TXB0304EVM: SPI lines experiencing high noise

Hallo,

First up all thank you for your time and consideration. I am using TXB0304EVM to communicate with a sensor (1.8V) and a controller (3V) using SPI. I am able to somehow read and write the registers of the sensor when the ground of TXB0304 kept floated. However, when connected when the ground pin of the TXB0304 is connected to the common ground, the signal lines experiences high noise and hence the read and write commands fail. 

here are the scope screenshots when ground pin of TXB0304 is connected to common ground. As you can see below, the signal lines are corrupted with noise.  

Here is a screenshot when ground pin is floating. I am able to read and write at low frequency, but as you can see this is not at all a proper way. The signals are not grounded properly.

There are no pullup resistors used in the signal lines. Below you can see the schematics. The SPI signal from TXB0304 (A1, A2, A3 and A4) is connected to spi pins of a microcontroller directly. nrfVDD and MAX(1.8) are the voltage 2.8V and 1.8V respectively. NOTE: We have not yet developed the custom board. So we are using EVM Boards of both microcontroller and logic level shifter. Therefore there are long jumper wires (~10cm or even large seperations) between each connections.  And the two power supplies are provided from a separate power sources for the moment. 

I have had tested the TBX0304 EVM board and it functions properly with direct DC signals applied. What could be the reason for such a big noise in the signal lines?

The frequency of SPI used is 4M. I tested with 125KHz, but even then the noise exists. 

Please inform me if anymore details are required. Please also suggest a method to debug this issue.

Thank you for your time.

Kind regards,

Adarsh