a) A wide band mixer that has at least the following characteristics:
The mixer should support the input and output frequency ranges within the same HW (I assume that there might be some degradation in low frequencies
b) 90 degrees phase shift device with the following properties:
This is for the image rejection mixer implementation.
Here are a few wide band mixers that can work with your application frequency range:
ADL5355 – passive mixer. But please keep in mind, this mixer require filters at the input / output ports
ADL5801 / ADL5802 – Active mixer
And maybe HMC557 / HMC557A