More generally, the receiver must have an input referred third-order intercept point high enough so that at maximum received signal level intermodulations generated in the receiver (generally in the first mixer) do not prevent the radio from operating satisfactorily at maximum received signal level (RSL).
* Some standards set a limit to the third-order distortion at threshold by requiring tones relative to signal at +19 dBr, spaced to put a third-order intermodulation product (IM3) at the receive frequency, to have a negligible effect on threshold.
This sets the levels for spurious rather than intermodulation products.
There is no rigorous way of predicting spectral growth from CW output third-order intermodulation intercept point (OIP3) measurements.
Traditionally, the nonlinearity of an RF amplifier is described by [IP.sub.3] or, equivalently, by the 1 dB compression point.[3,4] In experiments and analysis it was discovered that, in some situations, using [IP.sub.3] only is not enough to describe the spectrum regrowth, especially when the fifth-order intermodulation is relatively high compared to the third-order intermodulation.
In this article, based on the nature of the CDMA signal, explicit expressions are derived relating an estimation of' the out-of-band power emission levels of an amplifier to its nonlinear parameters ([IP.sub.3] and [IP.sub.5]) where [IP.sub.5] is a parameter defined in a similar manner as [IP.sub.3] to describe the fifth-order intermodulation quantitatively.
In the band B [less than] [absolute value of] f - [f.sub.0] [less than or equal to] 3B, the nonzero power spectrum density is generated by third-order as well as fifth-order intermodulation. This result shows that the out-of-band spectrum density is determined completely by the intermodulation.
The gain of the auxiliary amplifier [G.sub.LIN] is calculated with the understanding that appropriate signal levels must be maintained at the error injection coupler inputs in order to ensure perfect intermodulation cancellation.
The selected auxiliary amplifier LIN must be able to produce at the output of the error loop coupler a power level comparable to the intermodulation power level provided by the PA, as expressed by [P.sub.LIN][C.sub.2] = [P.sub.PA][f.sub.PA].
Jeong, "A Design of Predistortion Linearizer by Individual Order Control of Intermodulation Distortion Signals," PhD Dissertation, Sogang University, 1996.
In this article, a new type of analog predistortion linearizer is proposed to generate and control predistorted third and higher order intermodulation signals (IM) separately.
When signals are amplified in an HPA, unwanted harmonics and intermodulation distortion signals are generated, in addition to the amplified desired signals, by the nonlinear characteristics of the power amplifier.