Miniaturized dual-band dual-path low-noise receiving front end

Abstract

The application discloses a miniaturized double-frequency double-channel low-noise receiving front end, and the architecture of the receiving front end comprises an input double-passband filter, an input combiner, a two-stage low-frequency amplifier, a two-stage high-frequency amplifier, an output combiner and an output double-passband filter, wherein the input double-passband filter, the input combiner, the two-stage low-frequency amplifier, the output combiner and the output double-passband filter are sequentially connected; the output end of the input combiner is further connected with the input end of the two-stage high-frequency amplifier; and the output end of the two-stage high-frequency amplifier is further connected with the input end of the output combiner. The application adopts miniaturized design and supports double-frequency double-channel low-noise signal processing. The application can be widely applied to the technical field of multi-mode receiving.

Description

Technical Field

[0001] This invention relates to the field of multi-standard receiving technology, and in particular to a miniaturized dual-frequency dual-channel low-noise receiving front end. Background Technology

[0002] With the rapid development of wireless communication, spectrum monitoring, telemetry and remote control, and multi-standard receiving technologies, the ability to simultaneously cover two separate operating frequency bands with a single antenna and output through a common RF port has become an important application requirement for miniaturized receiving devices. Such devices have high requirements for receiving sensitivity, out-of-band interference immunity, dual-band link stability, and overall system integration. The performance of filtering, splitting, low-noise amplification, and combining after the antenna directly affects the effective receiving distance, weak signal identification capability, and system reliability.

[0003] While traditional dual-band dual-path receiver front-ends are convenient for modular design, they typically involve the antenna connecting to two branches (low-frequency and high-frequency) via a splitter. Each branch contains an input filter, two stages of low-noise amplifiers, and an output filter, before finally connecting to a single output via a standard broadband or combiner. This structure easily results in two sets of input filtering networks, two sets of output filtering networks, multiple fixed 50 Ω matching interfaces, and long cascaded transmission lines. This not only increases the number of inductors, capacitors, resonators, pads, and debugging points, but also directly worsens the overall noise figure due to filtering, splitting, and matching insertion losses before the first-stage low-noise amplifier. Furthermore, standard equal-power combiner structures may introduce distribution losses. Summary of the Invention

[0004] In view of this, in order to solve the problems of redundant branch filter networks, long RF transmission links, large passive insertion loss before the first-stage low-noise amplifier, and large overall board area in existing dual-frequency dual-channel receiver front-ends, this invention proposes a miniaturized dual-frequency dual-channel low-noise receiver front-end, wherein: This receiver front-end features a miniaturized design and supports dual-band, dual-channel low-noise signal processing. Its core architecture consists of an antenna, an input-stage dual-passband filter and combiner unit, two-stage amplification links for both high and low frequencies, and an output-stage combiner and dual-passband filter unit. The antenna's feed terminal is directly connected to the input terminal of the input dual-passband filter, serving as the signal input for the entire receiver.

[0005] The signal flow is as follows: The RF signal received by the antenna first enters the input dual-passband filter to complete the initial frequency band selection; the filtered signal is sent to the input combiner, which splits the signal into two paths, which are sent to the low-frequency amplification channel and the high-frequency amplification channel respectively. The low-frequency channel contains two cascaded low-noise amplifiers, and the high-frequency channel also contains two cascaded low-noise amplifiers. The two amplified signals are then merged into one output combiner; finally, a secondary frequency band selection is performed by the output dual-passband filter, thus outputting a front-end signal that meets the requirements.

[0006] The center frequency of the low-frequency operating band of the entire front end is 1.17 GHz, and the center frequency of the high-frequency operating band is 1.57 GHz, which correspond to the operating frequencies of the two amplification links mentioned above.

[0007] Based on the above solution, this invention provides a miniaturized dual-frequency dual-channel low-noise receiver front-end. This invention replaces four branch filter modules with two common dual-passband filters, reducing redundant filter modules, package pads, grounding vias, and branch connection microstrip lines, shortening the signal transmission path, and reducing the circuit board area. Under the condition that the insertion loss of the actual transmission link formed by the common dual-passband filter and combiner is lower than that of commonly used branch filter links, the passive insertion loss before the first-stage low-noise amplifier can be further reduced, improving the cascaded noise figure and effective gain of the receiver front-end. In terminal applications, the antenna is directly connected to the input dual-passband filter, realizing an integrated dual-frequency dual-channel low-noise receiver front-end that integrates antenna reception, common pre-selection filtering, dual-frequency split amplification, frequency selective combining, and common output filtering. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the structure of a miniaturized dual-frequency dual-channel low-noise receiver front-end of the present invention. Detailed Implementation

[0009] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0010] It should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0011] In the description of the embodiments of this application, "a plurality of" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0012] Reference Figure 1 This is a schematic diagram of an optional example of the miniaturized dual-frequency dual-path low-noise receiver front-end proposed in this invention. The receiver front-end proposed in this embodiment may include, but is not limited to, the following structures: An input dual-passband filter, the output of which is connected to the input of the input combiner; An input combiner, the output of which is connected to the input of the low-frequency branch and the output of the high-frequency branch, respectively; The low-frequency branch includes two stages of low-frequency low-noise amplifiers, the output of which is connected to the first input of the output combiner. The high-frequency branch includes two stages of high-frequency low-noise amplifiers, the output of which is connected to the second input of the output combiner. The output combiner is connected to the input of the output dual-passband filter. The output dual-passband filter is used to suppress harmonics, noise, and parasitic responses.

[0013] The RF input terminal is connected to an input dual-passband filter, which is positioned outside the common terminal of the input combiner. This filter allows simultaneous passage of low-frequency signals with a center frequency of 1.17 GHz and high-frequency signals with a center frequency of 1.57 GHz, while pre-selecting and suppressing interference signals outside the two operating frequency bands. The input combiner forms low-frequency and high-frequency transmission channels based on the signal frequencies. The low-frequency transmission channel is sequentially connected to two stages of low-frequency low-noise amplifiers, and the high-frequency transmission channel is sequentially connected to two stages of high-frequency low-noise amplifiers. The two branches can respectively use low-noise amplifiers adapted to the 1.17 GHz and 1.57 GHz operating frequency bands, and are equipped with bias networks, input matching networks, inter-stage matching networks, output matching networks, and stabilization networks. This ensures that the first active stage primarily controls the noise figure to match the input, and the second active stage primarily controls the gain and linearity to match the output, thus avoiding the problem that a single broadband low-noise amplifier cannot simultaneously achieve optimal performance in both frequency bands. The outputs of the two-stage low-frequency low-noise amplifier and the two-stage high-frequency low-noise amplifier are connected to the output combiner. The output combiner combines the low-frequency and high-frequency signals along their respective frequency-selective channels to the common terminal. The common terminal of the output combiner is connected to the output dual-passband filter. The output dual-passband filter simultaneously performs common filtering on the output signals of the two amplification branches to suppress harmonics, out-of-band noise generated by the low-noise amplifier, and parasitic responses of the combining node. Finally, the signal is output from the RF output terminal RF OUT.

[0014] This invention eliminates the four independent input and output filtering modules in the low-frequency and high-frequency branches, replacing them with a dual-passband filter before the input combiner and after the output combiner. This reduces the number of redundant filters, device packages, pads, grounding vias, and branch connections while maintaining independent amplification of both operating frequency bands. It also shortens the physical connection paths from the input to the first-stage low-noise amplifier and from the second-stage low-noise amplifier to the output, thereby reducing circuit area and parasitic parameters. Since the input dual-passband filter simultaneously performs pre-selection filtering for both frequency bands at the common terminal, there is no need for the signal to pass through multiple branch filtering modules sequentially. When the measured cascade insertion loss of the input dual-passband filter and the input combiner is lower than the corresponding insertion loss of the input combiner and branch filtering links in conventional schemes, the passive loss before the first-stage low-noise amplifier can be reduced, thus improving the overall noise figure. When the measured cascade insertion loss of the output dual-passband filter of the output combiner is lower than that of commonly used output branch filtering structures, the net gain loss on the output side can be reduced.

[0015] The two branches maintain high impedance isolation within each other's operating bands. The overall performance can be verified by the return loss, insertion loss, branch isolation, noise figure, net gain, out-of-band rejection, and unconditional stability under the same substrate, same component library, and same port reference plane. This overall structure can be used as a dual-band low-noise receiver module behind the antenna in RF terminals such as broadband monitoring, wireless communication reception, spectrum sensing, and multi-band IoT gateways. It can also be extended to three or more non-overlapping frequency bands while maintaining the cooperative relationship between the common-end filtering and the frequency selection splitter / combiner.

[0016] In some feasible embodiments, the two-stage low-frequency low-noise amplifier and the two-stage high-frequency low-noise amplifier have roughly the same structure, specifically including: Input matching network: Connected between the signal input and the first-stage amplifier, its function is to match the transistor's optimal noise source impedance to a standard 50Ω system. A commonly used structure is an LC ladder matching network.

[0017] First-stage low-noise amplifier: This is the core of the entire receiver front end. It typically uses a common-source (CS) structure and is equipped with a source degradation inductor to achieve optimal noise performance.

[0018] Interstage matching network: connects the first and second stage amplifiers to achieve matching between the maximum gain output of the first stage and the optimal noise input of the second stage.

[0019] The second-stage amplifier's main function is to provide additional power gain, and it can employ a common-source (CS) or common-source-cascode (Cascode) structure.

[0020] Output matching network: Matches the output impedance of the second-stage amplifier to 50Ω to ensure a good connection with the output combiner of the subsequent stage.

[0021] DC bias circuit: Provides stable, low-noise operating voltage and current for transistors. It often employs a single-supply self-biasing method to simplify power supply design.

[0022] Taking the low-frequency channel as an example, its working principle is as follows: Signal Input and Matching: The low-frequency signal separated from the input combiner first enters the input matching network to complete impedance transformation. First-Stage Low-Noise Amplification: The matched signal enters the first-stage amplifier, which uses a common-source + source degraded inductor structure as its core. This stage is carefully designed to operate with minimal noise, providing preliminary, low-noise amplification of weak RF signals. Interstage Matching and Second-Stage Amplification: The amplified signal enters the second-stage amplifier through the interstage matching network. This stage primarily provides further power gain to ensure the signal strength meets the requirements of subsequent circuitry. Signal Output: The amplified signal is finally output from the amplifier output through the output matching network.

[0023] In addition, to achieve the above design, the following key components and processes are typically employed: Transistors: Gallium arsenide (GaAs) pseudocrystalline high electron mobility transistors (pHEMTs) or silicon-germanium (SiGe) transistors are selected, as they possess excellent noise performance and high-frequency characteristics. Implementation Process: Implementation can be achieved using monolithic microwave integrated circuits (MMICs) or surface-mount processes based on high-frequency printed circuit boards (such as Rogers boards). Miniaturization Technology: To achieve miniaturization, advanced integrated circuits such as system-in-package (SiP) and three-dimensional multi-chip packaging can be used.

[0024] In some feasible embodiments, the DC bias circuit employs a resistor divider bias circuit, which provides the operating voltage to the transistor gate (or base) through resistor division. Specifically, a voltage divider consisting of two series resistors (such as R1 and R2) draws power from the supply voltage (VDD) to provide the bias voltage to the transistor gate. A choke resistor (such as Rg) is typically connected in series at the gate to prevent RF signals from leaking into the bias network. At the drain (or collector), a DC voltage is fed in through a choke inductor (RFC) or a high-impedance line, simultaneously blocking RF signals. To prevent power supply noise and signal crosstalk, a large number of bypass capacitors (such as C1) are added to ground in the circuit.

[0025] In some feasible embodiments, a method for loading an antenna onto the dual-band, dual-path low-noise receiving front-end with an external common filter for the combiner according to the present invention is also provided. The antenna serves as the receiving unit for dual-band radio frequency signals, and its feed terminal is directly connected to the input dual-passband filter. The input dual-passband filter performs common pre-selection filtering on the dual-band signals with center frequencies of 1.17 GHz and 1.57 GHz received by the antenna, and sends the filtered dual-band signals to the input combiner. The input combiner sends the low-frequency signal to a low-frequency amplification branch composed of two stages of low-frequency low-noise amplifiers, and sends the high-frequency signal to a high-frequency amplification branch composed of two stages of high-frequency low-noise amplifiers. After the two branches complete low-noise amplification, they are connected together to the output combiner. The output combiner merges the signals from the two frequency bands into a common output channel, and then the output dual-passband filter suppresses harmonics, out-of-band noise, and combined parasitic response before finally outputting the signal from the radio frequency output terminal.

[0026] In summary, this invention separates two different frequency signals along their respective low-loss paths by setting a pre-stage common dual-passband filter network between the antenna and the input frequency selection splitter network, and a post-combiner common dual-passband filter network after the common combiner of the low-frequency and high-frequency two-stage low-noise amplifier branches. This is complemented by input frequency selection noise matching branches designed for the two operating frequency bands, and a second-stage low-noise amplifier output matching and frequency selection combiner branch. By making the low-frequency branch high-impedance in the high-frequency operating band and the high-frequency branch high-impedance in the low-frequency operating band, and by coordinating the input splitter, out-of-band suppression, and noise matching of the first-stage low-noise amplifier, and by coordinating the output matching of the second-stage low-noise amplifier with the frequency selection combiner, this invention achieves separation of the two different frequency signals along their respective low-loss paths. By combining amplification and common-end convergence, this invention effectively solves the technical challenges of traditional dual-frequency receiver front-ends, which require repeated configuration of input filters, output filters, fixed 50Ω interfaces, and ordinary broadband power combiners in two branches. This results in a large number of components, high cascade insertion loss, deterioration of the pre-stage noise figure, and increased board area. It simultaneously achieves integrated optimization of multiple functions, including common filtering, low-noise amplification, frequency selection branching, and low-loss combining. This invention targets the operating band centered at 1.17 GHz and 1.57 GHz. The two branches can respectively select low-frequency low-noise devices and high-frequency broadband devices, and independently set bias, inter-stage stabilization, and output matching parameters, thereby taking into account the noise, gain, isolation, and stability requirements of far-separated frequency bands. This invention employs an integrated RF link consisting of a common dual-passband filter network, a complementary frequency-selective splitter network, two-way two-stage LNAs, and a frequency-selective combiner network. Compared to the repetitive cascaded structure of existing technologies that involves "independent input filtering for each branch—independent amplification—independent output filtering—ordinary 3 dB power combiner," this solution reduces the need for independent filter modules, 50Ω module interfaces, solder pads, connecting lines, debug points, and additional microstrip length, making it easier to connect to antennas and integrate with miniaturized RF terminals. Thanks to the joint synthesis of common pre-selective filtering and frequency-selective noise matching before the first-stage LNA, this invention does not require restoring the two branches to fixed 50Ω interfaces. When the actual insertion loss of this joint network is lower than the cascaded insertion loss of traditional branch filters, splitters, and independent matching networks, the overall noise figure can be improved approximately by the amount of pre-stage passive insertion loss saved. Thanks to the integrated design of the second-stage LNA output matching and frequency selection combiner, the non-working branch exhibits high impedance when viewed from the common node within the other party's frequency band, avoiding the inherent distribution characteristics of ordinary equal-power combiner structures. When the measured insertion loss from the second-stage LNA output reference plane to the common output terminal is lower than that of ordinary broadband power combiners, the output-side net gain can be further improved and the mutual loading between branches can be reduced.Furthermore, this invention can integrate a common dual-passband filter network with adjacent branch and combiner networks by sharing resonators, grounding inductors, impedance transformation sections, pads, or common node matching units. It only involves conventional lumped LC devices, microstrip lines, grounding vias, and active device mounting, without adding complex mechanical cavities or multi-level module connections. Under the condition that the total number of actual components in the common network is less than two independent networks and the passband coupling compensation does not introduce more devices, it can reduce the number of BOMs, assembly and debugging complexity. Its advantages of low loss, miniaturization and engineering integration can be quantitatively verified by testing BOM, S-parameters, noise figure, net gain, isolation, stability and board area under the same substrate, same device library, same port reference plane and same frequency step.

[0027] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A miniaturized dual-frequency dual-channel low-noise receiver front end, characterized in that, It includes an input dual-passband filter, an input combiner, two stages of low-frequency amplifiers, two stages of high-frequency amplifiers, an output combiner, and an output dual-passband filter, wherein: The input dual-passband filter, the input combiner, the two-stage low-frequency amplifier, the output combiner, and the output dual-passband filter are connected in sequence. The output terminal of the input combiner is also connected to the input terminal of the two-stage high-frequency amplifier; The output of the two-stage high-frequency amplifier is also connected to the input of the output combiner.

2. The miniaturized dual-frequency dual-channel low-noise receiver front-end according to claim 1, characterized in that, It also includes antennas, in which: The antenna's feed terminal is connected to the input terminal of the input dual-passband filter.

3. The miniaturized dual-frequency dual-channel low-noise receiver front-end according to claim 1, characterized in that, The two-stage low-frequency amplifier consists of an input matching network, a first-stage low-frequency amplifier, an inter-stage matching network, a second-stage low-frequency amplifier, and an output matching network, in sequence. The input dual-passband filter, the input combiner, the two-stage low-frequency amplifier, the output combiner, and the output dual-passband filter are connected in sequence.

4. The miniaturized dual-frequency dual-channel low-noise receiver front-end according to claim 3, characterized in that, It also includes a DC bias circuit, which specifically includes: A voltage divider, consisting of two series resistors, draws power from the power supply voltage to provide a bias voltage for the gate of a transistor. The transistor has a gate connected in series with a choke resistor to prevent radio frequency signals from leaking into the bias network, and its drain is fed with DC voltage through a choke inductor.

5. A miniaturized dual-frequency dual-channel low-noise receiver front-end according to any one of claims 1-4, characterized in that, The center frequency of the low-frequency operating band is 1.17 GHz, and the center frequency of the high-frequency operating band is 1.57 GHz.

6. The miniaturized dual-frequency dual-channel low-noise receiver front-end according to claim 2, characterized in that, Its working principle is as follows: The input dual-passband filter performs common pre-selection filtering on the dual-frequency signal received by the antenna, and sends the filtered dual-frequency signal into the input combiner. The input combiner sends the low-frequency signal from the filtered dual-frequency signal to the two-stage low-frequency amplifier, and sends the high-frequency signal from the filtered dual-frequency signal to the two-stage high-frequency low-noise amplifier. The signal, after low-noise amplification, is sent to the output combiner. The output combiner combines signals from two frequency bands into a common output channel, and then the output dual passband filter suppresses harmonics, out-of-band noise, and parasitic combining response, finally outputting the final signal from the RF output terminal.

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