AW: Info requested on EMS Phase Frequency Shifter

[Haible Juergen]

My reply comes a little late, but nevertheless:

>  It is a
> discrete chip digital oscillator that uses weighted summations of Walsh
> functions to produce the sin and cosine signals. This voltage controller
> oscillator can go continuously from 1000 Hz down to about 1 cycle per 20
> seconds or so. [...] The EMS will not
> do a through zero shift and the maximum shift is limited to 1 KHz. 
> 
Not doing thru zero is a shame, because it would have been so easy
with that solution (compared to an analogue solution).

	>Internally, the unit consists of 2 PC boards, one is the quadrature
	>oscillator, the other is everything else.

Thinking about it, they might have been able to replace the analogue
multipliers with DACs that accept an external ref voltage, when they
make the quadrature oscillator in the digital domain. 
It's just a guess, mind you.

JH.