[hpsdr] [CASMIR] System Requirements 07JUN2006

[Naylor Jonathan]

Hi Alex

Some of your RF values don't make any sense.

> 1.    CASMIR shall support transmitter frequency coverage from 0 MHz
> to 47GHz.

Once you get above 10 GHz, things get very difficult. Also bear in mind
that above a few GHz, people tend to mount their RF gear near to the
antenna due to losses. Hence the form factor of the uWSDR. Having a
(say) 5.7 GHz system in the shack is not going to be useful to most
serious microwave ops.

> 5.1.    A power level of 1 watt shall be supported from 0 MHz to 6
> GHz

The microwave world is used to working with components, don't try for
unreasonable power outputs. A few 100mW is cheap and enough to drive
more reasonable power devices (read $$$s).

> 5.1.1.    Variable power output level shall be supported with
> 1-3-6-10 dB steps per decade starting at -30 dBm
> 5.2.    A power level of 10mW shall be supported from 10GHz to 47GHz
> 5.2.1.     Power output level shall be fixed from 10GHz to 47GHz

If your system is a linear system as it needs to be to support the SDR
software, then the output power is a function of the software side. You
don't need to have any form of hardware gain control on transmit. A
fixed/variable output power distinction really make no sense.

> 14.    CASMIR shall support frequency resolution of 1Hz

Why? By adding this requirement you are increasing the complexity of
your local oscillator no end. Depending on your ADC sample rate, you
can afford to go in much larger steps and let the DSP do the rest. This
will ease your LO design and allow for better phase noise too. This is
a decision that was made early in the uWSDR project, and we have felt
no need since to change it.

> Alex, N3NP

Jonathan   ON/G4KLX


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