A broadband spread spectrum circuit

Abstract

The utility model discloses a broadband spectrum spreading circuit, including a frequency doubling unit, a low-pass filtering unit, a switching filtering unit, a power control unit and a coupling detection unit. The frequency doubling unit is composed of a first amplifier, a second amplifier and a third amplifier connected in sequence. The first amplifier and the second amplifier are used to amplify the radio frequency input signal, and the third amplifier is used to achieve saturation output of the amplified radio frequency input signal; the switching filtering unit is used to output the harmonics generated by the amplifier in the frequency doubling unit in frequency bands; the power control unit is used to couple the output radio frequency output signal and generate a detection voltage through a detector. The utility model utilizes the nonlinear characteristics of the amplifier chip, takes the amplifier harmonic signal as a secondary frequency doubling signal, realizes the double frequency function, reduces the types of devices, and reduces the hardware cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of communication, and relates to a radio frequency circuit, in particular to a broadband spread spectrum circuit which can reduce stray signals and facilitate the unification of device types. Background Art

[0002] Spread spectrum communication is a frequency extension technology commonly used in current communication circuits. It is a communication method that uses a radio frequency signal with a much wider bandwidth than the signal generated by the signal source. It is widely used in wireless communications, radar systems, test equipment and other fields. The current conventional solution is to use nonlinear components such as frequency multiplication or mixing to achieve a spread spectrum effect. Among them, the frequency multiplication scheme mostly uses diode multipliers, triode multipliers, phase-locked multipliers or integrated multipliers. There are many types of devices, which generate stray signals of different frequencies, affecting the communication effect of the system. Utility Model Content

[0003] Technical purpose: In view of the above problems, the utility model provides a broadband spread spectrum circuit to improve the input power of the amplifier chip. It utilizes the nonlinear characteristics of the amplifier chip, takes the amplifier harmonic signal as the secondary frequency multiplication signal, and obtains the required spread spectrum signal after being processed by a switch filter unit, a power control unit, a signal coupling detection unit, etc.

[0004] Technical solution: To achieve the above technical objectives, the utility model adopts the following technical solution:

[0005] A broadband spectrum spreading circuit includes a frequency multiplication unit, a low-pass filtering unit, a switch filtering unit, a power control unit and a coupling detection unit, wherein:

[0006] A first single-pole double-throw switch is provided at the front end of the frequency multiplication unit, which is used to divide the radio frequency input signal of the broadband spectrum spreading circuit into two paths, which are input into the low-pass filtering unit and the frequency multiplication unit respectively;

[0007] The frequency multiplication unit is composed of a first amplifier, a second amplifier and a third amplifier connected in sequence, the first amplifier and the second amplifier are used to amplify the radio frequency input signal, and the third amplifier is used to saturate the radio frequency input signal amplified by the first amplifier and the second amplifier;

[0008] The switch filter unit is used to output the harmonics generated by the amplifier in the frequency multiplication unit in frequency bands, and the switch filter unit includes a second single-pole three-throw switch, a third single-pole three-throw switch, and a first band-pass filter, a second band-pass filter, and a third band-pass filter connected in parallel between the second single-pole three-throw switch and the third single-pole three-throw switch;

[0009] The output ends of the low-pass filter unit and the switch filter unit are provided with a fourth single-pole double-throw switch for selecting an output signal to the power control unit;

[0010] The power control unit is used to adjust the signal power. A second low-pass filter is provided between the output end of the power control unit and the coupling detection unit. The coupling detection unit is used to output a detection voltage signal and a radio frequency output signal.

[0011] Preferably, the low-pass filtering unit is provided with a first low-pass filter, the first low-pass filter adopts an open-circuit short-stub low-pass filter of 10MHz to 13GHz, the first band-pass filter, the second band-pass filter, and the third band-pass filter BPF3 respectively adopt cross-coupled filters of 13GHz to 15.5GHz, 15.5GHz to 20GHz, and 20GHz to 26.5GHz, and the second band-pass filter LPF2 adopts an open-circuit short-stub low-pass filter of 10MHz to 26.5GHz.

[0012] Preferably, the power control unit comprises a voltage-controlled attenuator and a fifth amplifier connected in series, and the fifth amplifier is used to amplify the signal.

[0013] Preferably, the coupling detection unit comprises a directional coupler, a detector and an attenuator, the directional coupler is used to couple and output the radio frequency output signal and generate a detection voltage through the detector, and the attenuator is arranged at the isolation end of the directional coupler.

[0014] Beneficial effects: Due to the adoption of the above technical solution, the utility model has the following beneficial effects:

[0015] The utility model utilizes the nonlinear characteristics of the amplifier to achieve the frequency doubling function, saves a frequency multiplier or a mixer, can reduce the types of devices, facilitates the unification of chips, and reduces hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a broadband spread spectrum circuit proposed by the utility model.

[0017] Among them, A1-first amplifier, A2-second amplifier, A3-third amplifier, A4-fourth amplifier, A5-fifth amplifier; S1-first single-pole double-throw switch, S2-second single-pole triple-throw switch, S3-third single-pole triple-throw switch, S4-fourth single-pole double-throw switch; LPF1-first low-pass filter, LPF2-second low-pass filter, BPF1-first band-pass filter, BPF2-second band-pass filter, BPF3-third band-pass filter;

[0018] T1-voltage controlled attenuator, T2-attenuator, T3-detector, D1-directional coupler. DETAILED DESCRIPTION

[0019] The embodiments of the present utility model are described in detail below in conjunction with the accompanying drawings.

[0020] The utility model provides a broadband spread spectrum circuit, comprising:

[0021] The frequency doubling unit uses a three-stage amplifier to perform push-saturation processing on the input signal, and passes through a switching filter group to filter out the second harmonic, filter out the fundamental wave and unnecessary high-order harmonics, and generate a frequency doubling signal.

[0022] The switch filter unit includes a switch and a filter. The switch is used to select the frequency of the input signal to generate the required in-band signal. The filter is used to filter the input signal to select the required in-band signal and filter out the unnecessary out-of-band signal.

[0023] The power control unit includes a voltage-controlled attenuator and an amplifier. The voltage-controlled attenuator is used to adjust the signal power. The amplifier is used to amplify the signal power so that the signal reaches the required power.

[0024] The coupling detection unit includes a coupler and a detector, which is used to couple and output the radio frequency signal and generate a detection voltage through the detector.

[0025] like Figure 1 In the example shown, a radio frequency signal of 10MHz to 13GHz is input, wherein the frequency multiplication unit includes a first amplifier A1, a second amplifier A2, and a third amplifier A3. The first amplifier A1, the second amplifier A2, and the third amplifier A3 use amplifiers of the same model. The first amplifier A1 and the second amplifier A2 respectively linearly amplify the signal, and the signal power output by the second amplifier A2 is 4dB lower than the 1dB compression point of the amplifier output. The signal power output by the second amplifier A2 is lower than the maximum allowable input power of the amplifier of this model, and the third amplifier A3 will not be damaged due to excessive input power. After the signal power output by the second amplifier A2 passes through the third amplifier A3, the third amplifier A3 operates in the saturation region. The third amplifier A3 not only outputs the fundamental signal, but also generates a second harmonic signal with a higher power and generates other higher harmonic signals. The third amplifier A3 achieves saturated output of the signal. The switch filter unit outputs the harmonics of the amplifier in frequency bands, such as 13GHz to 15.5GHz, 15.5GHz to 20GHz, and 20GHz to 26.5GHz in this example. The second single-pole three-throw switch S2, the third single-pole three-throw switch S3, the first bandpass filter BPF1, the second bandpass filter BPF2, and the third bandpass filter BPF3 form a frequency selection network. The three bandpass filters are all cross-coupled filters. After the power control and coupling detection unit, the RF signal output of 10MHz to 26.5GHz is obtained.

[0026] The utility model utilizes the nonlinear characteristics of the amplifier chip to increase the input power of the amplifier chip, so that the final amplifier works in the saturation region, takes the second harmonic signal as the frequency multiplication signal, and passes through a switch filter unit, a power control unit, a coupling detection unit, etc., thereby obtaining the required spectrum spreading circuit.

[0027] The working principle of the broadband spread spectrum circuit of the utility model is as follows:

[0028] The source signal, i.e., the RF signal, is divided into two paths through the first single-pole double-throw switch S1. One path passes through the first low-pass filter LPF1; the other path passes through the frequency multiplication unit, i.e., passes through the first amplifier A1, the second amplifier A2, and the third amplifier A3 in sequence to generate a harmonic signal.

[0029] The harmonic signal output by the frequency multiplication unit is divided into three paths by the second single-pole triple-throw switch S2, and then input into the corresponding filters, namely the first bandpass filter BPF1, the second bandpass filter BPF2 and the third bandpass filter BPF3, to filter out the unnecessary signals, obtain the harmonic signal within the target frequency band, and then merge after passing through the third single-pole triple-throw switch S3. The signal output by the first low-pass filter LPF1 and the signal output by the third single-pole triple-throw switch S3 are selected and output by the fourth single-pole double-throw switch S4. Among them, the output end of the first bandpass filter BFP1 is provided with a fourth amplifier A4.

[0030] The signal output by the fourth single-pole double-throw switch S4 is input to the voltage-controlled attenuator T1. The attenuation of the voltage-controlled attenuator T1 is controlled by an external voltage input, thereby controlling the power of the entire link. The signal output by the voltage-controlled attenuator T1 is further filtered out of out-of-band noise after power adjustment by the fifth amplifier A5 and by the second low-pass filter LPF2.

[0031] Then the RF main signal is output through the directional coupler D1, and the directional coupler D1 couples out a part of the signal, which is output as a detection voltage after passing through the detector T3. The isolation end of the directional coupler D1 is added with an attenuator T2.

[0032] The above shows and describes the basic principle, main features and advantages of the utility model. Those skilled in the art should understand that the above embodiments do not limit the utility model in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the utility model.

Claims

1. A broadband spread spectrum circuit, characterized in that: It includes a frequency multiplication unit, a low-pass filtering unit, a switching filtering unit, a power control unit and a coupling detection unit, wherein: A first single-pole double-throw switch (S1) is provided at the front end of the frequency multiplication unit, which is used to divide the radio frequency input signal of the broadband spectrum spreading circuit into two paths, which are input into the low-pass filtering unit and the frequency multiplication unit respectively; The frequency multiplication unit is composed of a first amplifier (A1), a second amplifier (A2) and a third amplifier (A3) connected in sequence, the first amplifier (A1) and the second amplifier (A2) are used to amplify the radio frequency input signal, and the third amplifier (A3) is used to saturate the amplified radio frequency input signal; The switch filter unit is used to output the harmonics generated by the amplifier in the frequency multiplication unit in frequency bands, and the switch filter unit includes a second single-pole three-throw switch (S2), a third single-pole three-throw switch (S3), and a first band-pass filter (BPF1), a second band-pass filter (BPF2), and a third band-pass filter (BPF3) connected in parallel between the second single-pole three-throw switch (S2) and the third single-pole three-throw switch (S3); The output ends of the low-pass filter unit and the switch filter unit are provided with a fourth single-pole double-throw switch (S4) for selecting an output signal to be sent to the power control unit; The power control unit is used to adjust the signal power. A second low-pass filter (LPF2) is provided between the output end of the power control unit and the coupling detection unit. The coupling detection unit is used to output a radio frequency output signal and a detection voltage signal.

2. A broadband spectrum spreading circuit according to claim 1, characterized in that: The low-pass filtering unit is provided with a first low-pass filter (LPF1), the first low-pass filter (LPF1) adopts an open-circuit short-stub low-pass filter of 10MHz to 13GHz, the first band-pass filter (BPF1), the second band-pass filter (BPF2), and the third band-pass filter (BPF3) respectively adopt cross-coupled filters of 13GHz to 15.5GHz, 15.5GHz to 20GHz, and 20GHz to 26.5GHz, and the second low-pass filter (LPF2) adopts an open-circuit short-stub low-pass filter of 10MHz to 26.5GHz.

3. A broadband spectrum spreading circuit according to claim 1, characterized in that: The power control unit comprises a voltage-controlled attenuator (T1) and a fifth amplifier (A5) connected in series, and the fifth amplifier (A5) is used to amplify the signal.

4. The broadband spectrum spreading circuit according to claim 1, characterized in that: The coupling detection unit comprises a directional coupler (D1), a detector (T3) and an attenuator (T2); the directional coupler (D1) is used for coupling and outputting a radio frequency output signal and generating a detection voltage through the detector (T3); and the attenuator (T2) is arranged at the isolation end of the directional coupler (D1).

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