PIN attenuation control circuit

Abstract

The utility model relates to the field of PIN attenuation control, in particular to a PIN attenuation control circuit, which has the advantages of small size, wide frequency band, low loss, large attenuation range, fast response time and the like, and can realize accurate and fast scanning adjustment of system output power. The utility model provides a PIN attenuation control circuit, which is used for controlling radio frequency signal power and comprises a first PIN diode (D1) and a current source (I), an anode of the first PIN diode (D1) is respectively connected with an input end (RF1) and an output end (RF2) of a radio frequency signal, a cathode of the first PIN diode (D1) is grounded, and the current source (I) is connected between the input end (RF1) and the output end (RF2) of the radio frequency signal.

Description

Technical Field

[0001] The utility model relates to the field of PIN attenuation control, in particular to a PIN attenuation control circuit. Background Art

[0002] In the field of radio frequency and microwave technology, various control circuits are used. Among them, the attenuation control circuit can realize the control of radio frequency signal power and is widely used in signal generator amplitude stabilization, microwave power attenuation, pulse modulation, etc.

[0003] In broadband microwave test and measurement systems, the output power of the frequency source needs to be precisely controlled within a wide frequency band. Closed-loop control generally detects the signal first and then feeds it back to the attenuation control circuit for adjustment. Closed-loop control has high accuracy and strong anti-interference ability but complex system design. Open-loop control is relatively simple, but the accuracy is usually low and there is no automatic correction capability. The attenuation control performance mainly relies on the calibration fitting accuracy of the system and the stability of the device to ensure the performance of the attenuation control.

[0004] Currently, there are many integrated RF chips on the market that can be used as attenuators, but each has its own shortcomings. The attenuation accuracy of the digital controlled attenuator is not enough, the attenuation range of the voltage controlled attenuator is small, the variable gain amplifier has poor linearity, complex structure and high cost, and none of them can meet the needs of the actual system at the same time. Utility Model Content

[0005] The purpose of the utility model is to overcome the shortcomings of the prior art and provide a PIN attenuation control circuit, which has the advantages of small size, simple structure, wide bandwidth, low loss, large attenuation range, and extremely fast response time, and can realize accurate and fast scanning adjustment of system output power.

[0006] The utility model adopts the following technical scheme to achieve the above-mentioned purpose. The utility model provides a PIN attenuation control circuit for controlling the power of a radio frequency signal. The control circuit includes a first PIN diode D1 and a current source I. The anode of the first PIN diode D1 is respectively connected to the input terminal RF1 and the output terminal RF2 of the radio frequency signal, the cathode of the first PIN diode D1 is grounded, and the current source I is connected between the input terminal RF1 and the output terminal RF2 of the radio frequency signal.

[0007] Furthermore, in order to increase the attenuation range of the circuit, the control circuit further includes a second PIN diode D2, the anode of the second PIN diode D2 is respectively connected to the input terminal RF1 and the output terminal RF2 of the radio frequency signal, and the cathode of the second PIN diode D2 is grounded.

[0008] Furthermore, in order to prevent the direct current from being transmitted to the input end of the RF signal and affecting the operation of other devices outside the input end of the RF signal, the control circuit also includes a first capacitor C1, one end of the first capacitor C1 is connected to the input end RF1 of the RF signal, and the other end of the first capacitor C1 is connected to the anode of the first PIN diode D1.

[0009] Furthermore, in order to prevent the direct current from being transmitted to the output end of the RF signal and affecting the operation of other devices outside the output end of the RF signal, the control circuit also includes a second capacitor C2, one end of the second capacitor C2 is connected to the output end RF2 of the RF signal, and the other end of the second capacitor C2 is connected to the anode of the second PIN diode D2.

[0010] Furthermore, in order to prevent the radio frequency signal from entering the current source control circuit, the control circuit further includes an inductor L, one end of the inductor L is connected to the anode of the first PIN diode D1 , and the other end of the inductor L is connected to the current source I.

[0011] Furthermore, in order to filter out high-frequency noise transmitted to the Bias circuit, the control circuit further includes a third capacitor C3, one end of the third capacitor C3 is connected between the inductor L and the current source I, and the other end of the third capacitor C3 is grounded.

[0012] Furthermore, in order to reduce the volume and improve the adaptability, the inductor L is a broadband conical inductor.

[0013] Beneficial effects of the utility model:

[0014] The ultra-wideband attenuation circuit designed by the utility model covers a frequency range of 2GHz-50GHz. Within this frequency band, it has the characteristics of small size, wide bandwidth, low loss, large attenuation range, and extremely fast response time. It can ensure accurate and rapid scanning and adjustment of the system output power, and can well meet the use of actual systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of an attenuation control circuit provided by an embodiment of the utility model;

[0016] Figure 2 It is a schematic diagram of the assembly of the switch circuit provided by the embodiment of the utility model;

[0017] Figure 3 It is a test curve schematic diagram of frequency and insertion loss provided by an embodiment of the utility model;

[0018] Figure 4 It is a test curve diagram of frequency and attenuation provided by an embodiment of the utility model;

[0019] In the accompanying drawings, D1 is a first PIN diode, D2 is a second PIN diode, RF1 is an input end of a radio frequency signal, RF2 is an output end of a radio frequency signal, C1 is a first capacitor, C2 is a second capacitor, C3 is a third capacitor, L is an inductor, and I is a current source. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present utility model clearer, the technical solution in the embodiments of the present utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the present utility model.

[0021] The utility model provides a PIN attenuation control circuit for controlling the power of a radio frequency signal. Figure 1 As shown, RF1 and RF2 are the input and output ports of 2GHz-50GHz RF signals respectively. The first capacitor C1 and the second capacitor C2 are DC blocking capacitors to isolate DC bias. One end of the first capacitor C1 is connected to the input end RF1 of the RF signal, the other end of the first capacitor C1 is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the output end RF2 of the RF signal to prevent DC current from being transmitted to the two ports RF1 and RF2 and affecting the operation of other devices outside the ports. The DC blocking capacitors here need to use broadband capacitors, which can have smaller insertion loss and better echo characteristics in the 2GHz-50GHz frequency band. The inductor L is a broadband conical inductor, which is connected between the input end RF1 of the RF signal and the output end RF2 of the RF signal, and isolates the RF signal from entering the current source control circuit. The inductor frequency covers 2GHz-50GHz. The third capacitor C3 is a bypass filter. One end of the third capacitor C3 is connected between the inductor L and the current source I, and the other end of the third capacitor C3 is grounded to filter out high-frequency clutter transmitted to the Bias circuit. D1, D2, D3, and D4 are SMD PIN diodes. PIN diodes with low junction capacitance and low impedance are selected. The anodes of all PIN diodes are respectively connected to the input terminal RF1 and the output terminal RF2 of the RF signal, and the cathodes are grounded. They are bonded to the cavity structure using a micro-assembly process and connected to the ground. When the current source circuit is controlled, the RF resistance of the diode changes with the change of the conduction current, so that the circuit has different attenuation amounts. I is the current source. Under the control of the analog voltage at the V terminal, the Bias path current changes accordingly. Since the junction barrier of the PIN diode has a negative temperature coefficient, if it is biased with a voltage source, the bias current will increase with the increase in temperature. Therefore, the temperature stability is better when using a current source bias. The RF part is implemented using a micro-assembly process. Each device and circuit chip are bonded to the cavity shell with conductive glue. The device and the circuit chip are connected with gold wire to minimize parasitic parameters and improve high-frequency characteristics. The assembly diagram of the switch circuit is shown in the figure. Figure 2 shown.

[0022] Working principle of the circuit: When the analog voltage value is input to the V terminal, the current of the current source is I0. At this time, the PIN diodes D1, D2, D3, and D4 are forward-conducting, the conduction current is I0, and the conduction resistance is: R , where k0 is a constant related to the tube parameters. When the RF signal passes through the PIN diode, it is equivalent to the RF signal passing through the resistor connected in parallel to the ground. The signal is attenuated, and the attenuation is:

[0023] A= , where Z0 is the characteristic impedance of the transmission line. When the analog voltage V changes, the current I0 changes, and the resistance R changes accordingly, thereby achieving a change in attenuation to control the output power. The volt-ampere characteristic of the current source is similar to the volt-ampere characteristic of the diode:

[0024] I , where I S is the reverse saturation current, V D is the bias voltage, V T is the voltage equivalent of temperature, from which it can be deduced that the relationship between attenuation and control voltage is approximately: A ;

[0025] It shows that the attenuation has a good linear relationship with the control voltage, which has a direct impact on the calibration fitting of the system output power and is related to the accuracy of the output power attenuation control. Single-frequency linear fitting only requires calibration of two power points at a minimum, which is simple and efficient. The processor calculates the linear formula to obtain the control voltage value corresponding to the attenuation power, thereby realizing power attenuation control. Increasing the number of PIN diodes can increase the attenuation range of the circuit. In order to improve the attenuation control accuracy, it has been verified that appropriately increasing the power calibration points and using polynomial fitting can greatly improve the accuracy of the attenuation control circuit.

[0026] The ultra-wideband high harmonic suppression PIN switch circuit designed by the utility model has been actually measured, and the test curve is as follows Figure 3 , Figure 4 As shown, within the full frequency band of 2GHz-50GHz, the insertion loss is better than 4.5dB, the dynamic attenuation range is better than 50dB, and the attenuation accuracy is better than 0.2dB, which can well meet the use of actual systems.

[0027] The above is only a preferred embodiment of the utility model. It should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the scope of protection of the claims attached to the utility model.

Claims

1. A PIN attenuation control circuit for controlling radio frequency signal power, characterized in that: The control circuit comprises a first PIN diode (D1) and a current source (I), wherein the anode of the first PIN diode (D1) is respectively connected to an input end (RF1) and an output end (RF2) of a radio frequency signal, the cathode of the first PIN diode (D1) is grounded, and the current source (I) is connected between the input end (RF1) and the output end (RF2) of the radio frequency signal.

2. The PIN attenuation control circuit according to claim 1, characterized in that: The control circuit further comprises a second PIN diode (D2), the anode of the second PIN diode (D2) is respectively connected to the input end (RF1) and the output end (RF2) of the radio frequency signal, and the cathode of the second PIN diode (D2) is grounded.

3. The PIN attenuation control circuit according to claim 1, characterized in that: The control circuit also includes a first capacitor (C1), one end of which is connected to the input end (RF1) of the radio frequency signal, and the other end of which is connected to the anode of the first PIN diode (D1).

4. The PIN attenuation control circuit according to claim 3, characterized in that: The control circuit also includes a second capacitor (C2), one end of which is connected to the output end (RF2) of the radio frequency signal, and the other end of which is connected to the anode of the second PIN diode (D2).

5. The PIN attenuation control circuit according to claim 1, characterized in that: The control circuit also includes an inductor (L), one end of the inductor (L) is connected to the anode of the first PIN diode (D1), and the other end of the inductor (L) is connected to the current source (I).

6. The PIN attenuation control circuit according to claim 5, characterized in that: The control circuit also includes a third capacitor (C3), one end of the third capacitor (C3) is connected between the inductor (L) and the current source (I), and the other end of the third capacitor (C3) is grounded.

7. The PIN attenuation control circuit according to claim 5, characterized in that: The inductor (L) is a broadband tapered inductor.

Images