Compact low-noise frequency conversion receiver circuit

Abstract

The invention relates to the technical field of communication, discloses a compact low-noise frequency conversion receiver circuit, and provides a receiving architecture adopting a three-coil transformer in front of a frequency mixer to solve the problem that the area is increased and the power consumption is increased due to the fact that image noise suppression of an existing radio frequency receiving front-end circuit needs a large-area filter or an IQ generation circuit. Wherein the transformer is realized in an 8 shape, and under the condition that the area and complexity are not increased, mirror image noise is filtered out, and the noise coefficient of the circuit is reduced. Therefore, the invention aims to overcome the defect that the traditional image rejection receiver needs IQ frequency mixing or an on-chip large-size band-pass filter by optimizing the circuit architecture and adopting the 8-shaped inductor through the meticulous design of the three-coil transformer in front of the frequency mixer, and realizes lower noise of the frequency conversion receiver, thereby improving the overall performance of the receiver.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a compact low-noise frequency conversion receiver circuit. Background Art

[0002] Modern wireless communication systems (such as 5G, satellite communications, and radar) urgently require broadband, low-noise, and highly sensitive receivers. Traditional frequency-converting receivers experience significant noise figure degradation in wideband, high-frequency bands (such as millimeter-wave and terahertz). In particular, the presence of image noise further degrades the noise figure compared to unconverted receivers, making it difficult to meet the requirements of high-dynamic-range signal processing.

[0003] Existing methods address image noise primarily through two approaches. First, IQ mixing creates a 90° phase difference at the local oscillator signal port, suppressing the image noise within the converted intermediate frequency signal. Second, an on-chip image suppression filter is added after the low-noise amplifier (LNA) and before the mixer to suppress image noise. Both noise suppression methods have their own drawbacks. IQ mixing requires an IQ mixer and quadrature signal generation circuitry, which increases chip power consumption and area, making design more complex. On-chip filter technology, however, requires a significant area for the filter and incurs insertion loss, which can offset the noise figure reduction benefits of image noise suppression. Summary of the Invention

[0004] The present invention provides a compact low-noise frequency conversion receiver circuit, aiming to solve at least one of the above technical problems.

[0005] To achieve the above object, the present invention provides a compact low-noise frequency conversion receiver circuit, comprising: First-stage LNA, secondary LNA and mixer; A three-coil image noise suppression transformer is provided between the secondary LNA and the mixer, and the three-coil image noise suppression transformer includes an L1 inductor coil, an L2 inductor coil and an L3 inductor coil coupled to each other; The L1 inductor is connected to the output of the secondary LNA, the L2 inductor is connected to the input of the mixer, and the L3 inductor is connected to the terminal capacitor Ci; The L1 inductor, the L2 inductor, and the coupling coefficient between the L1 and L2 inductors are configured to convert the input impedance of the mixer into a conjugate impedance of the secondary LNA output impedance at the operating frequency of the secondary LNA. The coupled resonant cavity formed by the L1 inductor, the L3 inductor, and the terminal capacitor Ci is configured to make the impedance from the secondary LNA toward the three-coil image noise suppression transformer approach a value of 0 at the frequency of the image signal. The L3 inductor is configured to use an "8"-shaped inductor, and the "8"-shaped inductor causes the coupling coefficient between the L2 inductor and the L3 inductor to be configured to be a value of 0.

[0006] Optionally, an input matching circuit is provided between the first-stage LNA and the RF input terminal.

[0007] Optionally, an inter-stage matching balun is provided between the first-stage LNA and the secondary LNA, and the inter-stage matching balun is configured to convert a single-ended signal into a differential signal to achieve conjugate matching between the first-stage LNA and the secondary LNA.

[0008] Optionally, an interstage capacitor is provided between the first-stage LNA and the secondary LNA, a first end of the interstage capacitor is connected to the output end of the first-stage LNA, and a second end of the interstage capacitor is connected to the input end of the secondary LNA.

[0009] Optionally, a first input end of the three-coil image noise suppression transformer is connected to the output end of the secondary LNA, and a second input end of the three-coil image noise suppression transformer is grounded, so that the three-coil image noise suppression transformer converts a single-ended signal into a differential signal.

[0010] Optionally, in the coupled resonant cavity formed by the L1 inductor, the L3 inductor and the terminal capacitor Ci, noise at the image frequency flows into the terminal capacitor Ci, thereby preventing the mixer from being affected by the noise and causing the noise coefficient of the receiving circuit to deteriorate.

[0011] Optionally, the upper half of the "8"-shaped inductor used by the L3 inductor is located inside the multi-turn coil of the L1 inductor, so that the time-varying magnetic field in the L3 inductor passes through the overlapping part of the L3 inductor and the L1 inductor, forming a coupling coefficient between the L1 inductor and the L3 inductor.

[0012] Optionally, the "8"-shaped inductor used by the L3 inductor is integrally located inside the L2 inductor, so that the time-varying magnetic field within the L3 inductor passes through the overlapping part of the L3 inductor and the L2 inductor, forming a coupling coefficient between the L2 inductor and the L3 inductor.

[0013] Optionally, when the "8"-shaped inductor coil used by the L3 inductor coil is entirely inside the L2 inductor coil, the magnetic flux generated by the upper and lower parts of the "8"-shaped inductor coil are the same in magnitude and opposite in direction, so that the coupling coefficient between the L2 inductor coil and the L3 inductor coil is 0.

[0014] Optionally, an intermediate frequency amplifier is provided between the mixer and the intermediate frequency input terminal.

[0015] The beneficial effects of the present invention are: proposing a compact, low-noise frequency conversion receiver circuit. To address the issues of image noise suppression in existing RF receiver front-end circuits, which require large filters or IQ generation circuits, resulting in increased area and power consumption, a receiver architecture using a three-coil transformer before the mixer is proposed. The transformer is implemented in an 8-shaped configuration, filtering out image noise and reducing the circuit's noise figure without increasing area or complexity. Therefore, this patent aims to achieve lower noise in the frequency conversion receiver by optimizing the circuit architecture and carefully designing the three-coil transformer before the mixer using an 8-shaped inductor (or 8-shaped transformer). This avoids the shortcomings of conventional image suppression receivers, which require IQ mixing or large on-chip bandpass filters, thereby improving the overall performance of the receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the principle of the compact low-noise frequency conversion receiver circuit of the present invention; Figure 2 This is a schematic diagram of a three-coil image noise suppression transformer according to the present invention; Figure 3 This is a second schematic diagram of the three-coil image noise suppression transformer of the present invention; Figure 4 This is the third schematic diagram of the three-coil image noise suppression transformer of the present invention; Figure 5 Schematic diagram of the relationship between the impedance Z21 parameter and frequency of the present invention; Figure 6 The following are the noise figure simulation diagrams of the receiver using a 3-coil image noise suppression transformer and a noise figure simulation diagram of a common receiver; Figure 7 FIG1 is a practical circuit diagram of a compact low-noise frequency conversion receiver circuit of the present invention; Figure 8 This is a second actual circuit diagram of the compact low-noise frequency conversion receiver circuit of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] like Figure 1 As shown, an embodiment of the present invention provides a compact low-noise frequency conversion receiver circuit, comprising: a first-stage LNA, a secondary LNA and a mixer; A three-coil image noise suppression transformer is provided between the secondary LNA and the mixer, and the three-coil image noise suppression transformer includes an L1 inductor coil, an L2 inductor coil and an L3 inductor coil coupled to each other; The L1 inductor is connected to the output of the secondary LNA, the L2 inductor is connected to the input of the mixer, and the L3 inductor is connected to the terminal capacitor Ci; The L1 inductor, the L2 inductor, and the coupling coefficient between the L1 and L2 inductors are configured to convert the input impedance of the mixer into a conjugate impedance of the secondary LNA output impedance at the operating frequency of the secondary LNA. The coupled resonant cavity formed by the L1 inductor, the L3 inductor, and the terminal capacitor Ci is configured to make the impedance from the secondary LNA toward the three-coil image noise suppression transformer approach a value of 0 at the frequency of the image signal. The L3 inductor is configured to use an "8"-shaped inductor, and the "8"-shaped inductor causes the coupling coefficient between the L2 inductor and the L3 inductor to be configured to be a value of 0.

[0019] In a preferred embodiment, an input matching circuit is provided between the first-stage LNA and the radio frequency input terminal.

[0020] In a preferred embodiment, an inter-stage matching balun is provided between the first-stage LNA and the secondary LNA, and the inter-stage matching balun is configured to convert a single-ended signal into a differential signal to achieve conjugate matching between the first-stage LNA and the secondary LNA.

[0021] In a preferred embodiment, an interstage capacitor is provided between the first-stage LNA and the secondary LNA, a first end of the interstage capacitor is connected to the output end of the first-stage LNA, and a second end of the interstage capacitor is connected to the input end of the secondary LNA.

[0022] In a preferred embodiment, a first input end of the three-coil image noise suppression transformer is connected to an output end of the secondary LNA, and a second input end of the three-coil image noise suppression transformer is grounded, so that the three-coil image noise suppression transformer converts a single-ended signal into a differential signal.

[0023] In a preferred embodiment, in the coupled resonant cavity formed by the L1 inductor, the L3 inductor and the terminal capacitor Ci, noise at the image frequency flows into the terminal capacitor Ci, thereby preventing the mixer from being affected by the noise and causing the noise coefficient of the receiving circuit to deteriorate.

[0024] In a preferred embodiment, the upper half of the "8"-shaped inductor used by the L3 inductor is located inside the multi-turn coil of the L1 inductor, so that the time-varying magnetic field in the L3 inductor passes through the overlapping part of the L3 inductor and the L1 inductor, forming a coupling coefficient between the L1 inductor and the L3 inductor.

[0025] In a preferred embodiment, the "8"-shaped inductor used by the L3 inductor is entirely inside the L2 inductor, so that the time-varying magnetic field in the L3 inductor passes through the overlapping part of the L3 inductor and the L2 inductor, forming a coupling coefficient between the L2 inductor and the L3 inductor.

[0026] In a preferred embodiment, when the "8"-shaped inductor coil used by the L3 inductor coil is entirely inside the L2 inductor coil, the magnetic flux generated by the upper and lower parts of the "8"-shaped inductor coil are the same in magnitude and opposite in direction, so that the coupling coefficient between the L2 inductor coil and the L3 inductor coil is 0.

[0027] In a preferred embodiment, an intermediate frequency amplifier is provided between the mixer and the intermediate frequency input terminal.

[0028] Therefore, the present invention proposes a compact, low-noise, frequency-converting receiver circuit. The key technical feature lies in the use of a transformer matching network before the mixer in the receiver system. This transformer is a three-coil transformer, with the third coil being a figure-8 inductor. Through the rational design of the figure-8 inductor, the inductor's coupling coefficient, k12, is selected to maximize the receiver link gain, k23 is 0, and k13 ensures that the impedance looking into the three-coil transformer is minimal at the image frequency, thereby filtering out image noise.

[0029] Furthermore, while maintaining the same chip area, a three-coil transformer preceding the mixer filters out noise at the image frequency without affecting the RF signal or the receive channel gain, thereby reducing the receiver's noise figure. To address the problem that image noise suppression in existing RF receive front-end circuits requires large filters or IQ generation circuits, which increases area and power consumption, a receiver architecture using a three-coil transformer preceding the mixer is proposed. The transformer is implemented in a figure-of-eight configuration, filtering out image noise and reducing the circuit's noise figure without increasing area or complexity.

[0030] It should be noted that the purpose of the present invention is to realize a compact, low-noise frequency conversion receiver. The receiver receives the signal through the first-stage LNA, and converts the single-ended signal into a differential signal through the inter-stage matching balun between the first-stage LNA and the secondary LNA. It also realizes the conjugate matching between the two stages, ensuring the bandwidth and gain. Between the secondary LNA and the mixer, the present invention will adopt the following Figure 1 The three-coil image noise suppression transformer shown is formed by coupling three inductors, with the L1 inductor connected to the output of the secondary LNA, the L2 inductor connected to the input of the mixer, and the L3 inductor connected to a terminal capacitor Ci.

[0031] First, consider L1 and L2. These two inductors have a coupling coefficient of k12. To minimize losses from the secondary LNA to the mixer, L1, L2, and k12 transform the mixer's input impedance into a conjugate impedance of the secondary LNA's output impedance at the LNA's operating frequency. Next, consider the coupling between L1 and L3. The coupled resonant cavity formed by L1, L3, and Ci ensures that the impedance seen by the secondary LNA toward the transformer approaches zero at the image signal's frequency. At this point, noise at the image frequency flows into the Ci capacitor rather than into the mixer, degrading the receiver's noise figure. Regarding the coupling between L2 and L3, to prevent L3's thermal noise from coupling into L2 and, therefore, into the mixer, the coupling coefficient k23 is set to zero. This near-zero coupling coefficient is achieved by configuring L3 as a figure-eight inductor.

[0032] Specifically, in this embodiment, the layout of the "8"-shaped inductor is as follows: Figure 2 As shown. L1 and L2 are connected to the output of the front-stage LNA and the input of the back-stage mixer respectively, and L3 is connected to the capacitor Ci. First analyze L1 and L3, Figure 3 Only L1 and L3 are retained in the 3-coil inductor. The upper half of L3 is inside the multi-turn coil of L1. This means that the time-varying magnetic field in the L3 inductor will also pass through the overlapping part of L3 and L1. The magnetic flux in this part is assumed to be perpendicular to the plane of the picture and inward. The magnetic flux is as follows: Figure 3 As shown, this produces a coupling coefficient k13 between L1 and L3. Next, analyze L2 and L3. Figure 4 Only L2 and L3 are retained, and the L3 coil is entirely inside the L2 coil. This means that the time-varying magnetic field in the L3 inductor will also pass through the overlapping part of L3 and L2. The magnetic flux in this part is assumed to be perpendicular to the plane of the picture and inward. Considering that the magnetic flux generated by the upper and lower parts of the "8"-shaped L3 are in opposite directions, as shown in Figure 4As shown, the two sets of opposite magnetic fluxes are inside L2, so the induced currents of L2 cancel each other out, which results in the coupling coefficient k23 between L2 and L3 being 0. The coupling relationship between L1 and L2 is the same as that of an ordinary transformer and will not be explained here.

[0033] Figure 5 The diagram below shows the relationship between the impedance parameter Z21 and frequency for a three-winding transformer. The designed transformer exhibits a significantly lower Z21 value at the image frequency, indicating that the input impedance seen at this frequency is very low. Consequently, noise at the image frequency flows into the Ci port and is not added to the mixer. At the operating frequency, Z21 maintains an appropriate value, ensuring sufficient circuit gain. Figure 6 The noise coefficient simulation diagram of the receiver using 3-coil inductance and the noise coefficient simulation diagram of the ordinary receiver show that the noise coefficient of the present invention is significantly reduced within the same frequency band, thus achieving the purpose of the invention.

[0034] In a preferred embodiment, the present invention provides two practical circuit diagrams of compact low-noise frequency conversion receiver circuits, such as Figure 7 and Figure 8 As shown. Among them, Figure 7 The circuit diagram shown has been described in detail in the previous text and will not be repeated here. Figure 8 In the circuit diagram shown, both the primary and secondary LNAs are single-ended circuits. In this case, the three-coil transformer not only completes the impedance matching function between the LNA and the mixer, but also realizes the balun function of single-ended to differential conversion.

[0035] Therefore, to address the problem that image noise suppression in existing RF receiving front-end circuits requires large-area filters or IQ generation circuits, which results in increased area and power consumption, the present invention proposes a receiving architecture that uses a three-coil transformer before the mixer, wherein the transformer is implemented in an 8-shaped shape. This filters out image noise and reduces the noise coefficient of the circuit without increasing the area and complexity.

[0036] It should be understood that, in the description of this specification, reference to terms such as "one embodiment," "another embodiment," "other embodiments," or "first to Nth embodiments" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples.

[0037] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A compact low-noise frequency conversion receiver circuit, characterized in that: include: First-stage LNA, secondary LNA and mixer; A three-coil image noise suppression transformer is provided between the secondary LNA and the mixer, and the three-coil image noise suppression transformer includes an L1 inductor coil, an L2 inductor coil and an L3 inductor coil coupled to each other; The L1 inductor is connected to the output of the secondary LNA, the L2 inductor is connected to the input of the mixer, and the L3 inductor is connected to the terminal capacitor Ci; The L1 inductor, the L2 inductor, and the coupling coefficient between the L1 and L2 inductors are configured to convert the mixer's input impedance into a conjugate impedance of the secondary LNA's output impedance at the operating frequency of the secondary LNA. The coupled resonant cavity formed by the L1 inductor, the L3 inductor, and the terminal capacitor Ci is configured to make the impedance from the secondary LNA toward the three-coil image noise suppression transformer approach a value of 0 at the frequency of the image signal. The L3 inductor is configured to employ an "8"-shaped inductor, which ensures that the coupling coefficient between the L2 inductor and the L3 inductor is 0.

2. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: An input matching circuit is provided between the first-stage LNA and the radio frequency input terminal.

3. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: An inter-stage matching balun is provided between the first-stage LNA and the secondary LNA. The inter-stage matching balun is configured to convert a single-ended signal into a differential signal to achieve conjugate matching between the first-stage LNA and the secondary LNA.

4. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: An interstage capacitor is provided between the first-stage LNA and the secondary LNA, a first end of the interstage capacitor is connected to the output end of the first-stage LNA, and a second end of the interstage capacitor is connected to the input end of the secondary LNA.

5. The compact low-noise frequency conversion receiver circuit according to claim 4, wherein: A first input end of the three-coil image noise suppression transformer is connected to the output end of the secondary LNA, and a second input end of the three-coil image noise suppression transformer is grounded, so that the three-coil image noise suppression transformer converts a single-ended signal into a differential signal.

6. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: In the coupled resonant cavity formed by the L1 inductor, the L3 inductor and the terminal capacitor Ci, noise at the image frequency flows into the terminal capacitor Ci, thereby preventing the mixer from being affected by the noise and causing the noise coefficient of the receiving circuit to deteriorate.

7. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: The upper half of the "8"-shaped inductor used in the L3 inductor is located inside the multi-turn coil of the L1 inductor, so that the time-varying magnetic field in the L3 inductor passes through the overlapping part of the L3 inductor and the L1 inductor, forming a coupling coefficient between the L1 inductor and the L3 inductor.

8. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: The "8"-shaped inductor used in the L3 inductor is integrally located inside the L2 inductor, so that the time-varying magnetic field in the L3 inductor passes through the overlapping portion of the L3 inductor and the L2 inductor, forming a coupling coefficient between the L2 inductor and the L3 inductor.

9. The compact low-noise frequency conversion receiver circuit according to claim 8, wherein: When the "8"-shaped inductor coil used by the L3 inductor coil is entirely inside the L2 inductor coil, the magnetic flux generated by the upper and lower halves of the "8"-shaped inductor coil are of the same magnitude but in opposite directions, so that the coupling coefficient between the L2 inductor coil and the L3 inductor coil is 0.

10. The compact low-noise frequency conversion receiver circuit according to claim 1, wherein: An intermediate frequency amplifier is provided between the mixer and the intermediate frequency input terminal.

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