In the 1980s, the application direction of RF microwave circuit technology gradually transferred from traditional waveguide coaxial devices to microwave plane PCB circuits, and microwave planar circuit design has always been a more complex work. The current wireless communication products have gradually developed from early 2G to 3G, 4G or even 5G.
As the application frequency is gradually high, coupled with multi-band circuit coexisting and product miniaturization requirements, the design of RF circuits is getting harder and harder, and traditional design methods have not met the design requirements of modern RF communications product. Therefore, the circuit design of the RF microwave simulation software will be imperative.
What is RF simulation software?
RF simulation software is a product of computing electromaggcast and mathematical analysis research results. It collects electromagnetic, mathematical analysis, virtual experiments, etc., and through the simulation method to achieve various intuitive data, It is a powerful tool for radio engineers and researchers. RF simulation method is a scientific design method that reduces the amount of debugging work and various uncertainty factors that may occur in the later stage of the product, thereby shortening the research and development cycle of the product and improves productivity.
RF circuit design simulation software is currently mainstream is De Technology Keysight ADS (Design System), and ADS can provide standard comprehensive design and verification by means of wireless libraries in integrated platforms and circuitry and electromagnetic coeximation, it has Widely used in WiFi, GPS, Bluetooth, 2G / 3G / 4G circuit and communication system design.
Let's take ADS software as an example, explain the basic process of the circuit design!
RF circuit design and simulation include the following steps:
1, system simulation phase:
In the early stage of product project, the system index and determination circuit architecture of the product are first determined, including: sensitivity, total gain, noise coefficient, work bandwidth, dynamic range, etc., which need to be systematically simulated using ADS. Because most of our products are from abroad, the chip and circuit system architecture are determined, so this step is currently not involved in consumer products.
ADS multi-layer simulation
2, the schematic design simulation phase:
Samples and IC selection according to system indicators, including low noise amplifiers LNA, filter, power amplifier design, and grade matching circuits.
RX receiving link system simulation
3, PCB Joint Simulation Stage:
The schematic design is actually a very ideal situation, which does not take into account the parasitic effect of the device and the coupling effect of the PCB microstrip line. Therefore, scientific practice is to import the design PCB into the ADS Momentum to perform electromagnetic field simulation and re-adjust the optimization matching element value. According to the multi-year experience in RF Sister, if the model and simulation are set enough, the simulation result approximation is very high.
Low noise amplifier schematic simulation
4, product debugging stage:
Simulation actually only guarantees the design trend and the correctness of the direction, so the sample is returned, it is still necessary to debug optimization, record, and save test results, and compare the simulation. In principle: no matter how big is the difference, you must find the reason!
Combined with PCB low noise amplifier combined simulation
5, the project summary stage:
Doing a closed-loop analysis for the entire simulation and actual test results - the problem of model, or the problem of simulation parameter settings, or the problem of PCB dielectric constant and medium loss is not accurate, is it a problem? Here, We need very rich practical experience and problematic ability. Summary is important, will be the basis of the next success, similar to Huawei ZTE and other large enterprises will have a habit of writing a summary document.
A LTE terminal simulation compared to the measured input impedance
Tips
The method is always beautiful, but the process is always twisted. There are many small friends, and the measured and simulation gap is larger.) Active giving up, simulation and testing is close, in fact, it is mainly limited to the following factors:
(1) The proficiency of the simulation software is used. Need to understand the basic principle of simulation, know if the specific meaning of each item will affect parameters;
(2) Whether the method of testing is sufficiently correct. Learn what is Solt, TRL, and they have any advantages and disadvantages;
(3) Learn is not deep enough for component characteristics and S parameter models, SPICE models.
(4) Whether the experience is sufficient. No experience in closed-loop verification, it is considered to be closed;
(5) Important: Partners have research interests, but because the company's product is progressing, there is no excessive thinking and more analysis time.
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Source: Wiku Electronic Market Network
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