Self-backhauling radio transmitter

Abstract

A self-backing radio transmission apparatus has a transmitter and a backing network. The transmitter has a modulator and a power amplifier. The modulator is used to up-convert a first baseband signal to a first radio frequency signal based on a first local oscillator signal. The power amplifier is used to receive the first radio frequency signal and output a second radio frequency signal and a third radio frequency signal, the second radio frequency signal being transmitted by an antenna, the third radio frequency signal being backed up, wherein the third radio frequency signal is magnetically coupled from the second radio frequency signal. The backing network has a shielded series inductance and a demodulator. The shielded series inductance is used to receive the third radio frequency signal and output a fourth radio frequency signal. The demodulator is used to down-convert the fourth radio frequency signal to a second baseband signal based on a second local oscillator signal, wherein the shielded series inductance has a spiral form series inductance that includes a coil, the coil being disposed on a lower metal layer.

Description

Technical Field

[0001] This disclosure relates to a self-returning radio transmitter, and more particularly to a self-returning radio transmitter with a high linearity and low noise loopback network. Background Technology

[0002] like Figure 1 As shown, a radio transmitter 100 includes: a modulator 110 for receiving a baseband signal X1 and outputting a radio frequency (RF) signal X2; and a power amplifier 120 for receiving the RF signal X2 and outputting an antenna signal X3 for transmission by an antenna 130. Ideally, the antenna signal X3 is a frequency translation of the baseband signal X1 and is proportional to (or linearly dependent on) the baseband signal X1. However, in practice, the modulator 110 and power amplifier 120 may have a nonlinearity, which causes X3 to be disrupted and no longer perfectly proportional to (or linearly dependent on) the baseband signal X1. Helpfully, a monitoring circuit can be used to monitor and characterize the nonlinearity of the antenna signal X3, the modulator 110, and the power amplifier 120, and correct this nonlinearity by pre-distorting the baseband signal X1. However, the monitor circuit itself must not introduce any perceptible impairments (including nonlinearity and noise), otherwise the true nonlinearity of the modulator 110 and the power amplifier 120 may be obscured.

[0003] What is needed in this technical field is a radio transmitter with a monitoring circuit, which consists of a high linearity and low noise feedback network. Summary of the Invention

[0004] One of the purposes of this disclosure is to provide a self-returning radio transmitter with a high linearity and low noise return network.

[0005] In one embodiment of this disclosure, a self-returning radio transmitter includes: a transmitter comprising a modulator and a power amplifier, the modulator being configured to upmodulate a first baseband signal to a first radio frequency (RF) signal based on a first LO signal at a local oscillator (LO) frequency; the power amplifier being configured to receive the first RF signal and output a second RF signal and a third RF signal, the second RF signal being transmitted by an antenna and the third RF signal being returned, wherein the third RF signal is magnetically coupled from the second RF signal; and a return network comprising a shielded serial inductor. The shielded series inductor is used to receive the third RF signal and output a fourth RF signal. The demodulator is used to down-modulate the fourth RF signal into a second baseband signal based on a second LO signal of the LO frequency. The shielded series inductor is arranged in a multilayer structure, which includes an upper metal layer and a lower metal layer. The shielded series inductor includes a spiral series inductor, which includes a coil disposed in the lower metal layer. The lower metal layer is shielded by a shielding material disposed in the upper metal layer and connected to a ground node.

[0006] Furthermore, the power amplifier includes a stacked amplifier loaded with a load, the load including a resonant cavity, the resonant cavity including a main inductor and a capacitor connected in parallel, a primary inductor and a sensing inductor.

[0007] Furthermore, the cascaded amplifier receives the first radio frequency signal and outputs an amplified radio frequency signal through the primary inductor. The second radio frequency signal is established through the secondary inductor via a first magnetic coupling between the primary inductor and the secondary inductor. The third radio frequency signal is established through the sensing inductor via a second magnetic coupling between the secondary inductor and the sensing inductor.

[0008] Furthermore, the second magnetic coupling is much smaller than the first magnetic coupling.

[0009] Furthermore, the demodulator includes a mixer and a negative feedback amplifier.

[0010] Furthermore, the mixer includes a switch for coupling the fourth radio frequency signal to an internal node based on the second local oscillator signal; the negative feedback amplifier is used to receive a signal at the internal node and output the second baseband signal.

[0011] Furthermore, the negative feedback amplifier includes an operational amplifier, a feed network, and a feedback network; the operational amplifier is used to receive an input signal at an input node and output the second baseband signal at an output node; the feed network is used to couple the internal node to the input node; and the feedback network is used to provide negative feedback from the output node to the input node.

[0012] Furthermore, both the feedback network and the input network are passive.

[0013] Furthermore, the shielded series inductor further includes a parallel capacitor at one node to receive the third radio frequency signal.

[0014] Furthermore, the shielded series inductor further includes a parallel capacitor at one node to output the third radio frequency signal.

[0015] The features, implementation, and technical effects of the present invention are described in detail below with reference to the accompanying drawings, and preferred embodiments are described in detail. Attached Figure Description

[0016] Figure 1 This diagram shows a conventional radio transmitter.

[0017] Figure 2 A schematic diagram of a self-returning radio transmitter is shown according to an embodiment of the present disclosure;

[0018] Figure 3 Display available Figure 2 A schematic diagram of a modulator for a self-returning radio transmitter;

[0019] Figure 4 Display available Figure 2 A schematic diagram of a power amplifier for a self-returning radio transmitter;

[0020] Figure 5 Display available Figure 2 A top view of the layout of a shielded series inductor for a self-returning radio transmitter; and

[0021] Figure 6 Display available Figure 2 A schematic diagram of a demodulator for a self-returning radio transmitter.

[0022] Symbol Explanation

[0023] 100: Radio transmitter

[0024] 110: Modulator

[0025] 120: Power Amplifier

[0026] 130: Antenna

[0027] X1: Baseband signal

[0028] X2: Radio frequency (RF) signal

[0029] X3: Antenna signal

[0030] 200: Self-returning radio transmitter

[0031] 201: Teleporter

[0032] 202: Echo Network

[0033] 210: Modulator

[0034] 220: Power amplifier (with LC cavity load)

[0035] 230: Antenna

[0036] 240: Shielded series inductor

[0037] 250: Demodulator

[0038] B1: First baseband signal

[0039] S1: First radio frequency (RF) signal

[0040] S2: Second RF signal

[0041] S3: Third RF signal

[0042] S4: Fourth RF signal

[0043] B2: Second base frequency signal

[0044] First / Second LO Signal: First / Second Local Oscillator (LO) Signal

[0045] 300: Modulator

[0046] 310: First Amplifier

[0047] 311, 312: Two NMOS transistors in the first amplifier

[0048] 320: Second Amplifier

[0049] 321, 322: Two NMOS transistors in the second amplifier

[0050] 330: First Mixer

[0051] 331, 332, 333, 334: The four switches of the first mixer

[0052] 340: Second mixer

[0053] 341, 342, 343, 344: The four switches of the second mixer

[0054] 350: Load

[0055] 351: Inductor

[0056] 353: Capacitor

[0057] B 1I+ B 1I- The in-phase component B of the first fundamental frequency signal B1 1I Two voltages

[0058] B 1Q+ B 1Q- The quadrature phase component B of the first fundamental frequency signal B1 1Q Two voltages

[0059] Y 1I+ Y 1I- Output voltage of the first amplifier

[0060] Y 1Q+ Y 1Q- : Output voltage of the second amplifier

[0061] V I+ V I- : In-phase component V of the first / second LO signal I Two voltages

[0062] V Q+ V Q- V, the quadrature phase component of the first / second LO signal Q Two voltages

[0063] S 1+ S 1- The two voltages of the first RF signal S1

[0064] V DD Power supply node

[0065] 400: Power Amplifier

[0066] 410: Stacked Amplifier

[0067] 411, 412, 413, 414: Four NMOS transistors in the stacked amplifier; 420: Load.

[0068] 421: Main Inductor

[0069] 422: Secondary Inductor

[0070] 423: Sensing Inductor

[0071] 424: Capacitor

[0072] 430: Antenna

[0073] Y′ 2+ 、Y′ 2- Intermediate voltage of the cascaded amplifier

[0074] V CAS Bias voltage

[0075] Y 2+ Y 2- Output voltage of the cascaded amplifier

[0076] S 3+ S 3- The two voltages of the third RF signal S3

[0077] k1: First coupling coefficient

[0078] k2: Second coupling coefficient

[0079] 530: Shielding material

[0080] 510: First series inductor

[0081] 511: First coil

[0082] 512: First through hole

[0083] 513: Second coil

[0084] 520: Second series inductor

[0085] 521: Third coil

[0086] 522: Second through hole

[0087] 523: Fourth coil

[0088] S 4+ S 4- The two voltages of the fourth RF signal S4

[0089] 600: Demodulator

[0090] 610: First Mixer

[0091] 611, 612, 613, 614: The four switches of the first mixer

[0092] 615, 616: Nodes

[0093] 620: Second mixer

[0094] 621, 622, 623, 624: The four switches of the second mixer

[0095] 625, 626: Nodes

[0096] 630: First negative feedback amplifier

[0097] 631: First Operating Amplifier

[0098] 632, 633: Feedback Network

[0099] 634, 635: Output nodes

[0100] 636, 637: Feed network

[0101] 638, 639: Input nodes

[0102] 640: Second negative feedback amplifier

[0103] 641: Second Operational Amplifier

[0104] 642, 643: Feedback Network

[0105] 644, 645: Output nodes

[0106] 646, 647: Feed network

[0107] 648, 649: Input nodes

[0108] B 2i+ B 2I- The in-phase component B of the second fundamental frequency signal B2 2i Two voltages

[0109] B 2Q+ B 2Q- The quadrature phase component B of the second fundamental frequency signal B2 2Q Two voltages Detailed Implementation

[0110] This disclosure relates to a self-loopback radio transmitter. Although several embodiments of this disclosure are presented as preferred examples for carrying out the invention, the invention can be implemented in various ways and is not limited to the specific examples described below, nor to the specific manner in which the technical features of those specific examples are implemented. Furthermore, known details have not been shown or described to avoid obscuring the viewpoint of this disclosure.

[0111] Those skilled in the art will understand the microelectronics-related terms and basic concepts used in this disclosure, such as "voltage," "current," "signal," "noise," "nonlinearity," "amplifier," "differential signal," "mixer," "load," "capacitor," "resistor," "inductor," "impedance," "magnetic coupling," "LC (inductor-capacitor) tank," "circuit node," "ground," "power supply," "MOS (metal-oxide-semiconductor) transistor," "CMOS (composite metal-oxide-semiconductor) process technology," "NMOS (n-channel metal-oxide-semiconductor) transistor," and "PMOS (p-channel metal-oxide-semiconductor) transistor." When such terms and basic concepts are used in microelectronics articles, they are readily apparent to those skilled in the art, and therefore will not be described in detail herein.

[0112] Those skilled in the art can understand circuit diagrams and their contained electronic components such as inductors, capacitors, resistors, NMOS transistors, PMOS transistors, switches, etc., without requiring redundant explanations of how one component is connected to another. Those skilled in the art can also identify a ground symbol, a capacitor symbol, an inductor symbol, a resistor symbol, and the symbols for PMOS and NMOS transistors, and can identify the "source," "gate," and "drain" terminals of a MOS transistor. For the sake of brevity, in the following description, "source terminal" will be simply referred to as "source," "gate terminal" as "gate," and "drain terminal" as "drain."

[0113] A circuit is a collection of transistors, capacitors, resistors and / or other electronic devices interconnected in a particular manner to perform a specific function.

[0114] A network is a circuit or a collection of circuits.

[0115] In this disclosure, a "circuit node" is often simply referred to as a "node" to avoid redundancy, provided that its meaning is clear from the context.

[0116] A signal is a voltage or current with a variable level that carries specific information and can change over time. At any given moment, the voltage or current level of the signal represents the state of the signal at that moment.

[0117] In a differential signal transmission embodiment, a voltage signal comprises two voltages, one represented by a suffix "+" added to the subscript and the other by a suffix "-" added to the subscript, and the value of the voltage signal is represented by the voltage difference between the two voltages. For example, a voltage signal v1 comprises two voltages v 1+ With v 1- And the voltage of v1 is determined by "v 1+ -v 1- "to represent".

[0118] When a change in a signal originates from and is controlled by a first device, the signal can be said to be output from the first device to a second device, whereby the second device can be said to receive the signal and react according to the change in the signal.

[0119] A logic signal is a two-state voltage signal, which refers to a low state and a high state, relative to an associated trip point. For a logic signal Q, "Q is high" or "Q is low" means either "Q is in the high state" (i.e., above the associated trip point) or "Q is in the low state" (i.e., below the associated trip point).

[0120] A logic signal is often used as a control signal to enable or disable the function of a circuit. When the logic signal is in a logical state to enable the circuit, it is considered "asserted"; otherwise, it is considered "de-asserted". When the logic signal is high, if it is "asserted", it is considered "active high"; when it is low, if it is "asserted", it is considered "active low". When a "active low" logic signal is above a transition point, the logic signal is asserted; when it is below that transition point, it is de-asserted.

[0121] If a first logic signal and a second logic signal are always in opposite states, the first logic signal is considered to be the logical inverse of the second logic signal. That is, when the first logic signal is high, the second logic signal will be low; and when the first logic signal is low, the second logic signal will be high. When a first logic signal is the logical inverse of a second logic signal, the first logic signal is considered to be complementary to the second logic signal.

[0122] A switch is a device used to provide a connection between a first node and a second node based on a logic signal. When the logic signal is established, the switch is turned on and behaves as a short circuit; when the logic signal is de-established, the switch is turned off and behaves as an open circuit.

[0123] A clock is a logic signal that periodically toggles between a low level and a high level.

[0124] Resistors, capacitors, and inductors are “passive” and are typically highly linear.

[0125] Inductors are "reactive" and can effectively store magnetic energy, and generally do not contribute much noise.

[0126] like Figure 2 As shown, a self-returning radio transmitter 200 includes a transmitter 201 and a return network 202. The transmitter 201 includes a modulator 210 configured to operate according to a local oscillator (LO) frequency f. LO The system includes a first LO signal, receives a first baseband signal B1, and outputs a first radio frequency (RF) signal S1; and a power amplifier (with an LC cavity load) 220, which receives the first RF signal S1 and outputs a second RF signal S2 (to be transmitted by an antenna 230) and a third RF signal S3 (to be fed back to the feedback network 202). The feedback network 202 includes: a shielded series inductor 240, which receives the third RF signal S3 and outputs a fourth RF signal S4; and a demodulator 250, which adjusts the frequency according to the LO frequency f. LOThe transmitter 201 receives the fourth RF signal S4 and outputs a second baseband signal B2. One purpose of the transmitter 201 is to up-convert B1 to S2, which is suitable for wireless transmission by the antenna 230. One purpose of the loopback network 202 is to down-convert S3 (which is a replica of S2) to B2. If both the transmitter 201 and the loopback network 202 are perfectly linear, B2 will be completely linearly dependent on B1. When B2 is not completely linearly dependent on B1, this indicates that there is a nonlinearity in the transmitter 201 and / or the loopback network 202. If the nonlinearity of the loopback network 202 is much smaller than that of the transmitter 201, the nonlinearity of the transmitter 201 can be characterized by observing how B2 deviates from the case of complete linear dependence on B1, and may be corrected by pre-distortion of B1.

[0127] B1 is a two-dimensional signal, which can be represented by a complex signal containing a real part and an imaginary part. The real part usually refers to the in-phase component B. 1I The imaginary part usually refers to a quadrature component B. 1Q B1 can be expressed mathematically as follows:

[0128] B1(t)=B 1I (t)+jB 1Q (t) (1)

[0129] In the above formula, "j" is a unity imaginary number, which is equal to the square root of -1, while "t" represents a time variable.

[0130] The first LO signal is a clock generated by a local oscillator and is a two-dimensional signal containing a co-phase component V. i (t) and an orthogonal phase component V Q (t). In one embodiment, the in-phase component V I (t) is the LO frequency f LO A sine wave, and the orthogonal phase component V Q (t) is the same as the in-phase component V, except for a 90-degree phase shift. I (t). When the nonlinearity of modulator 210 is neglected, S1 is a frequency-translated replica of B1, and can be mathematically expressed as follows:

[0131]

[0132] In the above equation, G1 and θ1 are a gain and a phase shift of the modulator 210, respectively.

[0133] Power amplifier 220 amplifies S1 into S2. When the nonlinearity of power amplifier 220 is neglected, S2 can be mathematically expressed as follows:

[0134]

[0135] In the above formula, G2 and θ2 are the gain and phase shift of the power amplifier 220, respectively.

[0136] Power amplifier 220 includes a load consisting of an LC (inductor-capacitor) cavity, the resonant frequency of which is approximately f. LO Therefore, power amplifier 220 can provide a high gain to S2, meaning G2 can be quite large.

[0137] S3 is magnetically coupled from S2 via an inductor in the LC cavity of power amplifier 220, becoming a copy of S2. This copy is accompanied by a coupling loss and an additional phase shift. S3 can be mathematically expressed as follows:

[0138]

[0139] In the above equation, G3 and θ3 are the coupling loss and additional phase shift of the magnetic coupling, respectively.

[0140] The shielded series inductor 240 receives S3 and outputs S4, therefore S4 can be mathematically represented by the following formula:

[0141]

[0142] In the above formula, G4 and θ4 are the insertion loss and phase shift of the shielded series inductance 240, respectively.

[0143] Demodulator 250 performs an inverse frequency conversion to convert S4 to B2. B2 is a two-dimensional signal containing a co-phase component B. 2I With an orthogonal phase component B 2Q Furthermore, mathematically, it can be represented using a complex-signal notation as follows:

[0144] B2(t)=B 2I(t)+jB 2Q (t) (6)

[0145] When the nonlinearity of the demodulator 250 is neglected, B2 can be expressed by the following formula:

[0146]

[0147] In the above formula, G5 and θ5 are a gain and a phase shift caused by the demodulator 250, respectively. The total gain G from the first fundamental frequency signal B1(t) to the second fundamental frequency signal B2(t) is... T It can be expressed by the following formula:

[0148]

[0149] However, in the case of nonlinearity, the total gain G T It may be distorted and deviate from the total gain G shown in equation (8). T One of the purposes of the feedback network 202 is to detect the nonlinearity of the transmitter 201. If the nonlinearity of the feedback network 202 is much smaller than that of the transmitter 201, the total gain G can be observed. T How to deviate from the total gain G shown in equation (8) T The nonlinearity of transmitter 201 can be characterized. However, the feedback network 202 may introduce additional noise, which may obscure the total gain G. T Characterization.

[0150] In short, in order to effectively characterize the nonlinearity of the transmitter 201 by using the feedback network 202, the feedback network 202 must be highly linear and have low noise.

[0151] Figure 3 A schematic diagram of modulator 300 is shown. Modulator 300 can be used to implement... Figure 2 Modulator 210. Modulator 300 includes a first amplifier 310, a second amplifier 320, a first mixer 330, a second mixer 340, and a load 350, and is used to adjust the first LO signal (as previously described, which is a two-dimensional signal containing an in-phase component V) according to the first LO signal. I With orthogonal phase component V Q ), receive the in-phase component B1 1i With orthogonal phase component B 1Q And output S1. A differential-signaling embodiment is used here, where B 1I Includes two voltages B1I+ With B 1I- B 1Q Includes two voltages B 1Q+ With B 1Q- V I Includes two voltages V I+ With V I- V Q Includes two voltages V Q+ With V Q- S1 contains two voltages S 1+ With S 1- The first amplifier 310 includes two NMOS transistors 311 and 312, which are used to receive B respectively. 1I+ With B 1I- and two voltages Y are used to output the voltage respectively. 1I+ With Y 1I- The second amplifier 320 includes two NMOS transistors 321 and 322, which are used to receive B, respectively. 1Q+ With B 1Q- and two voltages Y are used to output the voltage respectively. 1Q+ With Y 1Q- The first mixer 330 includes four switches 331, 332, 333, and 334, while the second mixer 340 includes four switches 341, 342, 343, and 344. Switches 331 (332, 333, 334, 341, 342, 343, 344) are used according to V... I+ (V I+ V I- V I- V Q+ V Q+ V Q- V Q- ), Y 1I+ (Y 1I- Y 1I+ Y 1I- Y 1Q+ Y 1Q- Y 1Q+ Y 1Q- Connect to S 1+ (S 1- S 1- S 1+ S 1+ S 1- S 1- S 1+ The load 350 includes an inductor 351 connected in parallel (with a center tap connected to a power supply node V). DD ) and a capacitor 353, which is used to form a resonant network, so as to achieve f LO (That is: V) I With VQ (at its frequency) provides a high impedance. Mathematically, V I+ V I- V Q+ With V Q- It can be modeled in the time domain as follows:

[0152] V I+ =V trip +V C ·cos(2πf LO t) (9)

[0153] V I- =V trip -V C ·cos(2πf LO t) (10)

[0154] V Q+ =V trip -V C ·sin(2πf LO t) (11)

[0155] V Q- =V trip +V C ·sin(2πf Lo t) (12)

[0156] In the above formula, V trip It is the transition point of the logic control signals of switches 331, 332, 333, 334, 341, 342, 343 and 344, V C This represents the amplitude of the first LO signal. V I+ With V I- They are complementary, and V Q+ With V Q- They are complementary. When V I+ Higher than (lower than) V trip V I- It will be lower (higher) than V trip Incidentally, when V I+ Establish (de-establish) and V I- When the connection is released (established), switches 331 and 332 are turned on (off), while switches 333 and 334 are turned off (on). Similarly, when V... Q+ Higher than (lower than) V trip V Q- It will be lower (higher) than V trip Incidentally, when v Q+ Establish (de-establish) and V Q-When the confirmation is released (established), switches 341 and 342 are turned on (closed) while switches 343 and 344 are turned off (turned on).

[0157] It is known in this technical field that the modulator 300 can fulfill the function expressed by equation (2). This requires no further explanation.

[0158] Figure 4 This diagram shows a power amplifier 400, which can be used to implement... Figure 2 The power amplifier 220. The power amplifier 400 includes a cascode amplifier 410 and a load 420 for receiving the first RF signal S1 and outputting the second RF signal S2 and the third RF signal S3, wherein in a differential signal transmission embodiment, S1 includes two voltages S 1+ With S 1- S3 contains two voltages S 3+ With S 3- The stacked amplifier 410 includes four NMOS transistors 411, 412, 413, and 414, where NMOS transistors 411 and 412 implement a common-source amplifier, while NMOS transistors 413 and 414 implement an amplifier biased by a bias voltage V. CAS A cascode stage for biasing. The concepts of "cascode amplifier," "common-source amplifier," "cascode stage," and "bias" are well-known to those skilled in the art and will not be elaborated upon here. NMOS transistors 411 and 412 respectively receive S... 1+ With S 1- And output two intermediate voltages Y′ respectively. 2+ With Y′ 2- NMOS transistors 413 and 414 respectively receive Y′ 2+ With Y′ 2- And output two output voltages Y respectively. 2+ With Y 2- Load 420 includes: a primary inductor 421 connected in parallel (with a center tap connected to a power supply node V). DD The main inductor 421 and capacitor 424 form a resonant cavity to achieve the desired effect at f. LO Providing a high impedance, therefore the two output voltages Y 2+ With Y 2-The coupling coefficient can be quite large. A primary inductor 421 and a secondary inductor 422 are magnetically coupled and have a first coupling coefficient k1; while the secondary inductor 422 and a sensing inductor 423 are magnetically coupled and have a second coupling coefficient k2. The second coupling coefficient k2 is much smaller (or substantially smaller) than the first coupling coefficient k1. In one embodiment (this embodiment is only an example and not a limitation), k1 is approximately 0.8, and k2 is approximately 0.15. The primary inductor 421 and the secondary inductor 424 form a transformer, also known as a "balanced-to-unbalanced converter," which is common in the prior art and will not be described in detail. This balanced-to-unbalanced converter can effectively convert the two output voltages Y... 2+ With Y 2- Switching to S2, it will be transmitted by antenna 430. Sensing inductor 423 outputs S based on its magnetic coupling with secondary inductor 422. 3+ With S 3- Therefore, S3 is a copy of S2. The power amplifier 400, apart from the sensing inductor 423, is known prior art and will not be described further. Since the second coupling coefficient k2 is much smaller (or substantially smaller) than the first coupling coefficient k1, a load effect of the sensing inductor 423 is negligible and does not cause an appreciable loss to S2. The magnetic coupling between S2 and S3 is essentially linear due to passivity; therefore, apart from the loss and phase shift caused by this magnetic coupling, S3 is a copy of S2.

[0159] The shielded series inductor 240 is used to provide a low-pass filter function to filter the third RF signal S3 into the fourth RF signal S4, which in a differential signal transmission embodiment includes two voltages S. 4+ With S 4- This low-pass filter effectively suppresses a high-frequency noise in S4. The shielded series inductor 240 is arranged in a multi-layer structure, which includes an upper metal layer and multiple lower metal layers, including a first lower metal layer and a second lower metal layer. Figure 5 A top view of a shielded series inductor 240 is shown according to an embodiment of the present disclosure. The shielded series inductor 240 includes: a shield 530 disposed on the upper metal layer and connected to a ground node; and a first series inductor 510 for connecting S in a spiral topology. 3+ With S 4+The spiral configuration includes a first coil 511, a second coil 513, and a first via 512. The first coil 511 is disposed in the first lower metal layer, and the second coil 513 is disposed in the second lower metal layer. The first via 512 provides an inter-metal layer connection between the first coil 511 and the second coil 513; and a second series inductor 520 for connecting S in a spiral configuration. 3- With S 4- The spiral configuration includes a third coil 521, a fourth coil 523, and a second through-hole 522. The third coil 521 is disposed in the first lower metal layer, and the fourth coil 523 is disposed in the second lower metal layer. The second through-hole 522 provides an inter-metal layer connection between the third coil 521 and the fourth coil 523. A series inductor has a lower impedance to a lower frequency signal and a higher impedance to a higher frequency signal, making it easier for the lower frequency signal to flow compared to the higher frequency signal, thus achieving a low-pass filter function. Therefore, the first series inductor 510 and the second series inductor 520 together implement a low-pass filter to filter S3 into S4. However, the first series inductor 510 and the second series inductor 520 may pick up unwanted interference signals due to magnetic coupling. Shielding 530 is used to provide shielding. Shielding 530 is connected to a ground node to have a low impedance and thus provide effective shielding. In one embodiment (although not shown in) Figure 5 However, as will be clearly apparent to those skilled in the art, the shielded series inductor 240 further includes a shunt capacitor inserted into S. 3+ With S 3- In one embodiment (though not shown in...) Figure 5 (However, as is clearly apparent to those skilled in the art), the shielded series inductor 240 further includes a parallel capacitor inserted into S. 4+ With S 4- between.

[0160] Figure 6 A schematic diagram of a demodulator 600 is shown, which can be used to implement... Figure 2 The demodulator 250. In a differential signal transmission embodiment, the second fundamental frequency signal B2 is a two-dimensional signal containing a co-phase component B. 2I With a quadrature phase component B2Q, the in-phase component B 2I Includes two voltages B 2I+ With B 2I- The orthogonal phase component B 2Q Includes two voltages B 2Q+ With B 2Q-The demodulator 600 includes a first mixer 610, a second mixer 620, a first negative feedback amplifier 630, and a second negative feedback amplifier 640. In one embodiment, the second LO signal is the same as the first LO signal and includes four voltages V. I+ V I- V Q+ With V Q- As shown in equations (9), (10), (11), and (12), respectively. The first (second) mixer 610 (620) includes four switches 611 (621), 612 (622), 613 (623), and 614 (624). Switches 611 (612, 613, 614, 621, 622, 623, 624) are used according to V I+ (V I+ V I- V I- V Q- V Q- V Q+ V Q+ ), connect S 4+ (S 4- S 4+ S 4- S 4+ S 4- S 4+ S 4- ) and nodes 615 (616, 616, 615, 625, 626, 626, 625). The first (second) negative feedback amplifier 630 (640) includes a first (second) operational amplifier 631 (641) for receiving a differential input signal at two input nodes 638 (648) and 639 (649) via two feed-in networks 636 (646) and 637 (647), and outputting B at two output nodes 635 (645) and 634 (644). 2I+ (B 2Q+ ) and B 2I- (B 2Q- ), while B 2I+ (B 2Q+ ) and B 2I- (B 2Q-The signals are fed back to the two input nodes 639 (649) and 638 (648) via two feedback networks 633 (643) and 632 (642), respectively. The demodulator 600 is a known prior art device capable of implementing the function expressed in equation (7), and therefore will not be described in detail here. In one embodiment, each of the feedback networks 632, 633, 642, and 643 includes a passive element (such as a resistor or a capacitor). In one embodiment, each of the feedback networks 632, 633, 642, and 643 includes a resistor. In one embodiment, each of the feedback networks 632, 633, 642, and 643 includes a resistor and a capacitor connected in parallel. In one embodiment, each of the feed networks 636, 637, 646, and 647 includes a passive element (such as a resistor or a capacitor). In one embodiment, each of the feed networks 636, 637, 646, and 647 includes a resistor (in an extreme example, this resistor is very small, equivalent to a short-circuit circuit). Operating amplifiers are well known to those skilled in the art and will not be described in detail here. A negative feedback amplifier can be highly linear provided that both the feed and feedback networks are passive and the operating amplifier in the negative feedback amplifier has a high gain.

[0161] The self-returning radio transmitter 200 has several advantages. First, the self-returning network 202 can be highly linear; the shielded series inductor 240 is highly linear due to its passive nature; and the demodulator 250 can be highly linear due to the use of a negative feedback amplifier. Second, the shielded series inductor 240 provides low-pass filtering to resist high-frequency noise in the third RF signal S3 and protects itself from harmful electromagnetic coupling from the environment. Furthermore, the shielded series inductor 240, due to its reactive nature, does not contribute much additional noise itself.

[0162] While the embodiments of the present invention have been described above, these embodiments are not intended to limit the present invention. Those skilled in the art can make changes to the technical features of the present invention based on the explicit or implicit content of the present invention, and all such changes may fall within the scope of patent protection sought by the present invention. In other words, the scope of patent protection of the present invention shall be determined by the claims of this specification.

Claims

1. A self-returning radio transmitter, comprising: A transmitter includes a modulator and a power amplifier. The modulator upmodulates a first baseband signal to a first radio frequency signal based on a first local oscillator signal at a local oscillator frequency. The power amplifier receives the first radio frequency signal and outputs a second radio frequency signal and a third radio frequency signal. The second radio frequency signal is transmitted by an antenna, and the third radio frequency signal is fed back, wherein the third radio frequency signal is magnetically coupled from the second radio frequency signal. A feedback network includes a shielded series inductor and a demodulator. The shielded series inductor receives the third radio frequency signal and outputs a fourth radio frequency signal. The demodulator downmodulates the fourth radio frequency signal into a second baseband signal based on a second local oscillator signal with the local oscillator frequency, wherein: The shielded series inductor is arranged in a multi-layer structure, which includes an upper metal layer and a lower metal layer. The shielded series inductor includes a spiral series inductor, which includes a coil. The coil is arranged in the lower metal layer and is shielded by a shielding material. The shielding material is arranged in the upper metal layer and connected to a grounding node.

2. The self-returning radio transmitter as claimed in claim 1, wherein: The power amplifier includes a stacked amplifier with a load, the load including a resonant cavity, the resonant cavity including a main inductor and a capacitor connected in parallel, a primary inductor and a sensing inductor.

3. The self-returning radio transmitter of claim 2, wherein the cascaded amplifier receives the first radio frequency signal and outputs an amplified radio frequency signal through the main inductor, the second radio frequency signal is established through the secondary inductor via a first magnetic coupling between the main inductor and the secondary inductor, and the third radio frequency signal is established through the sensing inductor via a second magnetic coupling between the secondary inductor and the sensing inductor.

4. The self-returning radio transmitter of claim 3, wherein the second magnetic coupling is much smaller than the first magnetic coupling.

5. The self-returning radio transmitter of claim 1, wherein the demodulator comprises a mixer and a negative feedback amplifier.

6. The self-feedback radio transmitter of claim 5, wherein the mixer includes a switch for coupling the fourth radio frequency signal to an internal node based on the second local oscillator signal; the negative feedback amplifier is used to receive a signal at the internal node and output the second baseband signal.

7. The self-feedback radio transmitter of claim 6, wherein the negative feedback amplifier includes an operational amplifier, a feed network, and a feedback network; the operational amplifier is configured to receive an input signal at an input node and output the second baseband signal at an output node; the feed network is configured to couple the internal node to the input node; and the feedback network is configured to provide negative feedback from the output node to the input node.

8. The self-returning radio transmitter of claim 7, wherein both the feedback network and the feed-in network are passive.

9. The self-returning radio transmitter of claim 1, wherein the shielded series inductor further includes a parallel capacitor at one node to receive the third radio frequency signal.

10. The self-returning radio transmitter of claim 1, wherein the shielded series inductor further includes a parallel capacitor at one node to output the third radio frequency signal.

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