Precision self-calibration of phased array antennas

Abstract

Radio Frequency (RF) circuit (amplifier, mixer, etc.) designs using RFICs implemented in CMOS, CaAs, SiGe, and other silicon processes suffer from performance variations (gain phase, frequency, bandwidth, non-linearity) due to wafer process variations, temperature changes, and supply voltage changes, as well as random variations. In this invention, a method is proposed to precisely calibrate the bias currents of all active devices in the system and precisely calibrate the gains of the individual paths to each amplifier, so that the same Pout is achieved for all antenna elements in the system.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 246,221, filed September 20, 2021, entitled "Phase-Array Antenna Precision Self-Calibration," the subject matter of which is incorporated herein by reference.

[0002] The disclosed embodiments relate generally to phased array antennas, and more particularly to a method of self-calibration for phased array antennas. [Background technology]

[0003] In antenna theory, a phased antenna array refers to an array of antennas that typically generate beams of radio waves, which can be electronically steered to point in various directions without moving the antennas. Beamforming is a technique that allows an array of antennas to be steered to transmit radio signals in a specific direction. The phase and amplitude of each signal add constructively and destructively in a way that concentrates the energy within a narrow beam or lobe. In the case of multiple array antennas operating in high-density areas, each array antenna has its own beam that points toward a specific user (direction). In the case of a multibeam array antenna, each antenna beam points toward a specific direction. Mobile carriers increasingly experiencing bandwidth shortages are motivating them to explore unused millimeter wave (mmWave) frequency spectrum from approximately 24 GHz to 300 GHz for next-generation 5G broadband cellular communication networks. To support directional communication using narrow beams in mmWave networks, 5G base stations use phased array antennas to support multiple beams.

[0004] A typical phased-array antenna configuration uses multiple radio frequency integrated circuits (RFICs), such as beamforming RFICs. Each signal path for an antenna element includes fixed and variable-gain RF amplifiers and phase shifters. To achieve precise phased-array functionality, the amplifier gain and the phase shifters in each antenna element must be precisely controlled. However, the RF amplifiers in the RFICs are subject to 1) PVT variations (variations in wafer process, supply voltage, and temperature), which typically result in variations of several dB if uncorrected, and 2) random variations due to size variations of transistors or passive elements, which are usually met by limiting the minimum sizes of transistors, capacitors, and resistors used in the RFICs. To meet high-precision requirements for amplitude tapering across the antenna array (e.g., 0.375 dB), the RFICs and RF amplifiers across the antenna array must be calibrated.

[0005] Calibrating a phased array antenna system in an over-the-air (OTA) setting is expensive and complex due to the following reasons: 1) the need for an RF anechoic chamber; 2) while far-field chambers can significantly speed up calibration, large arrays require very large antenna chambers; 3) precision measurements are made to determine the gain and phase of each individual signal path (corresponding to each antenna element); 4) a large number of states need to be calibrated, which increases calibration time and system cost; and 5) sufficient gain adjustment range and gain resolution must be available for adjustment and calibration. To reduce manufacturing complexity and post-manufacturing antenna calibration costs, it is desirable for RFICs to be self-calibrated by design for different manufacturing or calibrated during the manufacturing process by automatic test equipment. It is desirable to have a self-calibrating system that does not require an OTA / chamber setting. Summary of the Invention [Problem to be solved by the invention]

[0006] Radio frequency (RF) circuit (e.g., amplifiers, mixers) designs using RFICs implemented in CMOS, CaAs, SiGe, and other silicon processes suffer from performance variations (gain, phase, frequency, bandwidth, nonlinearity) due to wafer process variations, temperature changes, supply voltage changes, and random variations. In phased array antennas, maintaining nearly identical performance for each RFIC and each signal path is crucial. Phased array antenna over-the-air testing requires expensive antenna chambers and is time-consuming (expensive). This invention proposes a method for precisely calibrating the bias currents of all active devices in a system and the gains of the individual signal paths leading to each amplifier, thereby achieving the same Pout for all antenna elements in the system. Note that this type of calibration involves only current measurements and does not involve test equipment or over-the-air (OTA) testing. Therefore, such calibration can be performed in the field or at the factory, significantly reducing chamber testing time for mass production. [Means for solving the problem]

[0007] In one embodiment, the calibration circuit powers off all active circuits and power amplifiers on the RFIC of the phased array antenna. The calibration circuit powers on the active circuits of the RFIC during calibration and monitors the current consumption of the active circuits. The calibration circuit measures the bias current of the active circuits and adjusts the bias current to a predetermined level during calibration. The calibration circuit repeats the bias current calibration for each active circuit of the RFIC and for all RFICs in the phased array antenna.

[0008] In another embodiment, the calibration circuit powers off all active circuits and power amplifiers on the RFIC of the phased array antenna and powers on the power amplifiers and the corresponding signal paths leading to the power amplifiers of the RFIC being calibrated. The calibration circuit provides an input signal having a predetermined signal level and measures the follow current of the power amplifier being calibrated. The calibration circuit adjusts the amplifier gain and output power of the corresponding signal path leading to the power amplifier until the desired follow current of the power amplifier is reached. The calibration circuit repeats the output power calibration for each power amplifier and corresponding signal path of the RFIC and for all RFICs in the phased array antenna using the same input signal having the predetermined signal level.

[0009] Other embodiments and advantages are described in the detailed description below. This summary does not define the invention. The invention is defined by the claims. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a simplified block diagram of a typical transmit phased array antenna configuration for a base station having a self-calibration mechanism, according to one aspect. [Figure 2] Shown is an RFIC bias generation system that generates bias currents used in RF amplifier circuits. [Figure 3] FIG. 1 is a simplified circuit diagram of a bias generator that supports a constant gm bias used in a radio frequency amplifier in an RFIC. [Figure 4] 1 illustrates an embodiment of a current measurement circuit that can be used for bias current calibration in a phased array antenna. [Figure 5] 10 is a flowchart of a procedure for self-calibrating bias currents in a phased array antenna according to another aspect. [Figure 6] 1 illustrates an embodiment of a bias current self-calibration system for a phased array antenna according to another aspect. [Figure 7] 1 shows the follow current for various power amplifier classes and the appropriate back-off operating points for the power amplifiers. [Figure 8] 10 is a flowchart of a procedure for self-calibrating output power in a phased array antenna according to another aspect. [Figure 9] 1 illustrates an embodiment of an output power self-calibration system for a phased array antenna according to another aspect. [Figure 10] 10 is a flowchart of a method for self-calibrating bias currents of active circuits on an RFIC of a phased array antenna according to another embodiment. [Figure 11] 10 is a flowchart of a method for self-calibrating the output power of a power amplifier on an RFIC of a phased array antenna according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying drawings.

[0012] FIG. 1 is a simplified block diagram of a typical transmit phased array antenna configuration for a base station 101 with a self-calibration mechanism, according to one embodiment. A beamforming cellular mobile communication network 100 includes a base station BS 101 and multiple user equipment (UEs), including UEs 102 and 103. The cellular mobile communication network uses directional communication with narrow beams and can support multi-gigabit data rates. One example of such a cellular network is a millimeter wave (mmWave) network, which utilizes the mmWave frequency spectrum. In such mmWave networks, directional communication is achieved through beamforming, in which multiple sets of beamforming weights (phase shift values) are applied to a phased antenna array 110 having multiple antenna elements to form multiple beam patterns, which are required to overcome high path loss in mmWave networks and provide mobility support for mobile terminals. In the example of FIG. 1, the phased antenna array 110 of BS 101 is directionally configured with a set of coarse TX / RX control beams (130) and a set of dedicated TX / RX data beams (140) to serve mobile stations including UE 102 and UE 103.

[0013] In the example of FIG. 1 , BS 101 includes a phased array antenna 110 coupled to a combiner / splitter network 120. For multiple array antennas operating in a high-density area, each array antenna has its own beam to point toward a specific UE (direction). A typical phased array antenna configuration uses multiple radio frequency integrated circuits (RFICs), such as beamforming RFICs. Each RFIC includes multiple signal paths to antenna elements. Each signal path for an antenna element includes fixed and variable gain amplifiers and phase shifters. To operate a precise phased array function, the amplifier gain and the phase shifters in each antenna element must be precisely controlled. However, RF amplifiers within RFICs are subject to 1) PVT variations (variations in wafer process, supply voltage, and temperature), which typically result in variations of several dB if uncompensated, and 2) random variations due to size and threshold variations of transistors or passive elements. This requirement is usually met by limiting the minimum size of transistors, capacitors, and resistors used within the RFIC. To meet high accuracy requirements (such as less than half of 0.375 dB) for amplitude tapering across the antenna array to achieve the desired sidelobe or interference suppression, it is necessary to calibrate the active circuits in the RFICs across the antenna array.

[0014] Calibrating phased array antenna systems in an over-the-air (OTA) setup is expensive and complex for the following reasons: 1) the need for an RF anechoic chamber; 2) while far-field chambers can significantly speed up calibration, large arrays require very large antenna chambers or field test ranges; 3) precision measurements are required to determine the gain and phase of each individual signal path (corresponding to each antenna element) at the operating frequency (e.g., millimeter wave); 4) a large number of states need to be calibrated, which increases calibration time and system cost; and 5) sufficient gain adjustment range and gain resolution must be available for adjustment and calibration. To reduce manufacturing complexity and post-manufacturing antenna calibration costs, it is desirable for RFICs to be self-calibrated by different manufacturing designs or calibrated during the manufacturing process by simple automated test equipment that requires only DC measurements. It is desirable to have a self-calibrating system that does not require an OTA / chamber setup.

[0015] According to another aspect, a procedure (150) for a phased array antenna having RFICs with precision self-calibration is proposed. In a first novel aspect, a calibration control procedure is proposed coupled to a calibration circuit consisting of a controller, a current meter, a switch, and a bias adjustment circuit for bias currents in the phased array antenna. The bias currents of active circuits in the system are self-calibrated after power-on. Initially, all active circuits are turned off. One by one, selected individual active circuits are turned on, and their bias currents are measured by current meter(s) in the system. Each active circuit includes a current adjustment circuit (i.e., a current DAC "digital-to-analog converter") that adjusts the bias current of the circuit. The bias current of a selected active circuit can be adjusted by changing the current DAC setting in the controller until a desired accuracy is reached for a given level of the selected active device. The calibration is repeated until the bias currents of all active circuits in the system are calibrated. In a second novel aspect, a self-calibration procedure is proposed for the output power of each signal path in a phased array antenna system. The gain of each individual path is precisely calibrated so that the same output power is achieved for all power amplifiers corresponding to all antenna elements in the system.

[0016] FIG. 2 shows an RFIC bias generation system 200 that generates constant bias currents used in RF amplifier circuits. The RFIC bias generation system 200 includes a bandgap (BG) voltage source 201 that provides a constant voltage, which is converted to a constant current (called a global reference current) by a V-to-I circuit 202. The global reference current is then used by a global one-to-many mirroring circuit 203 to generate a number of mirrored currents, such as 100 μPPE and 100 μPE, which are used by multiple one-to-many mirroring circuits 204 to output multiple reference currents 1, 2, ∼, etc. The reference currents are then fed through a mirrored or replica bias circuit 205 to generate bias currents used in the amplifier circuits. Each individual circuit has a custom-designed mirrored or replica bias circuit to generate the desired bias current proportional to the reference current. For example, bias current 1 for active circuit 1, bias current 2 for active circuit 2, ∼, etc. Ideally, each bias current should have a desired constant bias current level.

[0017] The gain of a transistor amplifier is determined by 1) the transistor size and width-to-length (W / L) ratio (which is subject to manufacturing variations). The rate of size variations is reduced when larger transistor sizes are used, and 2) the bias current at which the transistor amplifier operates. To achieve precise bias currents in the amplifiers, RFICs typically implement a bias generation system 200, as shown in FIG. 2 , which consists of 1) a bandgap reference voltage source, 2) a reference voltage / reference current conversion, 3) one-to-many reference current mirroring, and 4) delivery of reference currents to individual amplifiers. In each amplifier, the bias circuit uses either a mirroring circuit or a replica circuit to adjust the reference current to the desired operating bias current. One of the main contributors to errors in bias current mirroring or replicating circuits is the Vth threshold voltage, which may have random variations between transistors. Even if manufacturing variations in transistor size are acceptable, variations in the Vth threshold voltage can affect the precision of the bias current.

[0018] 3 is a simplified circuit diagram of a bias generator 301 that supports a constant gm bias for use in a radio frequency amplifier in an RFIC. The bias generator 301 comprises a pair of transistors M1 and M2, whose gates are coupled to an external resistor R EXT The transistor M1 has a size of W / L, and the transistor M2 has a size of K*(W / L). As shown in FIG. m The bias is R EXT and is determined only by the transistor size ratio K, and g m =2 / R EXT *(1-1 / √K), where R EXT is a precision resistor with zero temperature coefficient. Therefore, since Gm and the reference voltage are PVT independent, the constant current generated using these parameters is also PVT independent and can therefore be used as the main bias current for large RFICs. In Figure 3, Iref1 and Iref2 are different bias current mirrors used for different RF amplifiers.

[0019] Note that the size ratio K between transistors M1 and M2 is crucial to obtaining a precise value of Gm. Furthermore, transistor M1 must replicate the transistor used in the RF amplifier to maintain good tracking of Gm. Therefore, using the same transistor type and size is crucial. As a result, transistor M2 is formed by replicating transistor M1 with the same (W / L) size and identical K. Furthermore, the current density of the transistor must be the same as that of the RF amplifier. Therefore, while increasing the transistor size can improve the precision of the size ratio K, it is undesirable to have enlarged M1 and M2 transistors in order to achieve a smaller RFIC with lower power consumption.

[0020] As explained above, a constant Gm bias is used to maintain the transconductance gain of the amplifier across the wafer. Precision, temperature-stable off-chip resistors on each RFIC are used as a reference, and transistor size ratios are used to obtain a precise Gm. However, the precision depends on the transistor threshold voltage V th In a CMOS semiconductor process, the threshold voltage V th has a high level of variation even within the same wafer. The transistor threshold voltage of M1 is V th,1 and the transistor threshold voltage of M2 is V th,2 As shown in Figure 2, this is the main source of error in the amplifier bias current generated by the mirroring or replica bias circuit from the reference current. The error in the amplifier bias current affects the amplifier performance, for example, Gm ~ is the square root of the bias current. Therefore, to improve the amplifier performance, it is necessary to accurately calibrate the error in the bias current.

[0021] In one embodiment, a PTAT (proportional to absolute temperature) current source is used to generate bias currents for active devices in an IC. It is also employed in intra-bandgap reference circuits, which generate temperature-independent (or temperature-dependent) bias voltages and are often used as references in measurement systems. The bias current can be increased or decreased as a function of temperature to compensate for variations in the Gm (transconductance gain) of the transistors in order to maintain their performance over temperature.

[0022] FIG. 4 shows one embodiment of a current measurement circuit (current meter) 400 that can be used as a self-calibration system for a phased array antenna. The self-calibration system self-calibrates the bias current of the power amplifier in the phased array antenna after power-up. The self-calibration system consists of a μC with an analog-to-digital converter (ADC) that can measure the current or voltage drop across a precision resistor R. In addition, the μC controls the turning on and off of the circuits and the corresponding bias adjustment settings for each circuit. The self-calibration system has the ability to control bias generation in the RFIC to turn on and off the bias of each individual circuit and to turn on and off the main power management system that provides voltage to the RFIC. When the main voltage source for the system is turned off, an alternative supply voltage is provided to perform the calibration.

[0023] Calibration is performed one circuit at a time; that is, the current measured is small, allowing the ADC (typically in the μC) to measure the precise current (i.e., the voltage drop of the current across a precision resistor). Each circuit contains a current DAC that injects a correction current into the circuit's mirrored or replicated bias circuit to adjust the bias circuit under the μC's control. The main reason for using a separate supply voltage to perform the calibration is to avoid this precision resistor in the main power path, which may consume unnecessary power during operation (after calibration is complete). The RFIC can adjust the bias current during calibration until it reaches a predetermined level within tolerance.

[0024] In the example of FIG. 4, the current measurement circuit 400 includes a μC, an ADC, an iDAC, and a precision resistor R. The μC measures the current I using the ADC to measure the voltage V across the precision resistor R, e.g., I=V / R. To prevent the precision resistor R from wasting power during normal operation, the system's main voltage source is turned off and a calibration auxiliary voltage source is switched on during measurement. The μC adjusts a current digital-to-analog converter (iDAC) until the desired bias current is measured. For example, a 4- to 6-bit control signal can be used to adjust the iDAC until the desired bias current is achieved. Note that each amplifier or active circuit in the system can be turned on and off under μC control. This measurement is repeated for each active circuit in the system while all other circuits are turned off.

[0025] 5 is a flowchart of a procedure for self-calibrating the bias currents of power amplifiers in a phased array antenna according to another embodiment. Step 501 is an initialization phase in which the self-calibration system 1) turns off all amplifier circuits, 2) turns off all regulators providing DC supply voltages to all RFICs, and then in step 502, one by one, the self-calibration system turns on each power amplifier and measures the bias current, 1) turns on the voltage sources for self-calibration, the global bias generator, and the bias generator associated with the selected circuit and measures the current, 2) turns on the selected active circuit, 3) monitors the increase in current consumption of the selected circuit, and 4) the self-calibration system adjusts the bias current of each active device (by changing the settings of the iDAC) until the desired accuracy is reached.

[0026] FIG. 6 illustrates an embodiment of a bias current self-calibration system 600 for a phased array antenna according to another aspect. The self-calibration system 600 is similar to the current measurement circuit 400, but includes additional regulators and switches for the calibration circuit (the system under test) that has three different supply voltages for operation and is divided into four power domains. For example, the regulators and switches can be used to individually calibrate different supply voltages (e.g., 1 volt, 1.7 volts, and 3.3 volts). The four power domains can also be individually calibrated to reduce power consumption, with the calibration repeated for each power domain. This allows the use of low-cost, off-the-shelf power supplies. During calibration, all circuits except the one being tested are turned off. For each circuit, the DAC bias in the current mirror is adjusted until the desired voltage drop, measured by the ADC, is achieved.

[0027] Note that self-calibration occurs in the foreground, meaning the phased array antenna system is not in normal operation. Self-calibration can occur at initial power-up or while the system is idle or undergoing maintenance. Self-calibration allows for precise bias currents for the amplifiers, which in turn means precise amplifier gains can be achieved. A self-calibrating system does not require the use of an OTA chamber setup, reducing costs.

[0028] 3GPP® or IEEE wireless systems use high-order modulation schemes such as OFDM with 64QAM, 256QAM, or 1024QAM. This type of modulation requires power amplifiers to operate in their linear region to avoid high EVM (Error Vector Magnitude). In phased-array antennas, it is desirable to monitor the output power from the integrated circuits (ICs) in each antenna element to generate precise antenna patterns and avoid power amplifier nonlinearities (driving the PA with appropriate backoff). Because the input signal can pass through many stages of active devices before reaching the power amplifier, each stage of the device contributes some error to the amplifier gain. Therefore, it is desirable to measure the output power and adjust the gain to maintain the signal level at the appropriate power amplifier operating point.

[0029] Figure 7 shows the follow current for various power amplifier classes and the appropriate back-off operating point for the power amplifier. Note that the average power consumption of a power amplifier (if it is not a Class A amplifier) ​​depends on its operating level (signal level). When there is no input signal, the power amplifier will have a quiescent current. As the input signal increases, the PA bias current also increases. The follow current is the average operating bias current minus the quiescent current. As shown in Figure 7, a small signal will not induce conduction, while a stronger signal will produce a high conduction duty cycle.

[0030] The proposed invention involves implementing a power detector based on measuring the follow current of the PA at an appropriate back-off operating point for the PA. In a preferred embodiment of a CMOS Class AB PA, it is found that when backed off approximately 6-7 dB from the output power P1 dB, the follow current accurately reflects the output power level, regardless of semiconductor process corner and temperature.

[0031] FIG. 8 is a flowchart of a procedure for self-calibrating output power in a phased array antenna according to another embodiment. For output power measurement, the same bias current measurement system as previously described is applied to measure the follow current. In step 801, all active circuits except for those in the selected signal path being calibrated are turned off. In step 802, a signal of known signal level is input and the follow current of the PA is measured. Note that the input signal is typically CW (continuous wave), and the input signal level is selected at a predetermined output power level that corresponds to the most accurate follow current (i.e., the least dynamic variation due to process and supply voltage changes). First, the quiescent current is measured while the input is turned off, and then the bias current is measured when the input signal is turned on to derive the follow current (i.e., the operating bias current with the input signal minus the quiescent current). In step 803, the amplifier gain of the selected signal path leading to that power amplifier is adjusted until the desired follow current of the PA is achieved. The variable gain amplifier in each path is adjusted to correct for the error ΔG. In step 804, the same procedure is repeated for all power amplifiers in all signal paths in the system until all PAs reach the same follow current (Pout).

[0032] FIG. 9 illustrates an embodiment of an output power self-calibration system 900 for a phased array antenna according to another aspect. The output power self-calibration system 900 is similar to the bias current self-calibration system 600 shown in FIG. 6 , but includes additional regulators and switches to calibrate a circuit (the system under test) that has three different supply voltages for operation and is divided into four power domains. For example, by controlling the regulators and switches, the different supply voltages of 1 volt, 1.7 volts, and 3.3 volts can be calibrated separately. The four power domains can also be calibrated separately to reduce power consumption, for example, by controlling the regulators and switches. During calibration, all circuits except the one being tested are turned off. For each circuit, 1) the output power Pout is measured, 2) the gain G = Pout / Pin is measured, and 3) the error ΔG is corrected by adjusting the variable gain of the power amplifier of the selected path until the desired power amplifier follow current is achieved.

[0033] By monitoring the 1.7V PA follow current, the entire signal chain can be calibrated. Because the gain / power is more flat at the center frequency, all stages must be tuned to the correct center frequency to minimize gain / power sensitivity to process and temperature. The frequency tuning procedure must be accurate enough to limit the error to less than 1 / 2 LSB of 0.375 dB. Calibration can be performed by first fine-tuning the center frequencies of all stages to the desired frequency and then adjusting the gain to reach the desired 1.7V PA follow current. The conclusion is that above 6 dBm, the error is less than 1 / 2 LSB of 0.375 dBm across the entire process corner. The error over temperature (30°C to 80°C) is greater than 1.5 LSB and is due to the center frequency shift with temperature. Operating at the center frequency can result in a smaller error. Resimulations over temperature at the corresponding center frequency demonstrate that operating only at the center frequency reduces the temperature sensitivity to an acceptable level. The calibration procedure can be performed at different signal frequencies and the calibrated settings can be stored in the μC and loaded depending on which signal frequency is selected.

[0034] 10 is a flowchart of a method for self-calibrating bias currents of active circuits on an RFIC of a phased array antenna according to another embodiment. In step 1001, a calibration circuit powers off all active circuits and power amplifiers of the RFIC. In step 1002, the calibration circuit powers on the active circuits of the RFIC being calibrated and monitors the current consumption of the active circuits. In step 1003, the calibration circuit measures the bias currents of the active circuits and adjusts the bias currents to predetermined levels during calibration. In step 1004, the calibration circuit repeats the bias current calibration for each active circuit of the RFIC and for all RFICs in the phased array antenna.

[0035] 11 is a flowchart of a method for self-calibrating the output power of a power amplifier on an RFIC of a phased array antenna according to another embodiment. In step 1101, the calibration circuit powers off all active circuits and power amplifiers on the RFIC and powers on the power amplifier and the corresponding signal path leading to the power amplifier of the RFIC being calibrated. In step 1102, the calibration circuit provides an input signal having a predetermined signal level and measures the follow current of the power amplifier being calibrated. In step 1103, the calibration circuit adjusts the amplifier gain and output power of the corresponding signal path leading to the power amplifier until the desired follow current of the power amplifier is reached. In step 1104, the calibration circuit repeats the output power calibration for each power amplifier and corresponding signal path of the RFIC and for all RFICs in the phased array antenna using the same input signal having the predetermined signal level.

[0036] While the present invention has been described in connection with several specific embodiments for purposes of illustration, the invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments may be made without departing from the scope of the invention as set forth in the claims.

Claims

1. 1. A method for self-calibration of a radio frequency integrated circuit (RFIC) in a phased array antenna, comprising: powering off all active circuits and power amplifiers on the RFIC; A step of turning on only the power supply of the active circuits of the RFIC being calibrated out of all the active circuits on the RFIC that are turned off, and monitoring the current consumption of the active circuits; measuring a bias current of the active circuit and adjusting the bias current to a predetermined level during calibration; repeating the calibration of the bias currents for each active circuit of the RFIC and for all the RFICs in the phased array antenna.

2. 10. The method of claim 1, wherein the bias current is measured by a μC using an analog-to-digital converter (ADC) to measure the voltage across a precision resistor R.

3. The method of claim 2 , wherein the μC adjusts a current digital-to-analog converter (DAC) until a desired bias current is reached.

4. 10. The method of claim 1, wherein each active circuit in the RFIC can be turned on or off under the control of a μC.

5. The method of claim 1 , wherein a primary voltage supply is turned off and an auxiliary voltage supply is turned on during the bias current measurement.

6. 1. A method for self-calibration of a radio frequency integrated circuit (RFIC) in a phased array antenna, comprising: powering off all active circuits and power amplifiers on the RFIC, and powering on only the power amplifiers and corresponding signal paths leading to the power amplifiers of the RFIC being calibrated among all active circuits on the RFIC that are powered off; inputting an input signal having a predetermined signal level and measuring the follow current of the power amplifier during calibration; adjusting amplifier gain and output power of the corresponding signal path leading to the power amplifier until a desired follow current of the power amplifier is reached; and repeating the calibration of the output power for each power amplifier and the corresponding signal path of the RFIC, and for all RFICs in the phased array antenna, using the same input signal having the predetermined signal level.

7. 7. The method of claim 6, wherein measuring the follow current of the power amplifier includes measuring a quiescent current while the input signal is off, and then measuring a bias current when the input signal is turned on.

8. 8. The method of claim 7, wherein the follow current is equal to the average bias current minus the quiescent current.

9. 7. The method of claim 6, wherein the follow current is measured at a predetermined back-off operating point of the power amplifier corresponding to high accuracy.

10. 10. The method of claim 9, wherein the desired follow current reflects the output power level at the predetermined back-off operating point.

11. A phased array antenna including a plurality of radio frequency integrated circuits (RFICs), each RFIC comprising: a plurality of active circuits and power amplifiers that are initially powered off, wherein of all the active circuits on the RFIC that are powered off, only the active circuits of the RFIC being calibrated are powered on; a measurement circuit including a μC that monitors the current consumption of the active circuitry, the μC measuring a bias current of the active circuitry and adjusting the bias current during calibration; a plurality of regulators and switches for each active circuit of the RFIC that repeat the calibration of the bias current.

12. 12. The phased array antenna of claim 11, wherein the μC measures the bias current using an analog-to-digital converter (ADC) to measure a voltage across a precision resistor R.

13. 13. The phased array antenna of claim 12, wherein the μC adjusts a current digital-to-analog converter (DAC) until a desired bias current is reached.

14. 12. The phased array antenna of claim 11, wherein each active circuit in the RFIC can be turned on or off under the control of a μC.

15. 12. The phased array antenna of claim 11, wherein a primary voltage source is turned off and an auxiliary voltage source is turned on during the bias current measurement.

16. Each RFIC: an input node for receiving an input signal having a predetermined signal level, the input node at which a follow current of a power amplifier of the RFIC being calibrated is measured; 12. The phased array antenna of claim 11, further comprising: an output node that outputs an output power of a selected signal path to the power amplifier, the output power being adjusted by adjusting a gain of the selected signal path until a desired follow current is achieved, and the calibration of the output power being repeated for each power amplifier of the RFIC.

17. 17. The phased array antenna of claim 16, wherein measuring the follow current of the power amplifier comprises measuring a quiescent current while the input signal is turned off, and then measuring the bias current when the input signal is turned on.

18. 18. The phased array antenna of claim 17, wherein the follow current is equal to the average bias current minus the quiescent current.

19. 17. The phased array antenna of claim 16, wherein the follow current is measured at a back-off operating point of the power amplifier.

20. 20. The phased array antenna of claim 19, wherein the desired follow current reflects the output power level at the back-off operating point.

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