Output Power and Gain Monitoring in RF CMOS Class A Power Amplifiers by Thermal Imaging

Abstract

 Abstract-The viability of using off-chip single-shot imaging techniques for local thermal testing in integrated Radio Frequency (RF) power amplifiers (PA's) is analyzed. With this approach, the frequency response of the output power and power gain of a Class A RF PA is measured, also deriving information about the intrinsic operation of its transistors. To carry out this case study, the PA is heterodynally driven, and its electrical behavior is down converted into a lower frequency thermal field acquirable with an InfraRed Lock-In Thermography (IR-LIT) system. After discussing the theory, the feasibility of the proposed approach is demonstrated and assessed with thermal sensors monolithically integrated in the PA. As crucial advantages to RF-testing, this local approach is noninvasive and demands less complex instrumentation than the mainstream commercially available solutions.

BPF-Based Thermal Sensor Circuit for On-Chip Testing of RF Circuits

“…Both thermal amplitude and phase shift depend on the silicon physical properties (thermal conductivity and specific heat), the input frequency f i and the distance between the heater and the transducer [ 40 ]. The close proximity between the heater and the transducer ensures a good thermal coupling even in the MHz frequency range [ 32 , 40 , 50 , 51 ]. Then, the transducer output voltage can be written as: where V GST 1 is the DC gate-to-source voltage in T 1 , needed to sustain the drain current I B , and V A is the voltage amplitude generated by the oscillating temperature of amplitude T A .…”

“…The schematic of the RF PA is shown in Figure 10 . It is a class-A cascode amplifier with off-chip load, fully described in [ 32 ]. The cascode transistor M 2 was made of three transistors in parallel connection (inset in Figure 10 ).…”

“…This driving generated power dissipation in transistor M 2 , with a spectral component at Δ f and an amplitude P Δ f . Previous work [ 32 , 33 ] indicated that P Δ f depended on both the voltage gain of the amplifier at f RF and on the input-output matching at the same frequency. As elaborated in Section 3 , this power dissipation generated an AC sensor output voltage superimposed to V DD /2, whose content at Δ f can be written as: …”

An Intuitionistic Kernel-Based Fuzzy C-Means Clustering Algorithm With Local Information for Power Equipment Image Segmentation

“…At the same time, for a different x i , when x i is away from x k , the weight will also decrease, because the similarity between pixels usually decreases with increasing distance. For class j, when the membership of adjacent pixels of x k belonging to class j increases, the distance metric η ik d 2 IFS will become smaller, then x k will tend to be classified as the jth class. As a result, pixels in the same area will have different degrees of homogeneity.…”

“…Based on the imaging principle of the temperature characteristics of the object, the imaging environment of infrared image is not limited by weather or lighting conditions, and infrared images have a wide range of applications in military and civilian applications. With the introduction and continuous development of the concept of smart grid in recent years, infrared imaging technology has played an indispensable role in the field of power grid fault diagnosis [1], temperature monitoring [2], etc., which makes the application of infrared imaging technology have important civilian significance. Since the contrast of structure and shape information in the infrared image of power equipment is not high, infrared segmentation is a key step in target recognition and analysis.…”