An envelope restoration circuit

Abstract

This patent proposes an envelope recovery circuit, which is mainly used for demodulation of load modulation (including AM and ASK) signals, and can filter out the carrier of the load modulation signal (AM) and restore the envelope of the signal. The circuit mainly includes: a rectifier circuit (101) and a filter circuit (103). The rectifier circuit (101) allows the high level of the carrier of the amplitude modulation signal to pass through through rectification, and isolates the low level of the carrier. The filter circuit (103) filters out the carrier, so that the ripple of the restored envelope signal is reduced. The isolation diode (102) and the isolation diode (104) have an isolation effect, so that the intermediate node signal of the subsequent filter circuit will not generate reverse interference to the input signal of the isolation diode.

Description

Technical Field

[0001] Envelope detection technology is a commonly used signal demodulation technology and method in the field of communications. Envelope recovery circuit is one of the keys to envelope detection circuit design. The present invention adopts a new envelope recovery circuit, which can be widely used in envelope detection circuit design or filter circuit design. Background Art

[0002] The use of load modulation for communication is widely used, and envelope detection is a common method for demodulating load modulated signals. For example, the ISO / IEC 14443 protocol uses load modulation for communication, and infrared data (IRDA) and laser communications also use amplitude shift keying (ASK) for communication.

[0003] The envelope recovery circuit is the core circuit of the envelope detection circuit. The commonly used envelope detection signal is Figure 1 shown. Figure 1 The input amplitude modulation signal Vsin is a load modulated AM signal (or an amplitude shift keying ASK signal), and the output signal Vsout is an envelope recovery signal; the diode D2 has a rectifying effect, and the resistors R3, R4 and the capacitors C3, C4 constitute a low-pass filter circuit.

[0004] However, when the carrier frequency is comparable to the signal bandwidth, the envelope recovery circuit signal generated by the traditional envelope recovery circuit is highly distorted. In some cases, when the envelope recovery signal distortion is large enough, it will cause subsequent demodulation difficulties or even demodulation failure.

[0005] In order to reduce the distortion of the envelope recovery signal and ensure successful demodulation, improving the low-pass filtering performance in the envelope recovery circuit is the key solution. To this end, this patent proposes a new envelope recovery circuit. Summary of the invention

[0006] In order to reduce the distortion of the envelope recovery signal, the input amplitude modulation signal is rectified, and the subsequent low-pass filter design is the key. One of the typical envelope recovery circuits proposed in this patent is as follows: Figure 2 The function of the new envelope recovery circuit is to input the amplitude modulation signal Vsin and output the envelope recovery signal Vsout.

[0007] The novel circuit mainly comprises: a rectifier circuit (101) and a filter circuit (103). The rectifier circuit (101) allows the high level of the amplitude modulation signal carrier to pass through through rectification, and isolates the low level of the carrier. The filter circuit (103) filters out the carrier, so that the ripple of the restored envelope signal is reduced. The isolation diode (102) and the isolation diode (104) have an isolation effect, so that the intermediate node signal of the subsequent filter circuit will not generate reverse interference on the input signal of the isolation diode.

[0008] and Figure 1 Compared with the conventional envelope recovery circuit shown in FIG. 1 , the use of the isolation diode 104 is a novel envelope recovery circuit (eg Figure 2 The key to the design is shown in Figure 1. Figure 1 and Figure 2 The response characteristics to input and output signals are shown in Table 1.

[0009] Table 1 Comparison of input and output response characteristics of traditional structure and new structure circuit

[0010]

[0011] As shown in Table 1, if R1=R3, C1=C3, R2=R4, C2=C4 in the traditional circuit and the new circuit, but because the resistor R0 and capacitor C0 are added in the new circuit, the carrier filter cutoff frequency is larger, and the carrier ripple of the envelope recovery signal is smaller, so the output envelope recovery signal distortion is smaller. Conversely, if the carrier filter cutoff frequency of the traditional circuit and the new circuit is the same by adjusting the resistor and capacitor parameters, then it can also ensure that the new circuit can respond faster to the rising and falling edges of the envelope signal, and the envelope recovery signal output by the new circuit is less distorted. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Traditional Envelope Restoration Circuit

[0013] Figure 2 A new circuit for typical envelope restoration

[0014] Figure 3 PMOS transistor realizes isolation diode

[0015] Figure 4 NMOS transistor realizes isolation diode

[0016] Figure 5 An example of a multi-rectifier circuit cascade envelope recovery circuit

[0017] Figure 6 An example of a multi-filter circuit cascade envelope recovery circuit

[0018] Figure 7 An example of a rectifier circuit, filter circuit, hybrid cascade envelope recovery circuit DETAILED DESCRIPTION

[0019] The novel circuit capable of realizing envelope recovery signal fidelity mainly comprises: a rectifier circuit (101) and a filter circuit (103). The rectifier circuit (101) allows the high level of the amplitude modulation signal carrier to pass through through rectification, and isolates the low level of the carrier. The filter circuit (103) filters out the carrier, so that the ripple of the restored envelope signal is reduced. The isolation diode (102) and the isolation diode (104) have an isolation effect, so that the intermediate node signal of the subsequent filter circuit will not generate reverse interference to the input signal of the isolation diode.

[0020] The rectifier circuit (101) is as follows: Figure 2 As shown in , the circuit structure is as follows: the amplitude modulation signal Vsin is input from the P pole of the diode D0 (102), and the rectified signal is output from the N pole of the diode D0; the N pole of the diode P0 is connected to a node together with the resistor R0 and the capacitor C0, and the other ends of the resistor R0 and the capacitor C0 are grounded at the same time.

[0021] The rectifier circuit (103) is as follows: Figure 2 As shown in , the circuit structure is as follows: the input signal is input from the P pole of the diode D1 (104), the N pole of the diode D1 and the resistor R1, the capacitor C1, and the resistor R2 are connected to a node; the other end of the resistor R1 and the capacitor C1 are grounded at the same time; the other end of the resistor R2 is connected to one end of the capacitor C2, and this node is also the output node of the envelope recovery signal Vsout; the other end of the capacitor C2 is grounded. Isolation diode ( Figure 2 D0 and D1 in the figure can be realized by using normal diodes or by using Figure 3 The PMOS transistor circuit connection method shown in the figure can be realized by adopting the method shown in the figure. Figure 4 The NMOS transistor connection method shown is implemented.

[0022] The rectifier circuit (101) and the filter circuit (103) can be regarded as basic units, and a new envelope recovery circuit can be formed through different cascade combinations. For example, the envelope recovery circuit of three rectifier circuits (101) cascaded is as follows: Figure 5 As shown; the envelope recovery circuit of the two filter circuits (103) cascaded is as follows Figure 6 As shown; two rectifier circuits (101) and a filter circuit (103) are mixed cascaded as shown Figure 7 As shown. And these are protected as rights declaration items.

[0023] The above are only relatively ideal embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An envelope recovery circuit for AM load modulation and ASK amplitude shift keying signal envelope recovery, characterized in that: The envelope recovery circuit comprises a rectifier circuit (101) and a filter circuit (103); the input amplitude modulation signal Vsin is input from one end of the rectifier circuit (101); the other end of the rectifier circuit (101) is connected to one end of the filter circuit (103); and the other end of the filter circuit (103) outputs an envelope recovery signal; The rectifier circuit (101) comprises: an isolation diode (102), a resistor R0 and a capacitor C0 connected in parallel to the ground; an N-pole of the isolation diode (102) is connected to the other end of the resistor R0 and the capacitor C0 connected in parallel to the ground; The filter circuit (103) comprises: an isolation diode (104), a resistor R1 and a capacitor C1 connected in parallel to the ground, a series resistor R2 and a filter capacitor C2 connected to the ground; an N-pole of the isolation diode (104) is connected to the other end of the resistor R1 and the capacitor C1 connected in parallel to the ground and one end of the series resistor R2, The rectifier circuit (101) and the filter circuit (103) are used as basic units to form different envelope recovery circuits through different cascade combinations.

2. An envelope restoration circuit as claimed in claim 1, characterized in that: The P pole of the isolation diode (102) is connected to the input amplitude modulation signal Vsin, and the N pole of the isolation diode (102) is connected to the filter circuit (103).

3. An envelope restoration circuit as claimed in claim 1, characterized in that: The P pole of the isolation diode (104) is connected to the N pole of the isolation diode (102) in the rectifier circuit (101), the other end of the series resistor R2 is connected in series with the other end of the ground filter capacitor C2, and the output signal Vsout is at the series node of the series resistor R2 and the ground filter capacitor C2.

4. An envelope restoration circuit as claimed in claim 1, characterized in that: The isolation diode (102) can be implemented by using a diode device, a PMOS transistor device, or an NMOS transistor.

5. An envelope restoration circuit as claimed in claim 1, characterized in that: The isolation diode (104) can be implemented by using a diode device, a PMOS transistor device, or an NMOS transistor.

6. An envelope restoration circuit as claimed in claim 1, characterized in that: The rectifier circuit is formed by cascading n rectifier circuits (101), where n is greater than or equal to 1.

7. An envelope restoration circuit as claimed in claim 1, characterized in that: The filter circuit is formed by cascading m filter circuits (103), where m is greater than or equal to 1.

8. An envelope restoration circuit as claimed in claim 1, characterized in that: The filter circuit may be formed by mixing and cascading any number of rectifier circuits (101) or filter circuits (103).

9. An envelope restoration circuit as claimed in claim 1, characterized in that: The rectifier circuit may be formed by mixing and cascading any number of rectifier circuits (101) or filter circuits (103).

Images