Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
255 words
A method of compensating for non-linearities in an end amplifier (F) with a transfer function H R , H φ for the amplitude and phase respectively of an incoming radio signal, and included in a radio transmitter of quadrature type for linear, digital modulation based on table look-up and analogue-digital conversion containing register means (BHR, QM) which function to store binary values of a momentary phase angle and an accumulated phase angle of an information signal to the radio transmitter, so as together to form a signal vector α of given length which depends on the length of the impulse response h(t) of a premodulation filter of the radio transmitter; storage means (ST, CT) which function to store the digital values of sine and cosine waveform (I(t, α ), Q(t, α )) belonging to those quadrature components which are addressed by means of said signal vector α projected on two carrierwave components (sine w c t, cos w c t); and further containing multiplier and addition means (M1, M2; ADD) which form a quadrature-modulated radio signal r(t, α ) from said carrierwave components and said quadrature components, characterized in that the digital values I(t, α ), Q(t, α ) stored for the different waveforms in said storage means (ST, CT) are modified in dependence on said transfer functions H R and H φ of the final amplifier (F) so that new digital values i(t, α ), q(t, α ) are obtained for said waveforms which, upon quadrature modulation, compensate the radio signal for said non-linearities.
Claim 2
Dependent Claim
186 words
A method according to Claim 1, characterized by forming from the original digital values I(t, α ), Q(t, α ) a value R(t, α ) which gives the absolute value |r(t, α )| of the quadrature-modulated radio signal; adressably storing a plurality of digital values of the transmission functions H R and H φ of the end amplifier (F); addressing a given value of said transmission functions H R and H φ by said calculated value of R(t, α ), therewith to obtain a first value H R (R) of the amplitude-dependency of the end amplifier and a second value H φ (R) of the phase-dependency of the amplifier; and multiplying said first value H R (R) and sine-cosine components of said second value H φ (R) by the original digital values I(t, α ) and Q(t, α ) in a manner such that the new modified digital values i(t, α ) and q(t, α ) obtained in said storage means (ST, CT) have an absolute value which is equal to the absolute value of the original digital values multiplied by a factor 1/H R (R).
Claim 3
Dependent Claim
91 words
A method according to Claim 2, characterized by obtaining the new modified digital values i(t, α ), q(t, α ) of the waveforms from the relationships: i(t, α ) = H R ⁻¹ (R) [I(t, α ) cos H φ (R)-Q(t, α ) sine H φ (R)] q(t, α ) = H R ⁻¹ (R) [I(t, α ) sine H φ (R)+Q(t, α ) cos H φ (R)] where H R (R) and H φ (R) are said addressed values of the amplitude-dependency and phase-dependency respectively of the final amplifier (F).