Abstract: A phase shift circuit suitable for use in an FM detecting circuit of quadrature detection method adopted for a FM radio receiver, for example. The phase shift circuit includes first and second pairs of differential transistors to which input signals are applied as differential inputs in common, first and second current sources for driving the first and second pairs of differential transistors, respectively, a first load circuit connected to respective collectors of the first pair of differential transistors, a second load circuit connected to an output side collector of the second pair of differential transistors and a third pair of differential transistors to which a first signal and a second signal are applied as differential inputs, wherein the first signal is derived from one of the collectors of the first pair of differential transistors, whereas the second signal is derived from the output side collector of the second pair of differential transistors.

Abstract: A carrier generator circuit for use in a modem employed in a wireless communication system is described. The carrier generator circuit includes a voltage controlled oscillator comprising an N-stage ring oscillator to generate N balanced vectors of equal magnitude and arbitrary phase difference. The carrier generator circuit also includes a phase corrector to add two of the balanced vectors to generate a sum vector and to subtract the two balanced vectors to generate a difference vector. The sum vector and difference vector have a phase difference of 90 degrees. The sum vector represents an I (in-phase) carrier signal component and the difference vector represents a Q (quadrature-phase) carrier signal component. These I and Q carrier signal components can be used to transmit and receive data signals.

Abstract: An accurate phase shifting circuit providing two analog signals having a 90-degree phase shift between them from a single sampled-data input without the need for components external to a monolithic integrated circuit. A combination of two discrete-time circuits achieves the required 90-degree phase relationship over a broad frequency region. Several sample-and-hold circuits and multiplexors are used to produce two discrete-time versions of the analog input signal. Subtracting that older sample from the most-recent sample yields a forward difference signal and adding the most recent and the older samples produces a forward average signal. The phase difference between any single-frequency component of the forward difference and forward average signals is always 90 degrees. A pair of matched filters serves to reconstruct the sampled analog waveforms and to remove unwanted high-frequency noise in the +90.degree. output signal.