High power driver for wideband optical wireless communication

Abstract

An apparatus comprising: a radio frequency (RF) amplifier; and an RF-to-optical (RF2O) driver comprising: a transformer chain comprising a set of cascaded RF transformers; and an impedance matching circuit coupled in series with the transformer chain between the RF amplifier and a laser.

Description

Cross-reference to related applications

[0001] This patent application claims priority to pending U.S. nonprovisional application No. 18 / 628,270, filed April 5, 2024, which has been assigned to the assignee of this application and is expressly incorporated herein by reference, as fully set forth below and for all applicable purposes. Technical Field

[0002] This invention relates to optical wireless communication, and more particularly to a high-power driver for broadband optical wireless communication. Background Technology

[0003] Optical wireless communication systems can use optical signals to facilitate data communication between user equipment (UEs). Optical signals may be necessary in certain applications, such as where high bandwidth / data rates (e.g., one terabits per second (1 Tbps) per link) are required. Such high data rates can be useful in some indoor or relatively short-range applications, such as multimedia, virtual / augmented reality (XR), holographic telepresence, asset tracking, factory communications, etc. It may also be expected that such optical wireless communication systems will interface with radio frequency (RF) systems, such as those used in broadband wide area networks (WWANs) (e.g., WWANs compliant with fifth-generation (5G) New Radio (NR) and / or sixth-generation (6G)). Summary of the Invention

[0004] The following is a simplified overview of one or more specific implementations to provide a basic understanding of such implementations. This overview is not an exhaustive summary of all envisioned implementations, nor is it intended to identify key or essential elements of all implementations, nor to depict the scope of any or all implementations. Its sole purpose is to present some concepts of one or more implementations in a simplified form as a prelude to the more detailed descriptions that follow.

[0005] One aspect of this disclosure relates to an apparatus. The apparatus includes: a radio frequency (RF) amplifier; and an RF-to-optical (RF2O) driver, the RF-to-optical (RF2O) driver including: a transformer chain including a cascaded set of RF transformers; and an impedance matching circuit coupled in series with the transformer chain between the RF amplifier and a laser.

[0006] Another aspect of this disclosure relates to a method. The method includes: transforming a first complex impedance associated with a diffuse laser into a first substantially real impedance; and transforming the first substantially real impedance into a second substantially real impedance associated with a radio frequency (RF) amplifier via a cascaded set of RF transformers.

[0007] Another aspect of this disclosure relates to an optical communication device. The optical communication device includes: a modem; one or more up-conversion stages coupled to the modem; a local oscillator (LO) coupled to the one or more up-conversion stages; a radio frequency (RF) amplifier coupled to the one or more up-conversion stages; a diffuse laser; and an RF-to-optical (RF2O) driver, the RF-to-optical (RF2O) driver including: a transformer chain including a cascaded set of RF transformers; and an impedance matching circuit coupled in series with the transformer chain between the RF amplifier and the diffuse laser.

[0008] To achieve the foregoing and related objectives, one or more embodiments include the features fully described below and specifically pointed out in the claims. The following description and accompanying figures illustrate certain exemplary aspects of one or more embodiments in detail. However, these aspects are merely indications of a number of ways in which the principles of the various embodiments may be employed, and the description of the embodiments is intended to include all such aspects and their equivalents. Attached Figure Description

[0009] Figure 1 A block diagram illustrating an example optical wireless communication system according to one aspect of this disclosure is shown.

[0010] Figure 2 A block diagram illustrating an example optical wireless transceiver according to another aspect of this disclosure is shown.

[0011] Figure 3 A block diagram illustrating an example radio frequency to light (RF2O) driver according to another aspect of this disclosure is shown.

[0012] Figure 4 A schematic diagram of an example radio frequency (RF) transformer chain according to another aspect of this disclosure is illustrated.

[0013] Figure 5 A schematic diagram of an example impedance matching circuit according to another aspect of this disclosure is illustrated.

[0014] Figure 6 A schematic diagram illustrating an example biaser according to another aspect of this disclosure is shown.

[0015] Figure 7 A block diagram illustrating another example of a radio frequency to light (RF2O) driver according to another aspect of this disclosure is shown.

[0016] Figure 8 A schematic diagram of an example standing wave ratio (SWR) sensor according to another aspect of this disclosure is illustrated.

[0017] Figure 9 A schematic diagram illustrating an example of a configurable radio frequency (RF) transformer chain according to another aspect of this disclosure is shown.

[0018] Figure 10 A schematic diagram of an example tunable impedance matching circuit according to another aspect of this disclosure is illustrated.

[0019] Figure 11 A side view of an example high-intensity diffuse (HID) laser according to another aspect of this disclosure is shown.

[0020] Figure 12 A block diagram illustrating an example radio frequency to optical (RF2O) interface according to another aspect of this disclosure is shown.

[0021] Figure 13 A flowchart illustrating an example method for impedance matching between the output impedance of a radio frequency (RF) amplifier and the input impedance of a laser, according to another aspect of this disclosure, is provided. Detailed Implementation

[0022] The detailed description described below, in conjunction with the accompanying drawings, is intended as a description of various configurations and is not intended to represent the only configuration in which the concepts described herein can be practiced. To provide a comprehensive understanding of the various concepts, the detailed description includes specific details. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring such concepts. The term "substantially" means that the associated parameters (e.g., impedance) may not be as precise as indicated, but rather take into account some variations due to specified tolerances.

[0023] Figure 1A block diagram illustrating an example optical wireless communication system (or network) 100 according to one aspect of this disclosure is shown. The optical wireless communication system 100 includes an optical wireless transmitter (Tx) or transceiver (Tx / Rx) 110 and an optical wireless receiver (Rx) or Tx / Rx 120. The optical wireless Tx or Tx / Rx 110 and the optical wireless Rx or Tx / Rx 120 may be implemented in user equipment (UE), access point, or base station (e.g., gNB, etc.). Depending on the technology of network 100, base station 110 may include a node B, an evolved Node B (eNodeB or eNB), a transceiver base station (BTS), a radio base station (RBS), an NR NodeB (gNB), a next-generation eNB (ng-eNB), etc. In the case that network 110 is a 5G or 6G network, base station 110, as a gNB or ng-eNB, may be part of a next-generation radio access network (NG-RAN) that can connect to a 5G core network (5GC). System or network 100 may be part of a free-space optical wireless local area network (WLAN) or wireless wide area network (WWAN) communication system including a UE / gNB, which includes benefits such as higher data rates, lower latency, and immunity to electromagnetic interference (EMI). As previously mentioned, optical wireless communication system 100 may be part of an indoor or relatively short-range (e.g., <300 meters (m)) data communication system; however, it is not limited to indoor or short-range applications.

[0024] To enable communication between the Tx or Tx / Rx 110 and the optical wireless Rx or Tx / Rx 120, the optical wireless communication Tx or Tx / Rx 110 uses a high-intensity diffuse (HID) laser to generate a radio frequency (RF) modulated optical transmission signal. TX This is used for transmission to optical wireless communication Rx or Tx / Rx 120. The RF modulated signal can conform to various WWAN standards (e.g., 5G NR or 6G) and can have a relatively high percentage bandwidth (e.g., 67%). As an example, the RF modulated signal can have a bandwidth of 400 MHz, with a center frequency of 600 MHz. Therefore, the RF signal processing front end can be interfaced with an HID laser.

[0025] Furthermore, HID lasers can have relatively low impedance (e.g., approximately less than three (3) ohms (Ω)) and may also have complex impedance due to inductive wire bonding and die and / or package parasitics. Since most RF signal processing circuitry is configured for 50Ω signal transmission, docking an RF signal processing front-end with an HID laser presents challenges. Such challenges may arise from the implementation requirements of HID lasers, for example, having a impedance of 300 milliwatts per square meter (mW / m²).2 The relatively high power requirements of lasers, with a power density of 300m, are further exacerbated by the need for high-power lasers to transmit signals. In such applications, HID lasers can draw an operating current greater than one ampere (1A).

[0026] Figure 2 A block diagram illustrating an example optical wireless transceiver 200 according to another aspect of this disclosure is shown. The optical wireless transceiver 200 may be an example transceiver (Tx / Rx) implemented in either an optical wireless Tx or Tx / Rx 110 and / or an optical wireless Rx or Tx / Rx 120. Specifically, the optical wireless transceiver 200 includes a modem 210, one or more up-conversion stages 220, one or more local oscillators 230, one or more down-conversion stages 250, a radio frequency (RF) front-end 260, and an optical front-end 270.

[0027] Regarding signal transmission, modem 210 is configured to generate and transmit baseband signal D. TXBB One or more upconverter stages 220 are configured to use one or more transmit local oscillator signals V generated by one or more local oscillators 1130. TXLO To transmit baseband signal D TXBB Up-conversion is performed (e.g., directly or via one or more intermediate frequencies (IFs) from baseband (BB) to radio frequency (RF)) to generate a first transmitted RF signal V. TXRF1 Although the RF signals described herein are marked with a leading V to indicate voltage, it should be understood that RF signals can also be current. The RF front end 260 includes a power amplifier (PA) 262 configured to amplify the first transmitted RF signal V. TXRF2 To generate a second transmitted RF signal V TXRF2 Although PA262 is used as an example to explain the concepts in this article, it should be understood that PA can be any RF amplifier, such as a preamplifier, driver amplifier, or others.

[0028] The optical front end 270 may include a radio frequency to light (RF2O) driver 272 and a high-intensity diffuse (HID) laser 274. The RF2O driver 272 is configured to transmit a second RF signal V. TXRX2 To generate the RF modulation signal V for the HID laser 274 TXRX3As previously mentioned, PA 262 may have an output impedance of approximately 50 Ω. Furthermore, as previously mentioned, HID laser 274 may have a relatively low input impedance (e.g., <3 Ω). To reduce power losses in the form of reflected power due to the significant impedance mismatch between the output impedance of PA 262 and the input impedance of HID laser 274, RF2O driver 272 performs a gradual impedance transition from approximately 50 Ω to <3 Ω (or vice versa), as discussed further in more detail herein. Additionally, since HID laser 274 requires biasing (e.g., to operate in linear mode for 5G / 6G purposes), RF2O driver 272 may include a biaser for providing a bias current (e.g., >1 A) and for providing an RF modulation signal V to HID laser 274. TXRF3 Furthermore, it is configured to facilitate impedance matching between the output of PA 262 and the input of HID laser 274. HID laser 274 is configured to generate an RF-modulated signal V. TXRX3 Modulated optical transmission signal O TX , for use in sending to one or more remote optical wireless devices.

[0029] Regarding optional signal reception, the optical front end 270 may also include an optical receiver 276, which is configured to receive the received optical signal O. RX To generate the first received RF signal V RXRF1 For example, the optical receiver 276 may include a silicon photomultiplier tube (SiPM), an avalanche photodiode, or other similar device configured to convert an optical signal into an electrical signal. The RF front end 260 may also include a low-noise amplifier (LNA) 268 configured to amplify the first received RF signal V. RXRF1 To generate a second received RF signal V RXRF2 .

[0030] One or more downconverter stages 250 are configured to use one or more receive local oscillator signals V generated by one or more local oscillators 230. RXLO To receive the second RF signal V RXRF2 Perform downconversion (e.g., directly or via one or more IFs from RF to BB) to generate the received BB signal D. RXBB The modem 210 can receive and process the received BB signal D. RXBB To extract and / or recover the information or data contained therein.

[0031] Figure 3A block diagram illustrating an example radio frequency to optical (RF2O) driver 300 according to another aspect of this disclosure is shown. The RF2O driver 300 may be an example embodiment of the RF2O driver 272 of the optical wireless transceiver 200.

[0032] The RF2O driver 300 includes a transformer chain (e.g., a cascaded transformer assembly) 310, an impedance matching circuit 320, a bias circuit 330, and a high-intensity diffuse (HID) laser current source 340. The transformer chain 310 includes a terminal coupled to the output of a radio frequency (RF) power amplifier (e.g., PA 262) to receive an amplified RF signal (e.g., V). TXRF2 The input terminal of the PA. As discussed further herein, the transformer chain 310 is further configured to perform a coarse impedance transformation between the impedance ZPA (e.g., essentially 50Ω) at the output terminal of PA and the impedance Z1 (e.g., essentially a substantially low real impedance that is essentially an integer divisor of the impedance ZPA (e.g., 1 / 32), e.g., Z1 = 50Ω / 32 = 1.56Ω) at the input terminal of the impedance matching circuit 320.

[0033] Impedance transformation can be based on the effective or total turns ratio of the transformer chain according to the following relationship: Where NE1 is the effective or cumulative number of primary winding turns, and NE2 is the effective or cumulative number of secondary winding turns. The effective turns ratio NE1 / NE2 can be related to the individual turns ratios of the set of N cascaded RF transformers according to the following relationship: Where N1 k / N2 k This is the turns ratio of the k-th cascaded RF transformer in the set of N cascaded RF transformers of transformer chain 310. As an example, transformer chain 310 may have a turns ratio of 1 / 2. 5 Or a total turns ratio of 1 / 32 (e.g., five (5) cascaded RF transformers, each with a 1 / 2 turns ratio), which is configured to transform the ZPA=50Ω impedance at the output of PA to a Z1=1.56Ω impedance at the input of impedance matching circuit 320 (e.g., 50Ω / 2). 5 =50Ω / 32=1.56Ω, where 1 / 32 is the effective or total turns ratio of transformer chain 310).

[0034] Impedance matching circuit 320 can be configured to transform the complex impedance Z2 = a ± jb at the input of bias 330 into a substantially real impedance Z1 at the input of impedance matching circuit 320. This facilitates transformer chain 310 to transform the substantially real impedance (e.g., ZPA = 50Ω) at the output of PA into a real impedance (e.g., Z1 = 1.56Ω) at the input of impedance matching circuit 320.

[0035] Bias unit 330 is configured to receive the RF signal from impedance matching circuit 320 and the bias current I received from HID laser bias current source 340. BIAS Combining to provide an RF modulated signal (e.g., V) TXRF3 ) and bias current I for HID lasers (e.g., HID laser 274) BIAS Additionally, the bias 330 is further configured to transform the inherent complex impedance ZH=c±jd of the HID laser into a complex impedance Z2=a±jb at the input of the bias 330 based on the operating RF frequency range of the RF2O driver 300 (e.g., 400MHz to 800MHz).

[0036] An optional resistor R1 may be coupled between the transformer chain 310 and the impedance matching circuit 320. Alternatively, an optional resistor R2 may be coupled in parallel with the impedance matching circuit 320. Resistors R1 and / or R2 may be implemented to reduce the quality factor (Q) of the impedance matching circuit 320 to achieve greater bandwidth matching. Similarly, an optional resistor R3 may be coupled between the impedance matching circuit 320 and the biaser 330. Resistor R3 may be implemented to reduce the Q of the biaser 330 to achieve greater bandwidth matching.

[0037] Figure 4 A schematic diagram illustrating an example radio frequency (RF) transformer chain 400 according to another aspect of this disclosure is shown. The RF transformer chain 400 may be an example embodiment of the RF transformer chain 310 of the previously discussed RF2O driver 300.

[0038] RF transformer chain 400 includes a set of cascaded RF transformers 410-1 to 410-N, where N is a two (2) or larger integer. The cascaded set of RF transformers can be directly cascaded without any intermediate transmit lines. RF transformer chain 400 may also include an input transmit line 420-0 coupled between RF PA 262 and a first (e.g., upper) end of the primary winding of the first RF transformer 410-1 in the chain. Optionally, RF transformer chain 400 may also include a set of one or more transmit lines 420-1 to 420-N-1, which respectively couple the secondary to the first (e.g., upper) end of the primary winding of adjacent RF transformers 410-1 / 410-2 to 410-N-1 / 410-N. In addition, RF transformer chain 400 includes an output transmit line 420-N coupled between the first (e.g., upper) end of the secondary winding of the last RF transformer 420-N and impedance matching circuit 320. If included, each of the transmit lines 420-0 to 420-N can be configured to have a specific characteristic impedance Zo, such as the impedance ZPA at the output of PA 262 (e.g., 50Ω). The primary winding and the second (e.g., lower end) of the primary winding and the secondary winding of the cascaded RF transformers 410-1 to 410-N can be coupled to ground.

[0039] Each of the cascaded RF transformers 410-1 to 410-N can have turns ratios from N11 / N21 to N1. N / N2 N The set of components is used to achieve impedance transformation between the output of PA 262 (e.g., ZPA = 50Ω) and the input of impedance matching circuit 320 (e.g., Z1 = 1.56Ω). As an example, each of the cascaded RF transformers 410-1 to 410-N can utilize substantially the same turns ratio (e.g., N11 / N21 to N1...). N / N2 N Each of them is configured to have a turns ratio of 1 / 2 (1 / 2). In this case, if N=5, then RF transformers 410-1 to 410-5 can each have a turns ratio of 1 / 2 (where the effective turns ratio is 1 / 2). 5 Or 1 / 32), to transform the ZPA=50Ω impedance at the output of PA 262 to the Z1=1.56 impedance at the input of impedance matching circuit 320 (e.g., 50Ω / 2). 5 =50 / 32=1.56Ω). However, it should be understood that RF transformers 410-1 to 410-N can be configured with different turns ratios or a mixture of the same and different turns ratios.

[0040] Figure 5A schematic diagram illustrating an example impedance matching circuit 500 according to another aspect of this disclosure is shown. The impedance matching circuit 500 may be an example implementation of the impedance matching circuit 320 of the previously discussed RF2O driver 300.

[0041] Impedance matching circuit 500 can be implemented as a low-pass filter (LPF). Specifically, impedance matching circuit 500 includes a first series inductor L1 coupled between RF transformer chain 310 and first node n1. Impedance matching circuit 500 also includes a first parallel capacitor C1 coupled between first node n1 and ground. Furthermore, impedance matching circuit 500 includes a second series inductor L2 coupled between first node n1 and second node n2. Impedance matching circuit 500 also includes a second parallel capacitor C2 coupled between second node n2 and ground. Second node n2 may be coupled to the input of bias unit 330. It should be understood that impedance matching circuit 500 may include at least one series inductor and at least one parallel capacitor.

[0042] As previously discussed, the impedance matching circuit 500 is configured to transform the complex impedance Z2 = a ± jb at the input of the biaser 330 into a substantially real impedance Z1 at the output of the RF transformer chain 310. The inductances of inductors L1 and L2 and the capacitances of capacitors C1 and C2 can be configured to achieve the aforementioned impedance transformation. It should be understood that the impedance matching circuit 500 can be implemented in different ways to perform the desired impedance transformation.

[0043] Figure 6 A schematic diagram illustrating an example biaser 600 according to another aspect of this disclosure is shown. The biaser 600 may be an example of the biaser 330 of the previously discussed RF2O driver 300.

[0044] Bias unit 600 includes a capacitor C3 coupled between input port P1 and output port P2. Input port P1 may be coupled to the impedance matching circuit discussed earlier. Additionally, bias unit 600 includes an inductor L3 coupled between a third port P3 and output port P2, which is coupled to the HID laser current source discussed earlier. As previously discussed, bias unit 600 is configured to receive an RF signal from impedance matching circuit 320 or 500 and a bias current I from HID laser current source 340. BIAS Combined to provide an RF modulation signal V to the HID laser. TXRX3 and bias current I BIAS Capacitor C3 essentially blocks the bias current I. BIAS The current flows to the impedance matching circuit 320 or 500. Inductor L3 essentially blocks the RF modulation signal V. TXRX3 The current flows into the output terminal of the HID laser current source.

[0045] As previously discussed, bias 600 can be configured to transform the inherent complex impedance ZH=c±jd of the HID laser to the complex impedance Z2=a±jb at the output of impedance matching circuit 320 or 500 based on the operating RF frequency range. The capacitance of capacitor C3 and the inductance of inductor L3 can be configured to achieve the aforementioned impedance transformation. It should be understood that bias 600 can be implemented in different ways to perform the desired impedance transformation.

[0046] Figure 7 A block diagram illustrating another example of a radio frequency to optical (RF2O) driver 700 according to another aspect of this disclosure is shown. The RF2O driver 700 may be another example implementation of the RF2O driver 272 of the previously discussed optical transceiver 200. The RF2O driver 700 includes a standing wave ratio (SWR) sensor 710, a configurable radio frequency (RF) transformer chain 720, a tunable impedance matching circuit 730, a biaser 740, a high-intensity diffuse (HID) laser current source 760, and control circuitry 750. Although... Figure 7 Not shown, but the RF2O driver 700 may optionally include one or more Q-lowering resistors, such as R1 to R3, similar to those in the RF2O driver 300.

[0047] An SWR sensor 710 (e.g., first and second ports) is coupled between a power amplifier (PA) (e.g., PA262) and a configurable RF transformer chain 720. The RF transformer chain 720 (e.g., first and second ports) is in turn coupled between the SWR sensor 710 and a tunable impedance matching circuit 730. The tunable impedance matching circuit 730 (e.g., first and second ports) is in turn coupled between the configurable RF transformer chain 720 and a biaser 740. The biaser 740 (e.g., first and second ports) is in turn coupled between the tunable impedance matching circuit 730 and an HID laser (e.g., HID laser 274). The HID laser current source 760 includes an output that is coupled to a third port of the biaser 740. The control circuit 750 (e.g., microcontroller, microprocessor, processor, computing device, special circuit, etc.) includes an input terminal and a pair of output terminals. The input terminal is coupled to a third port of the SW sensor 710, and the pair of output terminals are coupled to the respective third ports of the configurable RF transformer chain 720 and the tunable impedance matching circuit 730.

[0048] The SWR sensor 710 is configured to generate a signal S at its third port that is related to the SWR signal at the output of PA 262. SWR Since the third port of the SW sensor 710 is coupled to the input of the control circuit 750, the control circuit 750 receives the SWR signal S. SWRThe SWR signal at the output of PA 262 is related to the impedance matching between PA and the configurable RF transformer chain 720. A higher peak-to-peak amplitude of the SWR signal indicates a greater impedance mismatch between PA and the configurable RF transformer chain 720. Conversely, a lower peak-to-peak amplitude of the SWR signal indicates a smaller impedance mismatch between PA and the configurable RF transformer chain 720. Therefore, the control circuit 750 is configured to base its signal SWR on the impedance matching between PA and the configurable RF transformer chain 720. SWR Control signals CS are generated at each of its two output terminals. TRN and CS MCH The control circuit 750 can be configured to execute a process (e.g., a machine learning (ML) algorithm, such as hill climbing or gradient descent) to essentially make the signal S SWR Minimize this signal, which is used as a cost function for the process.

[0049] Since the pair of output terminals of the control circuit 750 are coupled to the corresponding third ports of the configurable RF transformer chain 720 and the tunable impedance matching circuit 730, the control signal CS generated by the control circuit 750... TRN and CS MCH Adjust the impedance transformation parameters of the configurable RF transformer chain 720 and the tunable impedance matching circuit 730 respectively.

[0050] Regarding the configurable RF transformer chain 720, the control signal CS... TRN One or more cascaded RF transformers in the cascaded RF transformer set of the bypassable RF transformer chain 720. Since, as previously discussed, the number of cascaded RF transformers not bypassed affects the effective turns ratio NE1 / NE2 of the transformer chain 720, and the impedance ratio Z0 / Z1 is related to or substantially equal to the effective turns ratio NE1 / NE2, the control circuit 750 is able to tune the configurable RF transformer chain 720 to reduce the signal S. SWR To improve impedance matching between PA and the configurable RF transformer chain 720. As an example, if the substantially real impedance Z1 at the output of the configurable RF transformer chain 720 is 3.13Ω and there are five (5) RF transformers in the chain, the control circuit 750 can generate a control signal CS. TRN Bypassing one (1) RF transformer in the RF transformer, the remaining four (4) RF transformers (each with a 1 / 2 turns ratio) can be 1 / 2 4 Alternatively, an effective turns ratio of 1 / 16 transforms Z1=3.13Ω to Z0=ZPA=50Ω (e.g., 50Ω / 2). 4 =50Ω / 16=3.13Ω).

[0051] Regarding the tunable impedance matching circuit 730, the control signal CS MCHOne or more of its capacitive or inductive elements can be tuned to transform the complex impedance Z2 at the input of bias 740 into a substantially real impedance Z1 at the output of the configurable RF transformer chain 720. In this respect, one or more of the inductors L1 and L2 and capacitors C1 and C2 of the impedance matching circuit 500 can be variable, allowing the control circuit 750 to tune its inductance and capacitance to achieve a substantially real impedance Z1 at the output of the configurable RF transformer chain 720, as further illustrated herein.

[0052] Bias unit 740 can be implemented according to bias unit 330 or 500 previously discussed, to combine the RF signal from the output of tunable impedance matching circuit 730 with the bias current I generated by HID laser bias current source 760. BIAS Combined to output the RF modulation signal V for the HID laser. TXRF3 and bias current I BIAS As previously discussed, the capacitance of capacitor C3 in bias 740 and the inductance of inductor L3 (see, for example, [reference needed]). Figure 6 The complex impedance Z2 at the output of the tunable impedance matching circuit 730 can be set based on the operating RF frequency of the RF2O driver 700 to improve or optimize the inherent impedance ZH of the HID laser.

[0053] Figure 8 A schematic diagram illustrating an example standing wave ratio (SWR) sensor 800 according to another aspect of this disclosure is shown. The SWR sensor 800 may be an example embodiment of the SWR sensor 710 of the RF2O driver 700.

[0054] The SWR sensor 800 includes a directional coupler 810, a diode D1, a resistor RL, and an optional attenuation pad 805. The optional attenuation pad 805 (e.g., a three (3) dB) pad, which can be used to protect the PA, can be coupled between the PA and the directional coupler 810. The directional coupler 810 (e.g., a first port P1 and a second port P2) couples the PA or PAD 805 between the PA and a configurable RF transformer chain 720. The directional coupler 810 is configured to transmit the RF signal V TXRF2 A portion (e.g., -10dB) of the sample is routed to a third port P3 coupled to the anode of diode D1, where the cathode of the diode can be coupled to ground. Diode D1 is configured to generate a signal S at the third port P3 of the directional coupler 810. SWR RF signal V TXRF2 The remainder propagates between the first port P1 and the second port P2 to the configurable RF transformer chain 720.

[0055] If impedance transformation causes impedance mismatch between PA and configurable RF transformer chain 720, then signal S SWR This may include standing waves generated by such impedance mismatches. The ratio of the maximum to minimum voltage of the standing wave is related to the impedance mismatch. The third port P3 of the directional coupler 810 is coupled to the input of the control circuit 750 to provide the control circuit with a signal S. SWR Resistor RL terminates the fourth port P4 of the directional coupler 810 by coupling between the fourth port P4 and ground.

[0056] Figure 9 A schematic diagram illustrating an example configurable radio frequency (RF) transformer chain 900 according to another aspect of this disclosure is shown. The RF transformer chain 900 may be an example embodiment of the configurable RF transformer chain 720 of the previously discussed RF2O driver 700.

[0057] The configurable RF transformer chain 900 includes a set of cascaded RF transformers 910-1 to 910-N, where N is a two (2) or larger integer. Although not shown for simplicity, the configurable RF transformer chain 900 may include an input transmit line 420-0, a set of one or more transmit lines 420-1 to 420-N-1, and an output transmit line 420-N of an RF transformer chain 400 with the same or similar configuration. The configurable RF transformer chain 900 also includes a set of bypass switching devices SW1 to SWN coupled to the primary and secondary windings of the cascaded RF transformers 910-1 to 910-N, respectively. The set of switching devices SW1 to SWN is coupled to a corresponding output of a control circuit 750 to receive a control signal CS from the control circuit. TRN1 To CS TRNN This is used to control the on / off and off / open states of the set of switching devices SW1 to SWN respectively. If any switching device in the switching device is off / closed, the corresponding RF transformer is bypassed; or conversely, if any switching device in the switching device is off / open, the corresponding RF transformer is not bypassed.

[0058] As previously discussed, each of the cascaded RF transformers 910-1 to 910-N can be implemented using a set of turns ratios to achieve impedance transformation between the output of PA (e.g., ZPA = Z0 = 50Ω) and the input of impedance matching circuit 320 (e.g., Z1 = 1.56Ω), respectively. As an example, each of the cascaded RF transformers 910-1 to 910-N can be configured using substantially the same turns ratio (e.g., half (1 / 2)). In this case, if N = 5, the RF transformers 910-1 to 910-5 can transform the ZPA = Z0 = 50Ω impedance at the output of PA to the Z1 = 1.56Ω impedance at the input of impedance matching circuit 320 (e.g., 50Ω / 2). 5 =50 / 32=1.56Ω). However, it should be understood that RF transformers 910-1 to 910-N can be configured with different turns ratios or a mixture of the same and different turns ratios.

[0059] As discussed previously, the control signal CS TRN1 To CS TRNN The set of cascaded RF transformers 910-1 to 910-N in the controllable RF transformer chain 720 can bypass the cascaded RF transformers 910-1 to 910-N. Since the number of unbypassed cascaded RF transformers 910-1 to 910-N sets the effective turns ratio NE1 / NE2 of the transformer chain 900, while the bypassed transformers do not have an effective turns ratio NE1 / NE2, the control circuit 750 can tune the configurable RF transformer chain 900 to reduce the signal S. SWR To control the impedance transformation between Z0 and Z1. As an example, if the substantially real impedance Z1 at the output of the configurable RF transformer chain 720 is 3.13Ω, and there are five (5) RF transformers in the chain, then the control circuit 750 can generate a control signal CS. TRN5 Bypassing RF transformer 910-5, the remaining four (4) RF transformers 910-1 to 910-4 (each with a 1 / 2 turns ratio) can transform Z1=3.13Ω to Z0=50Ω (e.g., 50Ω / 2). 4 =50Ω / 16=3.13Ω), of which 2 4 Or 16 is the effective turns ratio of the configurable RF transformer chain 900.

[0060] Figure 10 A schematic diagram illustrating an example tunable impedance matching circuit 1000 according to another aspect of this disclosure is shown. The tunable impedance matching circuit 1000 may be an example implementation of the tunable impedance matching circuit 730 of the previously discussed RF2O driver 700.

[0061] Specifically, the impedance matching circuit 1000 includes a first variable / programmable inductor L3 coupled between the first (input) port P1 and node n1. The impedance matching circuit 1000 also includes a first variable / programmable capacitor C3 coupled between node n1 and ground. Furthermore, the impedance matching circuit 1000 includes a second inductor L4 coupled between node n1 and the second (output) port P2. The impedance matching circuit 1000 also includes a second variable / programmable capacitor C4 coupled between the second (output) port P2 and ground. The second (output) port can be coupled to the input of the biaser 740.

[0062] The first variable / programmable inductor L3 and the second variable / programmable inductor L4 are respectively coupled to the output of the control circuit 750. In this respect, the inductances of inductors L3 and L4 are based on the control signal CS generated by the control circuit 750. MCH1 and CS MCH3 Instead, they are variable / programmable. Similarly, the first variable / programmable capacitor C3 and the second variable / programmable capacitor C4 are coupled to the output of the control circuit 750, respectively. In this respect, the capacitances of capacitors C3 and C4 are based on the control signal CS generated by the control circuit 750, respectively. MCH2 and CS MCH4 Instead, it is variable / programmable, via the control signal CS. MCH1 To CSM CH4 The inductance of inductors L3 and L4 and the capacitance of capacitors C1 and C2 can be configured to achieve a transformation from the complex impedance Z2 at the input of bias 740 to the substantially real impedance Z1 at the output of the configurable RF transformer chain 720. It should be understood that the impedance matching circuit 1000 can be implemented in different ways to perform the desired impedance transformation.

[0063] Figure 11 A side view of an example high-intensity diffuse (HID) laser 1100 according to another aspect of this disclosure is illustrated. The HID laser 1100 may be an example embodiment of the HID laser 274.

[0064] The HID laser 1100 includes a housing or enclosure comprising a base 1110, opposing sidewalls 1115 and 1120 mounted on a peripheral portion of the base 1110, and a laser-transparent or translucent cover 1150 mounted on the sidewalls 1115 and 1120. The opposing sidewalls 1115 and 1120 include internally inclined portions on which laser diode mounts 1130 and 1140 are mounted. The HID laser 1100 includes a pair of laser diodes 1135 and 1145 mounted on the laser diode mounts 1130 and 1140, respectively. The HID laser 1100 also includes a diffuser (e.g., a phosphor diffuser) 1125 centrally mounted above the base 1110.

[0065] Laser diodes 1135 and 1145, mounting brackets 1130 and 1140, and the inclined portions of opposing sidewalls 1115 and 1120 are configured such that the laser energies LD1 and LD2 emitted by laser diodes 1135 and 1145 (as indicated by their respective darker and lighter shadow emissions) impact the top surface of diffuser 1125. The diffused laser energies LD1 and LD2 reflected by diffuser 1125 are dispersed in a vertical direction through a laser transparent or translucent cover 1150. The diffused laser energies LD1 and LD2 may have different divergence angles, wherein in this example, LD2 emission has a wider divergence than LD1 emission.

[0066] Laser diodes 1135 and 1145 can be implemented to generate laser LD1 and LD2 of the same or different wavelengths. For example, laser diode 1135 can be a blue laser diode, and laser diode 1145 can be an infrared (IR) laser diode. Regarding various specific implementations of RF2O drivers 272, 300, and 700, one of the laser diodes (e.g., blue laser diode 1135) can be used to generate the transmitted optical signal O. TX The other laser diode (e.g., IR laser diode 1145) may be unused or used for other purposes. However, it should be understood that both laser diode 1135 and laser diode 1145 can be implemented to generate one or more different transmitted optical signals.

[0067] Figure 12A block diagram illustrating an example radio frequency to optical (RF2O) interface 1200 according to another aspect of this disclosure is shown. The RF2O interface 1200 includes a radio frequency (RF) amplifier 1210 and an RF2O driver 1220. The RF2O driver 1220 further includes a transformer chain 1222 and an impedance matching circuit 1224, the transformer chain including a cascaded set of RF transformers, the impedance matching circuit being coupled in series with the transformer chain 1222 between the RF amplifier 1210 and the laser 1230.

[0068] Figure 13 A flowchart illustrating an example method 1300 for impedance matching of the output impedance of a radio frequency (RF) amplifier with the input impedance of a diffuse laser, according to another aspect of this disclosure, is shown.

[0069] Method 1300 includes transforming a first complex impedance associated with a diffuse laser into a first substantially real impedance (block 1310). Examples of components for transforming the first complex impedance associated with a diffuse laser into the first substantially real impedance include any of the impedance matching circuits described herein. Method 1300 also includes transforming the first substantially real impedance into a second substantially real impedance associated with a radio frequency (RF) amplifier via a cascaded set of RF transformers (block 1320). Examples of components for transforming the first substantially real impedance into the second substantially real impedance associated with an RF amplifier via a cascaded set of RF transformers include any of the transformer chains described herein.

[0070] Method 1300 may further include providing an RF signal and a bias current to a diffuse laser while transforming a second complex impedance associated with the diffuse laser into a first complex impedance. Examples of components for providing an RF signal and a bias current to a diffuse laser while transforming a second complex impedance associated with the diffuse laser into a first complex impedance include any of the biasers described herein.

[0071] Additionally, method 1300 may include: sensing the standing wave ratio (SWR) at a node between the RF amplifier and the cascaded RF transformer assembly; and adjusting at least one of the following based on the sensing of the SWR: transforming a first complex impedance into a first substantially real impedance, or transforming the first substantially real impedance into a second substantially real impedance. Examples of components for sensing the standing wave ratio (SWR) at a node between the RF amplifier and the cascaded RF transformer assembly include any of the SWR sensors described herein. Examples of components for adjusting at least one of the following based on the sensing of the SWR include any of the control circuitry described herein: transforming the first complex impedance into a first substantially real impedance, or transforming the first substantially real impedance into a second substantially real impedance.

[0072] The following provides an overview of the various aspects of this disclosure:

[0073] Aspect 1: An apparatus comprising: a radio frequency (RF) amplifier; and an RF-to-optical (RF2O) driver, the RF-to-optical (RF2O) driver comprising: a transformer chain including a cascaded set of RF transformers; and an impedance matching circuit coupled in series with the transformer chain between the RF amplifier and a laser.

[0074] Aspect 2: According to the apparatus of aspect 1, wherein the transformer chain is configured to perform impedance transformation on a first substantially real impedance at the input of the impedance matching circuit to a second substantially real impedance at the output of the RF amplifier based on the effective turns ratio of the set of cascaded RF transformers, wherein the second substantially real impedance is greater than the first substantially real impedance.

[0075] Aspect 3: The apparatus according to aspect 2, wherein the second substantially real impedance is substantially 50 ohms.

[0076] Aspect 4: The apparatus according to aspect 2 or 3, wherein the impedance matching circuit is configured to perform impedance transformation on the first complex impedance to transform it into the first substantially real impedance.

[0077] Aspect 5: The apparatus according to any one of Aspects 1 to 4, wherein the impedance matching circuit is configured as a low-pass filter (LPF).

[0078] Aspect 6: The apparatus according to any one of Aspects 1 to 5, wherein the impedance matching circuit comprises at least one series inductor and at least one parallel capacitor.

[0079] Aspect 7: The apparatus according to any one of Aspects 1 to 6, wherein the RF2O driver further comprises: a biasing device including a first port and a second port coupled between the impedance matching circuit and the laser; and a current source coupled to a third port of the biasing device.

[0080] Aspect 8: The apparatus according to aspect 8, wherein: the current source is configured to generate a bias current for the laser; and the biaser is configured to: receive an RF signal from the impedance matching circuit at the first port; receive the bias current from the current source at the third port; and combine the RF signal with the bias current at the second port.

[0081] Aspect 9: The apparatus according to any one of Aspects 7 or 8, wherein the biaser comprises: an inductor coupled between the first port and the second port; and a capacitor coupled between the third port and the second port.

[0082] Aspect 10: The apparatus according to any one of Aspects 1 to 9, wherein the RF2O driver further comprises: a standing wave ratio (SWR) sensor, the SWR sensor including a first port and a second port coupled between the RF amplifier and the transformer chain; and control circuitry including an input terminal coupled to a third port of the SWR sensor.

[0083] Aspect 11: The apparatus according to aspect 10, wherein the SWR sensor is configured to generate a signal related to the standing wave ratio (SWR) at the second port of the SWR sensor; and the input of the control circuit is configured to receive the SWR signal.

[0084] Aspect 12: The apparatus according to aspect 11, wherein: the control circuit is configured to generate at least one control signal based on the SWR signal; and the transformer chain is configured to receive the at least one control signal.

[0085] Aspect 13: According to the apparatus of aspect 12, at least one cascaded RF transformer in the set of cascaded RF transformers of the transformer chain is capable of being bypassed based on the at least one control signal.

[0086] Aspect 14: The apparatus according to aspect 12 or 13, wherein the effective turns ratio of the transformer chain is based on the at least one control signal.

[0087] Aspect 15: The apparatus according to any one of Aspects 11 to 14, wherein: the control circuit is configured to generate at least one control signal based on the SWR signal; and the impedance matching circuit is configured to transform the complex impedance at the output of the impedance matching circuit into a substantially real impedance at the input of the impedance matching circuit based on the at least one control signal.

[0088] Aspect 16: The apparatus according to aspect 15, wherein the impedance matching circuit includes at least one inductor or capacitor, the inductance or capacitance of the at least one inductor or capacitor being changeable based on the at least one control signal.

[0089] Aspect 17: The apparatus according to any one of Aspects 1 to 16, the apparatus further comprising a resistor coupled between the transformer chain and the impedance matching circuit.

[0090] Aspect 18: The apparatus according to any one of Aspects 1 to 17, the apparatus further comprising a resistor coupled in parallel with the impedance matching circuit.

[0091] Aspect 19: The apparatus according to any one of Aspects 7 to 18, the apparatus further comprising a resistor coupled between the impedance matching circuit and the biaser.

[0092] Aspect 20: The apparatus according to any one of aspects 7 to 19, the apparatus further comprising a resistor coupled in parallel with the biaser.

[0093] Aspect 21: A method comprising: transforming a first complex impedance associated with a diffuse laser into a first substantially real impedance; and transforming the first substantially real impedance into a second substantially real impedance associated with a radio frequency (RF) amplifier via a cascaded set of RF transformers.

[0094] Aspect 22: According to the method of aspect 21, the method further includes providing an RF signal and a bias current to the diffuse laser while transforming a second complex impedance associated with the diffuse laser into the first complex impedance.

[0095] Aspect 23: The method according to aspect 21 or 22 further includes: sensing the standing wave ratio (SWR) at a node between the RF amplifier and the set of cascaded RF transformers; and adjusting at least one of the following based on the sensing of the SWR: transforming the first complex impedance into a first substantially real impedance, or transforming the first substantially real impedance into a second substantially real impedance.

[0096] Aspect 24: An optical communication device comprising: a modem; one or more up-conversion stages coupled to the modem; a local oscillator (LO) coupled to the one or more up-conversion stages; a radio frequency (RF) amplifier coupled to the one or more up-conversion stages; a diffuse laser; and an RF-to-optical (RF2O) driver comprising: a transformer chain including a cascaded set of RF transformers; and an impedance matching circuit coupled in series with the transformer chain between the RF amplifier and the diffuse laser.

[0097] Aspect 25: The optical communication device according to aspect 24 further includes: an optical receiver; a low-noise amplifier (LNA) coupled to the optical receiver; and one or more down-conversion stages coupled to the LNA, the LO, and the modem.

[0098] The prior description of this disclosure is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of this disclosure. Thus, this disclosure is not intended to be limited to the examples described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus comprising: Radio frequency (RF) amplifier; and An RF-to-light (RF2O) driver, the RF-to-light (RF2O) driver comprising: Transformer chain, the transformer chain comprising a cascaded set of RF transformers; and An impedance matching circuit is provided, which is coupled in series with the transformer chain between the RF amplifier and the laser.

2. The apparatus of claim 1, wherein the transformer chain is configured to perform impedance transformation on a first substantially real impedance at the input of the impedance matching circuit to a second substantially real impedance at the output of the RF amplifier based on the effective turns ratio of the set of cascaded RF transformers, wherein the second substantially real impedance is greater than the first substantially real impedance.

3. The apparatus of claim 2, wherein the second substantially real impedance is substantially 50 ohms.

4. The apparatus of claim 2, wherein the impedance matching circuit is configured to perform impedance transformation on the first complex impedance to transform it into the first substantially real impedance.

5. The apparatus of claim 1, wherein the impedance matching circuit is configured as a low-pass filter (LPF).

6. The apparatus of claim 1, wherein the impedance matching circuit comprises at least one series inductor and at least one parallel capacitor.

7. The apparatus of claim 1, wherein the RF2O driver further comprises: A biasing device, the biasing device including a first port and a second port coupled between the impedance matching circuit and the laser; and A current source, which is coupled to the third port of the biaser.

8. The apparatus according to claim 7, wherein: The current source is configured to generate a bias current for the laser; and The bias is configured as follows: RF signals are received from the impedance matching circuit at the first port; The bias current is received from the current source at the third port; and The RF signal is combined with the bias current at the second port.

9. The apparatus of claim 7, wherein the biaser comprises: An inductor coupled between the first port and the second port; and A capacitor coupled between the third port and the second port.

10. The apparatus of claim 1, wherein the RF2O driver further comprises: A standing wave ratio (SWR) sensor, the standing wave ratio (SWR) sensor including a first port and a second port coupled between the RF amplifier and the transformer chain; and A control circuit, the control circuit including an input terminal coupled to a third port of the SWR sensor.

11. The apparatus according to claim 10, wherein: The SWR sensor is configured to generate a signal related to the standing wave ratio (SWR) at the second port of the SWR sensor; and The input terminal of the control circuit is configured to receive the SWR signal.

12. The apparatus according to claim 11, wherein: The control circuit is configured to generate at least one control signal based on the SWR signal; and The transformer chain is configured to receive the at least one control signal.

13. The apparatus of claim 12, wherein at least one of the cascaded RF transformers in the set of cascaded RF transformers is capable of being bypassed based on the at least one control signal.

14. The apparatus of claim 12, wherein the effective turns ratio of the transformer chain is based on the at least one control signal.

15. The apparatus according to claim 11, wherein: The control circuit is configured to generate at least one control signal based on the SWR signal; and The impedance matching circuit is configured to transform the complex impedance at the output of the impedance matching circuit into a substantially real impedance at the input of the impedance matching circuit based on the at least one control signal.

16. The apparatus of claim 15, wherein the impedance matching circuit comprises at least one inductor or capacitor, the inductance or capacitance of the at least one inductor or capacitor being changeable based on the at least one control signal.

17. A method comprising: Transform the first complex impedance associated with the diffuse laser into a first essentially real impedance; as well as The first substantially real impedance is transformed into a second substantially real impedance associated with the radio frequency (RF) amplifier via a cascaded set of RF transformers.

18. The method of claim 17, further comprising providing an RF signal and a bias current to the diffuse laser while transforming a second complex impedance associated with the diffuse laser into the first complex impedance.

19. The method of claim 17, further comprising: Sensing the standing wave ratio (SWR) at the node between the RF amplifier and the cascaded RF transformer. as well as Based on the sensing of the SWR, adjust at least one of the following: transform the first complex impedance into the first substantially real impedance, or transform the first substantially real impedance into the second substantially real impedance.

20. An optical communication device, the optical communication device comprising: modem; One or more upconversion stages, said one or more upconversion stages being coupled to the modem; A local oscillator (LO) coupled to one or more upconversion stages; A radio frequency (RF) amplifier coupled to one or more upconversion stages; Diffuse laser; and An RF-to-light (RF2O) driver, the RF-to-light (RF2O) driver comprising: Transformer chain, the transformer chain comprising a cascaded set of RF transformers; and An impedance matching circuit is provided, which is coupled in series with the transformer chain between the RF amplifier and the diffuse laser.

Images