Department, Cairo University, Giza, Egypt. The oscillation radian frequency is given by ... AND ROBERTO SORRENTINO. Abmct-The EM nature of trmmiahn zmx ...
PROCEEDINGS OF THE IEEE, VOL. 66, NO. 7, JULY 1978
800
A Novel Variable Frequency Sinusoidal Oscillator Using a Single Current Conwyor AHMED M. SOLIMAN
The oscillation radian frequency is given by wo = Ja11a22
- a12a21.
(8)
Thus
4 m c t - A new active RC secmd-order sinusoidal oscillator d n g a single second generition current COIIVOT is A sin@
w0 = G1
d m .
(9)
described. ~edmi&xadjuststhecircaitforoecilLtionmda&@egounded As cau be seen from (7) and (9), G2 adjusts the circuit for oscillation capprcitor
conttds the osciltrtion frequency Without affectingthe oscic
Ltion condition.
e
Recently active RC second-order sinusoidal oscillator using the second generation current conveyor (CC II) [ 11 as the active element has been given [2]. The frequency of oscillation is controlled by tuning a single grounded resistor or a grounded capacitor in the circuit. The oscillator circuit, however, requires two opposite polarity current conveyors [ 21. In this letter a noveloscillator circuit using a single CC I1 is described. Theoscillation frequency is controlled by tuning a single grounded capacitor without affecting the oscillation condition.
and the grounded capacitor C1 controls the fresuency of oscillation without affecting the oscillation condition. REFZRENCE9
[ 1 ] A. Sedra and K. C. Smith, “A second generation current convqgr and ita applications,” IEEE fians. Circuit ZReory, vol. CT-17,
pp. 132-134, Feb. 1970. 121 A. M. Solinan, “Simple sinusoidal active RC oscillators,” Inr. J. Elecrron.,vol. 39,110.4,pp.455-458, Oct. 1975.
On the Double Nature of Transmission Zeros mMiMicrostrip structures GUGLIELMO DWZEO, FRANC0 GIANNINI, PAOLO MALTESE, A N D ROBERTO SORRENTINO
I I” +
1
Fig. 1. A novel variablefrequency sinusoidal oxillator. Theterminal characteristics of the current conveyor are [ 1 ] ib = 0, ucr = ub, f, = ia.
The new sinusoidal oscillator circuit is shown in Fig. 1. By direct analysis the state equations for the circuit are given by
[=I:
a21 a22
G1 C1
a22 =
G+4G1 -Gz+G+2C1 -G2 Cl
zeros.
I. INTRODUCTION In the area ofmicrowave integrated circuits, several investigations have stressed the marked atering properties of rectangular structures. In particular, the existence of transmission zera has been pointed out both theoretidy and experimentany. Nevertheless, the interpretation of the physical nature of such zeros has been discussed for a long time; several authors seemed to believe that they were due to the excitation of higher order modes of propagation in the wider microstrip section [1]-(41. A recent theoretical analysis, however, supported by experimental data, has shown the existence of two types of transmission zeros: modal zeros and interaction zeros [SI. A perceptible evidence to such a result is given in the present letter through a liquid crystal technique recently set up [6] for detecting the magnetic field distribution inside microstrip structures. The experiments dearly conhrm the double nature of transmission zeros and the condition stated in [SI for their existence.
a11 a12
where a11 = -2
Abmct-The EM nature of trmmiahn z m x m miaostrip structured has been the subjed of several d s ic u d o a A liquid aystal thermal mapping technique is used for detecting the mrgnetic field distribution inside redqulx stn~ctumat the freqmcks of the transmission zeroa In this way a perceptible evidence is given to previous theoretical results, which h e pointed out the existence of two types of transmission zeros, alled modal zeros m d interaction
c2
The condition for oscillation is given by a11 +a22 = 0
which impliesthat
11. MODAL A N D INTERACTION ZEROS Modal transmission zeros in microwave two-port networks are due to the resonances of these modes of the s t r u c t u r e which can be excited only at one port, since they are uncoupled to the other port. This implies that: a) only nonsymmetrical structures1 present this type of transmission zeros, and b) the frequency of a modal zero coincides with the resonant frequency of the corresponding mode.
G2 = G + 2G1.
Manuscript received February 9,1978;re-d March 20,1978. The author is with the Electroaics and Communication Engineering Department, Cairo University, Giza, Egypt.
Manuscript received March 7,. 1978. The authora are wth the Istrtuto di Elettronica, Faculty of Engineering, Via Eudossiana 18, Rome, Italy. ‘Degenerate structures, i.e., structures with degenerate modes,should be regarded as special cases. Thus, for the sake of brevity, they are not considered here.
IEEE 0 0 1 8 - 9 2 1 9 / 7 8 / 0 7 ~ 8 0 ~ ~ .@7 1978 5
