CN111865253A - Program-controlled LC filter based on I2C protocol and sine wave generation method - Google Patents

Abstract

The invention discloses a program control LC filter based on an I2C protocol and a sine wave generation method. The system comprises an I2C interface, a microprocessor, a relay and a sub LC filter. The I2C interface is used to receive control signals from the transmission to the filter; the microprocessor is used for decoding the received I2C signal, converting the decoded signal into a control signal and controlling the on-off of the relay; the relay is used as a channel switch, receives a control signal from the microprocessor and is used for selecting a channel of the sub-filter; the sub-filters are basic filtering units for filtering square wave signals of different frequency ranges. The invention ensures that the sine wave signals filtered by the square waves do not have high-order harmonics such as second harmonics through selecting the passing LC filter path by a program, solves the problem that the square waves of the communication system are converted into sine waves under a wide working frequency band, and improves the automation level of the communication system.

Description

Program-controlled LC filter based on I2C protocol and sine wave generation method

Technical Field

The invention belongs to the field of electronic communication, relates to a signal processing and filter design method, and particularly relates to a program-controlled LC filter based on an I2C protocol and a sine wave generation method.

Background

As the existing signal environment becomes more complex, the operating frequency band of the sinusoidal signal that needs to be input by the analog communication system circuit becomes wider and wider. The anti-interference capability of the communication system can be improved by using a wider working frequency band in a channel coding mode, and the interference of earth surface noise of a low frequency band is avoided. The currently common frequency bands for digital communications have reached gigahertz (GHz) frequencies. For example, the 4G operating frequency range specified by 3GPP is 1880-2635MHz, and the operating frequency range required by IEEE 802.11ac is 5170-5835 MHz. The wide signal operating range requires the use of a tunable filter with a wider bandwidth.

A communication system, if operable, must require a local oscillator to provide its underlying operating frequency. The local oscillator of the communication system is generally provided by a Phase Locked Loop (PLL) or a crystal oscillator, a signal output by the crystal oscillator is a sine wave or a square wave, and a signal output by the PLL is a square wave. For a conventional communication system, a sine wave is required as its local oscillator. Since the crystal oscillator has a narrow operating frequency range, it is rarely used in a broadband communication system. Phase-locked loops are widely used in communication systems due to their wide operating frequency and controllable frequency. According to the Fourier expansion law, square waves are generated by overlapping multi-order sine wave signals, if a sine wave signal with the same frequency as the square waves is obtained, secondary signals need to be completely filtered, the secondary signals are often integral multiples of the square wave signals, and therefore the problem can be solved by using a filter.

Filters used in communication systems can be classified into passive filters and active filters according to used devices, and can be classified into high-pass filters, band-pass filters, low-pass filters and band-stop filters according to pass band frequency bands. The passive filter is composed of passive devices such as a capacitor, a resistor and an inductor, and the active filter is composed of active devices such as a transistor or an operational amplifier. The passive filter has low power consumption and high working frequency, is a commonly used filter in a high-frequency circuit, but has the problems of small working bandwidth and inconvenient program control and adjustment. Although the active filter is convenient for program control and has a high working bandwidth, the power consumption is high and the working frequency is low. Passive filters are the most commonly used filters in high frequency communication systems. In order to solve the problem of filtering out the sine wave from the square wave, the above problem can be effectively solved by using a low-pass filter.

The I2C bus protocol is a simple, bi-directional two-wire synchronous serial bus developed by Philips corporation. The protocol requires only two wires to transfer information between devices connected to the bus. The master device is used to initiate the bus to transfer data and generate a clock to open up the transferred devices when any addressed device is considered a slave device. The relationship of master and slave, send and receive on the bus is not constant, but depends on the direction of data transfer at the time. If the master device is to send data to the slave device, the master device addresses the slave device first, then actively sends the data to the slave device, and finally the master device terminates data transmission; if the master device is to receive the data of the slave device, the slave device is addressed by the master device first, then the master device receives the data sent by the slave device, and finally the master device terminates the receiving process. In this case, the master is responsible for generating the timing clock and terminating the data transfer. The I2C bus protocol is widely used in the fields of communication and automation control, and is a common signal communication protocol.

Disclosure of Invention

The inventor finds that after the design of the conventional passive filter is finished, the working frequency and the bandwidth of the conventional passive filter are fixed parameters, and the problem that the passband is short and flexible adjustment is difficult to realize exists in the generation of the local oscillator for the communication system with wide working frequency, so that the conventional passive filter is difficult to completely filter the multi-order harmonic waves contained in the square wave and is difficult to be used for the generation of the local oscillator. In order to solve the technical problem, the invention provides a program-controlled LC filter based on an I2C bus, which can effectively use a passive filter for local oscillator generation of a communication system. The specific technical scheme is as follows:

a programmed LC filter based on the I2C protocol, comprising: I2C interface, microprocessor, relay, sub LC filter. The I2C interface is used for receiving a control signal transmitted to the filter from the upper computer; the microprocessor is used for decoding the received I2C signal and converting the decoded signal into a control signal for controlling the on-off of the relay; the relay is used as a channel switch, receives a control signal from the microprocessor and is used for selecting a channel of the sub-filter; the sub-filter is a basic filtering unit and is used for filtering square wave signals in different frequency ranges, and whether the signals pass through the filtering path can be selected by the relay.

A sine wave generation method of a multi-order program-controlled filter based on an I2C bus communication protocol comprises the following steps:

(1) connecting a signal sent by a phase-locked loop to an input interface of a filter, and starting the phase-locked loop;

(2) the upper computer sends a corresponding control signal through an I2C bus, a corresponding filter channel is selected, and the microprocessor receives the I2C signal and transcodes the signal into a signal for controlling the relay;

(3) the relay receives the signal of the microprocessor and controls whether the sub-filter passage is on or off, thereby finishing the work of selecting the filter passage.

The invention has the following beneficial effects:

the invention can select the passing LC filter path through a program, ensures that sine wave signals filtered by square waves do not have high-order harmonics such as second harmonics, solves the problem that the square waves of a communication system are converted into sine waves under a wide working frequency band, and improves the automation level of the communication system.

Drawings

Fig. 1 is a schematic diagram of a programmable LC filter based on the I2C protocol.

In the figure: 1 is an I2C signal interface, 2 is a microprocessor, 3 is a square wave signal input interface, 4 is a sine wave signal output interface, 5 is a relay, and 6 is a sub LC filter.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, a schematic diagram of an embodiment 1 of a program-controlled LC filter based on I2C protocol according to an embodiment of the present invention is described below with reference to an example of converting an input square wave into a sine wave, where a corresponding square wave generating device may be a phase-locked loop, an output signal load may be a resistive load, and an upper computer control system may be a personal computer.

The system comprises: I2C signal interface 1, microprocessor 2, square wave signal input interface 3, sine wave signal output interface 4, relay 5, sub LC filter 6.

The I2C signal interface 1 is connected with a personal computer, the square wave signal input interface 3 is connected with a phase-locked loop output signal, and the sine wave signal output interface 4 is connected with a resistance load.

Those skilled in the art will appreciate that the signal interface has many forms, and any interface capable of ensuring the electrical characteristics can be used for the I2C signal interface 1, the square wave signal input interface 3 and the sine wave signal output interface 4. The present invention is not particularly limited.

It will be understood by those skilled in the art that the order of the LC filter and the parameters of the capacitance and inductance are related to the specific requirements of the filter, and therefore, the value, packaging and connection manner of each channel in the sub-LC filter 6 and its corresponding order and capacitance and inductance are not limited in any way.

Preferably, the number of sub LC filters may be greater or less than the three channels illustrated in fig. 1 to optimize the filtering level of the harmonics and broaden the operating frequency of the programmable LC filter, so the number of channels of the sub LC filters 6 is not specifically limited in the present invention.

Correspondingly, the present invention further provides an embodiment of a method for converting an input square wave into a sine wave, which can be applied to the program-controlled LC filter system described in the above embodiments, and the embodiment also takes the example of converting a square wave into a sine wave as an illustration. The method may specifically comprise the steps of:

s1, electrifying the program control LC filtering system, and outputting square waves to the square wave signal input interface 3 by the phase-locked loop;

S2, the personal computer sends control command through I2C bus to select LC channel or close all LC filter channels, the signal is received by I2C signal interface 1;

s3, after receiving the signal obtained by the I2C signal interface 1, the microprocessor 2 processes the command, converts the command into a signal for controlling the relay 5, and controls the on-off of the corresponding relay through a lead;

and S4, outputting the signal to a program-controlled LC filter through a sine wave signal output interface 4, and transmitting the sine wave to a resistance load.

The specific state diagram of this step can be referred to as shown in fig. 1.

Preferably, the parsing method and algorithm for the I2C protocol executed in the microprocessor 2 can be designed by the user, so as to improve the working efficiency of the programmable LC filter, which is not limited herein.

The technical scheme provided by the embodiment solves the problem of local oscillation generation of the communication system, so that the LC filter can be applied to a wide-bandwidth communication system, the communication system obtains a local oscillation source with higher purity, and the quality and the automation level of the communication system are improved.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (2)

1. A programmable LC filter based on I2C protocol, comprising:

an I2C interface, a microprocessor, a relay and a sub LC filter;

wherein, the I2C interface is used for receiving a control signal transmitted to the filter; the microprocessor is used for decoding the received I2C signal, converting the decoded signal into a control signal and controlling the on-off of the relay; the relay is used as a channel switch, receives a control signal from the microprocessor and is used for selecting a channel of the sub LC filter; the sub LC filters are basic filtering units for filtering square wave signals in different frequency ranges.

2. A sine wave generation method based on I2C protocol, comprising the steps of:

(1) connecting a signal sent by a phase-locked loop to an input interface of a filter, and starting the phase-locked loop;

(2) the upper computer sends a corresponding control signal through an I2C bus, a corresponding filter channel is selected, and the microprocessor receives the I2C signal and transcodes the signal into a signal for controlling the relay;

(3) the relay receives the signal of the microprocessor and controls whether the sub-filter passage is on or off, thereby finishing the work of selecting the filter passage.

Images