The ACLR / IMD model can simulate the broadband carrier spectrum in order to understand the ACLR source of the RF device, which is equivalent to an independent set of CW subcarriers. Each subcarrier will carry a portion of the total carrier power. The following figure shows such a model. The continuous RF carrier is simulated by four separate CW subcarriers, and the power of each subcarrier is a quarter of the total carrier power. The subcarriers are evenly distributed in the entire carrier bandwidth at the same interval.
Figure 1. Subcarrier model of broadband carrier signal
The green lines in Figure 1 are subcarriers 1, 2, 3, and 4 from left to right. If we only look at the two subcarriers (1 and 2) on the left, we can consider the third-order IMD component caused by any IMD3 distortion in the RF device. The third-order distortion appears as low-level subcarriers on both sides of the two subcarriers. The first "red" distortion component to the left of the two "green" subcarriers is the IMD3 distortion result of the two subcarriers.
IMD3 components from subcarriers 1 and 3 have IMD3 distortion components at the same frequency as carrier 1 spacing. This produces a second "red" IM component to the left of the carrier spectrum. Similarly, the distortion components generated by IMD3 from subcarriers 1 and 4 are farther from the carrier edge.
Note that there are other IMD components. The IM3 components generated by subcarriers 2 and 4 are directly superimposed on the IMD components generated by subcarriers 1 and 2. This cumulative effect causes the amplitude of the IMD component closer to the RF carrier edge to be higher than the IMD component farther from the RF carrier edge, resulting in a "shoulder" characteristic in the ACLR distortion spectrum. A paper published by Leffel¹ details this accumulation of IMD components from multiple subcarriers.
This method can quantitatively predict the actual level of the individual IMD3 distortion components. The accuracy of the model can be increased by increasing the number of individual subcarriers used in the model². The ACLR performance of multiple broadband carriers is very similar to the ACLR in this model, where each individual broadband carrier occupies a portion of the total broadband carrier bandwidth. In the adjacent part of the broadband carrier, the ACLR of the single carrier adjacent to the last carrier is at the high shoulder position of the distortion response caused by IMD3. This results in the ACLR of the multi-carrier situation being much worse than that of the single-carrier system. Again, this result can be quantified to accurately predict the ACLR performance of a single broadband carrier or multiple broadband carriers. This basic method uses only the OIP3 parameter to predict the ACLR performance of the RF device. Basic relationship The relationship between the third-order intermodulation component of the device and the third-order intermodulation intercept point is as follows:
IMD3 = (3 x Pm)-(2 x OIP3)
among them,
Pm = power of each tone in the two-tone test example
IMD3 = third-order IM3, expressed in dBm as the absolute power
OIP3 = third-order intercept point, indicating absolute power
For convenience, the formula can be rewritten as relative IMD3, that is, IM3 performance related to power level (P).
IMD3 = 2 x (Pm-OIP3)
among them,
Pm = power of each tone in the two-tone test example
IMD3 = third-order IM3, expressed in dBc, relative power
OIP3 = third-order intercept point, indicating absolute power
Example 1 takes a power amplifier (PA) with a total output power (Ptot) of + 30dBm and an OIP3 of + 45dBm as an example. The relative IMD3 of such a PA can be derived using the above formula. However, in the IM3 two-tone test, the output power of each tone is 3dB lower than the total output power of the PA, that is, + 27dBm per tone. So use these values ​​to calculate the IMD3 of the PA:
Ptot = + 30dBm (total output power of PA)
Pm = (+ 30dBm-3dB) = + 27dBm per tone
OIP3 = + 45dBm
IMD3 = 2 x (27-45) = -36dBc The relationship between ACLR and IMD3 The ACLR of the broadband carrier is related to the performance of dual tone IMD3 through a correction factor. The existence of this correction is due to the deterioration of ACLR performance due to IMD3 performance. This deterioration comes from the effects of various intermodulation components composed of the spectral density of the spread spectrum carrier. The effective relationship between ACLR and IMD3 is as follows:
ACLRn = IMD3 + Cn
The Cn is shown in the following table:
| No. of Carriers | 1 | 2 | 3 | 4 | 9 |
| CorrecTIon Cn (dB) | +3 | +9 | +11 | +12 | +13 |
We can combine the above relationship between IMD3 and ACLRn into a unified expression, and derive the ACLR of multiple spread spectrum carriers from the basic performance parameters of the RF device.
ACLRn = (2 x [(P-3)-(OIP3)]) + (Cn)
among them,
Ptot = total output power of all carriers in dBm
OIP3 = OIP3 of the device, in dBm
ACLRn = ACLR of "n" carrier in dBc
Cn = value in the above table
Example 2 repeats the above example. Now suppose that the power amplifier must generate four carriers with a power of 250mW and a total output power of 1W.
P / carrier = + 24dBm
Ptot = + 30dBm, total power
OIP3 = + 45dBm
ACLRn = 2 x ((30-3)-(45)) + 12
ACLRn = -36dBc + 12dB
ACLRn = -24dBc
Reorganizing the formula can deduce the OIP3 required to get the desired ACLR. The formula after rewriting is as follows:
OIP3 = 0.5 x ([2 x (P-3)]-[ACLRn] + [Cn])
among them,
P = total output power of all carriers in dBm
OIP3 = OIP3 of the device, in dBm
ACLRn = ACLR of "n" carrier in dBc
Cn = value in the above table
Example 3 repeats the above example. Now suppose that the expected value of the four-carrier ACLR of this power amplifier is -50 dBc.
P / carrier = + 24dBm
Ptot = + 30dBm, total power
ACLRn = -50dBc
OIP3 = 0.5 x ([2 x (30-3)]-[-45] + [12])
OIP3 = + 55.5dBm Conclusion The relationship between the carrier power level of general RF devices, OIP3 specifications and single carrier / multicarrier ACLR performance has been derived. This relationship applies to RF devices whose performance is affected by third-order distortion components. Many common RF devices are included, but the drive cannot be too close to the saturation level. Through observation, the prediction accuracy of the model for ACLR is close to ± 2dB.
MLF advise many types of USB chargers , USB Power Adapters, USB network adpaters . 2.0 Usb Adapters as well as 3.0 USB ac adapters .and also 3.1 USB type. USB power adpater widly use in various industry.Let us match a high quality Usb Power Adapter for your device !
The main type is single USB Adapter , but also dual USB and mutiple USB port type also .can charge the two or more devices at one time. Please don't hesitate to contact if you want to know more details about the USB adapters!
USB Adapter
Usb Power Adapter,Usb 2.0 Adapter,Usb Power Supply,Usb Network Adapter
Meile Group Limited , https://www.hkmeile.com