Modulator circuit architecture with high carrier suppression and high linearity

Abstract

The invention provides a high carrier suppression and high linearity modulator circuit architecture, which comprises a carrier coupling offset branch, the carrier coupling offset branch is respectively connected with an IQ modulator and a 0-degree power combiner, and the IQ modulator is connected with the 0-degree power combiner; the carrier coupling offset branch comprises a 90-degree bridge, a second fixed attenuator, a reverse isolation fixed gain amplifier, an attenuator, a multi-gear attenuator, a narrow-band band-pass filter, a third fixed attenuator, a phase shifter, a fourth fixed attenuator, an analog continuously adjustable amplifier and a first fixed attenuator; and the 90-degree bridge is also connected with the IQ modulator through a fifth fixed attenuator. A modulator carrier wave excitation signal is leaked to a modulation output port to become an in-band clutter signal, the in-band clutter signal is coupled with a carrier wave signal excitation port and then passes through an amplitude and phase adjustment signal, and after the in-band clutter signal is combined and output by a transmitting channel coupler, the amplitude is equal, the phase is opposite, and carrier wave leakage in-band clutter signal suppression is achieved; the defect that in the prior art, the difference of 70dB required indexes is about 40dB is overcome.

Description

Technical Field

[0001] The present invention belongs to the field of carrier communication technology, and in particular relates to a high carrier suppression and high linearity modulator circuit architecture. Background Art

[0002] The QPSK modulator used for modulation transmission can be I / Q low-frequency drive mode or carrier drive mode. In the I / Q drive mode, the carrier power is relatively small, about 0dBm, and the carrier suppression capability that the current device can guarantee can only stay at about 30-40dB suppression capability level, but the linearity is poor. In the carrier drive mode, the carrier power is larger, about 13-15dBm, and the carrier suppression capability that the current device can guarantee can only stay at about 25-30dB suppression capability level, but the linearity is better. If a higher carrier suppression capability greater than 70dB and better linear indicators are required, the current modulator cannot achieve this. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide a high carrier suppression and high linearity modulator circuit architecture to solve the problem that ordinary modulators in the prior art have strong carrier suppression but poor linearity or good linearity but poor carrier suppression.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution to achieve: a high carrier suppression and high linearity modulator circuit architecture, including a carrier coupling cancellation branch, wherein the carrier coupling cancellation branch is respectively connected to an IQ modulator and a 0° power synthesizer, and the IQ modulator is connected to the 0° power synthesizer.

[0005] The carrier coupling cancellation branch comprises a 90° bridge, a second fixed attenuator, a reverse isolation fixed gain amplifier, an attenuator multi-stage attenuator, a narrowband bandpass filter, a third fixed attenuator, a phase shifter, a fourth fixed attenuator, an analog continuously adjustable amplifier and a first fixed attenuator connected in sequence.

[0006] The 90° bridge is also connected to the IQ modulator via a fifth fixed attenuator.

[0007] The present invention also includes the following technical features:

[0008] The carrier input port of the IQ modulator is connected to the 90° bridge transmission branch output port of the carrier coupling cancellation branch through a first fixed attenuator.

[0009] The coupling port of the IQ modulator is connected to the first fixed attenuator.

[0010] The other port of the second fixed attenuator is connected to the input port of the reverse isolation fixed gain amplifier.

[0011] The output port of the reverse isolation fixed gain amplifier is connected to an attenuator with multiple gears.

[0012] Another port of the attenuator multi-stage attenuator is connected to the input port of the narrow-band bandpass filter.

[0013] The output port of the narrowband bandpass filter is connected to a third fixed attenuator.

[0014] Another port of the third fixed attenuator is connected to the input port of the phase shifter.

[0015] The output port of the phase shifter is connected to a fourth fixed attenuator.

[0016] The fourth fixed attenuator is connected to the input port of the analog continuously adjustable amplifier.

[0017] The output port of the analog continuously adjustable amplifier is connected to a first fixed attenuator.

[0018] The first fixed attenuator is connected to the 0° power combiner.

[0019] The high carrier suppression and high linearity modulator circuit architecture also includes a network thermostat and an analog voltage temperature fitting circuit.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] (I) The high carrier suppression and high linearity modulator circuit architecture provided by the present invention overcomes the shortcoming that the carrier suppression capability of the existing debugger is about 40 dB away from the system requirement of 70 dB, and designs a high carrier suppression and high linearity modulator circuit architecture, focusing on the following three aspects of innovation:

[0022] It is proposed that the modulator carrier excitation signal leaks to the modulation output port and becomes an in-band interference signal. After coupling with the carrier signal excitation port, the signal is adjusted in amplitude and phase. After being combined and output by the transmitting channel coupler, the amplitude is equal and the phase is opposite, thereby achieving the suppression of the carrier leakage in-band interference signal.

[0023] On the basis of the above, the modulator adopts a carrier excitation method, which can reduce the I / Q input signal level to a lower level, thereby greatly improving the linearity of the modulator.

[0024] (II) The high carrier suppression and high linearity modulator circuit architecture provided by the present invention has an ingenious product design method, a simple structure that is easy to implement, and can be expanded to higher frequency bands and wider dynamic requirements, and can be applied to various circuits and systems as needed.

[0025] (III) The high carrier suppression and high linearity modulator circuit architecture provided by the present invention adopts a highly plastic RF channel amplitude and phase temperature compensation circuit architecture and a modulator ultra-high carrier suppression network constant temperature heating concept to ensure the stability of the modulator carrier suppression.

[0026] (IV) The high carrier suppression and high linearity modulator circuit architecture provided by the present invention can be easily extended to other microwave circuits that require adaptive adjustment, such as microwave receiving and transmitting system gain temperature compensation control circuits, providing a very simple and practical design template for temperature adaptive control circuit design. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a block diagram of the suppression principle of the high carrier suppression and high linearity modulator circuit architecture of the present invention.

[0028] FIG. 2 is a schematic diagram of simulation results of the high carrier suppression and high linearity modulator circuit architecture of the present invention.

[0029] The numbers in the figure represent:

[0030] 1-IQ modulator, 2-0° power synthesizer, 3-90° bridge, 4-second fixed attenuator, 5-reverse isolation fixed gain amplifier, 6-multi-position attenuator, 7-narrowband bandpass filter, 8-third fixed attenuator, 9-phase shifter, 10-fourth fixed attenuator, 11-analog continuously adjustable amplifier, 12-first fixed attenuator, 13-network thermostat, 14-analog voltage temperature fitting circuit,

[0031] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0032] All components in the present invention, unless otherwise specified, are components known in the prior art.

[0033] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0034] Embodiment 1:

[0035] This embodiment provides a high carrier suppression and high linearity modulator circuit architecture, such as Figure 1 As shown in FIG. 2 , it includes a carrier coupling cancellation branch, wherein the carrier coupling cancellation branch is respectively connected to the IQ modulator 1 and the 0° power synthesizer 2 , and the IQ modulator 1 is connected to the 0° power synthesizer 2 .

[0036] The carrier coupling cancellation branch includes a 90° bridge 3, a second fixed attenuator 4, a reverse isolation fixed gain amplifier 5, an attenuator multi-speed attenuator 6, a narrowband bandpass filter 7, a third fixed attenuator 8, a phase shifter 9, a fourth fixed attenuator 10, an analog continuously adjustable amplifier 11 and a first fixed attenuator 12 connected in sequence.

[0037] The 90° bridge 3 is also connected to the IQ modulator 1 via a fifth fixed attenuator 15 .

[0038] Figure 1 In the figure, FLO represents the carrier frequency; RFout represents the modulation output; Vout1 represents the analog phase shifter control voltage; Vout2 represents the analog attenuator control voltage; I and Q represent the modulated RF signal input terminals of the QPSK modulator; and point P represents the output terminal after the modulator output signal and the cancellation circuit output signal are combined.

[0039] The carrier input port of the IQ modulator 1 is connected to the output port of the 90° bridge 3 transmission branch of the carrier coupling cancellation branch through the amplitude-adjustable fifth attenuator 13. The carrier signal power of the 90° bridge 3 input port of the carrier coupling cancellation branch is 16dBm. After adjustment by the amplitude-adjustable fifth attenuator 13, the carrier power entering the IQ modulator 1 meets the carrier excitation driving power requirement of 10dBm±1dB, so that the I and Q input voltages of the IQ modulator 1 can be reduced to less than or equal to ±0.1V, thereby greatly improving the linearity of the IQ modulator 1.

[0040] The carrier suppression at the output port of IQ modulator 1 can only maintain about 25 to 30 dB, that is, the carrier power at the output port of IQ modulator 1 is -20 to -15 dBm, which can easily saturate the amplifier link connected to the back end of the modulator, causing large signal blocking and the modulation signal cannot be transmitted normally. Therefore, the carrier coupling cancellation branch, which is the key to the high carrier suppression and high linearity modulator circuit architecture, mainly plays a role in improving the carrier suppression capability and the link linearity.

[0041] The technical solution of the present invention is:

[0042] 1). A method is proposed to couple a certain microwave power from the local oscillator branch of the transmission link through a coupler, reasonably distribute the gain distribution of the coupling branch, and ensure that the key module analog phase shifter is in a linear working state; the analog attenuator in the coupling branch must ensure that the adjustable range is greater than 30dB, and the analog phase shifter must ensure that the adjustable range is greater than 360° to achieve large dynamic cancellation capability; the coupling degree of the coupler is 20dB to ensure the thermal noise coefficient of the modulated emission.

[0043] 2). A method for full-temperature stable ultra-high carrier suppression of analog modulator is proposed. Set the modulator carrier suppression force. According to the carrier suppression value of the spectrum of the RFout output port as the target, adjust the coupling branch analog attenuator and analog phase shifter. When the ideal effect is achieved, record the control voltage of the analog attenuator and analog phase shifter, and use a highly plastic temperature compensation circuit structure for the secondary voltage after voltage stabilization to achieve accurate voltage output to the analog attenuator and analog phase shifter. Thereby improving the temperature stability of the carrier suppression capability. Greatly improve the practicality of the product and provide technical guarantee for the marketization of the product.

[0044] The working principle of the modulator ultra-high carrier suppression method is to couple a certain amount of microwave power from the local oscillator branch of the transmission link through a coupler. After the amplitude and phase of the signal are adjusted, the amplitude is equal to the carrier signal leaked from the output port of the transmission modulator through the coupler, and the phase difference of 180° is offset, thereby achieving the output carrier suppression of the transmission modulation system of about 70dB isolation requirement. In the carrier drive mode, appropriately reducing the input modulation signal level of the I / Q path can directly improve the linearity of the transmission link and reduce unnecessary intermodulation interference.

[0045] At the same time, this patent adopts conventional mature devices in its implementation, which has low cost and low risk. When used in higher frequency bands, it only needs to select high-frequency devices of the same type to replace them. It is a universally adaptable design idea.

[0046] As a preferred embodiment of this invention:

[0047] The carrier input port of the IQ modulator 1 is connected to the output port of the transmission branch of the 90° bridge 3 of the carrier coupling cancellation branch through a first fixed attenuator 12 .

[0048] The coupling port of the IQ modulator 1 is connected to the first fixed attenuator 12 .

[0049] Another port of the second fixed attenuator 4 is connected to the input port of the reverse isolation fixed gain amplifier 5 .

[0050] The output port of the reverse isolation fixed gain amplifier 5 is connected to the attenuator multi-stage attenuator 6 .

[0051] Another port of the attenuator multi-stage attenuator 6 is connected to the input port of the narrowband bandpass filter 7 .

[0052] The output port of the narrowband bandpass filter 7 is connected to the third fixed attenuator 8 .

[0053] Another port of the third fixed attenuator 8 is connected to the input port of the phase shifter 9 .

[0054] The output port of the phase shifter 9 is connected to the fourth fixed attenuator 10 .

[0055] The fourth fixed attenuator 10 is connected to the input port of the analog continuously adjustable amplifier 11 .

[0056] The output port of the analog continuously adjustable amplifier 11 is connected to the first fixed attenuator 12 .

[0057] The first fixed attenuator 12 is connected to the 0° power combiner 2 .

[0058] The connection relationship of all devices in the carrier coupling cancellation branch is as follows: Figure 1 As shown. The isolation port of the 90° bridge 3 is connected to a 50 load, and the coupling port is connected to the second fixed attenuator 4. Another port of the second fixed attenuator 4 is connected to the input port of the reverse isolation fixed gain amplifier 5. The output port of the reverse isolation fixed gain amplifier 5 is connected to the multi-level attenuator 6 to prevent the link signal after the amplifier C from being reversely injected into the coupler transmission branch and entering the IQ modulator 1. Another port of the multi-level attenuator 6 is connected to the input port of the narrowband bandpass filter 7. The multi-level attenuator 6 provides a coarse amplitude adjustment function. The narrowband bandpass filter 7 plays a role in filtering out the signal and preventing excess noise from flowing to the subsequent circuit, affecting the carrier-to-noise ratio. The output port of the narrowband bandpass filter 7 is connected to the third fixed attenuator 8. The third fixed attenuator 8 plays a role in gain adjustment, while improving the matching state of the narrowband filter and the back-end device to reduce reflection. Another port of the third fixed attenuator 8 is connected to the input port of the phase shifter 9. The third fixed attenuator 8 ensures that the phase shifter works in a linear and well-matched state. The phase shifter 9 realizes a continuous adjustment of the coupling branch carrier fLO phase greater than 360°. The output port of the phase shifter 9 is connected to the fourth fixed attenuator 10, which ensures that the output matching state of the phase shifter 9 is in a good state. The fourth fixed attenuator 10 is connected to the input port of the analog continuously adjustable amplifier 11. The output port of the analog continuously adjustable amplifier 11 is connected to the first fixed attenuator 12, which ensures that the output matching state of the analog continuously adjustable amplifier 11 is in a good state. The approximately 30dB dynamic analog continuously adjustable amplifier 11 adjusts the coupling branch carrier amplitude so that the amplitude of point P after passing through the 0° power synthesizer 2 is equal to the amplitude of the carrier leakage signal of the IQ modulator 1. The modulating phase shifter 9 makes the two signals phase-difference by 180°.

[0059] As a preferred embodiment of this invention:

[0060] The high carrier suppression and high linearity modulator circuit architecture further includes a network thermostat 13 and an analog voltage temperature fitting circuit 14 .

[0061] The analog voltage temperature fitting circuit 14 outputs the analog control voltage required by the phase shifter 9 and the adjustable amplifier I with temperature compensation function, ensuring that the high carrier suppression and high linearity modulator circuit architecture finally maintains the same amplitude and 180° phase difference of the IQ modulator 1 carrier leakage signal and the coupled branch carrier at point P within the operating temperature range, thereby achieving a better cancellation effect within the entire operating temperature range, that is, improving the carrier suppression capability of the IQ modulator 1.

[0062] The network constant temperature adjustment 13 controls the temperature of the entire high carrier suppression and high linearity modulator circuit architecture circuit, and has an automatic temperature monitoring and identification function, which can ensure that the temperature is disturbed within a very small range. This reduces the compensation pressure of the analog voltage temperature fitting circuit and reduces the overshoot reaction during the temperature change process, resulting in changes in the offset effect.

[0063] The network thermostat 13 and the analog voltage temperature fitting circuit 14 are both commonly used circuits in the art.

[0064] As a preferred embodiment of this invention:

[0065] This section provides a design example of an ultra-high carrier suppression method for an analog modulator.

[0066] The functional indicators and interface relationships of the modulator ultra-high carrier suppression are as follows:

[0067] Input and output frequency: 1020±1MHz.

[0068] Local oscillator coupler input level: 16dBm.

[0069] I / Q input level: ≤±0.25V.

[0070] Modulation coupler output level: not more than -10.41dBm.

[0071] Port characteristics: The insertion loss of the local oscillator coupler is no more than 1dB.

[0072] The insertion loss of the modulated output coupler is no more than 1dB.

[0073] The continuous adjustable range of the coupling branch amplitude is greater than 30dB, and the continuous adjustable range of the phase is greater than 360°.

[0074] Voltage standing wave ratio: less than or equal to 1.50:1.

[0075] Power supply: +5V, -5V (after voltage regulation).

[0076] The local oscillator input signal is coupled to the cancellation branch signal through a coupler, and after amplitude and phase adjustment, The same frequency signal as the modulated output When synthesized at point P, the amplitudes of the two signals are equal, that is, V1=V2, and the phases satisfy the condition of θ2=θ1±n×180° (n is an odd number), the two signals are completely canceled. The suppression degree to be completed is 58dB, and the modulator modulated signal output level is about -10.04dBm, so the carrier level needs to be canceled from -35dBm to -93.81dBm. The key lies in how to achieve precise amplitude and phase adjustment. The implementation method is to input the signal at the I / Q port and the carrier port through the coupler loss to excite the level of 10dBm, so that the modulated signal and the coupled branch signal are combined through the coupler to ensure that the carrier level is about -93dBm. When the carrier suppression target value is reached, the control voltage of the analog attenuator and the analog phase shifter is recorded, and the voltage is accurately output to the analog attenuator and the analog phase shifter by using a highly plastic temperature compensation circuit architecture for the secondary voltage after voltage stabilization.

[0077] Based on the circuit structure using a highly plastic temperature compensation circuit, in order to improve the suppression stability, the entire modulator ultra-high carrier suppression network can be self-adjusted at a constant temperature to reduce the value of the device changing with temperature, thereby achieving a higher carrier suppression effect.

[0078] The simulation results in Figure 2(a) show that the modulator ultra-high carrier suppression network connects the output port of the coupler to port 3, the carrier leakage power of port 3 is about -35dBm, and the input excitation carrier power of the coupling branch input port 1 is 16dBm. The input voltage of the I / Q port is no more than ±0.25V, and the I / Q input level is -2.04dBm obtained by conversion. The modulator loss is 8dB, and the useful signal level after modulation is -10.4dBm. If the carrier leakage signal is not cancelled by the coupling branch, the local oscillator leakage level is about -35dBm, and the carrier suppression is about 25dB.

[0079] The simulation results in Figure 2(b) show that when the carrier leakage signal and the coupling branch are cancelled using the patented product, the carrier power at port 4 is about -93.81dBm, and the carrier suppression is about 83.41dB, which is an improvement of about 58dB.

[0080] In summary, this patent solves the problem that the carrier suppression and linearity of the modulation transmission system are far from the actual application. It has a wide range of applications and has application prospects and practical value in all modulation transmission stand-alone machines. At the same time, it solves the mutual restriction problem between carrier suppression and linearity, which is the main factor that restricts and limits the application and development of the modulation transmission system, and creates a new situation in which the modulation transmission system can achieve ultra-high carrier suppression and linearity at the same time, greatly improving the information transmission quality, distance resolution and speed resolution, and improving the market competitiveness and survival ability.

[0081] The above technical solutions are only preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by any technician familiar with the field within the technical scope disclosed by the present invention without creative work are all covered within the protection scope of the present invention.

Claims

1. A high carrier suppression and high linearity modulator circuit architecture, characterized in that: It comprises a carrier coupling cancellation branch, wherein the carrier coupling cancellation branch is respectively connected to an IQ modulator (1) and a 0° power synthesizer (2), and the IQ modulator (1) is connected to the 0° power synthesizer (2); The carrier coupling cancellation branch comprises a 90° bridge (3), a second fixed attenuator (4), a reverse isolation fixed gain amplifier (5), an attenuator multi-stage attenuator (6), a narrowband bandpass filter (7), a third fixed attenuator (8), a phase shifter (9), a fourth fixed attenuator (10), an analog continuously adjustable amplifier (11) and a first fixed attenuator (12) which are connected in sequence; The 90° bridge (3) is also connected to the IQ modulator (1) via a fifth fixed attenuator (13).

2. The high carrier suppression and high linearity modulator circuit architecture as claimed in claim 1, characterized in that: The carrier input port of the IQ modulator (1) is connected to the output port of the 90° bridge (3) transmission branch of the carrier coupling cancellation branch via a first fixed attenuator (12); The coupling port of the IQ modulator (1) is connected to a first fixed attenuator (12); Another port of the second fixed attenuator (4) is connected to the input port of the reverse isolation fixed gain amplifier (5). The output port of the reverse isolation fixed gain amplifier (5) is connected to the attenuator multi-stage attenuator (6); Another port of the attenuator multi-stage attenuator (6) is connected to an input port of a narrow-band bandpass filter (7); The output port of the narrowband bandpass filter (7) is connected to a third fixed attenuator (8); Another port of the third fixed attenuator (8) is connected to an input port of the phase shifter (9); The output port of the phase shifter (9) is connected to a fourth fixed attenuator (10); The fourth fixed attenuator (10) is connected to the input port of the analog continuously adjustable amplifier (11); The output port of the analog continuously adjustable amplifier (11) is connected to the first fixed attenuator (12); The first fixed attenuator (12) is connected to the 0° power synthesizer (2).

3. The high carrier suppression and high linearity modulator circuit architecture as claimed in claim 1, characterized in that: The high carrier suppression and high linearity modulator circuit architecture also includes a network thermostat (14) and an analog voltage temperature fitting circuit (15).

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