Pan sharpening is for sharpening a low-resolution color (or multi-band) image using a high resolution single-band image. In your problem, you have two single-band images, which do not lend themselves to traditional pan sharpening. My first suggestion is to use false color imagery. Load up your low-res image on two colors (for instance, red and blue) and your high resolution image on the third (green, in this example). This will make a visually dramatic difference, but it will also muddy up the data. Another trick would be to load up both images and take the difference between them, invert the difference image, then use the inverted difference image in an HSV constructed image. Set the hue (H) to a fixed number, use the inverted difference image for saturation (S) and then use your low-res image for value (V). After that is done, reset the image mode to greyscale.

I'll try to include a picture sequence of the false color method below. The first image should be a low-res blue channel, the second should be a high-res pan chromatic channel, and the third should be a false-color composite. Hopefully ResearchGate will be fairly easy to upload to.

Pan sharpening is for sharpening a low-resolution color (or multi-band) image using a high resolution single-band image. In your problem, you have two single-band images, which do not lend themselves to traditional pan sharpening. My first suggestion is to use false color imagery. Load up your low-res image on two colors (for instance, red and blue) and your high resolution image on the third (green, in this example). This will make a visually dramatic difference, but it will also muddy up the data. Another trick would be to load up both images and take the difference between them, invert the difference image, then use the inverted difference image in an HSV constructed image. Set the hue (H) to a fixed number, use the inverted difference image for saturation (S) and then use your low-res image for value (V). After that is done, reset the image mode to greyscale.

I'll try to include a picture sequence of the false color method below. The first image should be a low-res blue channel, the second should be a high-res pan chromatic channel, and the third should be a false-color composite. Hopefully ResearchGate will be fairly easy to upload to.

have u tried erdas imagine or imageJ?

I recommend the answer Ray H. Kamps, and also you can do the following steps in ArcGIS as well:

1) Create a FCC from the low resolution image (Arctoolbox ->Data Management Tools ->Raster -> Raster Processing -> Composite bands) repeat the single band as the RGB bands,

2) Convert the RGB to HIS (In the Image Window: Highlight the RGB at top of window ->Processing->fx->Right click on Identity Function -> Insert->choose Color Model Conversion from list,

3) Make permanent the generated layer by exporting it to a specific drive in your PC,

4) Create Pan-sharpened Raster Dataset (Arctoolbox ->Data Management Tools ->Raster -> Raster Processing -> Create Pan-sharpened Raster Dataset): set Red channel 3; Green channel 2; Bue channel 1; Panchromatic Image: the high resolution image; and Pan-sharpened Type: SIMPLE_MEAN

Some references to pan-sharpening:

ArcGIS

http://desktop.arcgis.com/en/arcmap/10.3/manage-data/raster-and-images/applying-pansharpening-to-a-raster-layer-in-arcmap.htm

https://www.youtube.com/watch?v=udPVLiu2EXg

https://www.youtube.com/watch?v=RcLCO5AqDSY

QGIS

https://www.youtube.com/watch?v=SRf_lltOBYA

GRASS

https://grass.osgeo.org/grass76/manuals/i.pansharpen.html

Hope this will help.

Al Emran I wonder what is the reason you want to do this? The answer by Ray H. Kamps should work, but I do not know if the result would be useful for getting what you want. Not so sure about the method proposed by Omid Abdi , since the RGB image with the same information in RGB channels should produce no information in H and S of HIS, hence pan-sharpening would not be possible this way.