For the passive intermodulation (PIM) problem of nonlinear contact on microwave connectors, an effective method is presented to improve the computational accuracy of PIM. First of all, the contact stress distribution on contact surface is analyzed by finite-element method based on the Weierstrass–Mandelbrot model. The contact stress and real area of contact are evaluated under different loading conditions. Then, the electrical parameters of physical effects of nonlinear contact are derived based on the electric contact theory and the physical effects of metal–metal microcontact. Finally, the nonlinear I–V relation is established from the microcontact equivalent circuit, and the third-order PIM power level generated by contact nonlinearity is revealed in analytic form. The analytic results are verified by the PIM test experiments. This work provides a novel way for PIM calculation of rough surface contact.

Passive Intermodulation of Contact Nonlinearity on Microwave Connectors

This paper presents a novel passive intermodulation (PIM) prediction method considering random contact behavior using a Monte Carlo method for a coaxial connector. A smart contact model for a contact unit at a microcosmic level is proposed. Using Monte Carlo approximation and micromeasurements, different random distributed contact samples for different contact components inside the coaxial connector are reconstructed. In the experiment, PIM on inner and outer conductor was tested and compared with predication. A good agreement proves the proposed PIM prediction method is efficient. Rather than generating a single PIM prediction value, this method will give a PIM confidence interval for all the potential PIM values considering the contact force statistical behavior. The work will help analyze fluctuated PIM on coaxial connectors and inspire a new method to predict PIM risk.

Analytic Passive Intermodulation Behavior on the Coaxial Connector Using Monte Carlo Approximation

A measurement system which uses acoustic vibration to locate passive-intermodulation (PIM) sources in base station antennas is presented This measurement system uses mechanical vibration to modulate the PIM signal The modulation of the PIM signal is detected, and its strength or presence/absence is used as guidance for selecting the location of the vibrating transducer For the method to be successful, the PIM signal must be caused by loose mechanical contacts or loose nonlinear materials By introducing the acoustic vibration at different locations in the base station antenna and observing if the PIM signal is modulated by the acoustic frequency, the most likely location of the PIM source is identified

A Passive Intermodulation Source Identification Measurement System Using a Vibration Modulation Method

Permanent magnet machines are not free from the interaction between magnets and the stator and rotor slots, which causes an undesired disturbing torque. Such cogging or detent torque is especially larger with salient pole machines, as it is the case of the permanent magnet hybrid stepper machines (PMHSM). Depending on the application requirements, these torque perturbations can be unacceptable and the application of solutions that minimizes the cogging torque effects are mandatory. This paper analyzes the minimization of the cogging torque using resonant controllers. More specifically, this paper details the analysis and design of a speed-adaptive resonant controller, which is not only directly designed in the Z-domain but also considers the current (or torque) inner-loop delay. Pole-zero placement and the disturbance-rejection-frequency response are attained in the design of the speed and position speed-adaptive controllers. Experimental results with two off-the-shelf PMHSMs demonstrate the superior performance of the proposal in both speed and position closed-loop applications for tracking, as well as in disturbance (load impact) rejection tests and against inertia variations. A comparison with a conventional PI is carried out from the design stage to experimental results and the improvement of the proposal is numerically quantified.

/pdf/reducing-the-cogging-torque-effects-in-hybrid-stepper-4igfewk9pd.pdf

Reducing the Cogging Torque Effects in Hybrid Stepper Machines by Means of Resonant Controllers

Loose contact coaxial connectors are significant sources of passive intermodulation (PIM) in high-power and high-frequency communication systems. In this paper, a circuit model is presented to analyze PIM distortion in loose contact coaxial connectors. First, the loose contact surface model is built to calculate metal–insulator–metal and metal–metal contact resistance; and a method of time-domain reflectometry is used to verify the additional impedance of the loose contact surface. Then, the loose contact current is investigated to drive the equivalent circuit model of loose contact coaxial connectors. Finally, a two-tone experimental verification is conducted to show that the PIM of a loose contact coaxial connector can be analyzed by this model.

An Equivalent Circuit Model to Analyze Passive Intermodulation of Loose Contact Coaxial Connectors

This paper presents a phenomenological study about the passive intermodulation (PIM) behavior on a reconfigurable nickel-coated cell array. An artificial transmission line with reconfigurable nonlinearity is employed for demonstrating PIM generation and propagation behavior. This test fixture gets rid of metal contact distortion by using coupled power to stimulate nonlinear sources. Using the finite element analysis, the simulated magnetic field intensity is compared with the tested PIM data. A set of nonanalytic PIM models directed toward nickel-coated distributed PIM sources is demonstrated. Based on the proposed PIM fixture, a novel PIM reconfiguration method using nonlinearity array is proposed and a strength predictable PIM standard is obtained. The proposed test fixture can work as a practical PIM building-block to provide stable PIM reference. In the demo cases concerning three PIM test frequency spots, the minimal PIM of this device can reach below –112 dBm @ 2 × 43 dBm, while its maximal PIM dynamic range can reach about 20 dB. It exhibited a rudiment of PIM standard that can be applied in practical PIM test calibration field.

Reconfigurable Passive Intermodulation Behavior on Nickel-Coated Cell Array

A dual-port tunable intermodulation (IM) generator is reported. This IM generator employs a coupling network to distribute carrier waves and IM. The proposed coupling network is constructed by cascading four parallel-coupled directional couplers, while a Schottky diode is working as a tunable IM source. By adjusting the IM performance of diode using bias voltage and distributing IM along symmetrical IM paths, a pair of tunable IM signals is introduced into passive IM (PIM) test loop simultaneously, they can serve as bidirectional IM reference in dual-port PIM measurements. The provided IM3 can be tuned to be lower than −112 dBm at $2 \times 43$ dBm at either 710 or 2550 MHz, while their dynamic IM3 range can reach about 20 dB at $2 \times 43$ dBm. The work promotes the application of IM predistortion techniques and provides a solution to realize dual-port dynamic IM calibration in PIM test.

http://ieeexplore.ieee.org/iel7/7260/7921541/07911202.pdf

Broadband Dual-Port Intermodulation Generator for Passive Intermodulation Measurements

This letter presents a programmable passive intermodulation (PIM) generator with 50-dB-dynamic range using nonlinear mechanical rotating disk. Its implementation is based on a strip-line structured configuration; a nickel-plated disk is inserted into polytetrafluoroethylene substrate through the slots on upper and central conductor. The partly nickel coated copper disk works as an artificial nonlinear sources. Through rotating this disk using stepper motor controlled by micro control unit, PIM product can be automatically tuned by regulating the electromagnetic exposure area on the nickel-plated region. A rational PIM quantization method for nickel-plated nonlinear region is propounded. The experiments demonstrate this PIM generator can perform controllable PIM level, ranges from −127 to −77.4 dBm at $2 \times 43$ dBm, while its finest step can be smaller than 0.3 dB. This letter demonstrates a solution to realize a tunable PIM standard for potential PIM dynamic calibration application.

Novel Programmable Passive Intermodulation Generator Using Nonlinear Rotating Disk

The high-accuracy passive intermodulation (PIM) measurement shows great significance in PIM quality checking and related researches. As the key point to guarantee the test accuracy, the IM reference is essential in realizing precise PIM calibration. This paper presents a design of dual-port IM generator that can generate dynamic IM reference for this demand. The proposed generator employs a cascaded coupling network consists of two couplers, while a reverse biased Schottky diode is working as a tunable reflection IM source. The bias voltage and coupling coefficient are introduced to regulate the quiescent operation points of diode and the IM signal excitation strength respectively, they work together to put the IM reference signal on a desired level. Specially, a trimming strategy by using a compact terminal matching resistor is adopted to smartly regulate the IM tunable interval. These configurations can promote the utilization of this proposed IM generator to be flexible not only for design engineers but also for commercial users. The test results demonstrate that this generator can provide the tunable IM3 whose dynamic range can reach about 30 dB@2x43 dBm, 50 dB@2 × 31 dBm. Meanwhile, the significance of bidirectional dynamic IM reference signals is demonstrated.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2016.0413

Yongning He

Papers

Analytic Passive Intermodulation Behavior on the Coaxial Connector Using Monte Carlo Approximation

Reconfigurable Passive Intermodulation Behavior on Nickel-Coated Cell Array

Broadband Dual-Port Intermodulation Generator for Passive Intermodulation Measurements

Novel Programmable Passive Intermodulation Generator Using Nonlinear Rotating Disk

Reflection modulation basis dual-port intermodulation generator for dynamic calibration application in passive intermodulation measurements