, the FM antenna is formed by the ground line of the earphone or the left and right channel lines of the earphone are configured as an FM antenna. When using the ground pin in the headphone interface as the signal receiving point of the FM antenna, it is generally necessary to add an inductor to the ground pin to separate the reference point of the FM signal and the audio. Since the inductor has a certain impedance, the audio output distortion of the earphone is greatly degraded, thereby affecting the user's sense of hearing. When the left and right channel pins in the earphone interface are used as the signal receiving points of the FM antenna, the left and right channel lines of the headphones inserted by the user may be surrounded by the ground, thereby affecting the reception of the FM antenna.

In view of this, it is necessary to provide an FM-enabled electronic device and an FM antenna switching method thereof.

An FM-enabled electronic device includes an earphone interface, an FM chip, a processing unit, and a switching unit, the earphone interface including a left channel pin, a right channel pin, and a ground pin; the FM wafer and the processing The unit and the switching unit are electrically connected to process the FM signal, and feedback a Receive Signal Strength Indicator (RSSI) value to the processing unit, where the processing unit is configured by the switching unit The left channel pin, the right channel pin, and the ground pin are electrically connected, and the processing unit is configured to receive the RSSI value, and compare the RSSI value with a preset threshold, and further The switching of the switching unit is controlled according to the comparison result, so that the left channel pin and the right channel pin are selected to form a signal receiving point of the FM antenna or the ground pin is selected as a signal receiving point of the FM antenna.

An FM antenna switching method is applied to an electronic device, the electronic device includes at least an earphone interface, and the earphone interface includes a left channel pin, a right channel pin, and a ground pin, and the method includes:

(a) Insert a headset and turn on the FM function;

(b) selecting the left channel pin, the right channel pin as a signal receiving point of the FM antenna, or selecting the ground pin as a signal receiving point of the FM antenna;

(c) receiving an FM signal and outputting an RSSI value of the FM signal;

(d) comparing the RSSI value with a preset threshold, and switching the signal receiving point of the FM antenna to the left channel pin, the right channel pin or the grounding lead according to the comparison result. foot.

The electronic device is provided with the switching unit, so that the switching to the switching unit can be controlled according to the RSSI value of the received FM signal, thereby switching to the left channel pin and the right channel pin of the corresponding earphone interface or Ground pin, which effectively enhances the quality of the FM signal.

1 is a functional block diagram of an electronic device in accordance with a preferred embodiment of the present invention.

2 is a circuit diagram of the electronic device shown in FIG. 1.

3 is a schematic diagram showing a propagation path of the FM signal when the RSSI value of the FM signal in the electronic device shown in FIG. 2 is greater than a predetermined threshold.

4 is a schematic diagram showing a propagation path of the FM signal when the RSSI value of the FM signal in the electronic device shown in FIG. 2 is less than or equal to the preset threshold.

FIG. 5 is a flowchart of a method for switching an FM antenna according to a preferred embodiment of the present invention.

Referring to FIG. 1 , a preferred embodiment of the present invention provides an electronic device 100 having a Frequency Modulation (FM) function. The electronic device 100 can be a mobile phone, a tablet computer, a personal digital assistant (PDA), or the like. The electronic device 100 includes an earphone interface 11, an FM wafer 13, a processing unit 15, and a switching unit 17.

Referring to FIG. 2 , the earphone interface 11 is used to access the earphone, and at least includes a left channel pin 111 , a right channel pin 113 , and a ground pin 115 .

The FM wafer 13 can be an integrated FM radio receiving circuit. The FM wafer 13 is electrically connected to the left channel pin 111, the right channel pin 113, and the ground pin 115 of the headphone interface 11 by the switching unit 17. In this manner, when the earphone interface 11 is connected to an earphone, the FM chip 13 can be connected to the left channel pin 111 and the right channel pin of the earphone interface 11 by the switching of the switching unit 17. A signal receiving point constituting the FM antenna or a ground pin 115 of the earphone interface 11 constitutes a signal receiving point of the FM antenna, thereby receiving an FM signal, and converting the FM signal into an audio signal. The FM chip 13 is also electrically connected to the processing unit 15 for transmitting the audio signal to the processing unit 15. In addition, the FM chip 13 is further configured to feed back a Receive Signal Strength Indicator (RSSI) value to the processing unit 15.

The processing unit 15 can be a central processing unit (CPU). The processing unit 15 is electrically connected to the FM wafer 13 and the switching unit 17. The processing unit 15 is configured to receive the audio signal from the FM chip 13 and output the received audio signal to the left channel pin 111 and the right channel of the earphone interface 11 by the switching unit 17 Pin 113.

In this embodiment, the switching unit 17 includes a first switch SW1, a second switch SW2, a third switch SW3, and a fourth switch SW4. The first switch SW1 includes a set of input terminals IN1, a first group of output terminals OUT1, and a second group of output terminals OUT2. The input terminal IN1 of the first switch SW1 is electrically connected to the processing unit 15 for receiving an audio signal from the processing unit 15, and the audio signal is passed through one of the output terminals, for example, the first group. The output terminal OUT1 or the second group of output terminals OUT2 is output to the second switch SW2.

The second switch SW2 includes a first set of input terminals IN2, a second set of input terminals IN3, and a set of output terminals OUT3. The two sets of input ends of the second switch SW2 are electrically connected to respective output ends of the first switch SW1. For example, the first set of input terminals IN2 of the second switch SW2 are electrically connected to the first set of output terminals OUT1 of the first switch SW1. The second set of input terminals IN3 of the second switch SW2 are electrically connected to the second set of output terminals OUT2 of the first switch SW1. The output terminal OUT3 of the second switch SW2 is electrically connected to the left channel pin 111 and the right channel pin 113 of the earphone interface 11, respectively.

The third switch SW3 includes an input terminal IN4, a first output terminal OUT4, and a second output terminal OUT5. The input terminal IN4 of the third switch SW3 is electrically connected to the ground pin 115 of the earphone interface 11. The first output terminal OUT4 of the third switch SW3 is grounded by the inductor L1 and electrically connected to the fourth switch SW4. The second output terminal OUT5 of the third switch SW3 is directly grounded.

The fourth switch SW4 includes a first input terminal IN5, a second input terminal IN6, and an output terminal OUT6. The first input terminal IN5 of the fourth switch SW4 is electrically connected to the second group of output terminals OUT2 of the first switch SW1 and the second group of input terminals IN3 of the second switch SW2. The second input terminal IN6 of the fourth switch SW4 is electrically connected to the first output terminal OUT4 of the third switch SW3. The output terminal OUT6 of the fourth switch SW4 is electrically connected to the FM wafer 13.

It can be understood that, in this embodiment, a detection mechanism (not shown) is further disposed in the processing unit 15. The detecting mechanism is configured to receive an RSSI value from the FM chip 13, and compare the RSSI value with a preset threshold, and then control switching of the switching unit 17 according to the comparison result to select the The left channel pin 111 and the right channel pin 113 function as a signal receiving point of the FM antenna or a ground pin 115 as a signal receiving point of the FM antenna. For example, when the processing unit 15 determines that the RSSI value of the FM wafer 13 is higher than the preset threshold, the switching unit 17 can be controlled to switch, and then the left channel pin of the earphone interface 11 is turned on. 111 and right channel pin 113 are switched to the FM wafer 13 such that the left channel pin 111 and the right channel pin 113 serve as signal receiving points of the FM antenna to receive FM signals. When the processing unit 15 determines that the RSSI value of the FM wafer 13 is less than or equal to the preset threshold, the switching unit 17 can be controlled to switch, thereby switching the ground pin 115 of the earphone interface 11 to The FM chip 13 is such that the ground pin 115 serves as a signal receiving point of the FM antenna, thereby receiving the FM signal.

For details, please refer to FIG. 3. In this embodiment, when the RSSI value of the FM wafer 13 is higher than the preset threshold, the processing unit 15 controls the switching unit 17 to operate in the first mode. That is, the processing unit 15 controls the first switch SW1 to switch to the second group output terminal OUT2, the second switch SW2 switches to the second group input terminal IN3, and the third switch SW3 switches to the second output terminal OUT5. And the fourth switch SW4 is switched to the first input terminal IN5. In this manner, when the earphone interface 11 is inserted into an earphone, the electronic device 100 can feed the FM signal through the left channel pin 111 and the right channel pin 113 of the earphone interface 11. The FM signal is transmitted to the first input terminal IN5 of the fourth switch SW4 through the output terminal OUT3 of the second switch SW2 and the second input terminal IN3, and then transmitted through the output terminal OUT6 of the fourth switch SW4. To the FM wafer 13 (please refer to the propagation path P1). At the same time, the FM chip 13 processes the received FM signal to output a corresponding audio signal to the processing unit 15. The processing unit 15 outputs the received audio signal to the second group of input terminals IN3 of the second switch SW2 by the input terminal IN1 and the second group output terminal OUT2 of the first switch SW1. The output terminal OUT3 of the second switch SW2 is output to the left channel pin 111 and the right channel pin 113 of the earphone interface 11. Finally, the audio signal is grounded via the ground pin 115 of the earphone interface 11 and the second output terminal OUT5 of the third switch SW3 (refer to the propagation path P2).

Referring to FIG. 4 together, when the RSSI value of the FM wafer 13 is less than or equal to the preset threshold, the processing unit 15 controls the switching unit 17 to operate in the second mode. That is, the processing unit 15 controls the first switch SW1 to switch to the first group of output terminals OUT1, the second switch SW2 switches to the first group of input terminals IN2, and the third switch SW3 switches to the first output terminal OUT4 And the fourth switch SW4 is switched to the second input terminal IN6. In this manner, when the earphone interface 11 is inserted into an earphone, the electronic device 100 can feed the FM signal through the ground pin 115 of the earphone interface 11. The FM signal is then transmitted to the second input terminal IN6 of the fourth switch SW4 via the first output terminal OUT4 of the third switch SW3, and then transmitted to the FM chip via the output terminal OUT6 of the fourth switch SW4. 13 (please refer to propagation path P3). At the same time, the FM chip 13 processes the received FM signal to output a corresponding audio signal to the processing unit 15. The processing unit 15 outputs the received audio signal to the first group of input terminals IN2 of the second switch SW2 by the input terminal IN1 of the first switch SW1 and the first group of output terminals OUT1. The output terminal OUT3 of the second switch SW2 is output to the left channel pin 111 and the right channel pin 113 of the earphone interface 11. Finally, the audio signal is grounded via the ground pin 115 of the earphone interface 11 and the first output terminal OUT4 of the third switch SW3 and the inductor L1 (refer to the propagation path P4).

It can be understood that in other embodiments, the electronic device 100 further includes an audio unit 18 . The audio unit 18 is electrically connected between the processing unit 15 and the input terminal IN1 of the first switch SW1 for receiving an audio signal from the processing unit 15 to filter out the noise of the audio signal. . At the same time, the audio unit 18 is further configured to prevent the FM signal from being returned to the processing unit 15 by the first switch SW1, that is, preventing the FM signal from interfering with the audio signal. In this embodiment, the audio unit 18 includes a decoder 181 and two inductors L2 and L3 connected in parallel. The decoder 181 is electrically connected to the processing unit 15. One of the two inductors L2, L3 in parallel is electrically connected to the decoder 181 and electrically connected to the input terminal IN1 of the first switch SW1, respectively. The decoder 181 is configured to receive an audio signal from the processing unit 15 and decode the audio signal to filter out the noise of the audio signal. The two inductors L2 and L3 connected in parallel prevent the FM signal from being returned to the decoder 181 by the first switch SW1, that is, preventing the FM signal from interfering with the audio signal.

It can be understood that in other embodiments, the electronic device 100 further includes a matching circuit 19. One end of the matching circuit 19 is electrically connected between the second group of output terminals OUT2 of the first switch SW1 and the second group of input terminals IN3 of the second switch SW2. The other end of the matching circuit 19 is electrically connected to the first input terminal IN5 of the fourth switch SW4. The matching circuit 19 is configured to filter the FM signal to filter out the noise or unnecessary frequency outside the FM band, and simultaneously match the FM signal to improve the receiving effect on the FM signal. In the embodiment, the matching circuit 19 includes a first capacitor C1, a second capacitor C2, and an inductor L4. The first capacitor C1 is connected in parallel with the second capacitor C2 and is electrically connected to the second group of output terminals OUT2 of the first switch SW1 and the second group of input terminals IN3 of the second switch SW2. The first capacitor C1 and the second capacitor C2 connected in parallel are connected in series with the inductor L4, and are electrically connected to the first input terminal IN5 of the fourth switch SW4 by the inductor L4.

Please refer to FIG. 5, which is a flowchart of a method for switching an FM antenna according to a preferred embodiment of the present invention. The method includes the following steps:

In step S1, an earphone is inserted, and the FM function of the electronic device 100 is turned on.

In step S2, the processing unit 15 controls the switching of the switching unit 17 to select the left channel pin 111 and the right channel pin 113 of the earphone interface 11 as the signal receiving point of the FM antenna, or select the The ground pin 115 of the headphone interface 11 serves as a signal receiving point of the FM antenna.

In this embodiment, the left channel pin 111 and the right channel pin 113 of the earphone interface 11 are selected as the signal receiving point of the FM antenna when the initial state is preset. Of course, in other embodiments, the ground pin 115 of the earphone interface 11 can be preset as the signal receiving point of the FM antenna.

In step S3, the FM signal is received, and the RSSI value of the FM signal is output.

Step S4, comparing the RSSI value of the FM signal with a preset threshold, and controlling switching of the switching unit 17 according to the comparison result, to switch to the corresponding left channel pin 111, right channel pin 113 or the ground pin 115.

Specifically, the step S4 includes:

In step S41, it is determined whether the RSSI value of the FM signal is greater than the preset threshold. If yes, step S42 is performed; if no, step S43 is performed.

Step S42, when it is determined that the RSSI value of the FM signal is greater than the preset threshold, it indicates that the quality of the received FM signal is high. Thus, the left channel pin 111 and the right channel pin 113 of the earphone interface 11 can be switched to preferentially select the left channel pin 111 and the right channel pin 113 as signal receiving points of the FM antenna. In addition, the audio signal is directly grounded through the ground pin 115 of the earphone interface 11 and the second output terminal OUT5 of the third switch SW3. Therefore, the distortion of the audio signal can be greatly improved. After testing, the distortion can reach -88dB, which can also achieve the distortion requirement of WiFi audio signals, that is, less than -85dB.

Step S43, when it is determined that the RSSI value of the FM signal is less than or equal to the preset threshold, it indicates that the quality of the received FM signal is poor. In this way, the ground pin 115 of the earphone interface 11 can be switched to preferentially select the ground pin 115 as a signal receiving point of the FM antenna, thereby enhancing the receiving signal of the FM signal.

Obviously, the electronic device 100 of the present invention is provided with the switching unit 17, so that the switching to the switching unit 17 can be controlled according to the RSSI value of the received FM signal, and then switched to the left channel of the corresponding earphone interface 11. The foot 111 and the right channel pin 113 or the ground pin 115 further enhance the quality of the FM signal.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way. In addition, those skilled in the art can make other changes in the spirit of the present invention. Of course, the changes made in accordance with the spirit of the present invention should be included in the scope of the present invention.

100‧‧‧Electronic devices

11‧‧‧ headphone interface

111‧‧‧Left channel pin

113‧‧‧Right channel pin

115‧‧‧ Grounding Pin

13‧‧‧FM chip

15‧‧‧Processing unit

17‧‧‧Switch unit

SW1‧‧‧ first switch

IN1, IN4‧‧‧ input

OUT1‧‧‧ first set of outputs

OUT2‧‧‧Second set of outputs

SW2‧‧‧second switch

IN2‧‧‧ first set of inputs

IN3‧‧‧Second input

OUT3, OUT6‧‧‧ output

SW3‧‧‧ third switch

OUT4‧‧‧ first output

OUT5‧‧‧ second output

SW4‧‧‧fourth switch

IN5‧‧‧ first input

IN6‧‧‧ second input

18‧‧‧Audio unit

181‧‧‧Decoder

L1, L2, L3, L4‧‧‧ inductance

19‧‧‧Matching circuit

C1‧‧‧first capacitor

C2‧‧‧second capacitor

no

100‧‧‧Electronic devices

11‧‧‧ headphone interface

111‧‧‧Left channel pin

113‧‧‧Right channel pin

115‧‧‧ Grounding Pin

13‧‧‧FM chip

15‧‧‧Processing unit

17‧‧‧Switch unit

SW1‧‧‧ first switch

IN1, IN4‧‧‧ input

OUT1‧‧‧ first set of outputs

OUT2‧‧‧Second set of outputs

SW2‧‧‧second switch

IN2‧‧‧ first set of inputs

IN3‧‧‧Second input

OUT3, OUT6‧‧‧ output

SW3‧‧‧ third switch

OUT4‧‧‧ first output

OUT5‧‧‧ second output

SW4‧‧‧fourth switch

IN5‧‧‧ first input

IN6‧‧‧ second input

18‧‧‧Audio unit

181‧‧‧Decoder

L1, L2, L3, L4‧‧‧ inductance

19‧‧‧Matching circuit

C1‧‧‧first capacitor

C2‧‧‧second capacitor

Claims (11)

An electronic device with FM function, the improvement is that the electronic device comprises an earphone interface, an FM chip, a processing unit and a switching unit, and the earphone interface comprises a left channel pin, a right channel pin and a ground pin; The FM chip is electrically connected to the processing unit and the switching unit for processing an FM signal, and returns a Receive Signal Strength Indicator (RSSI) value to the processing unit, where the processing unit borrows The switching unit is electrically connected to the left channel pin, the right channel pin, and the ground pin, and the processing unit is configured to receive the RSSI value and compare the RSSI value to The preset threshold is compared, and then the switching of the switching unit is controlled according to the comparison result, so that the left channel pin and the right channel pin are selected to form a signal receiving point of the FM antenna or the ground pin is selected. As the signal receiving point of the FM antenna. The FM-enabled electronic device of claim 1, wherein the switching unit comprises a first switch, a second switch, a third switch, and a fourth switch, the first switch comprising a set of inputs, a first set of outputs and a second set of outputs, the second switch comprising a first set of inputs, a second set of inputs, and a set of outputs, the third switch comprising an input, a first output, and a a second output, the fourth switch includes a first input end, a second input end, and an output end; the input end of the first switch is electrically connected to the processing unit, and the first set of input ends of the second switch Electrically connected to the first set of output ends of the first switch, the second set of input ends of the second switch is electrically connected to the second set of output ends of the first switch, and the output ends of the second switch are respectively Electrically connected to the left channel pin and the right channel pin; the input end of the third switch is electrically connected to the ground pin, and the first output end of the third switch is grounded by an inductor The second output of the third switch is directly grounded, the fourth The first input terminal is electrically connected to the second group of output ends of the first switch and the second group of input terminals of the second switch, and the second input end of the fourth switch is electrically connected to the third A first output of the switch, the output of the fourth switch being electrically coupled to the FM wafer. The FM-enabled electronic device of claim 2, wherein the processing unit controls the switching unit to operate in the first mode when an RSSI value of the FM chip is higher than the preset threshold Controlling the first switch to switch to the second set of outputs, the second switch is switched to the second set of inputs, the third switch is switched to the second output, and the fourth switch is switched to the An input terminal, and further selecting the left channel pin and the right channel pin to form a signal receiving point of the FM antenna; when the RSSI value of the FM chip is less than or equal to the preset threshold, The processing unit controls the switching unit to operate in the second mode to control the first switch to switch to the first group of output ends, the second switch to switch to the first group of inputs, and the third switch to switch to the first The output terminal and the fourth switch are switched to the second input terminal, and the ground pin is selected to form a signal receiving point of the FM antenna. The FM-enabled electronic device of claim 3, wherein in the first mode, the FM signal is fed through a left channel pin and the right channel pin, and then the FM signal passes The output end of the second switch and the second input end are transmitted to the first input end of the fourth switch, and then transmitted to the FM chip via the output end of the fourth switch, and the FM chip pair receives The FM signal is processed to output a corresponding audio signal to the processing unit, and the audio signal is output to the second group of input ends of the second switch by the second group of output ends of the first switch, and then The output terminal of the second switch is output to the left channel pin and the right channel pin, and finally grounded via the ground pin and the second output end of the third switch. The FM-enabled electronic device of claim 3, wherein in the second mode, the FM signal is fed by the ground pin, and then the FM signal passes through the first of the third switch. The output end is transmitted to the second input end of the fourth switch, and then transmitted to the FM chip via the output end of the fourth switch, and the FM chip processes the received FM signal to output a corresponding audio signal. Up to the processing unit, the audio signal is output to the first group of input ends of the second switch by the first group of output ends of the first switch, and is output to the output end of the second switch The left channel pin and the right channel pin are finally grounded via the ground pin and the first output end of the third switch and the inductor. The FM-enabled electronic device of claim 3, wherein the electronic device further includes an audio unit, the audio unit is electrically connected between the processing unit and an input end of the first switch, And receiving the audio signal, and decoding the audio signal, and preventing the FM signal from being returned to the audio unit by the first switch. The FM-enabled electronic device of claim 6, wherein the audio unit comprises a decoder and two inductors connected in parallel, the decoder is electrically connected to the processing unit, and the two inductors in parallel are connected. One end is electrically connected to the decoder and electrically connected to an input of the first switch, respectively. The FM-enabled electronic device of claim 3, wherein the electronic device further comprises a matching circuit electrically connected to the second set of inputs and the fourth of the second switch The first input end of the switch is used to filter the FM signal to filter out the noise or unnecessary frequency outside the FM band, and at the same time match the FM signal to improve the receiving effect of the FM signal. The FM-enabled electronic device of claim 8, wherein the matching circuit comprises a first capacitor, a second capacitor, and an inductor, the first capacitor being connected in parallel with the second capacitor, and electrically connected to the a second set of output ends of the first switch and a second set of input ends of the second switch, the paralleled first capacitor and the second capacitor are connected in series with the inductor, and are electrically connected to the fourth by the inductor The first input of the switch. An FM antenna switching method is applied to an electronic device, the electronic device includes at least an earphone interface, and the earphone interface includes a left channel pin, a right channel pin, and a ground pin. The improvement is that the method includes: (a) Insert a headset and turn on the FM function; (b) selecting the left channel pin, the right channel pin as a signal receiving point of the FM antenna, or selecting the ground pin as a signal receiving point of the FM antenna; (c) receiving an FM signal and outputting an RSSI value of the FM signal; (d) comparing the RSSI value with a preset threshold, and switching the signal receiving point of the FM antenna to the left channel pin and the right channel pin according to the comparison result, or switching to the location Ground pin. The FM antenna switching method according to claim 10, wherein the step (d) comprises: Determining whether the RSSI value is greater than the preset threshold; When it is determined that the RSSI value is greater than the preset threshold, switching to the left channel pin and the right channel pin to select the left channel pin and the right channel pin as the FM antenna Signal receiving point; When it is determined that the RSSI value is less than or equal to the preset threshold, switching to the ground pin to select the ground pin as a signal receiving point of the FM antenna.